# Presentation: 669863

## Top and b-physics at the Tevatron

- Daniela Bauer

- for the  CDF and DØ collaborations

- International Symposium on Multiparticle Dynamics
- Sonoma, Jul 26-Aug 2 2004

## The Tevatron at Fermilab

- Tevatron

- protons

- anti-protons

**Run II **
**E****CM****= 1.96 TeV**
**> 500 pb****-1**

- Chicago

- Run I 1992-1995
- ECM = 1.8 TeV
- 125 pb-1

- Recycler

**CDF**

**D****Ø**

- April 2002

- July 2002

- April 2002

- July 2002

**Notes:**
1 km radius

## The CDF  and DØ detectors

- The CDF  and DØ detectors

**D****Ø**
-  excellent muon coverage |η| < 2.0
-  new tracking system (Silicon and
-                                  Fiber Tracker)
-  2 T magnetic field
-  impact parameter trigger

**                   ****CDF**
-  excellent tracking resolution
-  particle ID (TOF and dE/dx)
-  displaced vertex trigger
-  new plug calorimeter 1.6 < |η| < 3.6

**Notes:**
CDF: only bits leftover from Run I: central calorimeter (lead (EM), iron (HAD)) and central muon system.
the displaced vtx trigger is a hadronic b-trigger which D0 doesn’t have
New: Tracking system (SVX-II and COT (= central outer tracker i.e. a drift chamber))
COT up to eta < 1.0, SVX to 2.8
Plug calorimeters 1.6 < eta < 3.6 (mostly used till eta < 3.0)
extended muon coverage ( eta < 1.5)
trigger and DAQ: Level 2 trigger can trigger on secondary vtx in SVX
TOF (time of flight) for PID
magnetic filed: 1.4 Tesla
D0 tracking: the solenoid ends at eta = 1.65, full tracking coverage (SMT+CFT) up to about eta = 2.5

## Top physics at  the Tevatron 

-  The top quark is the only known fermion with a mass on the
-    electroweak scale:
-  decays as a ‘free quark’
-  may include non-SM contributions
-                                              in decay
-  mW and mtop together constrain
-                                   the Higgs mass

-  Discovered in Run I:
-    mass and cross-section, *W*-helicity
-    → missing: spin, charge, width
-  Run II programme
-  improve previous measurements:
-   mass, cross-section, *W*-helicity and
-   spin-correlations
-  single top
-  branching ratios (non-SM, Higgs)
-  anomalous kinematics (non-SM)
-  resonance production
-  anomalous couplings

**Notes:**
Branching ratios: top -> Wb = 100 % in SM
therefore sigma_dilepton/sigma_lepton+jets = 1 -> looking for deviation, sensitive to non-SM top decays
current CDF result 0.46 < sigma_ll/sigma_l+j < 4.45 and sigma_ll/sigma_l+j = 1.45 + 0.83 – 0.55
Also looking for top-> tau decays: seen Br(top->tau)/SM predicted branching ration < 5.0 (CDF) 
anomalous kinematics: models beyond SM predict anomalous (whatever that means) top pt spectra
anomalous couplings top-> u or c and Z, top -> u or c and gamma and yes it’s FCNC
D0 published Run I search for narrow resonances X->ttbar, Zprime ->ttbar in 2004, CDF in 2000, sigh

## Top quark production

- In pp-collisions at s = 1.96 TeV, top quarks are mostly produced in pairs:

- 90 %

- 10 %

- single top-production

- no single top observed (so far)
- current Run II **CDF** limits:
- σ(*s+t*) < 13.7 pb @ 95 % CL
- σ(*t* only) < 8.5 pb @ 95 % CL

- s-channel

- t-channel

**Notes:**
single top: top: Drell-Yan, bottom: W-gluon-fusion

## Top quark decay

- Top quark decay

**e+jets (12/81****)**

**mu+jets(12/81****)**

**tau+jets(12/81)**

**all jets (36/81)**

*Br*(*t*  *Wb*)  100% in the SM

-  **all jets**: Both *W* decay via
-                *W****qq*

-   **dilepton****:** Both *W* decay via *W****l*** (l=*e* or **, ~5%)
-   **lepton+jets**: One *W* decays via *W****l*** (l=*e* or **, ~30%),
-                    the other via *W****qq*

