DCPT/07/12
IPPP/07/06
arXiv:0704.0619
Search for Heavy Neutral MSSM Higgs Bosons with CMS:
Reach and Higgs-Mass Precision
S. Gennai 1∗, S. Heinemeyer 2†, A. Kalinowski 3‡, R. Kinnunen 4§, S. Lehti 4¶,
A. Nikitenko 5‖ and G. Weiglein 6∗∗
1 Centro Studi Enrico Fermi, Rome and INFN Pisa, Italy
2 Instituto de Fisica de Cantabria (CSIC-UC), Santander, Spain
3 Institute of Experimental Physics, Warsaw, Poland
4 Helsinki Institute of Physics, Helsinki, Finland
5 Imperial College, London, UK; on leave from ITEP, Moscow, Russia
6 IPPP, University of Durham, Durham DH1 3LE, UK
Abstract
The search for MSSM Higgs bosons will be an important goal at the LHC. We
analyze the search reach of the CMS experiment for the heavy neutral MSSM Higgs
bosons with an integrated luminosity of 30 or 60 fb−1. This is done by combining the
latest results for the CMS experimental sensitivities based on full simulation studies
with state-of-the-art theoretical predictions of MSSM Higgs-boson properties. The
results are interpreted in MSSM benchmark scenarios in terms of the parameters tan β
and the Higgs-boson mass scale, MA. We study the dependence of the 5 σ discovery
contours in the MA–tan β plane on variations of the other supersymmetric parameters.
The largest effects arise from a change in the higgsino mass parameter µ, which enters
both via higher-order radiative corrections and via the kinematics of Higgs decays into
supersymmetric particles. While the variation of µ can shift the prospective discovery
reach (and correspondingly the “LHC wedge” region) by about ∆ tan β = 10, we
find that the discovery reach is rather stable with respect to the impact of other
supersymmetric parameters. Within the discovery region we analyze the accuracy
with which the masses of the heavy neutral Higgs bosons can be determined. We
find that an accuracy of 1–4% should be achievable, which could make it possible in
favourable regions of the MSSM parameter space to experimentally resolve the signals
of the two heavy MSSM Higgs bosons at the LHC.
∗ email: Simone.Gennai@cern.ch
† email: Sven.Heinemeyer@cern.ch
‡ email: Artur.Kalinowski@cern.ch
§ email: Ritva.Kinnunen@cern.ch
¶ email: Sami.Lehti@cern.ch
‖ email: Alexandre.Nikitenko@cern.ch
∗∗ email: Georg.Weiglein@durham.ac.uk
http://arxiv.org/abs/0704.0619v1
http://arxiv.org/abs/0704.0619
1 Introduction
Identifying the mechanism of electroweak symmetry breaking will be one of the main goals of
the LHC. Many possibilities have been studied in the literature, of which the most popular
ones are the Higgs mechanism within the Standard Model (SM) and within the Minimal
Supersymmetric Standard Model (MSSM) [1]. Contrary to the case of the SM, in the MSSM
two Higgs doublets are required. This results in five physical Higgs bosons instead of the
single Higgs boson of the SM. These are the light and heavy CP-even Higgs bosons, h and
H , the CP-odd Higgs boson, A, and the charged Higgs boson, H±.1 The Higgs sector
of the MSSM can be specified at lowest order in terms of the gauge couplings, the ratio
of the two Higgs vacuum expectation values, tan β ≡ v2/v1, and the mass of the CP-odd
Higgs boson, MA. Consequently, the masses of the CP-even neutral Higgs bosons and the
charged Higgs boson are dependent quantities that can be predicted in terms of the Higgs-
sector parameters. Higgs-phenomenology in the MSSM is strongly affected by higher-order
corrections, in particular from the sector of the third generation quarks and squarks, so that
the dependencies on various other MSSM parameters can be important.
After the termination of LEP in the year 2000 (the final LEP results can be found in
Refs. [2, 3]), and the (ongoing) Higgs boson search at the Tevatron [4–6], the search will be
continued at the LHC [7–9] (see also Refs. [10, 11] for recent reviews). The current exclusion
bounds within the MSSM [3–5] and the prospective sensitivities at the LHC are usually dis-
played in terms of the parameters MA and tan β that characterize the MSSM Higgs sector
at lowest order. The other MSSM parameters are conventionally fixed according to certain
benchmark scenarios [12–14]. The most prominent one is the “mmaxh scenario”, which in the
search for the light CP-even Higgs boson allows to obtain conservative bounds on tan β for
fixed values of the top-quark mass and the scale of the supersymmetric particles [15]. Besides
the “no-mixing scenario”, which is similar to the mmaxh scenario, but assumes vanishing mix-
ing in the stop sector, other CP-conserving scenarios that have been studied in LHC analyses
(see e.g. Ref. [11]) are the “gluophobic Higgs scenario” and the “small αeff” scenario [13].
For the interpretation of the exclusion bounds and prospective discovery contours in
the benchmark scenarios it is important to assess how sensitively the results depend on
those parameters that have been fixed according to the benchmark prescriptions. While in
the decoupling limit, which is the region of MSSM parameter space with MA ≫ MZ , the
couplings of the light CP-even Higgs boson approach those of a SM Higgs boson with the
same mass, the couplings of the heavy Higgs bosons of the MSSM can be sizably affected
by higher-order contributions even for large values of MA. The kinematics of the heavy
Higgs-boson production processes, on the other hand, is governed by the parameter MA,
since in the region of large MA the heavy MSSM Higgs bosons are nearly mass-degenerate,
MA ≈ MH ≈ MH±. In Ref. [14] it has been shown that higher-order contributions to the
relation between the bottom-quark mass and the bottom-Yukawa coupling have a dramatic
effect on the exclusion bounds in the MA–tanβ plane obtained from the bb̄φ, φ → bb̄ channel
at the Tevatron.
In this article we investigate how the 5 σ discovery regions in the MA–tanβ plane for the
heavy neutral MSSM Higgs bosons (a corresponding analysis for the charged Higgs-boson
1We focus in this paper on the case without explicit CP-violation in the soft supersymmetry-breaking
terms.
search will be presented elsewhere) obtainable with the CMS experiment at the LHC depend
on the other MSSM parameters. For the experimental sensitivities achievable with CMS we
use up-to-date results based on full simulation studies for 30 or 60 fb−1(depending on the
channel) [9]. This information is combined with precise theory predictions for the Higgs-
boson masses and the involved production and decay processes incorporating higher-order
corrections at the one-loop and two-loop level. In our analysis we investigate the impact on
the discovery reach arising both from higher-order corrections and from possible decays of
the heavy Higgs bosons into supersymmetric particles.2
The search for the heavy neutral MSSM Higgs bosons at the LHC will mainly be pursued
in the b quark associated production with a subsequent decay to τ leptons [7–9]. In the region
of large tanβ this production process benefits from an enhancement factor of tan2 β compared
to the SM case. The main search channels are3 (here and in the following φ denotes the two
heavy neutral MSSM Higgs bosons, φ = H,A):
bb̄φ, φ → τ+τ− → 2 jets (1)
bb̄φ, φ → τ+τ− → µ+ jet (2)
bb̄φ, φ → τ+τ− → e+ jet (3)
bb̄φ, φ → τ+τ− → e+ µ . (4)
For our numerical analysis we use the program FeynHiggs [19–22]. We study in particular
the dependence of the “LHC wedge” region, i.e. the region in which only the light CP-even
MSSM Higgs boson can be detected at the LHC at the 5 σ level, on the variation of the
higgsino mass parameter µ. The dependence on µ enters in two different ways, on the one
hand via higher-order corrections affecting the relation between the bottom mass and the
bottom Yukawa coupling, and on the other hand via the kinematics of Higgs decays into
supersymmetric particles. We analyze both effects separately and discuss the possible impact
of other supersymmetric parameters.
Our results for the discovery reach of the heavy neutral MSSM Higgs bosons extend the
known results in the literature in various ways. In comparison with Refs. [23, 24], where the
prospective 5σ discovery contours for CMS in the MA–tanβ plane of the m
h benchmark
scenario were given for three different values of µ, the results in the present paper are based
on full simulation studies and make use of the most up-to-date CMS tools for triggering
and event reconstruction. Furthermore, in the analysis of Refs. [23, 24] relevant higher-
order corrections, in particular those depending on ∆b (see Sect. 2.2 below), have been
neglected. The effects induced by the ∆b corrections have been investigated in Ref. [14],
where the results were obtained by a simple rescaling of the experimental results given in
Refs. [7, 23–25]. Our present analysis, on the other hand, makes use of the latest CMS studies
and provides a separate treatment of the different τ final states, channels (1)–(4).
As a second step of our analysis we investigate the experimental precision that can be
achieved for the determination of the heavy Higgs-boson masses in the discovery channels (1)–
2We restrict our analysis to the impact of supersymmetric contributions. For a discussion of uncertainties
related to parton distribution functions, see e.g. Ref. [16].
3In our analysis we do not consider diffractive Higgs production, pp → p ⊕ H ⊕ p [17]. For a detailed
discussion of the search reach for the heavy neutral MSSM Higgs bosons in diffractive Higgs production we
refer to Ref. [18].
(4). We discuss the prospective accuracy of the mass measurement in view of the possibility
to experimentally resolve the signals of the heavy neutral MSSM Higgs bosons.
The paper is organized as follows: Sect. 2 introduces our notation and gives a brief sum-
mary of the most relevant supersymmetric radiative corrections to the Higgs-boson masses,
production cross sections and decay widths at the LHC. The relevant benchmark scenarios
are briefly reviewed. In Sect. 3 the experimental analysis is described. The results for the
variation of the 5 σ discovery contours, obtainable at CMS with 30 or 60 fb−1 are given
in Sect. 4, where we also discuss the achievable experimental precision in the Higgs mass
determination. The conclusions can be found in Sect. 5.
2 Phenomenology of the MSSM Higgs sector
2.1 Notation
The MSSM Higgs sector at lowest order is described in terms of two independent parameters
(besides the SM gauge couplings): tan β ≡ v2/v1, the ratio of the two vacuum expectation
values, and MA, the mass of the CP-odd Higgs boson A. Beyond the tree-level, large
radiative corrections can occur from the t/t̃ sector, and for large values of tanβ also from
the b/b̃ sector.
Our notations for the scalar top and scalar bottom sector of the MSSM are as follows:
the mass matrices in the basis of the current eigenstates t̃L, t̃R and b̃L, b̃R are given by
+m2t + cos 2β (
s2w)M
Z mtXt
mtXt M
+m2t +
cos 2β s2wM
, (5)
+m2b + cos 2β (−12 +
s2w)M
Z mbXb
mbXb M
+m2b − 13 cos 2β s
, (6)
where
mtXt = mt(At − µ cotβ ), mb Xb = mb (Ab − µ tanβ ). (7)
Here MQ̃, Mt̃R and Mb̃R are the diagonal soft SUSY-breaking parameters, At denotes the
trilinear Higgs–stop coupling, Ab denotes the Higgs–sbottom coupling, and µ is the higgsino
mass parameter.
For the numerical evaluation, it is often convenient to choose
MQ̃ = Mt̃R = Mb̃R =: MSUSY. (8)
Concerning analyses for the case where Mt̃R 6= MQ̃ 6= Mb̃R , see e.g. Refs. [20, 26, 27]. It
has been shown that the upper bound on the mass of the light CP-even Higgs boson, Mh,
obtained using eq. (8) is the same as for the more general case, provided that MSUSY is
identified with the heaviest mass of MQ̃,Mt̃R ,Mb̃R [20].
Accordingly, the most important parameters entering the Higgs-sector predictions via
higher-order corrections are mt, MSUSY, Xt, Xb and µ (see also the discussion in Sect. 2.2.2
below). The Higgs-sector observables furthermore depend on the SU(2) gaugino mass param-
eter, M2, the U(1) parameter M1 and the gluino mass, mg̃ (the latter enters the predictions
for the Higgs-boson masses only from two-loop order on). In numerical analyses the U(1)
gaugino mass parameter, M1, is often fixed via the GUT relation
M2. (9)
We will briefly comment below on the possible impact of complex phases entering the Higgs-
sector predictions via higher-order contributions.
2.2 Higher-order corrections in the Higgs sector
In the following we briefly summarize the most important higher-order corrections affecting
the observables in the MSSM Higgs-boson sector. As mentioned above, we focus on the
MSSM with real parameters. For our numerical analysis we use the program FeynHiggs [19–
22]4, which incorporates a comprehensive set of higher-order results obtained in the Feynman-
diagrammatic approach [20–22, 28–30].
2.2.1 Higgs-boson propagator corrections
Higher-order corrections to the Higgs-boson masses and the wave function normalization
factors of processes with external Higgs bosons arise from Higgs-boson propagator-type con-
tributions. These corrections furthermore contribute in a universal way to all Higgs-boson
couplings. For the propagator-type corrections in the MSSM the complete one-loop re-
sults [31–34], the bulk of the two-loop contributions [20, 27–29, 35–39] and even leading
three-loop corrections [40] are known. The remaining theoretical uncertainty on the light
CP-even Higgs-boson mass has been estimated to be below ∼ 3 GeV [21, 41]. The by far
dominant contribution is the O(αt) term due to top and stop loops (αt ≡ h2t/(4π), where ht
denotes the top-quark Yukawa coupling). Effects of O(αb) can be important for large values
of tan β.
