Randall Sundrum KK Graviton at CMS

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Randall Sundrum KK Graviton at CMS
Caroline Collard, LLR, Ecole Polytechnique,
France Work in collaboration with M.-C. Lemaire,
P. Traczyk and G. Wrochna
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Overview

• Extra Dimensions Randall Sundrum Model
• Search for RS graviton in the CMS detector
• The CMS detector
• Signal Background
• First Analysis 5 ? discovery limit
• The photon radiation with PHOTOS
• If no signal? 95 CL signal exclusion
• If a signal? Spin-2 analysis
• Conclusions

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Extra Dimensions

• Why?
• Unification of gravitation with other forces.
• Hierarchy problem MEW and MPL

Different models of ED
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Warped ED

• The Randall-Sundrum Model
• only one extra dimension ? 5D Anti-de-Sitter
  Spacetime
• metric e-2kr? ??? dx? dx? r2 d?2
• k ( MPL) AdS5 curvature, r compactification
  radius,
• r ? new coordinate and x? traditional 4D
  coordinates
• Gravity Scale ??MPL e-kr? no hierarchy if
  kr12

SM brane
Planck brane
bulk
r ?
r ? 0
r ? r ?
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Warped ED

• The Randall-Sundrum Model
• Two parameters in the model e-kr? and k/MPL
• Graviton in 5D ? KK graviton excitations in 4D
• Experimental measurement of the 1st KK graviton
• M1 Mn k xn e-kr? with J1(xn)0
• ?1 ?n ? Mn xn2 (k/MPL)2 with ?(open decay
  mode)
• Other parameter choice
• M1 and c k/MPL
• c is related to ?1 and also to the coupling

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Variation of c
0.01 c 0.1
c 0.1 c 0.05 c 0.02 c 0.01
d?/dM
MG
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The CMS detector

• pp collider
• 14 TeV in cms
• Start in 2007
• 1 year _at_ low lumi 10 fb-1
• 1 year _at_ high lumi 100 fb-1

Higgs Discovery and Search for New Physics
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Analysis

• Signal
• ffbar, gg ? G ? ?? (B.R. 4 )
• ffbar, gg ? G ? ee-, ??- (B.R.
  2 )
• Generation with PYTHIA
• Photon Radiation with PYTHIA or PHOTOS
• Detector response with CMSJET (Fast Simulation)

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CMS Performance in CMSJET

• ECAL For electron and ? detection
• Barrel (?lt1.56) ? E/E 3 /vE 0.2/E
  0.55
• Endcap (1.65lt ?lt 3) ? E/E 6 /vE 0.9/E
  0.55
• Tracker For muon detection
• ?p/p 4 vp

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Analysis
CMSJET

• Backgrounds
• For ?? ffbar, gg ? ??
• ( photon-jet ffbar ? g?,
• fg ?f?, gg ? g?
• dijet ff ? ff, ffbar ? ffbar,
• ffbar ? gg, fg ? fg,
• gg ? ffbar, gg ? gg)
• No K factor for ??.
• For ee-, ??- pp ? Z/? ? ll- (Drell Yan)
• K factor 1.38 from comparison between PYTHIA MC
  and CDF data

Events
M?? (GeV)
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MG 1500 GeV, c0.01,Lumi100 fb-1
CMSJET
G ? ??
Events
M?? (GeV)
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5 ? Discovery Limit
CMSJET
100 fb-1
G ? ?? c 0.01
?.B (fb)
MG (GeV)
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MG 1000 GeV, c0.01,Lumi100 fb-1
CMSJET
Difference in resolution for e (Energy in calo)
and ? (Momentum in tracker) gt Different mass
windows
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5 ? Discovery Limit
CMSJET
G ? ee- c 0.01
?.B (fb)
MG (GeV)
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? Radiation with PHOTOS

• Use of PHOTOS to generate ? radiation, in place
  of PYTHIA
• Dependence on the input parameters used in
  PHOTOS
• E? fraction, Double Bremsstrahlung flag,
  Interference flag
• With E? fraction 0.01, Double Bremsstrahlung
  flag T,
• Interference flagF, Mass Limits for 5 ?
  Discovery
• gt Results in agreement!

Lumi PYTHIA PHOTOS
300 fb-1 2300 GeV 2350 GeV
100 fb-1 2000 GeV 2080 GeV
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Use of PHOTOS
Impact of input parameters
CMSJET
RMS 42.44
RMS 40.01
PHOTOS (0.01, F, F)
PHOTOS (0.02, T, T)
Entries
RMS 39.92
RMS 41.32
PYTHIA
PHOTOS (0.01, T, F)
Mee (GeV)
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5 ? Discovery Limit with PHOTOS
Theoretical constraint on curvature
c
G ? ee-
Theroretical constraint for no new hierarchy
CMSJET
MG (GeV)
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If there is no signal

• NS number of expected signal events
• NB number of background events
• Nobsnumber of observed events
• 95 CL Exclusion Limit

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95 CL Exclusion Limit
CMSJET
Excluded
Signal Exclusion at 95 CL
c
R5 lt M52
?? 10 TeV
Region of interest
Photons
MG (GeV)
Muons
Electrons
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If there is a signal

• How to be sure it is a RS Graviton?
• Graviton? not a Z?
• RS model?

CMSJET
MG2000 GeV, c0.01
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Angular Distribution

• Graviton spin 2

CMSJET
pp ? G ? ??- MG1000 GeV c0.1
After ? cut ( ? lt 3.0 for e ? lt 2.4
for ? )
qqbar ? G ? ll 1-3cos2?4cos4?
gg ? G ? ll 1-cos4?
Cos?
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How different from Z?

• Kolmogorov-Smirnov Test
• Rem No ?? mode for Z

M 2000 GeV
CMSJET
Z 1 cos2?
G
For G number of events corresponding to Lumi,
randomly chosen
Cos?
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95 CL Exclusion Limit
Spin 1 rejection with 90 probability at 95 CL
Excluded
CMSJET
Electrons
Leptons
c
R5 lt M52
?? 10 TeV
Region of interest
MG (GeV)
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Detector acceptance
? lt 2.4
? lt 1.5
CMSJET
Cos?
Importance of the pattern recognition in the
endcap regions!
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RS model?
Davoudiasl, Hewett, Rizzo hep-ph/0006041
c1. c0.5 c0.1 c0.05 c0.01
d?/dM
Mll (GeV)
If the 1st graviton is found, there is a
prediction where to find the next resonances for
c not too big.
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Conclusions

• Signal? Test of Randall Sundrum model after 1
  year data taking at the high luminosity design
• Graviton? ?? channel or angular distributions of
  lepton decay products
• Next Step Full simulation-reconstruction chain