quark compositeness study and progress satyaki bhattacharya, sushil s. chauhan, brajesh c. choudhary...
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Quark Compositeness Study and Progress
Satyaki Bhattacharya, Sushil S. Chauhan, Brajesh C. Choudhary
& Debajyoti Choudhury
Department of Physics & Astrophysics
University of Delhi, India
India-CMS Meeting @ BARC
20-21 July 2007
2
Outline
• Status of quark compositeness study.
• Work done at CERN.
• Some preliminary distributions of Gamma + Jet through q* exchange.
• Future Plans.
3
Last India-CMS Meeting in April 2007
• qqbar Diphoton through q* exchange• We presented the final results
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CMS Internal NOTE
• BSM convenenor showed interest to make it as a CMS Internal Note.• The result was presented in the SUSY/BSM meeting at CERN on 8th Jun• Submitted as Internal Note. Waiting for response from referees
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Work done at CERN
• We have already started q* study with CMSSW.
• Currently using CMSSW_1_3_1
• Main focus is on isolation variable e.g, ECAL isolation, HCAL isolation, track isolation or some new variable e.g, Basic Clusters around photon.
∆ We have to provide the .cfg file for qq Diphoton through q*. (Interfacing it as an external process for better maintenance in future). Work is in progress..
∆ To prepare skim for 2 photon+ N Jet study. Work is in progress…..
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q* study for Gamma +Jet final state
• In continuation of qq diphoton through q* exchange.• Feynman diagrams for the signal.
• Feynman diagrams for the backgrounds.
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Matrix Element for qg gamma+Jet via q*
For Standard Parametrization f1=f3=1, n1=n3=1. Is the compositeness scale and Mq* is the mass of q*
By: Prof. Debajyoti Choudhury
SM Piece
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Event Generation with PYTHIA
For generation of events the matrix element has been included in PYTHIA with showering and hadronization effects
Q2 = s-hat and CTEQ5L Cross-Section for q* Signal with PT (hat) > 190 GeV
=Mq* (TeV) ª ( pb )1. 0.5 75.87 2. 0.7 58.78
3. 1.0 47.96 4. 2.0 43.10 5. 3.0 42.59
6. 4.0 42.61
7. 5.0 42.55 x-section decreases with increasing Λ and approaches to SM
cross section. ª For standard parametrization
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Event generation with PYTHIA
Variation with respect to couplings
f1=f3 (pb)
1. 1.0 75.87
2. 0.5 51.64
3. 0.4 48.46
4. 0.3 45.89
5. 0.2 44.04
6. 0.1 42.94
7. 0.05 42.62
Λ=Mq*= 0.5 TeV, n1=n3=1
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Backgrounds
Pt –hat
50-100
GeV
100-200
GeV
200-400
GeV
400-600
GeV
600-1000
GeV
1000-1500
GeV
>1500
GeV
qg 4458 425.3 33.2 1.517 2.22 x 10-1 1.19 x 10 -2 7.6 x 10-4
qqbar 375.4 47.44 5.01 3.15 x 10-1 5.662 x 10-2 3.77 x 10 -3 2.77x 10 -4
gg 1.528 8.01x 10-2 3.08 x 10 -3 7.02 x 10-5 6.33 x 10-6 1.75 x 10 -6 5.81 x 10 -9
Cross Section (pb) for background in different Pt-hat bin
Pt –hat 50-100
GeV
100-200
GeV
200-400
GeV
400-600
GeV
600-1000
GeV
1000-1500
GeV
>1500
GeV
Z+Jet (Z jj)
2.80 6.18 x 10-1 8.61 x 10-2 6.18x 10-3 1.20 x10-3 8.47x 10-5 6.54 x10-6
W+Jet (W jj )
2.54 4.81x 10-1 6.06 x 10-2 4.09 x 10-3 7.39 x10-4 4.68 x10-5 2.99 x10-6
Type-2
Type-1
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Preliminary plots
The Iterative cone algorithm is used for Jet with jet cone size of RJet=0.6, Ptseed≥ 5 GeV.
~ 94% matching between Iterative Jet and Parton Jet (for eta difference < 0.2).
CMS reconstruction algorithm for photon.
Mq*= 0.5TeV
Log scale
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Future Plans
• Prepare “.cfg” files for the signal (qqbarγγ).• Prepare the “skim” files for 2 Photon +N Jet
and give them to production team as soon as possible.
• Complete the Gamma +Jet study at the Generator level, sent it for publication and release as a CMS document.