## Top cross section: dilepton channels

**b**

**b**

****

****

**p**

**p**

**E**** T**

- 2 high pT isolated leptons
-                       (*e,***, not **)
- neutrinos: large missing ET
- 2 high pT jets (from *b*-quarks)

- Backgrounds:
*Z**l**+**l**-* (incl. **)
*WW**ee, ****, e*** + jets  (small,
-     but has very toplike signature)
- QCD leptons (esp. *** *)

- 3 channels:
*ee, **** , e***

- very clean, low yield

*l*

*l*

**Notes:**
difficult to distinguish isolated muons from other muons.
Z to tau tau, tau decays into e,mu equally

## di-lepton

- e-μ channel

- Mee

- Event selection:
-  trigger
-  missing ET > 25 GeV (eμ) /35 GeV (ee, μμ)
-  isolated leptons, pt lepton > 15 (20 for ee)
-  HTl > 120 /140 GeV
-  2 or more jets with pt > 20 GeV
-  105 (110) GeV < M(ee), (M(μμ)) < 75 (70)GeV

- combined: σttbar = 14.3       (stat)        (syst) ± 0.9 (lumi) pb

- +5.1
- -4.3

- +2.6
- -1.9

- ~145 pb -1

- MET

**Notes:**
35 GeV for mumu, ee
MTC muon tracking in calorimeter, i.e. a MIP trace
muon in jet 2 is soft (-> b-tagging)
Jet 1 has a displaced vtx (-> b-tagging)
The barely visible e is actually high pt.
“The ttbar cross-section is measured by maximizing the product of likelihood for each individual channel, based on the Poisson probability to observe a given number of events under the signal+background hypothesis.”
Luminosities are different as different types of bad run (calorimeter, tracking, muons) are excluded.
H_t^l = all transverse energies + transverse energy of leading lepton 

## Top cross-section: Lepton + jets 

-  “**Golden” mode for top studies:** ~30% yield and relatively clean

- t(W±b) t(W±b)

- e±,±

- qq

*jet*

*jet*

- One (and only one)
- high pT isolated lepton.
- Neutrino: large missing ET
- large jet multiplicity (  3,4)

- Background: QCD+multijet
-                       W+multijet

-  topological: event shape,
-  *b*-tagged: secondary vertex tag
-                    soft lepton tag

**Notes:**
Aplanarity measures how far final state particles lie out of a plane
top events have a higher aplanarity than QCD, i.e. are more spherical.

## lepton + jets

- run 155145
-  evt 132579

**Event selection**:
-  lepton trigger
-  missing ET > 20 GeV
-  ET, pt(μ) > 20 GeV
-  at least 3 jets with pt > 15 GeV
-    and |η| < 2.0
-  at least one *b*-tagged jet
-  HT = Σ ET + missing ET + ET (pt(μ))
-  HT > 200 GeV

- σ(t ̄) = 5.6       (stat)      (syst) pb

- 162 pb-1

- +1.2
-  -1.1

- +1.0
- -0.7

- t

**Notes:**
cross-section goes down with increasing top quark mass

## Top to all jets

**p**

**~45 % of all decays, but what a mess !**

- 50% of all ttjets have  5
-                  reconstructed jets
- but: swamped by background
- (QCD hard scatter 2  2 parton processes)

- 6 or more jets (one jet per parton)
- no isolated leptons
*b*-tagging
- event shape

- DØ    (neural net)

- CDF (tagging)

- σ(t ̄) = 7.7      (stat)     (syst) ± 0.5 (lumi)

- t

- +3.4
- - 3.3

- +4.7
-  -3.5

**Notes:**
no isolated leptons makes it orthogonal to other analyses, but only cuts the signal efficiency by 2%
jets in top events are spherically distributed, QCD  usually back to back (aplanarity, spherity)
QCD has lower energy distribution (HT) = sum over all ET of jets
there are more variables in each category but they are highly correlated.

## t ̄ Production Cross-Section Summary

- All observed cross sections consistent with each other...