2.2.2 Corrections to the relation between the bottom-quark mass and the bot-
tom Yukawa coupling
Concerning the corrections from the bottom/sbottom sector, large higher-order effects can
in particular occur in the relation between the bottom-quark mass and the bottom Yukawa
coupling (which controls the interaction between the Higgs bosons and bottom quarks as
well as between the Higgs and scalar bottoms), hb, for large values of tanβ. At lowest order
the relation reads mb = hbv1. Beyond the tree level large radiative corrections proportional
to hbv2 are induced, giving rise to tanβ-enhanced contributions [36–38,42]. At the one-loop
level the leading terms proportional to v2 are generated either by gluino–sbottom one-loop
diagrams of O(αs) or by chargino–stop loops of O(αt).
The leading one-loop contribution ∆b in the limit of MSUSY ≫ mt and tanβ ≫ 1 takes
the simple form [36]
mg̃ µ tanβ × I(mb̃1 , mb̃2 , mg̃) +
At µ tan β × I(mt̃1 , mt̃2 , µ) , (10)
4 The code can be obtained from www.feynhiggs.de .
where the function I is given by
I(a, b, c) =
(a2 − b2)(b2 − c2)(a2 − c2)
a2b2 log
+ b2c2 log
+ c2a2 log
max(a2, b2, c2)
The leading contribution can be resummed to all orders in the perturbative expansion [36–
38]. This leads in particular to the replacement
1 + ∆b
, (12)
where mb denotes the running bottom quark mass including SM QCD corrections. For the
numerical evaluations in this paper we choose mb = mb(mt) ≈ 2.97 GeV.
The ∆b corrections are numerically sizable for large tan β in combination with large values
of the ratios of µmg̃/M
SUSY or µAt/M
SUSY. Negative values of ∆b lead to an enhancement of
the bottom Yukawa coupling as a consequence of eq. (12) (for extreme values of µ and tanβ
the bottom Yukawa coupling can even acquire non-perturbative values when ∆b → −1),
while positive values of ∆b give rise to a suppression of the Yukawa coupling. Since a change
in the sign of µ reverses the sign of ∆b, the bottom Yukawa coupling can exhibit a very
pronounced dependence on the parameter µ.
For large values of tanβ the correction to the production cross sections of the Higgs
bosons H and A induced by ∆b enters approximately like tan
2 β/(1 + ∆b)
2, giving rise
to potentially large numerical effects. In the case of the subsequent Higgs-boson decay
φ → τ+τ−, however, the ∆b corrections in the production and the decay process cancel
each other to a large extent. The residual ∆b dependence of σ(bb̄φ) × BR(φ → τ+τ−) is
approximately given by tan2 β/((1+∆b)
2+9), which has a much weaker ∆b dependence (see
Ref. [14] for a more detailed discussion).
In the numerical analysis below the ∆b corrections, which have been discussed in this
section in terms of simple approximation formulae, will be supplemented by other higher-
order corrections as implemented in the program FeynHiggs (and possible decay modes into
supersymmetric particles are taken into account). Higher-order corrections to Higgs decays
into τ+τ− within the SM and MSSM have been evaluated in Refs. [34, 43].
2.2.3 Corrections to the Higgs production cross sections
For the prediction of Higgs-boson production processes at hadron colliders SM-type QCD
corrections in general play an important role. The SM predictions for the process bb̄ → φ+X
at the LHC are far advanced. In the five-flavor scheme the SM cross section is known at
NNLO in QCD [44]. The cross section in the four-flavor scheme is known at NLO [45, 46].
Results obtained in the two schemes have been shown to be consistent [47–49] (see also
Refs. [48, 50] and Refs. [45, 46] for results with one and two final-state b-quarks at high-pT ,
respectively).
The predictions for the bb̄ → φ + X cross sections in the MSSM have been obtained
with FeynHiggs [19–22]. The FeynHiggs implementation5 is based on the state-of-the-art
5The inclusion of the charged Higgs production cross sections is planned for the near future.
SM prediction, namely the NNLO result in the five-flavor scheme [44] using MRST2002
parton distributions at NNLO [51], with the renormalization scale set equal to MHSM and
the factorization scale set equal to MHSM/4. In order to obtain the MSSM prediction the
SM cross section is rescaled with the ratio of the partial widths in the MSSM and the SM,
Γ(φ → bb̄)MSSM
Γ(φ → bb̄)SM
. (13)
The evaluation of the partial widths incorporates one-loop SM QCD and SUSY QCD correc-
tions, as well as (in the SUSY case) the resummation of all terms of O((αs tanβ)n) [34,37,43]
and the proper normalization of the external Higgs bosons as discussed in Refs. [22, 52]. Since
the approximation of rescaling the SM cross section with the ratio of partial widths does not
take into account the MSSM-specific dynamics of the production processes, the theoretical
uncertainty in the predictions for the cross sections will in general be somewhat larger than
for the decay widths. It should be noted that in comparison with other approaches for treat-
ing the SM and SUSY contributions, for instance the program HQQ [53], sizable deviations
can occur as a consequence of differences in the scale choices and the inclusion of higher-order
corrections.
2.3 The mmaxh and no-mixing benchmark scenarios
While the phenomenology of the production and decay processes of the heavy neutral MSSM
Higgs bosons at the LHC is mainly characterised by the parametersMA and tanβ that govern
the Higgs sector at lowest order, other MSSM parameters enter via higher-order contribu-
tions, as discussed above, and via the kinematics of Higgs-boson decays into supersymmetric
particles. The other MSSM parameters are usually fixed in terms of benchmark scenarios.
The most commonly used scenarios are the “mmaxh ” and “no-mixing” benchmark scenar-
ios [12–14]. According to the definition of Ref. [13] the mmaxh scenario is given by
mmaxh : MSUSY = 1000 GeV, Xt = 2MSUSY, Ab = At,
µ = 200 GeV, M2 = 200 GeV, mg̃ = 0.8MSUSY . (14)
The no-mixing scenario differs from the mmaxh scenario only in that it has vanishing mixing
in the stop sector and a larger value of MSUSY
no-mixing: MSUSY = 2000 GeV, Xt = 0, Ab = At,
µ = 200 GeV, M2 = 200 GeV, mg̃ = 0.8MSUSY . (15)
The value of the top-quark mass in Ref. [13] was chosen according to the experimental central
value at that time. For our numerical analysis below, we use the value, mt = 171.4 GeV [54]
In Ref. [14] it was suggested that in the search for heavy MSSM Higgs bosons the mmaxh
and no-mixing scenarios, which originally were mainly designed for the search for the light
CP-even Higgs boson h, should be extended by several discrete values of µ,
µ = ±200,±500,±1000 GeV . (16)
6 Most recently the central experimental value has shifted to mt = 170.9± 1.8 GeV [55]. This shift has
a negligible impact on our analysis.
As discussed above, the variation of µ in particular has an impact on the correction ∆b,
modifying in this way the bottom Yukawa coupling. For very large values of tan β and
large negative values of µ the bottom Yukawa coupling can be so much enhanced that a
perturbative treatment is no longer possible. We have checked that in our analysis of the
LHC discovery contours the bottom Yukawa coupling stays in the perturbative regime, so
that all values of µ down to µ = −1000 GeV can safely be inserted.
The variation of the parameter µ also modifies the mass spectrum and the couplings in
the chargino and neutralino sector of the MSSM. Besides the small higher-order corrections
induced by loop diagrams involving charginos and neutralinos, a change in the mass spectrum
of the chargino and neutralino sector can have an important effect on Higgs phenomenology
because decay modes of the heavy neutral MSSM Higgs bosons into charginos and neutralinos
open up if the supersymmetric particles are sufficiently light (the mass spectrum in the mmaxh
and no-mixing scenarios respects the limits from direct searches for charginos at LEP [56]
for all values of µ specified in eq. (16)).
Differences between the mmaxh and no-mixing scenarios in the searches for heavy neutral
MSSM Higgs bosons are induced in particular by a difference in the ∆b correction. While in
the mmaxh scenario both the O(αs) and O(αt) contributions to ∆b can be sizable, see eq. (10),
in the no-mixing scenario the O(αt) contribution is very small because At is close to zero in
this case. The larger value of MSUSY in the no-mixing scenario gives rise to an additional
suppression of |∆b| compared to the mmaxh scenario.
3 Experimental analysis
In this section we briefly review the recent CMS analysis of the φ → τ+τ− channel, see
Ref. [9], yielding the number of events needed for a 5 σ discovery (depending on the mass
of the Higgs boson). The analysis was performed with full CMS detector simulation and
reconstruction for the following four final states of di-τ -lepton decays: τ+τ− → jets [57],
τ+τ− → e+ jet [58], τ+τ− → µ+ jet [59] and τ+τ− → e + µ [60].
The Higgs-boson production in association with b quarks, pp → bb̄φ, has been selected
using single b-jet tagging in the experimental analysis. The kinematics of the gg → bb̄φ
production process (2 → 3) was generated with PYTHIA [61]. It has been shown that in
this way the NLO kinematics is better reproduced than using the PYTHIA gb → bφ process
(2 → 2) [62]. The backgrounds considered in the analysis were QCD muli-jet events (for the
ττ → jets mode), tt̄, bb̄, Drell-Yan production of Z, γ∗, W+jet, Wt and ττbb̄. All background
processes were generated using PYTHIA, except for τ+τ−bb̄, which was generated using
CompHEP [63].
The results for the various channels, eqs. (1) – (4), are given in Tabs. 1 – 4. For every
Higgs-boson mass point studied we show the number of signal events needed for 5 σ discovery,
NS, the total experimental selection efficiency, εexp, and the ratio of the di-τ mass resolution
to the Higgs-boson mass, RMφ . The last row in Tabs. 1 – 4 shows the expected precision of
the Higgs-boson mass measurement, evaluated as explained below, for parameter points on
the 5 σ discovery contour. Detector effects, experimental systematics and uncertainties of
the background determination were taken into account in the evaluation of the NS. These
effects reduce the discovery region in the MA–tanβ plane as shown in previous analyses [9]
φ → τ+τ− → jets, 60 fb−1
MA [GeV] 200 500 800
NS 63 35 17
εexp 2.5× 10−4 2.4× 10−3 3.6× 10−3
RMφ 0.176 0.171 0.187
∆Mφ/Mφ [%] 2.2 2.8 4.5
Table 1: Required number of signal events, NS, with L = 60 fb−1 for a 5 σ discovery in
the channel φ → τ+τ− → jets. Furthermore given are the total experimental selection
efficiency, εexp, the ratio of the di-τ mass resolution to the Higgs-boson mass, RMφ, and the
expected precision of the Higgs-boson mass measurement, ∆Mφ/Mφ, obtainable from NS
signal events.
φ → τ+τ− → e+ jet, 30 fb−1
MA [GeV] 200 300 500
NS 72.9 45.5 32.8
εexp 3.0× 10−3 6.4× 10−3 1.0× 10−2
RMφ 0.216 0.214 0.230
∆Mφ/Mφ [%] 2.5 3.2 4.0
Table 2: Required number of signal events, NS, with L = 30 fb−1 for a 5 σ discovery in the
channel φ → τ+τ− → e+ jet. The other quantities are defined as in Tab. 1.
φ → τ+τ− → µ+ jet, 30 fb−1
MA [GeV] 200 500
NS 79 57
εexp 7.0× 10−3 2.0× 10−2
RMφ 0.210 0.200
∆Mφ/Mφ [%] 2.4 2.6
Table 3: Required number of signal events, NS, with L = 30 fb−1 for a 5 σ discovery in the
channel φ → τ+τ− → µ+ jet. The other quantities are defined as in Tab. 1.
φ → τ+τ− → e + µ, 30 fb−1
MA [GeV] 200 250
NS 87.8 136.7
εexp 6.4× 10−3 1.1× 10−2
RMφ 0.262 0.412
∆Mφ/Mφ [%] 2.8 3.5
Table 4: Required number of signal events, NS, with L = 30 fb−1 for a 5 σ discovery in the
channel φ → τ+τ− → e+ µ. The other quantities are defined as in Tab. 1.
(see in particular Fig. 5.6 of Ref. [9] for the τ+τ− → µ+ jet mode).
Now we turn to the evaluation of the expected precision of the Higgs-boson mass mea-
surement. In spite of the escaping neutrinos, the Higgs-boson mass can be reconstructed
in the H,A → ττ channel from the visible τ momenta (τ jets) and the missing transverse
energy, EmissT , using the collinearity approximation for neutrinos from highly boosted τ ’s. In
the investigated region of MA and tanβ the two states A and H are nearly mass-degenerate.
