Search for Resonance inphoton+jet final state using
CMS Data
Jyoti Babbar
Panjab University, Chandigarh, INDIA
on behalf of CMS Collaboration

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

Introduction
๏ Standard Model gives an extraordinary insight tofundamental nature of matter, but yet can notexplain everything in the universe๏ Beyond Standard Model searches : why only three

generations of quarks and leptons??
➡ Models predict the quarks and leptons are notfundamental and there is an underlying
structure for the fermions families.

Gravitons escapes
into multi D space๏ Outstanding enigma of particle physics: thehierarchy problem, i.e. the large diﬀerence between
the scale of electroweak and the Planck scale➡ The existence of extra dimensions can explainsuch large diﬀerence. Standard Modelconfined to a 3-brane and only gravity
propagates in extra dimensions
Standard Model exists
in 3+1D space time
Jyoti Babbar (CMS)2

Previous Results
A search for new resonances decaying tophoton+jet state with luminosity 137fb-1(2016-2018)
๏ More data leads to more potential for๏Existing results by CMS & ATLAS at √s =13TeV decaying to photon + jet channel :➡ q* and b* are excluded by CMS up to5.5 TeV and 1.8 TeV with 35.8 fb-1
Phys. Lett. B 781 (2018) 390

new signals➡

q* excluded by ATLAS up to 5.3 TeV
with 36.7fb-1 Eur. Phys. J. C (2018) 102➡

ADD and RS1 model of the QBH upto
7.1 TeV and 4.4 TeV by ATLAS withluminosity 36.7fb-1 Eur. Phys. J. C (2018) 102

๏ New techniques implementedCMS Simulation
q*b*ADD
RS10.25a.u

0.2

Phys. Lett. B 781 (2018) 390

0.15

0.1

0.05

012345678

Resonance Mass (TeV)

Jyoti Babbar (CMS)3

Signal Modelling
Composite models
๏qComposite models predicts the substructure ofthe quarks ( light flavor quarks q* and heavy
flavor quarks b*)

q*,b*jet➡ The search for excited light and heavy

quarks signals with coupling multipliers toStandard Model f = 1.0, 0.5 and 0.1 isperformed

Quantum Black Hole models
๏๏๏

The Quantum Black Holes (QBH) which are
the quantum analogs of the black holes canbe produced at the LHC. Due to radiation andexperimental eﬀects it appears as aresonance.

gqq

1QBHjetQBHs are non thermal objects, expected todecay predominantly to pairs of particles
Two well known models of QBH are studied :➡

ADD (with n=6 extra dimensions) and➡

RS1 (with n=1 extra dimension)

Jyoti Babbar (CMS)gq
QBH (RS1)
photon+jet
studied first time in the CMS

14CMS Detector• Photons energy are calibrated in theelectromagnetic calorimeter of CMSdetector with no tracks associatedwith it.

• Jets are reconstructed in Hadron
Calorimeter of the detector

๏ Jets with ΔR < 1.1 between them

are merged together to form wide
jets to account for the final stateradiation.
Jet 1﹜ Wide jet

If ΔR < 1.1
merged together
JetPhoton

Jet 2
Jyoti Babbar (CMS)5SM Backgrounds• The major background to the study is thestandard model photon+jet background,with small contribution from QCD andelectroweak background.
qq,bgq• To reduce the background and improve the• The multi-jet backgrounds

also contributes when π0
decays to two overlapping
photons
๏ To reduce the QCD
background further,Δη(photon, jet) < 1.5 is
imposed.

signal eﬃciency, selections are applied:1

๏ A high pT photon in the barrel region
photonof the detector (|η|< 1.44 )๏ A high pT wide-jet in the central
region of the detector

photon๏ For resonance to exist, photon andjet produced via hard scattering
would decay mostly back to backJyoti Babbar (CMS)

photonphoton6

Analysis Strategy

๏ Distribution after selection
๏ Data/Background agreement for

diﬀerent year (2016-2018) distributions
๏ Similar distribution with 35.8fb-1 and41.7 fb-1 is observed
๏ Data is consistent with SM
expectations
Jyoti Babbar (CMS)

