1. Randall Sundrum KK Graviton at CMS
Caroline Collard, LLR, Ecole Polytechnique, France
Work in collaboration with M.-C. Lemaire,
P. Traczyk and G. