Dark matter searches at CMS
Maria Savina, JINR, Dubna
on behalf of the CMS Collaboration
Maria.Savina@cern.chDark matter approaches: from EFT to complete models

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LHC Dark Matter Working Group documents for RUN 2 analyses
arXiv:1507.00966
Simplified DM models – main requirements:
arXiv:1603.04156
1. Minimal set of DM fields, s- and t-channel mediated models
arXiv:1506.03116
2. Minimal set of physically relevant parameters (couplings, masses and widths)
3. Minimal flavor violation (MVF): new interactions are invariant under global flavor symmetry groupor all violating transitions are governed by the CKM matrix (SM FCNC structure, also CPV)DM mediator(s): spin-0, ½, 1
1. The (axial)vector Z’, spin-1
2. The (pseudo)scalar, spin-0 – Higgs portals (special importance of Higgs connected studies).
3. Fermionic portals, spin-1/2 – SUSY, dark SUSY… (often – flavour violation)
4. Double (scalar-vector) portals
DM particle(s): spin-0, ½, 1 (and even spin-2 for Kaluza-Klein DM in TeV-scale gravity models)
Spin-1/2 DM: for fermion case only one DM particle  nonperturbative description for the scalar mediator(see f. e. arXiv:1903.03616)  need to extend fermion sector
 Isodoublet-isosinglet model (faces difficulties in imposing collider and astrophysical constraints
for minimal mediator models, higgs portals)
 New vector-like fermion family (VLL, VLQ, VLF in general)
Spin-0 DM: inert higgs doublet
Spin-1 DM: dark photon
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The simplest s-channel DM
One DM particle, one mediator, plus the SM content. Visible and invisible (MET) FS
A cross section as a function of
5 only model parameters:

mmed, gq, gl, mDM, gDM

Mono Jet

The invisible signature: DM mediator  𝜒𝜒ҧ  Mono X + MET;
Mono X = ISR Jet/W(Z)/γ/h125/𝑡/𝑡𝑡ҧ

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CMS-PAS-EXO-20-004
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V/AV combined Dijet & Mono X + 𝐸𝑇𝑚𝑖𝑠𝑠
The leptophobic mediator, gl = 0CMS EXO summary plots

interpretation for the axial-vector mediatorinterpretation for the vector mediator
V/VAgqgq

Visible (ffbar) and invisible (X+MET) channels combined
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Leptophilic mediator 𝑔𝑙 ≠ 0: dileptons and dijets (combined)
CMS EXO summary plots
95% CL observed and expected exclusion
regions in mMed–mDM plane for dijet anddilepton searches from CMS for the axialvector and the vector DM mediator

The exclusions are computed for the universal
quark coupling of gq = 0.1, lepton coupling
gl = 0.1 (0.01 fron DY process) for the VA(V)model, and for the DM coupling of gDM = 1.0

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Collider and DD constraints on DM: CMS Mono Jet/V+ MET, V/AV mediator
Comparison of the inferred limits with theconstraints from direct-detection experimentson spin-independent (the V mediator) andspin-dependent (the AV mediator)
WIMP-nucleon scattering cross-section

σSIVector

Collider and DD constraints on DM: CMS Mono Jet/V+ MET, V/AV mediatorComparison of the inferred limits with theconstraints from direct-detection experimentson spin-independent (the V mediator) andspin-dependent (the AV mediator)
WIMP-nucleon scattering cross-section

σSIσSD
Axial-vector

From the simplest s-channel DM to Simplified Dark matter Model (SDM)ധℎ(𝑏𝑏)/𝑍(𝑙𝑙)VBC

Extended simplified DM:
 2HDM-based DM Dark portal
 t-channel VFC SDM…
f, χV/VAgq