DataWJGJ
QBH ADD = 4.5TeV

105
104

EventsDYQCD
q* = 4TeV

Photon pT

103
102
10
110−110−210−310−4

Data-MC
Data

2
1.50
10.50− 0.5−1− 1.5− 20500

1000 γ500

1000

CMSPreliminary
CMSPreliminary107
Work710Work
106 in Progress
610 in Progress
105

105
104
104
103
103102
102
10101
110−1−11010−210−210−310−310−4102−41.50
1 20.51.50
0 1− 0.50.5−1 0− 0.5
− 1.5−1− 20− 1.5− 20

1500

2000

2500

1500

2000

2500

PT (GeV)γP T (GeV)

58.7 fb-1-1(13 TeV)
58.7 fb (13DYTeV)

Data
Data
WJ
WJ
GJ
GJ ADD = 4.5TeV
QBH
QBH ADD = 4.5TeV

DYQCD
q*QCD
= 4TeVq* = 4TeV

Jet pT

EventsEventsperformed by looking for a bump in
the invariant mass distribution of
the final state particles• Background estimation is done fromdata• MC is used for optimizing theselections and validation with data

Data-MC
Data-MCData
Data• The search for resonance is58.7 fb-1 (13 TeV)CMSPreliminary
710Work
610 in Progress

500
500

1000
jet1500
1000 PT jet(GeV)
1500

2000
2000

2500
2500

3000
3000

500
500

1000
1000

2000
2000

2500
2500

3000
3000

PT (GeV)
jet1500

P T jet(GeV)1500
P T (GeV)

7

Background Modelling• To look for any excess of events, the invariant distribution of photon+jet
is fitted with functional form

137.34 fb-1 (13 TeV)

P1

Functional form :➡ Numerator represents the massdependence of parton distributions➡ Denominator refers to mass dependence ofQCD matrix element.

105

๏ Light quarks (M𝝲+jet = 1TeV and M𝝲+jet =4TeV)
๏ QBH ( ADD M𝝲+jet = 3TeV and RS1 M𝝲+jetADD(3.0 TeV)q*(2.0 TeV, f = 1.0)

310102101210−1−2 − 18×10 1

BackgroundFit to bkg
Fit ± 1 s.d.
Fit ± 2 s.d.

q*(4.0 TeV, f = 1.0)

Bkg-Fitstat. unc.

• Expected signals mass points shapes :RS1(1.0 TeV)

104

• The function is chosen on the basis of fisher
test and Goodness of fit test with p values
significance > 0.05

Workin Progess

10Events/binP0(1 − m/ s)
dσ=dm (m/ s)P2+P3ln(m/ s)

CMS

623mγ +jet [TeV]4567 8

Data is blinded,and MC simulations are used as proxy for Data

= 1TeV )Jyoti Babbar (CMS)8

Systematic Uncertainties
๏

The major systematics contribution comes from the uncertainties onthe parameters in the background functional form.

๏Bias study is also performed to account for the possible bias due tothe choice of the functional form chosen➡ The systematic due to bias is negligible, compared to the statisticaluncertainty of the fit of invariant mass distribution๏

Other Signal uncertainty dominated by photon ID ineﬃciency (10%)
and b quark tagging (14%)

Jyoti Babbar (CMS)

9Results• The expected limits with MC are calculated.
• Expected Upper limits on cross section is measured and :๏ q* is excluded up to 6.0 TeV
๏ b* is excluded up to 2.3 TeV
๏ ADD is excluded up to 7.6 TeVWorkin Progress

CMSPreliminary

10−1

q* → qγ

10−210−3
95% CL limits
Expected
Expected ± 1σ
Expected ± 2σ
Excited quark (f=1.0)−41010−5123

Resonance mass [TeV]

Jyoti Babbar (CMS)

