search for new physics with dijet angular...search for new physics with dijet angular distributions...
TRANSCRIPT
Search for New Physics with Dijet
Angular Distributions
USLUA Annual Meeting Fermilab, Batavia, IL 1-3 Nov. 2017
Jingyu Zhang University of Illinois at Chicago
(on behalf of the CMS collaboration)
• Probe parton-parton scattering angle • New Physics will change the χdijet distribution at low χdijet at high Mjj
2
χdijet = e|y1−y2| ~ 1+ | cosθ
* |1− | cosθ* |
Dijet Angular Distributions
Jingyu Zhang Nov-3-2017
• Quark Contact Interactions – 4 fermion contact interactions (CI) term – The quark compositeness
• Large Extra Spatial Dimension (ADD Model) – Proposed to solve the hierarchy problem – The plank scale in the 4+n dimensional space ~ TeV – Virtual Kaluza-Klein graviton exchange processes
• Quantum Black Holes – Two benchmark quantum black hole scenarios: ADD with nED = 6 and Randall-Sundrum (RS) with nED = 1
• Dark Matter Model – Dark mater particles interact with quarks via a spin-1 mediator – 4 parameters in the model: mediator mass (MMed), dark matter mass (mDM), quark coupling (gq), and dark matter coupling (gDM) – Search for Dark Matter mediator
New Physics Models
Mono-X channel
Dijet channel
Z'
Z '
Jingyu Zhang Nov-3-2017 3
4 Nov-3-2017 Jingyu Zhang
Data Analysis
• Event Selection – At least two AK4 jets with pT > 30 GeV
–
– y < |2.5|
• Data are unfolded to particle level
– Correct effect of event migrations between Mjj and χdijet bins due to finite jet pT resolution
– Data will be compared to theoretical predictions at particle level
y* = 12| y1 − y2 |<1.39yboost =
12(y1 + y2) <1.11
1< χdijet <16
dijetχ
2 4 6 8 10 12 14 16
dije
tχ
/ddi
jet
σ d
dije
tσ
1/
0.050.1
0.150.2
0.25
0.3
> 6.0 TeVjjM
DataNLO QCD+EW prediction
(CI) = 13 TeV+LLΛ
(GRW) = 10 TeVTΛ
= 6 ADD) = 8 TeVED
(nQBHM = 1.0) = 4.5 TeVq (DM gMedM
Preliminary CMS (13 TeV)-135.9 fb
dijetχ
2 4 6 8 10 12 14 16
0.050.1 < 6.0 TeVjjM5.4 <
dijetχ
2 4 6 8 10 12 14 16
0.050.1 < 5.4 TeVjjM4.8 <
dijetχ
2 4 6 8 10 12 14 16
0.050.1 < 4.8 TeVjjM4.2 <
dijetχ
2 4 6 8 10 12 14 16
0.050.1 < 4.2 TeVjjM3.6 <
dijetχ
2 4 6 8 10 12 14 16
0.050.1 < 3.6 TeVjjM3.0 <
dijetχ
2 4 6 8 10 12 14 160.05
0.1 < 3.0 TeVjjM2.4 <
5
Results
• Measured distributions are in agreement compare with QCD+EWK predictions – Largest upward fluctuations are found to be in the
highest and 4th highest mass bin with ~2.0 sigma significance
• Observed (expected) limits for New Physics Models – Contact interactions
• Λ+ : 13.1 (15.2) TeV • Λ- : 14.7 (17.3) TeV
– KK graviton exchange scale: • ΛT : 10.6 (12.1) TeV
– Minimum quantum black hole masses: • ADD QBH: 8.3 (8.7) TeV • RS QBH: 6.0 (6.5) TeV
Nov-3-2017 Jingyu Zhang
CMS-PAS-EXO-16-046
6 Jingyu Zhang
[GeV]MedM2500 3000 3500 4000 4500 5000 5500 6000
qg
0
0.2
0.4
0.6
0.8
1
1.2
1.4
Med
/MΓ
0.1
0.2
0.3
0.4
0.5
0.60.70.80.91
=1.0q
g
= 1.0DM
= 1 GeV, gDM mVector/Axial-Vector Mediator
95% CL upper limitsObservedExpected
σ 1±Expected σ 2±Expected
Preliminary CMS (13 TeV)-135.9 fb
CMS-PAS-EXO-16-046
• The >1 sigma access for MMed>4.5 TeV is due to the upward fluctuation in 4.2-4.8 and 6.0-13.0 TeV mass bins in the measured distributions
Dark Matter Interpretation
Nov-3-2017
7
Dark Matter Interpretation
• Limits for mDM vs MMed • For gq=1.0 and gDM=1.0, quark
decay dominate such that mDM has little dependence on MMed
• Limits are compared to constraints from the cosmological relic density of DM
• Also compared to the limits from monojet search with 12.9 fb-1
(CMS-EXO-16-037) • This analysis extend the current
CMS limits for gq=1.0 and gDM =1.0
CMS-EXO-16-046 [GeV]MedM
0 1000 2000 3000 4000 5000 6000 7000 8000 9000
[GeV
]D
MM
0
500
1000
1500
2000
2500
3000
DM
= 2 x m
MedM
0.12≥ 2 hcΩ
= 1.0DM
g = 1.0qg
& Dirac DMVector Mediator
CMS 95% CL Upper Limits
)-1Dijet Chi Observed (35.9 fb
)-1Dijet Chi Expected (35.9 fb
)-1 Observed (12.9 fbqqDM + j/V
)-1 Expected (12.9 fbqqDM + j/V
Preliminary CMS (13 TeV)-112.9 & 35.9 fb [GeV]MedM
0 1000 2000 3000 4000 5000 6000 7000 8000 9000
[GeV
]D
MM
0
500
1000
1500
2000
2500
3000
DM
= 2 x m
MedM 0.