Darkportal

new couplings

extended higgs/gauge sector:
extra states = extra graphs

2HDM+𝑍𝑉′gq,χ
𝑓,Ӗ 𝜒Ӗnew states

one DM particle,
one mediator + SM

ZVFC

flavour violation
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SDM models and signatures
Generalized or model specific search, combinations of visible and MET signatures
The (axial)vector mediator
V(ector)/A(xial)V(ectThe (pseudo)scalar mediatoror)

dijet (dilepton), diboson hW/Z pair, 𝑡𝑡
resonance

S(calar)/PS(eudoscalar)

jet/V/h+𝐸𝑇𝑚𝑖𝑠𝒔 , 𝑡𝑡(𝑏𝑏) resonance,𝑡𝑡(𝑏𝑏)+𝐸𝑇𝑚𝑖𝑠𝒔 , h inv, X hh

V(ector)F(lavour)C(ct+𝐸𝑇𝑚𝑖𝑠𝑠 , same-sign tt

S(calar)C(olor)C(harged)b𝑏(𝑏𝑏) +𝐸𝑇𝑚𝑖𝑠𝑠

SCCtt(𝑡𝑡) +𝐸𝑇𝑚𝑖𝑠𝑠

2HDM+a (pseudoscalarh+𝐸𝑇𝑚𝑖𝑠𝑠 , Z(ll)/V(qq’)/Z(𝑞𝑞)+𝐸𝑇𝑚𝑖𝑠𝑠 ,h inv, X hh, diboson Zh(+𝑏𝑏),𝑡𝑡(𝑏𝑏) resonance, 𝑡𝑡(𝑏𝑏)+𝐸𝑇𝑚𝑖𝑠𝑠 , 𝑡𝑡𝑡𝑡hanging)

V(ector)B(aryonnumber)C(harged)h(𝑏𝑏/γγ/ττ) +𝐸𝑇𝑚𝑖𝑠𝑠

2HDM+𝑍𝑉′ (vector
2HDM based)h(𝑏𝑏/γγ/ττ) +𝐸𝑇𝑚𝑖𝑠𝑠 , diboson W/Z/h pairs,
𝑡𝑡 resonance

Dark higgs 𝑍𝑉′ +ss(𝑏𝑏) +𝐸𝑇𝑚𝑖𝑠𝑠

2HDM based)

A key: separation/reinterpretation and a wide complementary search with all available signatures

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Mono h(𝑏𝑏) + 𝐸𝑇𝑚𝑖𝑠𝑠 , SDM 𝑍𝑉′ interpretations
ധℎ(𝑏𝑏)/𝑍(𝑙𝑙)VBC

EPJC 79 (2019) 280

Decay h 𝑏𝑏 , new vector/pseudoscalar in invisible modeZb’ : Vector Baryon-number-Charged mediator (VBC)
Free parameters of the SDM used in the analyses: mA, mH, mZ’, 𝑚𝜒 ,coupling 𝑍𝑉′ to SM matter 𝑔𝑍′ (=0.25), coupling to DM 𝑔𝜒 (=1.0)
2HDM+𝑍𝑉′

2HDM+𝑍𝑉′ : mA, mH, mZ’, 𝑚𝜒 (=100 GeV), coupling 𝑍𝑉′ to SM matter𝑔𝑍′ (=0.8), coupling to DM 𝑔𝜒 (=1.0), 𝑡𝑎𝑛𝛽=1Zb’

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Mono h(𝑏𝑏) + 𝐸𝑇𝑚𝑖𝑠𝑠 , SDM 2HDM+a interpretations
2HDM+aDecay h 𝑏𝑏 , new pseudoscalar in invisible mode

EPJC 79 (2019) 280

Free parameters of a simplified description used in
an analyses: mA, mH, mS, mixing angle between a and A 𝑠𝑖𝑛𝜃,VEV ratio for two higgs doublets 𝑡𝑎𝑛𝛽, couplings to SM andDM particles

See also JHEP 03 (2020) 25 forcombined h  𝑏𝑏 /WW/ZZ/γγ/ττ

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Mono Z(ll) + 𝐸𝑇𝑚𝑖𝑠𝑠 , different SDM interpretations

2HDM+aV/AVHiggs portal(h  invisible)

V

AV

2HDM+aEPJC 81 (2021) 13
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Dark Higgs model, resolved decay of s(W+W-) + 𝐸𝑇𝑚𝑖𝑠𝑠
 “Double portal”: both “dark higgs” s and massive 𝑍𝑉′ coupledto SM.
 A new higgs state is weakly mixed with SM h,a new U(1)’  SSB(s)  massive 𝑍𝑉′ coupled to quarks only
arXiv:1701.08780+
 s  W W decay dominates at large s mass values

Model parameters : ms, mZ’, 𝑚𝜒 , gq, 𝑔𝜒 , sinθ (h–s mixing)