6CMS
Preliminary

710−395% CL limits
Expected
Expected ± 1σ
Expected ± 2σ
Excited b-quark (f=1.0)

11.5

2

2.5

3137.3 fb-1 (13 TeV)Work
in Progress

10−1

10−210−551b* → bγ

10−44

Work
in Progress

10−1

σ × Β [pb]σ × Β [pb]1137.3 fb-1 (13 TeV)σ × Β [pb]1137.3 fb-1 (13 TeV)CMS
Preliminary
BlackHole(ADD) → qγ

95% CL limits
Expected
Expected ± 1σ
Expected ± 2σBlackHole (ADD)

10−2

10−3

10−410−5
3.5

4Resonance mass [TeV]4.55345678

Mth [TeV]

10

Summary๏ The search for excited state of light and heavy flavor ofquarks is performed using CMS data๏ The possibility of Quantum Black hole at the LHC anddecaying to two particle state is also considered.
๏ The expected exclusion limits on signals are calculated,since the Data is blinded till the selections are optimized
from simulations.

Thank you!!!
Jyoti Babbar (CMS)11

Additional Material

Jyoti Babbar (CMS)

12Efficiency Tables
CMSWorkin Progress

0.5

0.4

0.30.2
2016 q*2017 q*2018 q*2016 1b-tag

2017 1b-tag

2018 1b-tag

0.1

12

34

0.6

56

Work
in Progress

Simulation

0.5

0.4

0.3

0.2

0.1
1

Jyoti Babbar (CMS)

Mass (TeV)

CMS

Acceptance * Efficiency• The eﬃciency of the signals after
the selections applied
normalized to 2016 data, 2017
data and 2018 data,
corresponding to the luminosity
35.8 fb-1, 41.7 fb-1 and 58.7 fb-1
respectively.

Acceptance * Efficiency

0.6 Simulation

234

2016 ADD2016 RS12017 ADD

2017 RS12018 ADD

2018 RS15Mass (TeV)

678913

Systematics table

Jyoti Babbar (CMS)

14

Signal, Data and Background
Data : CMS full RunII data
corresponding to luminosity 137.4
fb-1

Signals :๏ q* and b* stimulated withPythia8 generator at theleading order (LO)

Background : Standard Modelphoton+jet background is the major
background, with small contribution
from QCD and Electroweak
processes.

๏ QBH: generated with

QBHv3.0 generator

SMBSMqqq,bgq
Jyoti Babbar (CMS)gg

QBHq*,b*q,b+qq+qgqgq
15

Event Selection
The search for resonance is performed bylooking for a bump in the invariant mass
distribution of the final state particles

58.7 fb-1 (13 TeV)CMSPreliminary
107Work
610 in Progress

Data
WJ
GJ
QBH ADD = 4.5TeV

105
104

Photon pT

Events103

Photons :DY
QCD
q* = 4TeV

102
101𝝲

๏ |η| < 1.44

Jets :

10

10−2
10−3
10−421.50
10.5
0− 0.5−1− 1.5− 20

Data-MCData๏ Photon pT > 240 GeV−1500

1000 γ

500

1000

1500

2000

2500

1500

2000

2500

PT (GeV)γ

P T (GeV)๏ Jet pT > 170 GeV

๏ Heavy flavor quarks (b*) passes the neural

based discriminator

10558.7 fb-1 (13 TeV)
Data
WJGJ
QBH ADD = 4.5TeV

DYQCD
q* = 4TeV

Jet pT

104
103

Events๏ |η|jet < 2.4CMSPreliminary107Work
106 in Progress102

๏ ΔR(photon, jet) > 1.1
๏ Δη(photon, jet) < 1.5๏ Invariant Mass(photon, jet) > 761 GeV

Jyoti Babbar (CMS)

110−1
10−210−310−421.50
10.5
0− 0.5−1− 1.5− 20

Data-MC
Data

Photon + jet selection :

10500

1000

500

1000

jet1500

2000

2500

3000

jet1500

2000

2500

3000

PT (GeV)P T (GeV)

16