12≥ 2
hcΩ
= 1.0DM
g = 1.0qg
& Dirac DMAxial-Vector Mediator
CMS 95% CL Upper Limits
)-1Dijet Chi Observed (35.9 fb
)-1Dijet Chi Expected (35.9 fb
)-1 Observed (12.9 fbqqDM + j/V
)-1 Expected (12.9 fbqqDM + j/V
Preliminary CMS (13 TeV)-112.9 & 35.9 fb
Jingyu Zhang Nov-3-2017
8 Jingyu Zhang
Dark Matter Interpretation
[GeV]MedM0 1000 2000 3000 4000 5000 6000
' qg
0
0.2
0.4
0.6
0.8
1
1.2
1.4 Med
/MΓ
0.1
0.2
0.3
0.40.50.60.70.80.91
=10%Med/MΓ'=0.4, qg
=50%Med/MΓ'=1.0, qg
CMS 95% CL Upper LimitsDijet Chi ObservedDijet Chi ExpectedDijet Resonance ObservedDijet Resonance ExpectedBoosted Dijet Resonance ObservedBoosted Dijet Resonance Expected
= 0DMΓVector/Axial-Vector Mediator
Preliminary CMS (13 TeV)-135.9 fb
• Limits for the DM mediator that only decays to quarks (2mDM > MMed) obtained from CMS dijet searches: • Boosted dijet resonance search (EXO-17-001) • Dijet narrow resonance search (EXO-16-056) • Dijet angular analysis (EXO-16-046)
• The sensitivity for dijet resonance searches fade away above = 0.4 • Dijet chi analysis is sensitive to large value of quark couplings and mediator widths
CMS-EXO-16-046
gq '
Nov-3-2017
9 Jingyu Zhang
Conclusions
• Dijet angular distributions unfolded to particle level are measured using 35.9 fb-1
– Results are in good agreement with QCD+EW predictions
• Limits for New Physics models are extracted – Limits on CI, ADD, and QBH models:
• ΛLL+ : 13.1 TeV • ΛLL- : 17.4 TeV • ADD ΛT : 10.6 TeV • ADD nED=6 MQBH: 8.3 TeV • MMed (gq=1.0 and gDM=1.0): 2.0-5.0 TeV
• Documentation: CMS-EXO-16-046
Nov-3-2017
10 Jingyu Zhang
Back Up
Nov-3-2017
11 Jingyu Zhang
The CMS Detector
Nov-3-2017
Run 1 Results
12 Jingyu Zhang
4.2 TeV
0.25 TeV
Mjj Limits on CI at NLO and ADD Phys.Lett.B746(2015)79 • Λ+: 9.0 TeV • Λ- : 11.7 TeV • ADD (GWR): 7.1 TeV • ADD (HLZ): 5.0 TeV
(nED=6)
Limits on CI for at LO PhysRevLett.106(2011)201804 • Λ+: 5.6 TeV • Λ-: 6.7 TeV
Limits for CI at NLO (JHEP05(2012)055) • Λ+: 7.5 TeV • Λ-: 10.5 TeV
Nov-3-2017
dijetχ
2 4 6 8 10 12 14 16
dije
tχ
/ddi
jet
σ d
dije
tσ
1/
0.05
0.1
0.15
0.2
> 4.8 TeVjjM
Data
NLO QCD+EW
= 6 ADD) = 7.5 TeVED
(nQBHM
(CI) = 11 TeV+LLΛ
(GRW) = 10 TeVTΛ
dijetχ
2 4 6 8 10 12 14 16
0.05
0.1 < 4.8 TeVjjM4.2 <
dijetχ
2 4 6 8 10 12 14 16
0.05
0.1 < 4.2 TeVjjM3.6 <
dijetχ
2 4 6 8 10 12 14 16
0.05
0.1 < 3.6 TeVjjM3.0 <
dijetχ
2 4 6 8 10 12 14 16
0.05
0.1 < 3.0 TeVjjM2.4 <
dijetχ
2 4 6 8 10 12 14 160.05
0.1 < 2.4 TeVjjM1.9 <
(13 TeV)-12.7 fb
CMS
Previous Results • Accepted by JHEP (arXiv:1703.09986)
• Observed (expected) limits for Contact Interactions, Extra Dimensions, and Quantum Black Holes – Contact Interactions
