Exotic physics signatures at CMS

Amandeep Kaur(on behalf of CMS collaboration)

20th Lomonosov Conference on Elementary Particle Physics
August 19-25, 2021

Amandeep Kaur (CMS) (Lomonosov 2021)

Exotic physics signatures at CMS

August 19-25, 2021

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Introduction• CMS (Compact muon solenoid) : a multipurpose detector atthe LHC ring resulted in the discovery of Higgs Boson in2012• With successful data taking during Run-II and having several

upgrades for implementing fast electronics, CMS has recordedup to ~139 fb−1 of data from 2016-2018 at 13 TeV• This led to more precise SM measurements and better
understanding of standard model physic• Opened doors to explore rare physics signatures beyond
standard model physics

CMS Average 3ileuS (SS,0s 13 TeV)

5ecRrded /umLnRsLty (pb1 /1.00)

6000

2015-2018

6000

5000

4000

5un II: <µ>34

2018: <µ>372017: <µ>38

2016: <µ>27

2015: <µ>

13

3000
pp
in (13 TeV) )8(.( mb2000

1000

20 Exotic physics signatures at CMS
s2000

1000

4060

800ean number RI LnteractLRns per crRssLng 

4000

300000Amandeep Kaur (CMS) (Lomonosov 2021)

5000

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10002 //2323

Why looks for exotic signatures?
•Standard model successfully explains the structure ofmatter and the forces acting between them. Still, it
fails to answer many important questions• Inclusion of the forth fundamental force i.egravitational forc
• Why only 5% of matter made of ordinary SM
particles• Why there are only three families of quarks andleptons• Is there a more fundamental theory of which theStandard Model is a low energy approximation?

To answer such questions , new models beyond standard model have evolved with time anpredicts "new phenomena" at the "TeV" scale
August 19-25, 2021d

Exotic physics signatures at CMS:e?

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What do we look for Beyond SM?
New resonance ?

Dark matter ?

Long lived particles ?

Amandeep Kaur (CMS) (Lomonosov 2021)

New quarks?

Exotic physics signatures at CMS

August 19-25, 2021

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Wγ resonancesNEW

CMS : arXiv:2106.10509
Full Run 2 dataset• Hadronic decays of W bosons leading to single

large-radius jet (AK8) with two sub-jet• Boosted jet topology due to high Lorentz boost ofthe W boso
• “Soft drop” (SD): jet grooming algorithm toremove soft, wide-angle radiation coming mainly
from QCD

No signi cantexcess oversmoothly fallingbackground isobserved

Considered both spin
hypothesis
benchmark heavy
scalar (vector) triplet
bosons with masses
between 0.75 (1.15)
and 1.40 (1.36) TeV
are excluded
at 95% CL

Model independent limits

Excess around 1.58 TeV with local signi cance of 2.8 σ
is examined to be a statistical uctuation in dataExotic physics signatures at CMS
sfiflnfi

Amandeep Kaur (CMS) (Lomonosov 2021)

August 19-25, 2021

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CMS : arXiv:2103.02708

ee & μμ resonances

Full Run 2 dataset• Search for Spin-1particles and Spin-2 graviton• Lepton avor universality tested at TeV scale by comparing the μμ andee mass spectra NEW

Most stringent limits to date on themasses for various spin-1 particles,
spin-2 gravitons in the RS modelee channel

Lower mass limits of 5.15 (4.56) TeV
are set at Z′SSM(Z′ψ ) model

Lepton avor universality Test
Lower mass limits of
2.47–4.78 TeV are set
for Spin-2 gravitons inRS modelNEW

Exotic physics signatures at CMSsfi

fl￼

Amandeep Kaur (CMS) (Lomonosov 2021)
fl￼

No signi cantdeviation from theSM expectation ofunity is observed
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CMS : PAS-EXO-20-007

Trijet resonances : GKK → ggg

NEWFull Run 2 dataset
gM(R1) ≥ 2TeV, M(R2)/M(R1) ≤ 0.2• First LHC results for a trijet resonance with a boosted
dijet and a single je• KK gluon (R1) decays into 3 SM gluons (P1, P2and P3)

ϕvia a radion (R2)(spin-0)

gGKK• Boosted dijet reconstructed as a single jet with twobody jet sub-structure

Boostedg

No statistically signi cant excesses above the background predictions are observed.