CMS-PAS-EXO-20-013𝑚𝜒 =300 GeV

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Dark sector, how might it look?
DS might be extended and rich presence of new “dark” particles thatmanifests itself through SM-darkinteractions (portals)
 new symmetries (new “dark”QCD, EW, SUSY…)

NB: not only dark sector:
see Backup slides forfull list 0f models thatgive LLP signatures

DS: small couplings, compressed spectra, large hierarchy  large cτ  LLP

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Dark sector with Long-Lived Particles at the LHC
LLP:
a proper lifetime cτ0is greater than orcomparable to thecharacteristic size ofthe (sub)detectors

LLP White Paper:
arXiv:1903.04497
LLP theory motivations:
arXiv:1806.07396
displaced jets small cτ0 thatcomparable to theinner tracker size, nodisplaced tracks “standard” prompt
decay intermediate cτ0 LLP
 very large/infinite
large cτ0  stableparticles, “standard”
MET signatures
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Dark photon from dark SUSY, displaced LJ
SUSY portalh – Higgs boson (visible)
n1 – neutralino,nD – dark neutralinoγDγ conversion, εSee also full RUN 2 statistics of 137 fb-1 analyses for γD in VBFand ZH associated prod. and for the light narrow vectorresonance ZD -> 𝜇𝜇 in Backup slides

Higgs decay to dark photons: displaced muon jets
CMS-PAS-EXO-20-014

Z–ZD conversion, ε2Higgs – dark higgs conversion, κM. Savina, JINR, Russia

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Emerging jets/dark showers from dark QCD
scalar charged under both colour and dark colour

vector coupled to(dark) quarks

background from QCD
multijet dominates One of the most striking DM-targetedsignatures (dark QCD  dark showers)
 Tracks start near the edge of the tracker,in the ECAL and HCAL and even in theinner muon stations
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Summary and outlook on DM searches
 Wide variety and an extensive list of analyses on DM at CMS, simplified s-channel DM modeland slightly beyond it Model specific/non-specific signatures, reinterpretation of common to many models, separation throughspecial signatures
 Still no signals of new DM particles/mediator Further development of an analysis and related theory/simplified model approaches, new interactionchannels, new frameworks:
 t-channel studies
 LHC Dark Matter Working Group: Next generation spin-0 dark matter models(in the 2HDM+a framework)
CMS analyses summary on DM search and much more:https://twiki.cern.ch/twiki/bin/view/CMSPublic/PhysicsResultsEXO
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Thank you for your attention!

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Backup slides

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Spin of DM mediator: Higgs/gauge (or both) portals to dark matter
Higgs portal: DM interacts with our world only through coupling with the Higgs sector 
special importance of Higgs connected studies
Additional higgs bosons needed to accommodate DM  an extended Higgs sector. How to extend?
SM style…
 SM + one singlet (real/complex) – SM + S, the simplest singlet-doublet model (the doublet corresponds to the SM) SM + one doublet (real/complex) – 2H(iggs)D(oublet)M(odel), flavor conserving 4 types (type II – MSSM), 5 physicalstates: h, H (CP-even), A (CP-odd), 𝐻 +/− ; h–H mixing, “the aligment (decoupling) limit”  h125 = h SM + doublet + scalar singlet (r/c) – 2HDM+S or N(ext/non-minimal)2HDM, flavor conserving 4 types (type II –NMSSM), 7 physical states, one is the pseudoscalar  2HDM+a in the simplified description
 SM + 2 doublets – 3HDM etc.
and non-SM style (SM: isosinglet and isodoublet reps. under SU(2) weak symmetry group). Then how?
 isotriplet representations of SU(3) for Higgs fields (Georgi-Machacek model etc.)…

Bright experimental signatures: extra Higgs states, neutral and (doubly)charged, CP-odd and CP-even ones, lighter andheavier than the SM Higgs h125

Also: gauge portal  the (axial)vector mediator and double portal  both vector + scalar mediators
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The simplest s-channel DM: (axial)vector mediator V/AVJHEP 05 (2020) 033