• Λ+ (NLO): 11.5 (12.1) TeV • Λ- (NLO): 17.4 (23.9) TeV
– Extra Dimensions • ΛT (GRW): 9.4 (9.8) TeV
– Quantum Black Holes • ADD QBH: 7.8 (7.7) TeV • RS QBH: 5.3 (5.3) TeV
• Analysis extended to higher Mjj using 35.9 fb-1 of data
13 Jingyu Zhang
arXiv:1703.09986
Nov-3-2017
ATLAS 13 TeV Results
14 Jingyu Zhang
• https://arxiv.org/abs/1703.09127
• Expected limits set for Contact Interactions – Sensitivity on CI
• Λ+ : 15.0 TeV • Λ- : 28.3 TeV
Nov-3-2017
15 Jingyu Zhang
Theoretical Predictions • 13 TeV AK4 NLO QCD calculation with EWK correction
– QCD scale uncertainty from 6 variations of µr and µf
– PDF uncertainty from CT14 PDF set – EWK correction is 5% in highest mass bin
• CI predictions are calculated at LO and include QCD corrections at NLO – Scale and PDF uncertainties from CI have been taken into account and combined with
those from NLO QCD
• Leading order ADD + leading order ADD and QCD interference predictions in GWR from Pythia8
• Quantum Black Hole production predictions from QBH generator version 3.0
• Dark Matter predictions from MadGraph – Samples with different MMed and gq are generated with fixed values of MDM = 1 GeV and
gDM=1.0
Nov-3-2017
16 Jingyu Zhang
Summary of Systematic Uncertainties
• Experimental uncertainty dominated by statistical uncertainty • Theoretical uncertainty dominated by QCD scale uncertainty
Source of uncertainty 2.4 < Mjj < 3.0 TeV Mjj > 6.0 TeVStatistical 0.7% 27%Jet energy scale 3.6% 9.2%Jet energy resolution (core) 1.0% 1.0%Jet energy resolution (tails) 1.0% 1.5%Unfolding, modelling 0.2% 1.5%Unfolding, detector simulation 0.5% 1.0%Pileup <1% <1%Total experimental 4.1% 29%QCD NLO scale (6 changes in µR and µF) +8.5%
3.0%+19%5.8%
PDF (CT14 eigenvectors) 0.2% 0.6%Non-perturbative effects <1% <1%Total theoretical 8.5% 19%
CMS-PAS-EXO-16-046
Nov-3-2017
17 Nov-3-2017 Jingyu Zhang
Limits
• The asymptotic LHC-style CLs method is used for limit calculation • Observed limits smaller than expected due to upward fluctuation in the measured distributions
Model Observed lower limit (TeV) Expected lower limit (TeV)L+
LL/RR (NLO) 13.1 15.2 ± 0.9L
LL/RR (NLO) 17.4 23.9 ± 3.0L+
VV (NLO) 15.1 17.3 ± 1.0L
VV (NLO) 22.2 31.2 ± 3.8L+
AA (NLO) 15.2 17.3 ± 1.0L
AA (NLO) 22.1 31.0 ± 3.8L+
(VA) (NLO) 9.1 11.7 ± 1.0L
(VA) (NLO) 9.3 11.9 ± 1.1ADD LT (GRW) 10.6 12.1 ± 0.9ADD MS (HLZ) nED = 2 11.4 13.3 ± 1.0ADD MS (HLZ) nED = 3 12.6 14.4 ± 1.1ADD MS (HLZ) nED = 4 10.6 12.1 ± 0.9ADD MS (HLZ) nED = 5 9.6 10.9 ± 0.8ADD MS (HLZ) nED = 6 8.9 10.2 ± 0.8QBH MQBH (ADD nED = 6) 8.3 8.7 ± 0.3QBH MQBH (RS nED = 1) 6.0 6.5 ± 0.4DM Vector/Axial-Vector MMed 2.5–5.0 2.5–5.2
CMS-PAS-EXO-16-046