- Theory predicts

- at mtop = 175 GeV

- t

## DØ Run I Top Quark Mass Measurement

- mt = 180.1  3.6 (stat)  3.9 (syst) GeV/c2

- Nature  (429, pp. 638-642)

- Statistical uncertainty reduced from 5.6 to 3.6 GeV/c2
-     → equivalent to a 2.4x larger dataset

- The probability for a top (or background) event to give rise to observed jets, leptons and MET is computed.
- Mtop  is measured by maximizing Poisson likelihood for entire event sample.

**Advantages:**

- - all jet permutations contribute
- - event-by-event resolutions considered
-  non-Gaussian detector response
-                                accounted for

**Problems:**

-  - only leading-order tt cross section is used
-     → only events with exactly four jets can be used
-   - gluon fusion diagrams neglected
-   - only background process computed is
-                                                  W + jets

- This measurement increases the
- world-average top mass from
- 174 ± 5.1 GeV to 178 ± 4.3 GeV

**Notes:**
mention constraint on the Higgs mass:
with this measurement the lower limit on the Higgs mass goes from 96 GeV to 117 GeV and the upper limit from 219 to 251 

## Run II top mass CDF

**Lepton+ jets**:
-  template (Run I)
-  multivariate
-  dynamical likelihood

- Systematic error is dominated by
- modeling of the calorimeter response

- First Run II DØ mass measurement soon.

- improved result for Winter 2005

**M****top**** = 177.8 ±     (stat.) ± 6.2 (syst.)GeV/c****2**

- → best Run II CDF result so far

**4.5**
**5.0**

**Notes:**
template: fits mass (kinematic fit) uses best fit, templates for signal and bkg, likelihood fit on fitted masses.
multivariate: refined kinematic fitter with jet energy scale correction 
dynamic likelihood: all combinations, maximum likelihood, exactly 4 jets, so far 22 events, uses sec vtx b-tag (one or two tags ?) , matrix method (= very close to  D0 Run I paper)

## W-helicity in top decays

*W*-helicity in top decays

- F0

- ≡

- Γ(*t*→W0*b*)

- Γ(*t*→W0*b*) + Γ(*t*→WT*b*)

- 1⁄2 (mt/mW)2

- 1+ 1⁄2(mt/mW)2

-  In the SM only left-handed (W_) and longitudinally
-    polarized (W0) are produced.

- =

- With mt = 175 GeV

- F0 = 0.703

- Run  I  results:
- CDF (2000): F0 = 0.91 ± 0.37 (stat) ± 0.13 (syst)
- DØ (2004): F0 = 0.56 ± 0.32 (stat+ mt) ± 0.07 (syst)

**Notes:**
W0 = longitudinal
analyse pt spectrum: left handed W are emitted in a directin opposite the line of flight of the W -> soft pt spectrum. Longitudinally polarized W emit leptons transverse (?) to the line of flight-> harder pt spectrum 

## W-helicity Run II 

- Updated DØ measurement soon

- lepton + jets:
- F0 = 0.88+0.12 (stat+syst)
- F0 > 0.24 @ 95 % CL

- di-lepton:
- F0 < 0.52 @ 95 % CL
- F0 < 0.94 @ 99 % CL

- lepton+ jets

- combined:
- F0 = 0.27+0.35 (stat + syst)
- F0 < 0.88 @ 95 %CL

- -0.47

- -0.21

## b-physics at the Tevatron

- The Tevatron is a *b*-factory:
- σ(*pp*  *bb*) = 150 *μ*b (at 1.96 TeV)
- All types of *B*-hadrons are being produced (Bd, Bs, B**, Λb etc)

- CDF and DØ have a large and varied b-physics programme
**→** can only present a limited selection today

-  X
-  *B*s → ΦΦ
-  *B*s/d → μμ
-  Pentaquarks

-  Mixing
-  Lifetimes
-  Lifetime difference in Bs →J/Ψ Φ

- not covered:
* **b* and quarkonia production
-  CP violation
-  hadronic moments
-  *B*c
-  *B***
-  *B* → D** X
-  Helicity amplitudes in
-               *B* → J/Ψ K*/Φ
- etc.