Preliminary

Background fit
Signal M(R )=2.9 TeV ρm=0.14
11data - fit
uncertainty

10−1

420−2−4210

MR2 = Mϕ = 0.4 TeV

138 fb-1 (13 TeV)

0.2

CMS

R1= GKK R2= φ : JHEP 05 (2017) 078
ggrav = 6.0 g= 3.0

Preliminary

10−1GKK0.18

Observed exclusion (95% CL)
Expected exclusion (95% CL)

0.16

10−2

Excluded (95% CL)
CMS Dijet: JHEP 05 (2020) 033

0.14
2500

3000

10−3

3500

0.1210−4

2500

3000

3500

mjj [GeV] 

tfi

Amandeep Kaur (CMS) (Lomonosov 2021)

0.1
2000

3000

Exotic physics signatures at CMS

4000

5000

6000

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95% upper limit on σ(R1) x BR(R2+g → 3g) [pb]

Data

1102

CMS

Comparison of GKK → ϕ + g → ggg and GKK → qq̄
ρm= M(R )/ M(R )Weighted Events / GeV

138 fb-1 (13 TeV)

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M(R1) [GeV]

August 19-25, 2021

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CMS : PAS-EXO-19-007

Heavy charged boson (W′ → ℓν)

Full Run 2 dataset• W′ decaying to e/μ + MET is probe• Single high pT lepton back-to-back with pTmiss
difference between lepton pT and• Angular
miss
misspT(Δϕ(pT , pT

Similarly e channel) ∼ 0.8π

• MT (ℓ, MET ): Final t variable
Effective eld theory (EFT) interpretations quantify potential deviations fromSM expectations through the oblique electroweak W parameteFirst constraints on W and Y parameters
No signi cant deviation from the SM background is observed
σ × Β (fb)

137 fb (13 TeV)105

CMSPreliminary

Observed

e,µ+pmissT410

Fit results using
2017+2018 data :σ SSM W' NNLO

−5W = − 12+5−6 × 10Expected
310± 1 s.d.
± 2 s.d.

102

best exclusion limit
obtained is 5.7 TeV on themass of a sequential
standard model W′ boson

10
110−1
10−2

1000

2000

3000

4000

5000

MW' (GeV)

101 fb-1 (13 TeV)2015

CMS Preliminary

Allowed region:e, µ + pmiss

LEP I-II, 2 s.d.

T

CMS Observed

10± 1 s.d.
± 2 s.d.

5SM0−5−10−15−20−25

6000−20−15−10−505 

Exotic physics signatures at CMSrd)

fififi￼

Amandeep Kaur (CMS) (Lomonosov 2021)

101520254W × 10￼

￼

Y × 104-1

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Leptoquark searches (LQs)• LQ appears in many BSM models to answer the question: Whysame number of generation for leptons and quark• Leptoquarks carry both lepton and baryon numbe• carry fractional electric charge (+2/3e, -1/3e: up/down types)• decay in lepton-je• Motivated by models such as grand uni ed theories, technicolor
models, compositeness scenario and R-parity violatingsupersymmetry

provide an explanation fora series of anomalies
observed in the measurement of B meson decays incharged-current (b → cℓv) and neutral b (b → sℓℓ)
processes observed by Babar, Belle and LHCbs r

Exotic physics signatures at CMS
fit

Amandeep Kaur (CMS) (Lomonosov 2021)

August 19-25, 2021

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CMS : arXiv:2012.04178

Probing for Leptoquarks

Full Run 2 dataset• Third generation vector leptoquarks : pair + single production mode
• Couples to a top quark plus a τ lepton (tτ) or a bottom quark plus a neutrino (bν, scalar LQ), or else totν or bτ (vector LQ), leading to the nal states tτνb and tτν• high pTmiss, high HT, one hadronic top candidate and one hadronic τ