For most values of the other MSSM parameters the mass difference of A and H is much
smaller than the achievable mass resolution. In this case the difference in reconstructing the
A or the H will have no relevant effect on the achievable accuracy in the mass determina-
tion. In some regions of the MSSM parameter space, however, a sizable splitting between
MA and MH can occur even for MA ≫ MZ . We will discuss below the prospects in scenarios
where the splitting between MA and MH is relatively large. The precision ∆Mφ/Mφ shown
in Tabs. 1 – 4 is derived for the border of the parameter space in which a 5 σ discovery
can be claimed, i.e. with NS observed Higgs events. The statistical accuracy of the mass
measurement has been evaluated via
. (17)
A higher precision can be achieved if more than NS events are observed. The corresponding
estimate for the precision is obtained by replacing NS in eq. (17) by the number of observed
signal events, Nev. It should be noted that the prospective accuracy obtained from eq. (17)
does not take into account the uncertainties of the jet and missing ET energy scales. In
the τ+τ− → jets mode these effects can lead to an additional 3% uncertainty in the mass
measurement [57]. A more dedicated procedure of the mass measurement from the signal
plus background data still has to be developed in the experimental analysis. However, we do
not expect that the additional uncertainties will considerably degrade the accuracy of the
Higgs boson mass measurement as calculated with eq. (17).
4 Results
The results quoted in Sect. 3 for the required number of signal events depend only on the
Higgs-boson mass, i.e. the event kinematics, but are independent of any specific MSSM
scenario. In order to determine the 5 σ discovery contours in the MA–tan β plane these
results have to be confronted with the MSSM predictions. The number of signal events, Nev,
for a given parameter point is evaluated via
Nev = L × σbb̄φ × BR(φ → τ+τ−)× BRττ × εexp . (18)
Here L denotes the luminosity collected with the CMS detector, σbb̄φ is the Higgs-boson pro-
duction cross section, BR(φ → τ+τ−) is the branching ratio of the Higgs boson to τ leptons,
BRττ is the product of the branching ratios of the two τ leptons into their respective final
state,
BR(τ → jet +X) ≈ 0.65 , (19)
BR(τ → µ+X) ≈ BR(τ → e+X) ≈ 0.175 , (20)
and εexp denotes the total experimental selection efficiency for the respective process (as
given in Tabs. 1 – 4). The Higgs-boson production cross sections and decay branching ratios
have been evaluated with FeynHiggs as described in Sect. 2.2.
4.1 Discovery reach for heavy neutral MSSM Higgs bosons
The number of signal events, Nev, in the MSSM depends besides the parameters MA and
tan β, which govern the MSSM Higgs sector at lowest order, in principle also on all other
MSSM parameters. In the following we analyze how stable the results for the 5σ discovery
contours in theMA–tanβ plane are with respect to variations of the other MSSM parameters.
We take into account both effects from higher-order corrections, as discussed in Sect. 2.2,
and from decays of the heavy Higgs bosons into supersymmetric particles. As starting point
of our analysis we use the mmaxh and no-mixing benchmark scenarios, where we investigate
in detail the sensitivity of the discovery contours with respect to variations of the parameter
µ. We then discuss the possible impact of varying other MSSM parameters.
We have evaluated Nev in the two benchmark scenarios as a function of MA and tan β.
For fixed MA we have varied tan β such that Nev = NS (as given in Tabs. 1 – 4). This tanβ
value is then identified as the point on the 5 σ discovery contour corresponding to the chosen
value of MA. In this way we have determined the 5 σ discovery contours for the m
h and
the no-mixing scenarios for µ = ±200,±1000 GeV.
In Figs. 1 – 3 we show the 5σ discovery contours obtained from the process bb̄φ, φ → τ+τ−
for the final states τ+τ− → jets, τ+τ− → e + jet and τ+τ− → µ + jet. As can be seen
from Tab. 4, the fourth channel discussed above, τ+τ− → e + µ, contributes for 30 fb−1
only in the region of relatively small MA values and has a lower sensitivity than the other
three channels. We therefore omit this channel in the following discussion. The discovery
contours in Figs. 1 – 3 are given for the mmaxh and no-mixing benchmark scenarios with µ =
±200,±1000 GeV. As explained above, the 5 σ discovery contours are affected by a change
in µ in two ways. Higher-order contributions, in particular the ones associated with ∆b,
,GeV/cAM
100 200 300 400 500 600 700 800
2 = -1000 GeV/cµ
2 = -200 GeV/cµ
2 = 200 GeV/cµ
2 = 1000 GeV/cµ
CMS, 60 fb
 j+j→ ττ → φ bb→pp 
 scenariomaxhm
2 = 1 TeV/cSUSYM
2 = 200 GeV/c2M
SUSY = 0.8 Mgluinom
SUSY = 2 MtStop mix: X
,GeV/cAM
100 200 300 400 500 600 700 800
2 = -1000 GeV/cµ
2 = -200 GeV/cµ
2 = 200 GeV/cµ
2 = 1000 GeV/cµ
CMS, 60 fb
 j+j→ ττ → φ bb→pp 
no mixing scenario
2 = 2 TeV/cSUSYM
2 = 200 GeV/c2M
SUSY = 0.8 Mgluinom
 = 0tStop mix: X
Figure 1: Variation of the 5σ discovery contours obtained from the channel bb̄φ, φ → τ+τ− →
jets in the mmaxh (left) and no-mixing (right) benchmark scenarios for different values of µ.
,GeV/cAM
100 200 300 400 500 600 700 800
2 = -1000 GeV/cµ
2 = -200 GeV/cµ
2 = 200 GeV/cµ
2 = 1000 GeV/cµ
CMS, 30 fb
 e+j→ ττ → φ bb→pp 
 scenariomaxhm
2 = 1 TeV/cSUSYM
2 = 200 GeV/c2M
SUSY = 0.8 Mgluinom
SUSY = 2 MtStop mix: X
,GeV/cAM
100 200 300 400 500 600 700 800
2 = -1000 GeV/cµ
2 = -200 GeV/cµ
2 = 200 GeV/cµ
2 = 1000 GeV/cµ
CMS, 30 fb
 e+j→ ττ → φ bb→pp 
no mixing scenario
2 = 2 TeV/cSUSYM
2 = 200 GeV/c2M
SUSY = 0.8 Mgluinom
 = 0tStop mix: X
Figure 2: Variation of the 5σ discovery contours obtained from the channel bb̄φ, φ → τ+τ− →
e+ jet in the mmaxh (left) and no-mixing (right) benchmark scenarios for different values of µ.
,GeV/cAM
100 200 300 400 500 600 700 800
2 = -1000 GeV/cµ
2 = -200 GeV/cµ
2 = 200 GeV/cµ
2 = 1000 GeV/cµ
CMS, 30 fb
+jµ → ττ → φ bb→pp 
 scenariomaxhm
2 = 1 TeV/cSUSYM
2 = 200 GeV/c2M
SUSY = 0.8 Mgluinom
SUSY = 2 MtStop mix: X
,GeV/cAM
100 200 300 400 500 600 700 800
2 = -1000 GeV/cµ
2 = -200 GeV/cµ
2 = 200 GeV/cµ
2 = 1000 GeV/cµ
CMS, 30 fb
+jµ → ττ → φ bb→pp 
no mixing scenario
2 = 2 TeV/cSUSYM
2 = 200 GeV/c2M
SUSY = 0.8 Mgluinom
 = 0tStop mix: X
Figure 3: Variation of the 5σ discovery contours obtained from the channel bb̄φ, φ → τ+τ− →
µ+ jet in the mmaxh (left) and no-mixing (right) benchmark scenarios for different values of µ.
modify the Higgs-boson production cross sections and decay branching ratios. Furthermore
the mass eigenvalues of the charginos and neutralinos vary with µ, possibly opening up the
decay channels of the Higgs bosons to supersymmetric particles, which reduces the branching
ratio to τ leptons.
The results for the 5 σ discovery contours for the final state τ+τ− → jets are shown in
Fig. 1 for themmaxh (left) and the no-mixing (right) scenario. As expected from the discussion
of the ∆b corrections in Sect. 2.2, the variation of the 5 σ discovery contours with µ is more
pronounced in the mmaxh scenario, where a shift up to ∆ tanβ = 12 can be observed for
MA = 800 GeV. For lowMA values (corresponding also to lower tanβ values on the discovery
contours) the variation stays below ∆ tanβ = 3. In the no-mixing scenario the variation does
not exceed ∆ tan β = 5. The τ+τ− → jets channel has also been discussed in Ref. [14]. Our
results, which are based on the latest CMS studies using full simulation [57], are qualitatively
in good agreement with Ref. [14], in which the earlier CMS studies of Refs. [23, 24] had beed
used. The 5 σ discovery regions are largest for µ = −1000 GeV and pushed to highest tanβ
values for µ = +200 GeV. In the low MA region our discovery contours are very similar
to those obtained in Ref. [14]. In the high MA region, MA ∼ 800 GeV, corresponding to
larger values of tan β on the discovery contours, our improved evaluation of the 5 σ discovery
contours gives rise to a shift towards higher tan β values compared to Ref. [14] of about
∆ tanβ = 8 (mostly due to the up-to-date experimental input). Accordingly, we find a
smaller discovery region compared to Ref. [14] and therefore an enlarged “LHC wedge”
region where only the light CP-even MSSM Higgs boson can be detected at the 5 σ level.
The results for the channel τ+τ− → e+ jet are shown in Fig. 2. Again the mmaxh scenario
shows a stronger variation than the no-mixing scenario. The resulting shift in tan β reaches
up to ∆ tan β = 8 for MA = 500 GeV in the m
h scenario, but stays below ∆ tanβ = 4
for the no-mixing scenario. Finally in Fig. 3 the results for the channel τ+τ− → µ+ jet are
depicted. The level of variation of the 5 σ discovery contours is the same as for the e + jet
final state.7
,GeV/cAM
100 200 300 400 500 600 700 800
2 = -1000 GeV/cµ
2 = -200 GeV/cµ
2 = 200 GeV/cµ
2 = 1000 GeV/cµ
CMS, 60 fb
 j+j→ ττ → φ bb→pp 
)=0χ χ → φ, BR(maxhm
2 = 1 TeV/cSUSYM
2 = 200 GeV/c2M
SUSY = 0.8 Mgluinom
SUSY = 2 MtStop mix: X
,GeV/cAM
100 200 300 400 500 600 700 800
2 = -1000 GeV/cµ
2 = -200 GeV/cµ
2 = 200 GeV/cµ
2 = 1000 GeV/cµ
CMS, 60 fb
 j+j→ ττ → φ bb→pp 
)=0χ χ → φno mixing, BR(
2 = 2 TeV/c
2 = 200 GeV/c2M
 = 0.8 M
gluino
 = 0tStop mix: X
Figure 4: Variation of the 5σ discovery contours obtained from the channel bb̄φ, φ → τ+τ− →
jets in the mmaxh (left) and no-mixing (right) benchmark scenarios for different values of µ in
the case where no decays of the heavy Higgs bosons into supersymmetric particles are taken
into account (see text).
In order to gain a better understanding of how sensitively the discovery contours in the
MA–tan β plane depend on the chosen SUSY scenario, it is useful to separately investigate the
different effects caused by varying the parameter µ. For simplicity, we restrict the following
discussion to the bb̄φ, φ → τ+τ− → jets channel. In Fig. 4 we show the same results as
in Fig. 1, but for the case where no decays of the heavy Higgs bosons into supersymmetric
particles are taken into account. As a consequence, the variation of the 5 σ discovery contours
with µ shown in Fig. 4 is purely an effect of higher-order corrections, predominantly those
entering via ∆b. The difference between Fig. 1 and Fig. 4, on the other hand, is purely an
effect of the change in BR(φ → τ+τ−) caused by the variation of the partial Higgs-boson
decay widths into supersymmetric particles arising from a shift in the masses of the charginos
and neutralinos.
In Fig. 4 the dependence of the 5 σ discovery contours on µ significantly differs from the
case of Fig. 1. While in Fig. 1 the inclusion of decays into supersymmetric particles gives
7Since the results of the experimental simulation for this channel are available only for two MA values,
the interpolation is a straight line. This may result in a slightly larger uncertainty of the results shown in
Fig. 3 compared to the other figures.
rise to the fact that the smallest discovery region is found for small µ values, µ = +200 GeV
(with the exception of the region of very small MA), in Fig. 4 the 5 σ discovery contours
are ordered monotonously in µ: the largest (smallest) 5 σ discovery regions are obtained for
µ = −(+)1000 GeV, i.e. for the largest (smallest) values of the bottom Yukawa coupling.
As expected, the effect of the higher-order corrections is largest in the high tanβ-region
(corresponding to large values of MA on the discovery contours). In this region the variation
of µ shifts the discovery contours by up to ∆ tanβ = 11 for the case of the mmaxh scenario
(left plot of Fig. 4), i.e. the effect is about the same as for the case where decays into
supersymmetric particles are included. For lower values of tanβ (corresponding to smaller
values of MA on the discovery contours), on the other hand, the modification of the Higgs
branching ratio as a consequence of decays into supersymmetric particles yields the dominant
effect on the 5 σ discovery contours. Accordingly, the observed variation with µ in this
region is significantly smaller in Fig. 4 as compared to the full result of Fig. 1. The reduced
sensitivity of the discovery contours on µ can also clearly be seen for the case of the no-
mixing scenario (right plot), where as discussed above the ∆b correction is smaller than in
the mmaxh scenario.