## Mixing

-  proper decay time cτ
-  identify *b*-flavour at production
-  identify *b*-flavour at decay

- To measure B-mixing:

- Flavour tagging:

-  same side tagging: charge of ‘nearby’
-    track correlated  with b-quark flavour
-    (*b*  +, *bbar* -)

-  opposite side jet charge tagging:
-     sign of *b*-quark ~ sign of momentum
-     weighted sum of particles charges in jet

-  opposite side lepton (here:) tagging:
-    from semileptonic *b*-decays
-    (*b*l-, *bbar*l+)

- Tagging efficiency =Ntag/Ntot
- Dilution D=(NR-NW)/(NR+NW)
- Tag power=D2

- M = mass matrix
- Γ = decay matrix

## Mixing Results from CDF

-  semileptonic *b*-decays using same side tagging

- Δmd = 0.443  0.052 (stat.)  0.030 (s.c.)  0.012 (syst.) ps–1
- D0 = 12.8  1.6 (stat.)  1.0 (s.c.)  0.6 (syst.) %
- D+ = 28.3  1.3 (stat.)  1.1 (s.c.)  1.0 (syst.) %
- εD2(*B*0) = 1.1  0.3 (stat.)  0.2 (s.c.)  0.1 (syst.) %

-   exclusive decays
-  *B*0 → J/Ψ K*0
-  *B*0 → D- π+

- md =  0.55 ± 0.10 ± 0.01  ps-1

- world average: Δmd = 0.502 ± 0.007

**Notes:**
s.c. sample composition (B+ -> D** -> and other things that go bump in the night.
D_+ dilution for B+, D_0 for B_0, there is apparently a paper hat gives a reason why they are different:
Dunietz, Rosner, Phys Rev D51 2471 (1995) ... need to look it up.

## Mixing Results from DØ

- Mixing Results from DØ

******m****d**** = 0.506 ******** 0.055 (stat.) ******** 0.049 (syst.) ps****-1**

- B → D*- μ+ ν X
-     D*- → D0 π-
-                D0 → K+π-

- Semileptonic *B*-decays:

- opposite-side muon tagging

- world average: Δmd = 0.502 ± 0.007

-  Tagging efficiency:  4.8  0.2 %
-  Tagging purity, NR/(NR+NW) = 73.0  2.1 %
-  → D = 46 %,  εD2 = 1.0 %

## Run II lifetime measurements

| B meson |   N(B) |         τ(B) in ps | PDG 03 in ps |
| --- | --- | --- | --- |
| B+→ J/Ψ K+  | ~3390 | 1.662 ± 0.033 ± 0.008 | 1.671± 0.018 |
| B0 → J/Ψ K*0 | ~1160 | 1.539 ± 0.051 ± 0.008 | 1.537± 0.015 |
| Bs→ J/Ψ Φ |   ~260 | 1.369 ± 0.100 +0.008
                                   - 0.010 | 1.461± 0.057 |

**CDF**

******B****+****) / ******** (B****0****) = 1.080  ****±****  0.042 (*****tot.*****)**
******B****s****) / ******** (B****0****) = 0.890  ****±****  0.072 (*****tot.*****)**

******(B****+****)/********(B****0****) = 1.093 ******** 0.021 (stat) ******** 0.022 (syst)****  **** ****  **

- HQET/OPE  predict lifetime ratios:  τ(B+)/τ(B0d) = 1.053 ± 0.016 ± 0.017

- correlated errors

**D****Ø**

- semileptonic
- decays

*preliminary*

- updated DØ measurements in exclusive modes (Bd, Bs, Λb) at ICHEP

**Notes:**
mention that we are looking into the lifetime rations involing Bs, Lambda_b as well

## Lifetime difference and in Bs →J/Ψ Φ (Method)

- Lifetime difference and in Bs →J/Ψ Φ (Method)

- scalar → VV  decay
-   3 amplitudes
-  L = 0 (even),1 (odd), 2 (even)
-  described in ***transversity*** basis

- In J/Ψ restframe:
*K**+**K**-* plane defines (*x,y*) plane
- K+ defines +y direction
**Θ****, ****Ψ** polar and azimuthal angles of μ+
**φ** in Φ restframe: angle(K+, -J/Ψ)

**Notes:**
“analyze angular distributions of the final state”

## Lifetime difference and in Bs →J/Ψ Φ (Results)

- Lifetime difference and in Bs →J/Ψ Φ (Results)