Major backgrounds: real top production checked in control
region and backgrounds from misidenti ed τ from data

hadronically decaying top
quark reconstructed in themerged topology

hadronically decaying top
quark reconstructed in theresolved topology

Lower limits at 95% CL are set on the LQ massin the range 0.98-1.73 TeV, depending on the LQ
spin and the LQ-lepton-quark vertex coupling λ,and assuming equal branching fractions for thetwo LQ decay modes consideredfiRegions to the leftof lines areexcluded!!

s

Exotic physics signatures at CMS
fi

Amandeep Kaur (CMS) (Lomonosov 2021)

Similarly for k = 0

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CMS : PAS-EXO-20-003

Exotic Higgs decays (ZH → ZSS → 4ℓ4b)

Full Run 2 dataset• Targeting “exotic decays” to Long Lived particles produced in`association with Z bosonp• Z decays to ee or μμ providing sensitivity to light (<15 GeV) LLPs
• Prompt dilepton + ≥ 2 displaced jets with hits in tracker volume`Zff
fSh

Most stringent constraints on Higgs decaying to light (< 15GeV) LLPs → bb̄ p

Sf displacedjets

H → SS branching ratio is constrained to be below 5–10% for proper decays lengths of 10–100 m
and masses between 40 and 55 GeV117 fb-1 (13 TeV)

01234Data*Z/ γtt+tOtherBackground pred.

567No signi cantdeviation from theSM background isobserved
Signal region

1.750− 1.75− 3.5

VR1 VR2 VR3 VR4 VR5 VR6 VR7Ndis≥2j fiAmandeep Kaur (CMS) (Lomonosov 2021)-Observed limit (95% CL)
Median expected limit

S → d d¯103102mS = 15 GeV

mS = 40 GeV

mS = 55 GeV

68%
expected

68%
expected

68%
expected

10110−110−2SR

Similarly

104

pp → ZH → Z(l+l ) H(SS); S → bb (100%)

110102103

S proper decay length [mm]Exotic physics signatures at CMS

August 19-25, 2021
m3.5ZH; H→ SS; S→ bb; cτS = 20 mm
Β (H → SS) = 20%
MS = 55 GeV
MS = 15 GeV Data - pred.
σData1012
10 111010109
108107106105
104
103
102
1010
110−−2110−310117 fb-1 (13 TeV)CMS Preliminary
95 % CL Upper Limit on BR(H → SS)

CMS Preliminary
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CMS : arXiv:2107.04838

Exotic Higgs decays (H → SS → 4j)rϕ plane
S → bb̄

ME3/2 ME4/2

Steel

0.80.7600 MB30.6500 MB24000.5MB1Solenoid

0.40.3Steel500 600

700800

HCAL

100
400

ME4/1

300200Signal Efficiency

ME2/20.20.1

900 1000 1100095% CL Limit on BRz decay position [cm]1137 fb-1 (13 TeV)CMS Preliminary

10−1

10−2

S → τ+τ-CSC Hits

10−3

Green lines : tracks
Yellow lines : jets
Red arrow : MET direction
Red and Blue cones : ECAL and HCALenergy deposits)

mfl

Amandeep Kaur (CMS) (Lomonosov 2021)
fiME1/3

ME3/1

No signi cant deviation from the SM¯ bb̄ and τ τ̄background is observed in d d,MB4ME2/1• Clusters are built in the CSCs with [-5, 12.5] ns cluster timing

700

ME1/2

calorimeter (4 layers

CMS Simulation Preliminary

ME1/1• Magnetic ux-return yoke (steel) + CSC used as a samplingr decay position [cm]• First CMS search for long lived “hadronic showers” in theendcap muon syste

Full Run 2 dataset

mS = 7 GeV± 1 σ Expected

Median ExpectedmS = 15 GeV
mS = 40 GeV
mS = 55 GeV± 1 σ Expected± 1 σ Expected± 1 σ Expected10−110Observed

10−4 −210

Exotic physics signatures at CMS

1102August 19-25, 2021

103104cτ [m]

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Exotic Higgs decays → displaced jets