,GeV/cAM
100 200 300 400 500 600 700 800
2 = 200 GeV/c
gluino
2 = 500 GeV/c
gluino
2 = 1000 GeV/c
gluino
2 = 2000 GeV/c
gluino
CMS, 60 fb
 j+j→ ττ → φ bb→pp 
 scenariomaxhm
2 = 1 TeV/cSUSYM
2 = 200 GeV/c2M
2 = 1000 GeV/cµ
SUSY = 2 MtStop mix: X
,GeV/cAM
100 200 300 400 500 600 700 800
2 = 200 GeV/c
gluino
2 = 500 GeV/c
gluino
2 = 1000 GeV/c
gluino
2 = 2000 GeV/c
gluino
CMS, 60 fb
 j+j→ ττ → φ bb→pp 
no mixing scenario
2 = 2 TeV/cSUSYM
2 = 200 GeV/c2M
2 = 1000 GeV/cµ
 = 0tStop mix: X
Figure 5: Variation of the 5σ discovery contours obtained from the channel bb̄φ, φ → τ+τ− →
jets in the mmaxh (left) and no-mixing (right) benchmark scenarios with µ = +1000 GeV for
different values of mg̃.
A parameter affecting the ∆b corrections, see eq. (10), but not the kinematics of the
Higgs-boson decays is the gluino mass, mg̃. We now investigate the impact of varying this
parameter, which is normally fixed to the values mg̃ = 800, 1600 GeV in the m
h and
no-mixing benchmark scenarios, respectively. The results for four different values of the
gluino mass, mg̃ = 200, 500, 1000, 2000 GeV, are shown in Fig. 5. The µ parameter has been
set to µ = +1000 GeV in Fig. 5, such that the Higgs decay channels into charginos and
neutralinos are suppressed. As one can see from eq. (10), the change of mg̃ affects the O(αs)
part of ∆b and corresponds to a monotonous increase of ∆b. As an example, this yields for
µ = 1000 GeV, tan β = 50 in the two scenarios:
mmaxh , mg̃ = 200 GeV : ∆b = 0.50
mmaxh , mg̃ = 2000 GeV : ∆b = 0.94
no-mixing, mg̃ = 200 GeV : ∆b = 0.06
no-mixing, mg̃ = 2000 GeV : ∆b = 0.29 . (21)
In the no-mixing scenario the At value is close to zero, suppressing the mg̃-independent
contribution to ∆b, while the higher SUSY mass scale results in an overall reduction of ∆b in
this scenario. The value of ∆b in the no-mixing scenario would slightly increase if mg̃ were
raised to even larger values, but this effect would not change the qualitative behaviour.
Fig. 5 shows that the results for the discovery reach in the MA–tanβ plane are relatively
stable with respect to variations of the gluino mass. The shift in the discovery contours
remains below about ∆ tanβ = 4 for the mmaxh scenario (left plot) and ∆ tanβ = 1 for the
no-mixing scenario (right plot). For the positive sign of µ chosen in Fig. 5, where the ∆b
correction yields a suppression of the bottom Yukawa coupling, the largest discovery reach
is obtained for small mg̃, while the smallest discovery reach is obtained for large mg̃. This
behaviour would be reversed by a change of sign of µ.
We have also investigated the possible impact of other MSSM parameters (besides µ and
mg̃) on the 5 σ discovery contours in the MA–tan β plane. The ∆b corrections depend also on
the parameters in the stop and sbottom sector, see eq. (10). While the formulas in Sect. 2.2.2
have been given for the region where MSUSY ≫ mt, the qualitative effect of reducing the
stop and sbottom masses can nevertheless be inferred. Sizable ∆b corrections require relative
large values of µ and mg̃. If these parameters are kept large while the stop and sbottom
masses are reduced, the ∆b corrections tend to decrease. It is obvious from eq. (10) that
reducing the absolute value of At decreases the electroweak part of the ∆b correction. As
discussed above, this effect of the ∆b corrections manifests itself in the comparison of the
mmaxh and no-mixing scenarios, see Figs. 1–5. Concerning the possible impact of the ∆b
corrections on the 5 σ discovery contours for the bb̄φ, φ → τ+τ− channel in the MA–tanβ
plane we conclude that larger effects than those shown in Figs. 1–5 (where we have displayed
the discovery contours up to tan β = 50) would only arise if the variation of µ were extended
over an even wider interval than −1000 GeV ≤ µ ≤ +1000 GeV as done in our analysis
above.
We now turn to the possible effects of other higher-order corrections beyond those entering
via ∆b on the 5 σ discovery contours for the bb̄φ, φ → τ+τ− channel. These effects are in
general non-negligible, see the discussions in Sect. 2.2 and in Sect. 4.2 below, but smaller
than those induced by ∆b. As a consequence, the impact on the 5 σ discovery contours in the
MA–tan β plane of other supersymmetric parameters entering via higher-order corrections is
in general much smaller than the effect of varying µ in the high-tanβ region of Fig. 4. As
an example, the difference observed in Figs. 1–5 between the mmaxh and no-mixing scenarios
arising from the different values of At and MSUSY in the two scenarios (see eqs. (14), (15))
is mainly an effect of the ∆b corrections, while the impact of other higher-order corrections
involving At and MSUSY is found to be small.
Also the decays of the heavy neutral MSSM Higgs bosons into supersymmetric particles
are in general affected by other supersymmetric parameters in addition to the dependence
on µ, MA and tan β. The resulting effects on BR(φ → τ+τ−) turn out to be rather small,
however. We find that sizable deviations from the values of BR(φ → τ+τ−) occurring in
the mmaxh and no-mixing scenarios for −1000 GeV ≤ µ ≤ +1000 GeV are only possible in
quite extreme regions of the MSSM parameter space that are already highly constrained by
existing experimental data.
Our discussion above has been given in the context of the MSSM with real parameters.
Since the sensitivity of the 5 σ discovery contours in the MA–tan β plane on the other super-
symmetric parameters can mainly be understood as an effect of higher-order corrections to
the bottom Yukawa coupling and of the kinematics of Higgs-boson decays into supersymmet-
ric particles, no qualitative changes of our results are expected for the case where complex
phases are taken into account.
4.2 Higgs-boson mass precision
The discussion in the previous section shows that the prospective discovery reach of the
bb̄φ, φ → τ+τ− channel in theMA–tanβ plane is rather stable with respect to variations of the
other MSSM parameters. We now turn to the second part of our analysis and investigate the
expected statistical precision of the Higgs-boson mass measurement. The expected statistical
precision is evaluated as described in Sect. 3, see eq. (17). In Figs. 6 – 7 we show the expected
precision for the mass measurement achievable from the channel bb̄φ, φ → τ+τ− using the
final states τ+τ− → jets and τ+τ− → e + jet. Within the 5 σ discovery region we have
indicated contour lines corresponding to different values of the expected precision, ∆M/M .
The results are shown in the mmaxh benchmark scenario for µ = −200 GeV (left plots) and
µ = +200 GeV (right plots).
We find that experimental precisions of ∆Mφ/Mφ of 1–4% are reachable within the dis-
covery region. A better precision is reached for larger tanβ and smaller MA as a consequence
of the higher number of signal events in this region. The other scenarios and other values of
µ discussed above yield qualitatively similar results to those shown in Figs. 6, 7.
As discussed above, for large values of MA the heavy neutral MSSM Higgs bosons are
nearly mass-degenerate, MH ≈ MA. The experimental separation of the two states H and A
(or the corresponding mass eigenstates in the CP-violating case) will therefore be challenging.
The results shown in Figs. 6 – 7 have been obtained using the combined sample of H and
A events. It is important to note, however, that even in the region of large MA the mass
splitting between MH and MH can reach the level of a few %. An example of such a scenario
is (as above, we consider the CP-conserving case, i.e. the MSSM with real parameters; the
corresponding scenario in the case of non-vanishing complex phases has been discussed in
Ref. [22])
MSUSY = 500 GeV, At = Ab = 1000 GeV, µ = 1000 GeV,
M2 = 500 GeV, M1 = 250 GeV, mg̃ = 500 GeV . (22)
In Fig. 8 the mass splitting
|MH −MA|
min(MH ,MA)
is given as a function of Xt for tanβ = 40 and two MA values, MA = 300 GeV (solid
line) and MA = 500 GeV (dashed line). The dot-dashed and dotted parts of the contours for
Figure 6: The statistical precision of the Higgs-boson mass measurement achievable from
the channel bb̄φ, φ → τ+τ− → jets in the mmaxh benchmark scenario for µ = −200 GeV (left)
and µ = +200 GeV (right) is shown together with the 5 σ discovery contour.
Figure 7: The statistical precision of the Higgs-boson mass measurement achievable from
the channel bb̄φ, φ → τ+τ− → e + jet in the mmaxh benchmark scenario for µ = −200 GeV
(left) and µ = +200 GeV (right) is shown together with the 5 σ discovery contour.
-1500 -1000 -500 0 500 1000 1500
 [GeV]
 = 500 GeV, tanβ = 40
 = 300 GeV
 = 300 GeV, LEP excl.
 = 500 GeV
 = 500 GeV, LEP excl.
Figure 8: The mass splitting between the heavy neutral MSSM Higgs bosons, ∆MHA/M ≡
|MH −MA| /min(MH ,MA), is shown as a function ofXt forMA = 300, 500 GeV in a scenario
with MSUSY = 500 GeV, µ = 1000 GeV and tanβ = 40. The other parameters are given in
eq. (22). The dot-dashed (dotted) parts of the contours forMA = 300 GeV (MA = 500 GeV)
indicate parameter combinations that are excluded by the search for the light CP-even Higgs
boson of the MSSM at LEP [3].
MA = 300, 500 GeV, respectively, in the region of small |Xt| indicate parameter combinations
that result in relatively low Mh values that are excluded by the search for the light CP-even
Higgs boson of the MSSM at LEP [3]. One can see in Fig. 8 that the mass splitting between
MH and MA shows a pronounced dependence on Xt in this scenario. Mass differences of up
to 5% are possible for large Xt (while the widths of the Higgs bosons are at the 1–1.5% level
in this parameter region).
The example of Fig. 8 shows that a precise mass measurement at the LHC may in
favourable regions of the MSSM parameter space open the exciting possibility to distin-
guish between the signals of H and A production. In confronting Fig. 8 with the expected
accuracies obtained in Figs. 6 – 7 one of course needs to take into account that a separate
treatment of the H and A channels in Figs. 6 – 7 would reduce the number of signal events by
a factor of 2, resulting in a degradation of the expected accuracies (for the same luminosity)
by a factor of
2. A more detailed analysis of the potential for experimentally resolving two
mass peaks would furthermore have to include effects arising from overlapping Higgs signals.
Such an analysis goes beyond the scope of the present paper.
5 Conclusions
We have analyzed the reach of the CMS experiment with 30 or 60 fb−1 for the heavy neutral
MSSM Higgs bosons, depending on tanβ and the Higgs-boson mass scale, MA. We have
focused on the channel bb̄H/A,H/A → τ+τ− with the τ ’s subsequently decaying to jets
and/or leptons. The experimental analysis, yielding the number of events needed for a
5 σ discovery (depending on the mass of the Higgs boson) was performed with full CMS
detector simulation and reconstruction for the final states of di-τ -lepton decays. The events
were generated with PYTHIA.
The experimental analysis has been combined with predictions for the Higgs-boson masses,
production processes and decay channels obtained with the code FeynHiggs, taking into ac-
count all relevant higher-order corrections as well as possible decays of the heavy Higgs
bosons into supersymmetric particles. We have analyzed the sensitivity of the 5 σ discov-
ery contours in the MA–tanβ plane to variations of the other supersymmetric parameters.
We have shown that the discovery contours are relatively stable with respect to the im-
pact of additional parameters. The biggest effects, resulting from higher-order corrections
to the bottom Yukawa coupling and from the kinematics of Higgs decays into charginos
and neutralinos, are caused by varying the absolute value and the sign of the higgsino mass
parameter µ. The corresponding shift in the 5 σ discovery contours amounts up to about
∆ tanβ = 10. The effects of other contributions to the relation between the bottom-quark
mass and the bottom Yukawa coupling, arising from the gluino mass and the parameters in
the stop and sbottom sector, are in general smaller than the shifts induced by a variation
of µ. The same holds for the impact of higher-order contributions beyond the corrections to
the bottom Yukawa coupling and for the possible effects of other decay modes of the heavy
Higgs bosons into supersymmetric particles. The results of our analysis, which was carried
out in the framework of the CP-conserving MSSM, should not be substantially affected by
the inclusion of complex phases of the soft-breaking parameters.
We have analyzed the prospective accuracy of the mass measurement of the heavy neu-
tral MSSM Higgs bosons in the channel bb̄H/A,H/A → τ+τ−. We find that statistical
experimental precisions of 1–4% are reachable within the discovery region. These results,
obtained from a simple estimate of the prospective accuracies, are not expected to consid-
erably degrade if further uncertainties related to background effects and jet and missing ET
scales are taken into account. We have pointed out that a %-level precision of the mass
measurements could in favourable regions of the MSSM parameter allow to experimentally
resolve the signals of the two heavy MSSM Higgs bosons.