- Γ = 1⁄2 (Γ*L*+Γ*H*)* ≡ *1/τ
- ΔΓ = ΓL - ΓH

- τ*L* = 1.13      ± 0.02 ps
- τ*H* = 2.38      ± 0.03 ps

- ΔΓ = 0.46 ± 0.18 ± 0.01 ps-1

- +0.13
- -0.09

- +0.56
- - 0.43

- ΔΓ/Γs = 0.71      ± 0.01

- +0.24
-  -0.28

- theory:
- ΔΓ/Γs = 0.12 ± 0.06

- constrained fit
- Γs = Γd

- unconstrained fit: ΔΓ/Γs = 0.65      ± 0.01

- +0.25
- - 0.33

## X(3872) →J/Ψ π+π-

**Belle: M****X**** = 3872.0 ******** 0.6 (stat) ******** 0.5 (sys) MeV/c****2**

- X(3872) →J/Ψ π+π-

| Exp | Lumi 
[pb-1] | range | Mass [MeV] | Mass res [MeV] | Signal | Signi-
ficance |
| --- | --- | --- | --- | --- | --- | --- |
| CDF | 220 | |y| < 1 | 3871.3 ± 0.7 ± 0.3 | 4.9 | 730 ± 90 | ≈ 12 |
| DØ | 230 | |y| < 2 | 3871.8 ± 3.1 ± 3.0 | 17 | 522 ± 100 | ≈ 5 |

## X(3872) – Ψ(2S) comparison

- No significant differences between** ********(2S)**** **and ***X***** ** have been observed yet.

- Decay Length < 0.01cm

- cos() < 0.4

- pT (J/)> 15 GeV

- |y(J/)| < 1

- cos() < 0.4

- helicity:
- angle between
- π(μ) and X in
- di-π(μ) restframe

- Isolation = 1

- Is the X(3872) charmonium, molecule, ...  ?

- Similar in decay length and isolation → similar prompt production fraction as Ψ(2S)

**Notes:**
The molecule would be DD* or so.
From isolation and decay length comparisons, the production of X appears to have
   the same mixture of prompt and long-lived fractions as the (2S). 
Observation of the charged analog X+  J/ + 0 would rule out cc hypothesis.
Observation of radiative decays X   c would favour cc hypothesis (Belle set limit).

## Charmless B-decays: Bs → ΦΦ

- Charmless *B*-decays: Bs → ΦΦ

*BR*(Bs → ΦΦ) = (1.4 ± 0.6 (stat) ± 0.2 (syst) ± 0.5 (BRs)) * 10-5

- gluonic penguin decay

- 12 events  seen
- expected bkg 1.95 events

- b

- s

- q

- s

- s

- s

- s

-  ̄

-  ̄

-  ̄

-  ̄

- First ‘observation’ (σ = 4.7) at CDF

**Notes:**
nearly observation Observation
CP violation in Bd -> Phi Ks from Babar

## Rare decays: Bs/d → μ+μ-

- Rare decays: Bs/d → μ+μ-

**D****Ø**
**Sensitivity **@ 95 % CL **:**
*BR*(Bs  + -) < 9.1  10-7 (stat only)
*BR*(Bs  + -) < 1.0  10-6 (stat+syst)
- Box will be opened for ICHEP

- ~180 pb-1

- CDF Run II limits:
*BR*(Bs → μ μ) < 5.8 · 10-7 @ 90 % CL
*BR***(**Bd → μ μ) < 1.5 · 10-7 @ 90 % CL

- SM prediction: *BR*(Bs → μ μ) = (3.4± 0.5)· 10-9
- Bd  → μμ  suppressed by |Vtd/Vts|  410-2

**Notes:**
Bd- -> mumu suppressed by at least factor 10 compared to Bs -> mumu 
CDF Run II better than CDF Run I
B physics at the Tevatron report states we could find Bs -> mumu with 15 fb-1 hahahaha
CDF and D0 normalize to B+ -> J/Psi K+
main uncertainty in D0 measurement from b-> Bs, b-> B+-
decay can be enhanced through MSSM, which these days seems to be possibly enhancing anything
CDF Run I limits (98 pb-1)
B(Bs → μ μ) < 2.6 · 10-6 @ 95 % CL
B(Bd → μ μ) < 8.6 · 10-7 @ 95 % CL

##   + (uudd ̄))   p Ks  p 

-   + (uudd ̄))   p Ks  p 
-   c (uudd ̄)   D*- p  D0  p
-   03/2 (ssdu ̄)  - +  + -
-   --3/2 (ssdd ̄)  - -  -

- Pentaquarks

- s

- c

- d

- u

- So far CDF has not observed any pentaquark states.