One DM particle (spin-1/2), one mediator + SM, fully visible decay
V/VA

2gq,lgq
Mmed3 𝑔𝑞′ 𝑀𝑚𝑒𝑑
Γ𝑚𝑒𝑑 =≃2𝜋(18𝑔𝑞2 + 1)𝑀𝑚𝑒𝑑
12𝜋mediator on/off-shell production, dijet/dilepton FS A cross section as a function of the 3 parameters : Mmed, gq, gl mDM = 1 GeV (can differ)
 limits on gl from DY (the V mediator): gl ≤ 0.01
𝑔𝐵′
 Universal quark coupling: 𝑔𝑞 = 6𝑔𝑞′ =𝑔𝑞
1 + 1Τ 3𝑁𝑞 (𝑀𝑚𝑒𝑑 )𝑞𝑞2

𝑁𝑞 (𝑀𝑚𝑒𝑑 )=෍ 1−4𝑞

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General dijet results: CMS + ATLAS (also CDF, UA2, precision Z0 and Υ widths)
CMS EXO summary plots

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S/PS limits combined: Jet/V(qq)/Z(ll)/t(𝑡𝑡) + 𝐸𝑇𝑚𝑖𝑠𝑠
Model non-specific interpretation
CMS EXO summary plots

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ATLAS: combination of collider and DD
constraints on DM (LHCP 2020)
interpretation for the leptophobic and leptophilic
V mediator, σSI

leptophobic

A comparison of the inferred limits with theconstraints from direct-detection experimentson spin-independent WIMP-nucleon scatteringcross- section

leptophilic
𝜎𝑆𝐼=2𝑓 2 (𝑔𝑞 )𝑔𝜒2 𝜇𝑛𝜒
4𝜋𝑚𝑚𝑒𝑑See a talk by Fady Bishara on EFT for
DD experiments and collider data decoding!

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LHCP2020

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ATLAS: combination of collider and DD
constraints on DM (LHCP 2020)
interpretation for the leptophobic and leptophilic
AV mediator, σSD

leptophobic

leptophilic
A comparison of the inferred limits with the constraints fromdirect-detection experiments on spin-dependent WIMP-nucleon
scattering cross- section
2𝜎𝑆𝐷

See a talk by Fady Bishara on EFT for
DD experiments and collider data decoding!

M. Savina, JINR, Russia=23𝑓 (𝑔𝑞 )𝑔𝜒2 𝜇𝑛𝜒
4𝜋𝑚𝑚𝑒𝑑LHCP2020

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Inelastic dark matter at the LHC/LLP
https://arxiv.org/abs/1901.04040
 Dark photon Heavy neutral leptons (quarks)
 Dark GB and/or Higgs(es)…
 Higgs/GB/gluon/SUSY portals
 (Asymmetric DM/Baryogenesis)
Dark SUSY
Dark QCD
 Twin Higgs
 ALPs (CP-violation)…
DS: small couplings, compressed spectra, large hierarchy
 large cτ
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Dark photon, prompt/displaced jets
The coupling to SM particles
proportional to electric charge

1 or 2 loops: naively 10−5 ≲ 𝜖 ≲ 10−3𝜶′ = 𝝐𝟐 𝜶𝑬𝑴

LLP

Not only LLP (1): dark photon in VBF and Z(ll)H(𝛾𝛾𝐷 )“Standard” (non-LLP) analyses:
 Prompt, resolved decay, γ + MET
 Associated ZH production andpartially invisible (semi-invisible)
H decay ℬ 𝐻 → 𝑖𝑛𝑣𝑖𝑠𝑖𝑏𝑙𝑒 + 𝛾 ≤ 5%
 in SM ℬ 𝐻 → 𝑍𝛾 → 𝜈𝜈𝛾 = 3 × 10−4
 Bckgr. from WZ, ZZ, WW, tVBF

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ZH

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Not only LLP (2): light narrow vector resonance ZD -> 𝜇𝜇
𝑈 1 𝐷 × 𝑈 1 𝑌 , mixing in a gauge sector with a parameter ε:𝜀ℒ𝑔𝑎𝑢𝑔𝑒 𝑚𝑖𝑥𝑖𝑛𝑔 = 𝐵𝜇𝜈 𝑏 𝜇𝜈2

 Search for new light spin-1 resonance ZD produced on the LHC via mixing with ordinary SM weak bosons.
 Prompt, collimated decay, LJPhys. Rev. Lett. 124, 131802 (2020)
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Emerging jets/dark showers
Dark QCD

 One of the most striking DM-targeted signatures(Dark QCD  dark showers)
 Tracks start near the edge of the tracker, in the
ECAL and HCAL and even in the inner muon stations
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Disappearing tracks

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