Acknowledgements
S.H. and G.W. thank M. Carena and C.E.M. Wagner for collaboration on some of the
theoretical aspects employed in this analysis.
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	Introduction
	Phenomenology of the MSSM Higgs sector
	Notation
	Higher-order corrections in the Higgs sector
	Higgs-boson propagator corrections
	Corrections to the relation between the bottom-quark mass and the bottom Yukawa coupling
	Corrections to the Higgs production cross sections
	The mhmax and no-mixing benchmark scenarios
	Experimental analysis
	Results
	Discovery reach for heavy neutral MSSM Higgs bosons
	Higgs-boson mass precision
	Conclusions

  The search for MSSM Higgs bosons will be an important goal at the LHC. We
analyze the search reach of the CMS experiment for the heavy neutral MSSM Higgs
bosons with an integrated luminosity of 30 or 60 fb^-1. This is done by
combining the latest results for the CMS experimental sensitivities based on
full simulation studies with state-of-the-art theoretical predictions of MSSM
Higgs-boson properties. The results are interpreted in MSSM benchmark scenarios
in terms of the parameters tan_beta and the Higgs-boson mass scale, M_A. We
study the dependence of the 5 sigma discovery contours in the M_A-tan_beta
plane on variations of the other supersymmetric parameters. The largest effects
arise from a change in the higgsino mass parameter mu, which enters both via
higher-order radiative corrections and via the kinematics of Higgs decays into
supersymmetric particles. While the variation of $\mu$ can shift the
prospective discovery reach (and correspondingly the ``LHC wedge'' region) by
about Delta tan_beta = 10, we find that the discovery reach is rather stable
with respect to the impact of other supersymmetric parameters. Within the
discovery region we analyze the accuracy with which the masses of the heavy
neutral Higgs bosons can be determined. We find that an accuracy of 1-4% should
be achievable, which could make it possible in favourable regions of the MSSM
parameter space to experimentally resolve the signals of the two heavy MSSM
Higgs bosons at the LHC.

Introduction
Identifying the mechanism of electroweak symmetry breaking will be one of the main goals of
the LHC. Many possibilities have been studied in the literature, of which the most popular
ones are the Higgs mechanism within the Standard Model (SM) and within the Minimal
Supersymmetric Standard Model (MSSM) [1]. Contrary to the case of the SM, in the MSSM
two Higgs doublets are required. This results in five physical Higgs bosons instead of the
single Higgs boson of the SM. These are the light and heavy CP-even Higgs bosons, h and
H , the CP-odd Higgs boson, A, and the charged Higgs boson, H±.1 The Higgs sector
of the MSSM can be specified at lowest order in terms of the gauge couplings, the ratio
of the two Higgs vacuum expectation values, tan β ≡ v2/v1, and the mass of the CP-odd
Higgs boson, MA. Consequently, the masses of the CP-even neutral Higgs bosons and the
charged Higgs boson are dependent quantities that can be predicted in terms of the Higgs-
sector parameters. Higgs-phenomenology in the MSSM is strongly affected by higher-order
corrections, in particular from the sector of the third generation quarks and squarks, so that
the dependencies on various other MSSM parameters can be important.
After the termination of LEP in the year 2000 (the final LEP results can be found in
Refs. [2, 3]), and the (ongoing) Higgs boson search at the Tevatron [4–6], the search will be
continued at the LHC [7–9] (see also Refs. [10, 11] for recent reviews). The current exclusion
bounds within the MSSM [3–5] and the prospective sensitivities at the LHC are usually dis-
played in terms of the parameters MA and tan β that characterize the MSSM Higgs sector
at lowest order. The other MSSM parameters are conventionally fixed according to certain
benchmark scenarios [12–14]. The most prominent one is the “mmaxh scenario”, which in the
search for the light CP-even Higgs boson allows to obtain conservative bounds on tan β for
fixed values of the top-quark mass and the scale of the supersymmetric particles [15]. Besides
the “no-mixing scenario”, which is similar to the mmaxh scenario, but assumes vanishing mix-
ing in the stop sector, other CP-conserving scenarios that have been studied in LHC analyses
(see e.g. Ref. [11]) are the “gluophobic Higgs scenario” and the “small αeff” scenario [13].
For the interpretation of the exclusion bounds and prospective discovery contours in
the benchmark scenarios it is important to assess how sensitively the results depend on
those parameters that have been fixed according to the benchmark prescriptions. While in
the decoupling limit, which is the region of MSSM parameter space with MA ≫ MZ , the
couplings of the light CP-even Higgs boson approach those of a SM Higgs boson with the
same mass, the couplings of the heavy Higgs bosons of the MSSM can be sizably affected
by higher-order contributions even for large values of MA. The kinematics of the heavy
Higgs-boson production processes, on the other hand, is governed by the parameter MA,
since in the region of large MA the heavy MSSM Higgs bosons are nearly mass-degenerate,
MA ≈ MH ≈ MH±. In Ref. [14] it has been shown that higher-order contributions to the
relation between the bottom-quark mass and the bottom-Yukawa coupling have a dramatic
effect on the exclusion bounds in the MA–tanβ plane obtained from the bb̄φ, φ → bb̄ channel
at the Tevatron.
In this article we investigate how the 5 σ discovery regions in the MA–tanβ plane for the
heavy neutral MSSM Higgs bosons (a corresponding analysis for the charged Higgs-boson
1We focus in this paper on the case without explicit CP-violation in the soft supersymmetry-breaking
terms.
search will be presented elsewhere) obtainable with the CMS experiment at the LHC depend
on the other MSSM parameters. For the experimental sensitivities achievable with CMS we
use up-to-date results based on full simulation studies for 30 or 60 fb−1(depending on the
channel) [9]. This information is combined with precise theory predictions for the Higgs-
boson masses and the involved production and decay processes incorporating higher-order
corrections at the one-loop and two-loop level. In our analysis we investigate the impact on
the discovery reach arising both from higher-order corrections and from possible decays of
the heavy Higgs bosons into supersymmetric particles.2
The search for the heavy neutral MSSM Higgs bosons at the LHC will mainly be pursued
in the b quark associated production with a subsequent decay to τ leptons [7–9]. In the region
of large tanβ this production process benefits from an enhancement factor of tan2 β compared
to the SM case. The main search channels are3 (here and in the following φ denotes the two
heavy neutral MSSM Higgs bosons, φ = H,A):
bb̄φ, φ → τ+τ− → 2 jets (1)
bb̄φ, φ → τ+τ− → µ+ jet (2)
bb̄φ, φ → τ+τ− → e+ jet (3)
bb̄φ, φ → τ+τ− → e+ µ . (4)
For our numerical analysis we use the program FeynHiggs [19–22]. We study in particular
the dependence of the “LHC wedge” region, i.e. the region in which only the light CP-even
MSSM Higgs boson can be detected at the LHC at the 5 σ level, on the variation of the
higgsino mass parameter µ. The dependence on µ enters in two different ways, on the one
hand via higher-order corrections affecting the relation between the bottom mass and the
bottom Yukawa coupling, and on the other hand via the kinematics of Higgs decays into
supersymmetric particles. We analyze both effects separately and discuss the possible impact
of other supersymmetric parameters.
Our results for the discovery reach of the heavy neutral MSSM Higgs bosons extend the
known results in the literature in various ways. In comparison with Refs. [23, 24], where the
prospective 5σ discovery contours for CMS in the MA–tanβ plane of the m
h benchmark
scenario were given for three different values of µ, the results in the present paper are based
on full simulation studies and make use of the most up-to-date CMS tools for triggering
and event reconstruction. Furthermore, in the analysis of Refs. [23, 24] relevant higher-
order corrections, in particular those depending on ∆b (see Sect. 2.2 below), have been
neglected. The effects induced by the ∆b corrections have been investigated in Ref. [14],
where the results were obtained by a simple rescaling of the experimental results given in
Refs. [7, 23–25]. Our present analysis, on the other hand, makes use of the latest CMS studies
and provides a separate treatment of the different τ final states, channels (1)–(4).
As a second step of our analysis we investigate the experimental precision that can be
achieved for the determination of the heavy Higgs-boson masses in the discovery channels (1)–
2We restrict our analysis to the impact of supersymmetric contributions. For a discussion of uncertainties
related to parton distribution functions, see e.g. Ref. [16].
3In our analysis we do not consider diffractive Higgs production, pp → p ⊕ H ⊕ p [17]. For a detailed
discussion of the search reach for the heavy neutral MSSM Higgs bosons in diffractive Higgs production we
refer to Ref. [18].
(4). We discuss the prospective accuracy of the mass measurement in view of the possibility
to experimentally resolve the signals of the heavy neutral MSSM Higgs bosons.
The paper is organized as follows: Sect. 2 introduces our notation and gives a brief sum-
mary of the most relevant supersymmetric radiative corrections to the Higgs-boson masses,
production cross sections and decay widths at the LHC. The relevant benchmark scenarios
are briefly reviewed. In Sect. 3 the experimental analysis is described. The results for the
variation of the 5 σ discovery contours, obtainable at CMS with 30 or 60 fb−1 are given
in Sect. 4, where we also discuss the achievable experimental precision in the Higgs mass
determination. The conclusions can be found in Sect. 5.
2 Phenomenology of the MSSM Higgs sector
2.1 Notation
The MSSM Higgs sector at lowest order is described in terms of two independent parameters
(besides the SM gauge couplings): tan β ≡ v2/v1, the ratio of the two vacuum expectation
values, and MA, the mass of the CP-odd Higgs boson A. Beyond the tree-level, large
radiative corrections can occur from the t/t̃ sector, and for large values of tanβ also from
the b/b̃ sector.
Our notations for the scalar top and scalar bottom sector of the MSSM are as follows:
the mass matrices in the basis of the current eigenstates t̃L, t̃R and b̃L, b̃R are given by
+m2t + cos 2β (
s2w)M
Z mtXt
mtXt M
+m2t +
cos 2β s2wM
, (5)
+m2b + cos 2β (−12 +
s2w)M
Z mbXb
mbXb M
+m2b − 13 cos 2β s
, (6)
where
mtXt = mt(At − µ cotβ ), mb Xb = mb (Ab − µ tanβ ). (7)
Here MQ̃, Mt̃R and Mb̃R are the diagonal soft SUSY-breaking parameters, At denotes the
trilinear Higgs–stop coupling, Ab denotes the Higgs–sbottom coupling, and µ is the higgsino
mass parameter.
For the numerical evaluation, it is often convenient to choose
MQ̃ = Mt̃R = Mb̃R =: MSUSY. (8)
Concerning analyses for the case where Mt̃R 6= MQ̃ 6= Mb̃R , see e.g. Refs. [20, 26, 27]. It
has been shown that the upper bound on the mass of the light CP-even Higgs boson, Mh,
obtained using eq. (8) is the same as for the more general case, provided that MSUSY is
identified with the heaviest mass of MQ̃,Mt̃R ,Mb̃R [20].
Accordingly, the most important parameters entering the Higgs-sector predictions via
higher-order corrections are mt, MSUSY, Xt, Xb and µ (see also the discussion in Sect. 2.2.2
below). The Higgs-sector observables furthermore depend on the SU(2) gaugino mass param-
eter, M2, the U(1) parameter M1 and the gluino mass, mg̃ (the latter enters the predictions
for the Higgs-boson masses only from two-loop order on). In numerical analyses the U(1)
gaugino mass parameter, M1, is often fixed via the GUT relation
M2. (9)
We will briefly comment below on the possible impact of complex phases entering the Higgs-
sector predictions via higher-order contributions.
2.2 Higher-order corrections in the Higgs sector
In the following we briefly summarize the most important higher-order corrections affecting
the observables in the MSSM Higgs-boson sector. As mentioned above, we focus on the
MSSM with real parameters. For our numerical analysis we use the program FeynHiggs [19–
22]4, which incorporates a comprehensive set of higher-order results obtained in the Feynman-
diagrammatic approach [20–22, 28–30].
2.2.1 Higgs-boson propagator corrections
Higher-order corrections to the Higgs-boson masses and the wave function normalization
factors of processes with external Higgs bosons arise from Higgs-boson propagator-type con-
tributions. These corrections furthermore contribute in a universal way to all Higgs-boson
couplings. For the propagator-type corrections in the MSSM the complete one-loop re-
sults [31–34], the bulk of the two-loop contributions [20, 27–29, 35–39] and even leading
three-loop corrections [40] are known. The remaining theoretical uncertainty on the light
CP-even Higgs-boson mass has been estimated to be below ∼ 3 GeV [21, 41]. The by far
dominant contribution is the O(αt) term due to top and stop loops (αt ≡ h2t/(4π), where ht
denotes the top-quark Yukawa coupling). Effects of O(αb) can be important for large values
of tan β.
2.2.2 Corrections to the relation between the bottom-quark mass and the bot-
tom Yukawa coupling
Concerning the corrections from the bottom/sbottom sector, large higher-order effects can
in particular occur in the relation between the bottom-quark mass and the bottom Yukawa
coupling (which controls the interaction between the Higgs bosons and bottom quarks as
well as between the Higgs and scalar bottoms), hb, for large values of tanβ. At lowest order
the relation reads mb = hbv1. Beyond the tree level large radiative corrections proportional
to hbv2 are induced, giving rise to tanβ-enhanced contributions [36–38,42]. At the one-loop
level the leading terms proportional to v2 are generated either by gluino–sbottom one-loop
diagrams of O(αs) or by chargino–stop loops of O(αt).