**Notes:**
theta plus and theta_c 1540 MeV
the letter I don’t know is also at 1530

## Summary

-  *b*-physics
-  Rich programme, not all covered in this talk
-  Competitive and complementary to *b*-factories

-  The Tevatron integrated luminosity > 500 pb-1/experiment

-  Top
-  Run II luminosity in measurements now exceeds Run I
-  Sophisticated analysis techniques in place
-  Measurement of top properties in progress

***** Many more results coming soon *****

## Backup Slides

## Tagging Tools: Vertexing and Soft Muons

- B hadrons in top signal events

- Identify low-pt muon from decay

- Vertex of displaced tracks

## Lepton+jets: topological

- Aplanarity *A* = 3/2  smallest eigenvalue of the normalized
- momentum tensor *M**ij*

- Highly correlated with the top mass!

- Large values of *A* indicate spherical (top) events.

**Notes:**
Aplanarity measures how far final state particles lie out of a plane
top events have a higher aplanarity than QCD
Behrends: empiracal, initial state radiation gluon spectrum for W events, biased by trigger

## Top Quark Mass Measurements

- DØ: New analysis of Run I Data    Nature 429, 638 (2004)

** **Rather than a kinematic fit, the probability for a top  (or background) event to give rise to observed jets, leptons and MET is computed
-  Also define background probability for each event
-  Mt   measured by maximizing Poisson likelihood for entire event sample
-  Advantages
-   - all jet permutations contribute
-   - additional kinematic information used
-   - event-by-event resolutions considered
-   - non-Gaussian detector response accounted for
-  Compromises
-   - only leading-order tt cross section is used
-      only events with exactly four jets can be used
-   - gluon fusion diagrams neglected
-   - only background process computed is W + jets

-         22 events including 10 background
- Mt  = 180.1 ± 3.6 (*stat*) ± 4.0 (*syst*) GeV

## Lepton + jets CDF Run II mass measurements -- methods

-  Kinematic fitter to reconstruct top mass
-  Kinematic constraints (mt =mtbar etc)
-  Use best (smallest χ2) of 12 (4 if double btag) solutions
-  One dinemsional templates parametrized for top and background as function of top mass

**Multivariate Template Method**:
-  Refined kinematic fitter with jet energy scale optimization
-  Kinematic constraints
-  best combination, weight according to correct permutation probability
-  mulitidimensional non-parametric templates

**Dynamical Likelihood Method**:
-  Matrix Element Method
-  use all 12 (4) combinations
-  calorimeter transfer functions

## Top mass constraint on the Higgs mass

## b - Lifetimes

**Heavy Quark Effective Theory **(mQ >>ΛQCD)  but not top !

- spectator model

**Notes:**
spectator model->lifetime of all B-mesons would be equal
1/m = free quark
1/m3 differences between B-mesons
1/m2  for Lambda

## Mixing

- Bs mixing via top quarks

- xs = ΔmBs/Γ > 19.0
-        at 95 % confidence level
- xd = ΔmBd/Γ = 0.755  0.015

- ΔΓs/Γ < 0.52 at 95% c.l.
- ΔΓs/Γlight = 0.26 ( +0.30) ALEPH
- theory: 0.12  0.06

- M = mass matrix
- Γ = decay matrix

- Bs (~bs), Bs(~bs) are produced
- in one of the two possible flavour
- states. This initial state evolves into
- a time-dependent superposition
- of the two states according to:

-  ̄

-  ̄

-  ̄

**Notes:**
theoretical pred from B-phys report

## Rare decays: Bs/d → μ μ – theoretical predictions

- Rare decays: Bs/d → μ μ – theoretical predictions