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Compositeness scale
Compositeness scale:• Λ >> sqrt (s-hat) : Contact interaction• Λ << sqrt (s-hat) : Excited state• Λ ~ sqrt (s-hat) : Model Dependent
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Efficiency after Pt and eta cuts
• Y+jet 1.43 % (1.5 x 10-2 %)
• Box 51.42 % ( 42.84 %)
• Born 62.42 % ( 53.54 %)
For Y+jet :
• Cos (theta) ~1.1 % (Pt and eta)
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Those events where EGamma Super Clusters < Generated EGamma Super Clusters
Generator Level Reconstruction Vs FAMOScont..
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Present Limit on M*
– CDF: M* > 80 GeV (q*q )– CDF: M* > 150 GeV (q* q W )– CDF (All channels): M* >200 GeV – D0 : M*> 200 GeV
• Simulation study: Mass reach up to 0.94 TeV at Tevatron ( 2 TeV, 2 fb-1, q*q-qbar)
• ATLAS Study: upto 6.5 TeV at LHC ( f=fs=1, q*q )
Limits from Tevatron:
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Motivation
• Are quarks fundamental particles? OR Do they have sub-structure?
• Replication of three generation of quarks and leptons suggests the possibility that may have composite structures made up of more fundamental constituents
• Large Hadron Collider (LHC) will explore physics “Beyond the Standard Model” @ the TeV scale
• Excited quark state represents signal for substructure of quarks and physics beyond the SM
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Effects of Different Cuts
Events Type Cut A# events (efficiency)
Cut B# events (efficiency)
Cut C# events efficiency)
Cut A+Cut B+Cut C# events (efficiency)
Signal Events 52.13 ( 88.6 % ) 56.98( 96.87 % ) 56.09( 95.36 % ) 50.79 ( 86.35 % )
Total Background
43.91 ( 6.815 %) 55.32 ( 8.58 %) 63.62 ( 9.87 %)
42.66 ( 6.62 %)
S/B 1.18 1.03 0.88 1.19
+ Jet 6.63 ( 1.10 %) 14.51 ( 2.40 %) 23.49 ( 2.40 %) 6.35 ( 1.05 %)
gg 1.96 ( 85.73 %) 2.17 ( 94.94 %) 2.151 ( 93.96 %) 1.91 ( 83.41 %)
qqbar 35.324 ( 88.84 %)
38.63 ( 97.18 %) 37.98 ( 95.53 %) 34.39 ( 86.51 %)
So far best variables to discriminate the signal from background are,
Cut A: Riso< 0.35, ETsum< 5.0 GeVCut B: Riso< 0.35, Highest Tracks PT < 4.0 GeVCut C: Riso< 0.10, # of Tracks < 2
For L= 1 fb-1
Event Type without isolation cuts Total # of Events for L=1fb-1
Signal 58
Total Background+ Jet
q-qbargg
644
602
38
04
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Effects of Different Cuts …..
Events Type Cut A# events (efficiency)
Cut B# events (efficiency)
Cut C# events (efficiency)
Cut A +Cut B+ Cut C# events (efficiency)
Signal Events
52.13 (88.6% ) 51.11 ( 86.90 % ) 56.09 ( 95.36%) 48.17 ( 81.90 % )
Total Background
43.91 (6.815%) 44.24 ( 6.86 %) 63.62 ( 9.87 %) 40.09 ( 6.22 %)
S/B 1.18 1.15 0.88 1.20
+ Jet 6.63 ( 1.10%) 7.57 ( 1.25 %) 23.49 (2.409%) 5.64 ( 0.93%)
gg 1.96 ( 85.73%) 1.93 ( 84.34 %) 2.151 ( 93.96%) 1.80 ( 78.70 %)
qqbar 35.32 ( 88.84%) 34.74 ( 87.38%) 37.98 ( 95.53%) 32.65 ( 82.12 %)
Cut A: Riso< 0.35, ETsum< 5.0 GeVCut B: Riso< 0.35, Highest Tracks PT < 2.0 GeVCut C: Riso< 0.10, # of Tracks < 2
For L= 1 fb-1
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Confidence Limits
• Earlier we were using LLR as the estimator for Confidence Limits (CL).
• But at 200 fb^-1 all the parameter space was getting excluded!! Did some checks e.g.:
As the mass bin are Gaussian distributed hence both should give same results Yet to understand the whole parameter space exclusion with LLR (May be we
would do it with full GEANT simulation).