The leading one-loop contribution ∆b in the limit of MSUSY ≫ mt and tanβ ≫ 1 takes
the simple form [36]
mg̃ µ tanβ × I(mb̃1 , mb̃2 , mg̃) +
At µ tan β × I(mt̃1 , mt̃2 , µ) , (10)
4 The code can be obtained from www.feynhiggs.de .
where the function I is given by
I(a, b, c) =
(a2 − b2)(b2 − c2)(a2 − c2)
a2b2 log
+ b2c2 log
+ c2a2 log
max(a2, b2, c2)
The leading contribution can be resummed to all orders in the perturbative expansion [36–
38]. This leads in particular to the replacement
1 + ∆b
, (12)
where mb denotes the running bottom quark mass including SM QCD corrections. For the
numerical evaluations in this paper we choose mb = mb(mt) ≈ 2.97 GeV.
The ∆b corrections are numerically sizable for large tan β in combination with large values
of the ratios of µmg̃/M
SUSY or µAt/M
SUSY. Negative values of ∆b lead to an enhancement of
the bottom Yukawa coupling as a consequence of eq. (12) (for extreme values of µ and tanβ
the bottom Yukawa coupling can even acquire non-perturbative values when ∆b → −1),
while positive values of ∆b give rise to a suppression of the Yukawa coupling. Since a change
in the sign of µ reverses the sign of ∆b, the bottom Yukawa coupling can exhibit a very
pronounced dependence on the parameter µ.
For large values of tanβ the correction to the production cross sections of the Higgs
bosons H and A induced by ∆b enters approximately like tan
2 β/(1 + ∆b)
2, giving rise
to potentially large numerical effects. In the case of the subsequent Higgs-boson decay
φ → τ+τ−, however, the ∆b corrections in the production and the decay process cancel
each other to a large extent. The residual ∆b dependence of σ(bb̄φ) × BR(φ → τ+τ−) is
approximately given by tan2 β/((1+∆b)
2+9), which has a much weaker ∆b dependence (see
Ref. [14] for a more detailed discussion).
In the numerical analysis below the ∆b corrections, which have been discussed in this
section in terms of simple approximation formulae, will be supplemented by other higher-
order corrections as implemented in the program FeynHiggs (and possible decay modes into
supersymmetric particles are taken into account). Higher-order corrections to Higgs decays
into τ+τ− within the SM and MSSM have been evaluated in Refs. [34, 43].
2.2.3 Corrections to the Higgs production cross sections
For the prediction of Higgs-boson production processes at hadron colliders SM-type QCD
corrections in general play an important role. The SM predictions for the process bb̄ → φ+X
at the LHC are far advanced. In the five-flavor scheme the SM cross section is known at
NNLO in QCD [44]. The cross section in the four-flavor scheme is known at NLO [45, 46].
Results obtained in the two schemes have been shown to be consistent [47–49] (see also
Refs. [48, 50] and Refs. [45, 46] for results with one and two final-state b-quarks at high-pT ,
respectively).
The predictions for the bb̄ → φ + X cross sections in the MSSM have been obtained
with FeynHiggs [19–22]. The FeynHiggs implementation5 is based on the state-of-the-art
5The inclusion of the charged Higgs production cross sections is planned for the near future.
SM prediction, namely the NNLO result in the five-flavor scheme [44] using MRST2002
parton distributions at NNLO [51], with the renormalization scale set equal to MHSM and
the factorization scale set equal to MHSM/4. In order to obtain the MSSM prediction the
SM cross section is rescaled with the ratio of the partial widths in the MSSM and the SM,
Γ(φ → bb̄)MSSM
Γ(φ → bb̄)SM
. (13)
The evaluation of the partial widths incorporates one-loop SM QCD and SUSY QCD correc-
tions, as well as (in the SUSY case) the resummation of all terms of O((αs tanβ)n) [34,37,43]
and the proper normalization of the external Higgs bosons as discussed in Refs. [22, 52]. Since
the approximation of rescaling the SM cross section with the ratio of partial widths does not
take into account the MSSM-specific dynamics of the production processes, the theoretical
uncertainty in the predictions for the cross sections will in general be somewhat larger than
for the decay widths. It should be noted that in comparison with other approaches for treat-
ing the SM and SUSY contributions, for instance the program HQQ [53], sizable deviations
can occur as a consequence of differences in the scale choices and the inclusion of higher-order
corrections.
2.3 The mmaxh and no-mixing benchmark scenarios
While the phenomenology of the production and decay processes of the heavy neutral MSSM
Higgs bosons at the LHC is mainly characterised by the parametersMA and tanβ that govern
the Higgs sector at lowest order, other MSSM parameters enter via higher-order contribu-
tions, as discussed above, and via the kinematics of Higgs-boson decays into supersymmetric
particles. The other MSSM parameters are usually fixed in terms of benchmark scenarios.
The most commonly used scenarios are the “mmaxh ” and “no-mixing” benchmark scenar-
ios [12–14]. According to the definition of Ref. [13] the mmaxh scenario is given by
mmaxh : MSUSY = 1000 GeV, Xt = 2MSUSY, Ab = At,
µ = 200 GeV, M2 = 200 GeV, mg̃ = 0.8MSUSY . (14)
The no-mixing scenario differs from the mmaxh scenario only in that it has vanishing mixing
in the stop sector and a larger value of MSUSY
no-mixing: MSUSY = 2000 GeV, Xt = 0, Ab = At,
µ = 200 GeV, M2 = 200 GeV, mg̃ = 0.8MSUSY . (15)
The value of the top-quark mass in Ref. [13] was chosen according to the experimental central
value at that time. For our numerical analysis below, we use the value, mt = 171.4 GeV [54]
In Ref. [14] it was suggested that in the search for heavy MSSM Higgs bosons the mmaxh
and no-mixing scenarios, which originally were mainly designed for the search for the light
CP-even Higgs boson h, should be extended by several discrete values of µ,
µ = ±200,±500,±1000 GeV . (16)
6 Most recently the central experimental value has shifted to mt = 170.9± 1.8 GeV [55]. This shift has
a negligible impact on our analysis.
As discussed above, the variation of µ in particular has an impact on the correction ∆b,
modifying in this way the bottom Yukawa coupling. For very large values of tan β and
large negative values of µ the bottom Yukawa coupling can be so much enhanced that a
perturbative treatment is no longer possible. We have checked that in our analysis of the
LHC discovery contours the bottom Yukawa coupling stays in the perturbative regime, so
that all values of µ down to µ = −1000 GeV can safely be inserted.
The variation of the parameter µ also modifies the mass spectrum and the couplings in
the chargino and neutralino sector of the MSSM. Besides the small higher-order corrections
induced by loop diagrams involving charginos and neutralinos, a change in the mass spectrum
of the chargino and neutralino sector can have an important effect on Higgs phenomenology
because decay modes of the heavy neutral MSSM Higgs bosons into charginos and neutralinos
open up if the supersymmetric particles are sufficiently light (the mass spectrum in the mmaxh
and no-mixing scenarios respects the limits from direct searches for charginos at LEP [56]
for all values of µ specified in eq. (16)).
Differences between the mmaxh and no-mixing scenarios in the searches for heavy neutral
MSSM Higgs bosons are induced in particular by a difference in the ∆b correction. While in
the mmaxh scenario both the O(αs) and O(αt) contributions to ∆b can be sizable, see eq. (10),
in the no-mixing scenario the O(αt) contribution is very small because At is close to zero in
this case. The larger value of MSUSY in the no-mixing scenario gives rise to an additional
suppression of |∆b| compared to the mmaxh scenario.
3 Experimental analysis
In this section we briefly review the recent CMS analysis of the φ → τ+τ− channel, see
Ref. [9], yielding the number of events needed for a 5 σ discovery (depending on the mass
of the Higgs boson). The analysis was performed with full CMS detector simulation and
reconstruction for the following four final states of di-τ -lepton decays: τ+τ− → jets [57],
τ+τ− → e+ jet [58], τ+τ− → µ+ jet [59] and τ+τ− → e + µ [60].
The Higgs-boson production in association with b quarks, pp → bb̄φ, has been selected
using single b-jet tagging in the experimental analysis. The kinematics of the gg → bb̄φ
production process (2 → 3) was generated with PYTHIA [61]. It has been shown that in
this way the NLO kinematics is better reproduced than using the PYTHIA gb → bφ process
(2 → 2) [62]. The backgrounds considered in the analysis were QCD muli-jet events (for the
ττ → jets mode), tt̄, bb̄, Drell-Yan production of Z, γ∗, W+jet, Wt and ττbb̄. All background
processes were generated using PYTHIA, except for τ+τ−bb̄, which was generated using
CompHEP [63].
The results for the various channels, eqs. (1) – (4), are given in Tabs. 1 – 4. For every
Higgs-boson mass point studied we show the number of signal events needed for 5 σ discovery,
NS, the total experimental selection efficiency, εexp, and the ratio of the di-τ mass resolution
to the Higgs-boson mass, RMφ . The last row in Tabs. 1 – 4 shows the expected precision of
the Higgs-boson mass measurement, evaluated as explained below, for parameter points on
the 5 σ discovery contour. Detector effects, experimental systematics and uncertainties of
the background determination were taken into account in the evaluation of the NS. These
effects reduce the discovery region in the MA–tanβ plane as shown in previous analyses [9]
φ → τ+τ− → jets, 60 fb−1
MA [GeV] 200 500 800
NS 63 35 17
εexp 2.5× 10−4 2.4× 10−3 3.6× 10−3
RMφ 0.176 0.171 0.187
∆Mφ/Mφ [%] 2.2 2.8 4.5
Table 1: Required number of signal events, NS, with L = 60 fb−1 for a 5 σ discovery in
the channel φ → τ+τ− → jets. Furthermore given are the total experimental selection
efficiency, εexp, the ratio of the di-τ mass resolution to the Higgs-boson mass, RMφ, and the
expected precision of the Higgs-boson mass measurement, ∆Mφ/Mφ, obtainable from NS
signal events.
φ → τ+τ− → e+ jet, 30 fb−1
MA [GeV] 200 300 500
NS 72.9 45.5 32.8
εexp 3.0× 10−3 6.4× 10−3 1.0× 10−2
RMφ 0.216 0.214 0.230
∆Mφ/Mφ [%] 2.5 3.2 4.0
Table 2: Required number of signal events, NS, with L = 30 fb−1 for a 5 σ discovery in the
channel φ → τ+τ− → e+ jet. The other quantities are defined as in Tab. 1.
φ → τ+τ− → µ+ jet, 30 fb−1
MA [GeV] 200 500
NS 79 57
εexp 7.0× 10−3 2.0× 10−2
RMφ 0.210 0.200
∆Mφ/Mφ [%] 2.4 2.6
Table 3: Required number of signal events, NS, with L = 30 fb−1 for a 5 σ discovery in the
channel φ → τ+τ− → µ+ jet. The other quantities are defined as in Tab. 1.
φ → τ+τ− → e + µ, 30 fb−1
MA [GeV] 200 250
NS 87.8 136.7
εexp 6.4× 10−3 1.1× 10−2
RMφ 0.262 0.412
∆Mφ/Mφ [%] 2.8 3.5
Table 4: Required number of signal events, NS, with L = 30 fb−1 for a 5 σ discovery in the
channel φ → τ+τ− → e+ µ. The other quantities are defined as in Tab. 1.
(see in particular Fig. 5.6 of Ref. [9] for the τ+τ− → µ+ jet mode).
Now we turn to the evaluation of the expected precision of the Higgs-boson mass mea-
surement. In spite of the escaping neutrinos, the Higgs-boson mass can be reconstructed
in the H,A → ττ channel from the visible τ momenta (τ jets) and the missing transverse
energy, EmissT , using the collinearity approximation for neutrinos from highly boosted τ ’s. In
the investigated region of MA and tanβ the two states A and H are nearly mass-degenerate.
For most values of the other MSSM parameters the mass difference of A and H is much
smaller than the achievable mass resolution. In this case the difference in reconstructing the
A or the H will have no relevant effect on the achievable accuracy in the mass determina-
tion. In some regions of the MSSM parameter space, however, a sizable splitting between
MA and MH can occur even for MA ≫ MZ . We will discuss below the prospects in scenarios
where the splitting between MA and MH is relatively large. The precision ∆Mφ/Mφ shown
in Tabs. 1 – 4 is derived for the border of the parameter space in which a 5 σ discovery
can be claimed, i.e. with NS observed Higgs events. The statistical accuracy of the mass
measurement has been evaluated via
. (17)
A higher precision can be achieved if more than NS events are observed. The corresponding
estimate for the precision is obtained by replacing NS in eq. (17) by the number of observed
signal events, Nev. It should be noted that the prospective accuracy obtained from eq. (17)
does not take into account the uncertainties of the jet and missing ET energy scales. In
the τ+τ− → jets mode these effects can lead to an additional 3% uncertainty in the mass
measurement [57]. A more dedicated procedure of the mass measurement from the signal
plus background data still has to be developed in the experimental analysis. However, we do
not expect that the additional uncertainties will considerably degrade the accuracy of the
Higgs boson mass measurement as calculated with eq. (17).