CMS : arXiv:2012.01581
Full Run 2 datasetq• Distinctive topology: pair of jets originating at a secondary vertex• Models targeted : LLP decaying to q-qbar, Exotic decays of Higgs: gg→H→2S, S→qqp

Sq

SqH(cτ ∼ 1mm to 1m)

pLong Lived Scalarsq• A dedicated secondary vertex reconstruction is performe• Dominant background : QCD multije• Gradient Boosted decision tree (GBDT) which includes variables likebranching fractions (>1%) are excluded
for cτ0 between 1 and 340 mm withmS ≥ 40 GeV (for light avor quarks)

σ/ σSM(gg→H)

vertex track multiplicity, signed IP2D and Lxy
132 fb-1 (13 TeV)

107

Preliminary

105

Median expected
Observed

104

gg → H, mH = 125 GeV

3

H → SS, S → dd

2

Similarly for bb̄

1010branching fractions (>10%) are excluded
for cτ0 between 1 and 530 mm
with mS ≥ 40 GeV (for bb̄)

95% CL upper limits

CMS106mS = 15 GeVmS = 40 GeVmS = 55 GeV

10110−110−210−3Signal region

10−4110102103

cτ0 [mm]dt 

Exotic physics signatures at CMS flAmandeep Kaur (CMS) (Lomonosov 2021)

August 19-25, 2021

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CMS : PAS-EXO-20-014

Probing for very low mass bosons

Scalar resonance ϕ• Dedicated dimuon trigger stream with low transverse
momentum thresholds to select displaced muons withtransverse displacement range Ixy < 11cm from theinteraction poin
• Explored inaccessible phase-space at low dimuon mas• Bump hunt in mass range : 0.3 - 50 Ge• Most stringent constraints to date on the BSM signal
models in a wide range of signal mass and lifetime
hypotheses
403530

two isolated muons

2015

4.8

BK ⇤0dd

On shell long lived resonance in the decay ofB-hadron

4.9

5

5.1

5.2

x

CMS Preliminary
10−6

φ−7

10

10−8

4.9

5

5.1

5.2

10−10

x
4.8

4.9

55.1

0.4

Dimuon mass [GeV]

0.5s

Exotic physics signatures at CMS
VtMedian expected limit
68% expected
95% expected

10−11

5.2

Amandeep Kaur (CMS) (Lomonosov 2021)

Observed limit (95% CL)

known SM
resonance

4.8101 fb-1 (13 TeV)

pp → B → φ X → 2µ X (cτ0=100 mm)

10−9fisW+0known SM resonance

Data/pred.

Vtsbknown SM resonance

5Data - pred.
σData

Vtbknown SM resonance10420−2−4µt

Limits set for cτ0ϕ : 1 mm, 10 mm and 100 mm

ZD

25

1.4
1.2
10.80.6

displacedmuons

No signi cant excess over smoothly falling background is observed

Data [0.2 < lxy (cm) < 1.0, 0 < p (GeV) < 25, 2 iso. µ]
TBackground pred. (fit)
ZSignal (m = 5 GeV, cτ 0 D=1 mm) [× 5]0µ+101 fb -1 (13 TeV)

B (B → φ X) B (φ → µµ)

Events/ 0.0055 GeV

CMS Preliminary

2017-2018 dataset

0.6

0.7 0.8 0.9 1

2August 19-25, 2021

345mφ [GeV]

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To Summarize…
• Wide range of searches with all possible nal states for exotic signatures at CMS probing in
multi-dimensional phase spac

• Many new searches and results with Run2 dat• Rise in new techniques and tagging algorithms for Run3 (going to start next year
• New tools using ML are in practice now!
• Excited to look for “Exotic signatures” with upgraded detector with advanced technology

SM

August 19-25, 2021)

afi

Exotic physics signatures at CMS!

eAmandeep Kaur (CMS) (Lomonosov 2021)?

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Additional Slides

Amandeep Kaur (CMS) (ICPPA-2020)

Exotic searches by ATLAS and CMS

September 6, 2020

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EXO Summary plot

Amandeep Kaur (CMS) (Lomonosov 2021)

Exotic physics signatures at CMS

August 19-25, 2021

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