4 Results
The results quoted in Sect. 3 for the required number of signal events depend only on the
Higgs-boson mass, i.e. the event kinematics, but are independent of any specific MSSM
scenario. In order to determine the 5 σ discovery contours in the MA–tan β plane these
results have to be confronted with the MSSM predictions. The number of signal events, Nev,
for a given parameter point is evaluated via
Nev = L × σbb̄φ × BR(φ → τ+τ−)× BRττ × εexp . (18)
Here L denotes the luminosity collected with the CMS detector, σbb̄φ is the Higgs-boson pro-
duction cross section, BR(φ → τ+τ−) is the branching ratio of the Higgs boson to τ leptons,
BRττ is the product of the branching ratios of the two τ leptons into their respective final
state,
BR(τ → jet +X) ≈ 0.65 , (19)
BR(τ → µ+X) ≈ BR(τ → e+X) ≈ 0.175 , (20)
and εexp denotes the total experimental selection efficiency for the respective process (as
given in Tabs. 1 – 4). The Higgs-boson production cross sections and decay branching ratios
have been evaluated with FeynHiggs as described in Sect. 2.2.
4.1 Discovery reach for heavy neutral MSSM Higgs bosons
The number of signal events, Nev, in the MSSM depends besides the parameters MA and
tan β, which govern the MSSM Higgs sector at lowest order, in principle also on all other
MSSM parameters. In the following we analyze how stable the results for the 5σ discovery
contours in theMA–tanβ plane are with respect to variations of the other MSSM parameters.
We take into account both effects from higher-order corrections, as discussed in Sect. 2.2,
and from decays of the heavy Higgs bosons into supersymmetric particles. As starting point
of our analysis we use the mmaxh and no-mixing benchmark scenarios, where we investigate
in detail the sensitivity of the discovery contours with respect to variations of the parameter
µ. We then discuss the possible impact of varying other MSSM parameters.
We have evaluated Nev in the two benchmark scenarios as a function of MA and tan β.
For fixed MA we have varied tan β such that Nev = NS (as given in Tabs. 1 – 4). This tanβ
value is then identified as the point on the 5 σ discovery contour corresponding to the chosen
value of MA. In this way we have determined the 5 σ discovery contours for the m
h and
the no-mixing scenarios for µ = ±200,±1000 GeV.
In Figs. 1 – 3 we show the 5σ discovery contours obtained from the process bb̄φ, φ → τ+τ−
for the final states τ+τ− → jets, τ+τ− → e + jet and τ+τ− → µ + jet. As can be seen
from Tab. 4, the fourth channel discussed above, τ+τ− → e + µ, contributes for 30 fb−1
only in the region of relatively small MA values and has a lower sensitivity than the other
three channels. We therefore omit this channel in the following discussion. The discovery
contours in Figs. 1 – 3 are given for the mmaxh and no-mixing benchmark scenarios with µ =
±200,±1000 GeV. As explained above, the 5 σ discovery contours are affected by a change
in µ in two ways. Higher-order contributions, in particular the ones associated with ∆b,
,GeV/cAM
100 200 300 400 500 600 700 800
2 = -1000 GeV/cµ
2 = -200 GeV/cµ
2 = 200 GeV/cµ
2 = 1000 GeV/cµ
CMS, 60 fb
 j+j→ ττ → φ bb→pp 
 scenariomaxhm
2 = 1 TeV/cSUSYM
2 = 200 GeV/c2M
SUSY = 0.8 Mgluinom
SUSY = 2 MtStop mix: X
,GeV/cAM
100 200 300 400 500 600 700 800
2 = -1000 GeV/cµ
2 = -200 GeV/cµ
2 = 200 GeV/cµ
2 = 1000 GeV/cµ
CMS, 60 fb
 j+j→ ττ → φ bb→pp 
no mixing scenario
2 = 2 TeV/cSUSYM
2 = 200 GeV/c2M
SUSY = 0.8 Mgluinom
 = 0tStop mix: X
Figure 1: Variation of the 5σ discovery contours obtained from the channel bb̄φ, φ → τ+τ− →
jets in the mmaxh (left) and no-mixing (right) benchmark scenarios for different values of µ.
,GeV/cAM
100 200 300 400 500 600 700 800
2 = -1000 GeV/cµ
2 = -200 GeV/cµ
2 = 200 GeV/cµ
2 = 1000 GeV/cµ
CMS, 30 fb
 e+j→ ττ → φ bb→pp 
 scenariomaxhm
2 = 1 TeV/cSUSYM
2 = 200 GeV/c2M
SUSY = 0.8 Mgluinom
SUSY = 2 MtStop mix: X
,GeV/cAM
100 200 300 400 500 600 700 800
2 = -1000 GeV/cµ
2 = -200 GeV/cµ
2 = 200 GeV/cµ
2 = 1000 GeV/cµ
CMS, 30 fb
 e+j→ ττ → φ bb→pp 
no mixing scenario
2 = 2 TeV/cSUSYM
2 = 200 GeV/c2M
SUSY = 0.8 Mgluinom
 = 0tStop mix: X
Figure 2: Variation of the 5σ discovery contours obtained from the channel bb̄φ, φ → τ+τ− →
e+ jet in the mmaxh (left) and no-mixing (right) benchmark scenarios for different values of µ.
,GeV/cAM
100 200 300 400 500 600 700 800
2 = -1000 GeV/cµ
2 = -200 GeV/cµ
2 = 200 GeV/cµ
2 = 1000 GeV/cµ
CMS, 30 fb
+jµ → ττ → φ bb→pp 
 scenariomaxhm
2 = 1 TeV/cSUSYM
2 = 200 GeV/c2M
SUSY = 0.8 Mgluinom
SUSY = 2 MtStop mix: X
,GeV/cAM
100 200 300 400 500 600 700 800
2 = -1000 GeV/cµ
2 = -200 GeV/cµ
2 = 200 GeV/cµ
2 = 1000 GeV/cµ
CMS, 30 fb
+jµ → ττ → φ bb→pp 
no mixing scenario
2 = 2 TeV/cSUSYM
2 = 200 GeV/c2M
SUSY = 0.8 Mgluinom
 = 0tStop mix: X
Figure 3: Variation of the 5σ discovery contours obtained from the channel bb̄φ, φ → τ+τ− →
µ+ jet in the mmaxh (left) and no-mixing (right) benchmark scenarios for different values of µ.
modify the Higgs-boson production cross sections and decay branching ratios. Furthermore
the mass eigenvalues of the charginos and neutralinos vary with µ, possibly opening up the
decay channels of the Higgs bosons to supersymmetric particles, which reduces the branching
ratio to τ leptons.
The results for the 5 σ discovery contours for the final state τ+τ− → jets are shown in
Fig. 1 for themmaxh (left) and the no-mixing (right) scenario. As expected from the discussion
of the ∆b corrections in Sect. 2.2, the variation of the 5 σ discovery contours with µ is more
pronounced in the mmaxh scenario, where a shift up to ∆ tanβ = 12 can be observed for
MA = 800 GeV. For lowMA values (corresponding also to lower tanβ values on the discovery
contours) the variation stays below ∆ tanβ = 3. In the no-mixing scenario the variation does
not exceed ∆ tan β = 5. The τ+τ− → jets channel has also been discussed in Ref. [14]. Our
results, which are based on the latest CMS studies using full simulation [57], are qualitatively
in good agreement with Ref. [14], in which the earlier CMS studies of Refs. [23, 24] had beed
used. The 5 σ discovery regions are largest for µ = −1000 GeV and pushed to highest tanβ
values for µ = +200 GeV. In the low MA region our discovery contours are very similar
to those obtained in Ref. [14]. In the high MA region, MA ∼ 800 GeV, corresponding to
larger values of tan β on the discovery contours, our improved evaluation of the 5 σ discovery
contours gives rise to a shift towards higher tan β values compared to Ref. [14] of about
∆ tanβ = 8 (mostly due to the up-to-date experimental input). Accordingly, we find a
smaller discovery region compared to Ref. [14] and therefore an enlarged “LHC wedge”
region where only the light CP-even MSSM Higgs boson can be detected at the 5 σ level.
The results for the channel τ+τ− → e+ jet are shown in Fig. 2. Again the mmaxh scenario
shows a stronger variation than the no-mixing scenario. The resulting shift in tan β reaches
up to ∆ tan β = 8 for MA = 500 GeV in the m
h scenario, but stays below ∆ tanβ = 4
for the no-mixing scenario. Finally in Fig. 3 the results for the channel τ+τ− → µ+ jet are
depicted. The level of variation of the 5 σ discovery contours is the same as for the e + jet
final state.7
,GeV/cAM
100 200 300 400 500 600 700 800
2 = -1000 GeV/cµ
2 = -200 GeV/cµ
2 = 200 GeV/cµ
2 = 1000 GeV/cµ
CMS, 60 fb
 j+j→ ττ → φ bb→pp 
)=0χ χ → φ, BR(maxhm
2 = 1 TeV/cSUSYM
2 = 200 GeV/c2M
SUSY = 0.8 Mgluinom
SUSY = 2 MtStop mix: X
,GeV/cAM
100 200 300 400 500 600 700 800
2 = -1000 GeV/cµ
2 = -200 GeV/cµ
2 = 200 GeV/cµ
2 = 1000 GeV/cµ
CMS, 60 fb
 j+j→ ττ → φ bb→pp 
)=0χ χ → φno mixing, BR(
2 = 2 TeV/c
2 = 200 GeV/c2M
 = 0.8 M
gluino
 = 0tStop mix: X
Figure 4: Variation of the 5σ discovery contours obtained from the channel bb̄φ, φ → τ+τ− →
jets in the mmaxh (left) and no-mixing (right) benchmark scenarios for different values of µ in
the case where no decays of the heavy Higgs bosons into supersymmetric particles are taken
into account (see text).
In order to gain a better understanding of how sensitively the discovery contours in the
MA–tan β plane depend on the chosen SUSY scenario, it is useful to separately investigate the
different effects caused by varying the parameter µ. For simplicity, we restrict the following
discussion to the bb̄φ, φ → τ+τ− → jets channel. In Fig. 4 we show the same results as
in Fig. 1, but for the case where no decays of the heavy Higgs bosons into supersymmetric
particles are taken into account. As a consequence, the variation of the 5 σ discovery contours
with µ shown in Fig. 4 is purely an effect of higher-order corrections, predominantly those
entering via ∆b. The difference between Fig. 1 and Fig. 4, on the other hand, is purely an
effect of the change in BR(φ → τ+τ−) caused by the variation of the partial Higgs-boson
decay widths into supersymmetric particles arising from a shift in the masses of the charginos
and neutralinos.
In Fig. 4 the dependence of the 5 σ discovery contours on µ significantly differs from the
case of Fig. 1. While in Fig. 1 the inclusion of decays into supersymmetric particles gives
7Since the results of the experimental simulation for this channel are available only for two MA values,
the interpolation is a straight line. This may result in a slightly larger uncertainty of the results shown in
Fig. 3 compared to the other figures.
rise to the fact that the smallest discovery region is found for small µ values, µ = +200 GeV
(with the exception of the region of very small MA), in Fig. 4 the 5 σ discovery contours
are ordered monotonously in µ: the largest (smallest) 5 σ discovery regions are obtained for
µ = −(+)1000 GeV, i.e. for the largest (smallest) values of the bottom Yukawa coupling.
As expected, the effect of the higher-order corrections is largest in the high tanβ-region
(corresponding to large values of MA on the discovery contours). In this region the variation
of µ shifts the discovery contours by up to ∆ tanβ = 11 for the case of the mmaxh scenario
(left plot of Fig. 4), i.e. the effect is about the same as for the case where decays into
supersymmetric particles are included. For lower values of tanβ (corresponding to smaller
values of MA on the discovery contours), on the other hand, the modification of the Higgs
branching ratio as a consequence of decays into supersymmetric particles yields the dominant
effect on the 5 σ discovery contours. Accordingly, the observed variation with µ in this
region is significantly smaller in Fig. 4 as compared to the full result of Fig. 1. The reduced
sensitivity of the discovery contours on µ can also clearly be seen for the case of the no-
mixing scenario (right plot), where as discussed above the ∆b correction is smaller than in
the mmaxh scenario.
,GeV/cAM
100 200 300 400 500 600 700 800
2 = 200 GeV/c
gluino
2 = 500 GeV/c
gluino
2 = 1000 GeV/c
gluino
2 = 2000 GeV/c
gluino
CMS, 60 fb
 j+j→ ττ → φ bb→pp 
 scenariomaxhm
2 = 1 TeV/cSUSYM
2 = 200 GeV/c2M
2 = 1000 GeV/cµ
SUSY = 2 MtStop mix: X
,GeV/cAM
100 200 300 400 500 600 700 800
2 = 200 GeV/c
gluino
2 = 500 GeV/c
gluino
2 = 1000 GeV/c
gluino
2 = 2000 GeV/c
gluino
CMS, 60 fb
 j+j→ ττ → φ bb→pp 
no mixing scenario
2 = 2 TeV/cSUSYM
2 = 200 GeV/c2M
2 = 1000 GeV/cµ
 = 0tStop mix: X
Figure 5: Variation of the 5σ discovery contours obtained from the channel bb̄φ, φ → τ+τ− →
jets in the mmaxh (left) and no-mixing (right) benchmark scenarios with µ = +1000 GeV for
different values of mg̃.
A parameter affecting the ∆b corrections, see eq. (10), but not the kinematics of the
Higgs-boson decays is the gluino mass, mg̃. We now investigate the impact of varying this
parameter, which is normally fixed to the values mg̃ = 800, 1600 GeV in the m
h and
no-mixing benchmark scenarios, respectively. The results for four different values of the
gluino mass, mg̃ = 200, 500, 1000, 2000 GeV, are shown in Fig. 5. The µ parameter has been
set to µ = +1000 GeV in Fig. 5, such that the Higgs decay channels into charginos and
neutralinos are suppressed. As one can see from eq. (10), the change of mg̃ affects the O(αs)
part of ∆b and corresponds to a monotonous increase of ∆b. As an example, this yields for
µ = 1000 GeV, tan β = 50 in the two scenarios:
mmaxh , mg̃ = 200 GeV : ∆b = 0.50
mmaxh , mg̃ = 2000 GeV : ∆b = 0.94
no-mixing, mg̃ = 200 GeV : ∆b = 0.06
no-mixing, mg̃ = 2000 GeV : ∆b = 0.29 . (21)
In the no-mixing scenario the At value is close to zero, suppressing the mg̃-independent
contribution to ∆b, while the higher SUSY mass scale results in an overall reduction of ∆b in
this scenario. The value of ∆b in the no-mixing scenario would slightly increase if mg̃ were
raised to even larger values, but this effect would not change the qualitative behaviour.
Fig. 5 shows that the results for the discovery reach in the MA–tanβ plane are relatively
stable with respect to variations of the gluino mass. The shift in the discovery contours
remains below about ∆ tanβ = 4 for the mmaxh scenario (left plot) and ∆ tanβ = 1 for the
no-mixing scenario (right plot). For the positive sign of µ chosen in Fig. 5, where the ∆b
correction yields a suppression of the bottom Yukawa coupling, the largest discovery reach
is obtained for small mg̃, while the smallest discovery reach is obtained for large mg̃. This
behaviour would be reversed by a change of sign of µ.
We have also investigated the possible impact of other MSSM parameters (besides µ and
mg̃) on the 5 σ discovery contours in the MA–tan β plane. The ∆b corrections depend also on
the parameters in the stop and sbottom sector, see eq. (10). While the formulas in Sect. 2.2.2
have been given for the region where MSUSY ≫ mt, the qualitative effect of reducing the
stop and sbottom masses can nevertheless be inferred. Sizable ∆b corrections require relative
large values of µ and mg̃. If these parameters are kept large while the stop and sbottom
masses are reduced, the ∆b corrections tend to decrease. It is obvious from eq. (10) that
reducing the absolute value of At decreases the electroweak part of the ∆b correction. As
discussed above, this effect of the ∆b corrections manifests itself in the comparison of the
mmaxh and no-mixing scenarios, see Figs. 1–5. Concerning the possible impact of the ∆b
corrections on the 5 σ discovery contours for the bb̄φ, φ → τ+τ− channel in the MA–tanβ
plane we conclude that larger effects than those shown in Figs. 1–5 (where we have displayed
the discovery contours up to tan β = 50) would only arise if the variation of µ were extended
over an even wider interval than −1000 GeV ≤ µ ≤ +1000 GeV as done in our analysis
above.
We now turn to the possible effects of other higher-order corrections beyond those entering
via ∆b on the 5 σ discovery contours for the bb̄φ, φ → τ+τ− channel. These effects are in
general non-negligible, see the discussions in Sect. 2.2 and in Sect. 4.2 below, but smaller
than those induced by ∆b. As a consequence, the impact on the 5 σ discovery contours in the
MA–tan β plane of other supersymmetric parameters entering via higher-order corrections is
in general much smaller than the effect of varying µ in the high-tanβ region of Fig. 4. As
an example, the difference observed in Figs. 1–5 between the mmaxh and no-mixing scenarios
arising from the different values of At and MSUSY in the two scenarios (see eqs. (14), (15))
is mainly an effect of the ∆b corrections, while the impact of other higher-order corrections
involving At and MSUSY is found to be small.
Also the decays of the heavy neutral MSSM Higgs bosons into supersymmetric particles
are in general affected by other supersymmetric parameters in addition to the dependence
on µ, MA and tan β. The resulting effects on BR(φ → τ+τ−) turn out to be rather small,
however. We find that sizable deviations from the values of BR(φ → τ+τ−) occurring in
the mmaxh and no-mixing scenarios for −1000 GeV ≤ µ ≤ +1000 GeV are only possible in
quite extreme regions of the MSSM parameter space that are already highly constrained by
existing experimental data.
Our discussion above has been given in the context of the MSSM with real parameters.
Since the sensitivity of the 5 σ discovery contours in the MA–tan β plane on the other super-
symmetric parameters can mainly be understood as an effect of higher-order corrections to
the bottom Yukawa coupling and of the kinematics of Higgs-boson decays into supersymmet-
ric particles, no qualitative changes of our results are expected for the case where complex
phases are taken into account.
4.2 Higgs-boson mass precision
The discussion in the previous section shows that the prospective discovery reach of the
bb̄φ, φ → τ+τ− channel in theMA–tanβ plane is rather stable with respect to variations of the
other MSSM parameters. We now turn to the second part of our analysis and investigate the
expected statistical precision of the Higgs-boson mass measurement. The expected statistical
precision is evaluated as described in Sect. 3, see eq. (17). In Figs. 6 – 7 we show the expected
precision for the mass measurement achievable from the channel bb̄φ, φ → τ+τ− using the
final states τ+τ− → jets and τ+τ− → e + jet. Within the 5 σ discovery region we have
indicated contour lines corresponding to different values of the expected precision, ∆M/M .
The results are shown in the mmaxh benchmark scenario for µ = −200 GeV (left plots) and
µ = +200 GeV (right plots).
We find that experimental precisions of ∆Mφ/Mφ of 1–4% are reachable within the dis-
covery region. A better precision is reached for larger tanβ and smaller MA as a consequence
of the higher number of signal events in this region. The other scenarios and other values of
µ discussed above yield qualitatively similar results to those shown in Figs. 6, 7.
As discussed above, for large values of MA the heavy neutral MSSM Higgs bosons are
nearly mass-degenerate, MH ≈ MA. The experimental separation of the two states H and A
(or the corresponding mass eigenstates in the CP-violating case) will therefore be challenging.
The results shown in Figs. 6 – 7 have been obtained using the combined sample of H and
A events. It is important to note, however, that even in the region of large MA the mass
splitting between MH and MH can reach the level of a few %. An example of such a scenario
is (as above, we consider the CP-conserving case, i.e. the MSSM with real parameters; the
corresponding scenario in the case of non-vanishing complex phases has been discussed in
Ref. [22])
MSUSY = 500 GeV, At = Ab = 1000 GeV, µ = 1000 GeV,
M2 = 500 GeV, M1 = 250 GeV, mg̃ = 500 GeV . (22)
In Fig. 8 the mass splitting
|MH −MA|
min(MH ,MA)
is given as a function of Xt for tanβ = 40 and two MA values, MA = 300 GeV (solid
line) and MA = 500 GeV (dashed line). The dot-dashed and dotted parts of the contours for
Figure 6: The statistical precision of the Higgs-boson mass measurement achievable from
the channel bb̄φ, φ → τ+τ− → jets in the mmaxh benchmark scenario for µ = −200 GeV (left)
and µ = +200 GeV (right) is shown together with the 5 σ discovery contour.
Figure 7: The statistical precision of the Higgs-boson mass measurement achievable from
the channel bb̄φ, φ → τ+τ− → e + jet in the mmaxh benchmark scenario for µ = −200 GeV
(left) and µ = +200 GeV (right) is shown together with the 5 σ discovery contour.
-1500 -1000 -500 0 500 1000 1500
 [GeV]
 = 500 GeV, tanβ = 40
 = 300 GeV
 = 300 GeV, LEP excl.
 = 500 GeV
 = 500 GeV, LEP excl.
Figure 8: The mass splitting between the heavy neutral MSSM Higgs bosons, ∆MHA/M ≡
|MH −MA| /min(MH ,MA), is shown as a function ofXt forMA = 300, 500 GeV in a scenario
with MSUSY = 500 GeV, µ = 1000 GeV and tanβ = 40. The other parameters are given in
eq. (22). The dot-dashed (dotted) parts of the contours forMA = 300 GeV (MA = 500 GeV)
indicate parameter combinations that are excluded by the search for the light CP-even Higgs
boson of the MSSM at LEP [3].
MA = 300, 500 GeV, respectively, in the region of small |Xt| indicate parameter combinations
that result in relatively low Mh values that are excluded by the search for the light CP-even
Higgs boson of the MSSM at LEP [3]. One can see in Fig. 8 that the mass splitting between
MH and MA shows a pronounced dependence on Xt in this scenario. Mass differences of up
to 5% are possible for large Xt (while the widths of the Higgs bosons are at the 1–1.5% level
in this parameter region).
The example of Fig. 8 shows that a precise mass measurement at the LHC may in
favourable regions of the MSSM parameter space open the exciting possibility to distin-
guish between the signals of H and A production. In confronting Fig. 8 with the expected
accuracies obtained in Figs. 6 – 7 one of course needs to take into account that a separate
treatment of the H and A channels in Figs. 6 – 7 would reduce the number of signal events by
a factor of 2, resulting in a degradation of the expected accuracies (for the same luminosity)
by a factor of
2. A more detailed analysis of the potential for experimentally resolving two
mass peaks would furthermore have to include effects arising from overlapping Higgs signals.
Such an analysis goes beyond the scope of the present paper.
5 Conclusions
We have analyzed the reach of the CMS experiment with 30 or 60 fb−1 for the heavy neutral
MSSM Higgs bosons, depending on tanβ and the Higgs-boson mass scale, MA. We have
focused on the channel bb̄H/A,H/A → τ+τ− with the τ ’s subsequently decaying to jets
and/or leptons. The experimental analysis, yielding the number of events needed for a
5 σ discovery (depending on the mass of the Higgs boson) was performed with full CMS
detector simulation and reconstruction for the final states of di-τ -lepton decays. The events
were generated with PYTHIA.
The experimental analysis has been combined with predictions for the Higgs-boson masses,
production processes and decay channels obtained with the code FeynHiggs, taking into ac-
count all relevant higher-order corrections as well as possible decays of the heavy Higgs
bosons into supersymmetric particles. We have analyzed the sensitivity of the 5 σ discov-
ery contours in the MA–tanβ plane to variations of the other supersymmetric parameters.
We have shown that the discovery contours are relatively stable with respect to the im-
pact of additional parameters. The biggest effects, resulting from higher-order corrections
to the bottom Yukawa coupling and from the kinematics of Higgs decays into charginos
and neutralinos, are caused by varying the absolute value and the sign of the higgsino mass
parameter µ. The corresponding shift in the 5 σ discovery contours amounts up to about
∆ tanβ = 10. The effects of other contributions to the relation between the bottom-quark
mass and the bottom Yukawa coupling, arising from the gluino mass and the parameters in
the stop and sbottom sector, are in general smaller than the shifts induced by a variation
of µ. The same holds for the impact of higher-order contributions beyond the corrections to
the bottom Yukawa coupling and for the possible effects of other decay modes of the heavy
Higgs bosons into supersymmetric particles. The results of our analysis, which was carried
out in the framework of the CP-conserving MSSM, should not be substantially affected by
the inclusion of complex phases of the soft-breaking parameters.
We have analyzed the prospective accuracy of the mass measurement of the heavy neu-
tral MSSM Higgs bosons in the channel bb̄H/A,H/A → τ+τ−. We find that statistical
experimental precisions of 1–4% are reachable within the discovery region. These results,
obtained from a simple estimate of the prospective accuracies, are not expected to consid-
erably degrade if further uncertainties related to background effects and jet and missing ET
scales are taken into account. We have pointed out that a %-level precision of the mass
measurements could in favourable regions of the MSSM parameter allow to experimentally
resolve the signals of the two heavy MSSM Higgs bosons.
Acknowledgements
S.H. and G.W. thank M. Carena and C.E.M. Wagner for collaboration on some of the
theoretical aspects employed in this analysis.
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	Introduction
	Phenomenology of the MSSM Higgs sector
	Notation
	Higher-order corrections in the Higgs sector
	Higgs-boson propagator corrections
	Corrections to the relation between the bottom-quark mass and the bottom Yukawa coupling
	Corrections to the Higgs production cross sections
	The mhmax and no-mixing benchmark scenarios
	Experimental analysis
	Results
	Discovery reach for heavy neutral MSSM Higgs bosons
	Higgs-boson mass precision
	Conclusions
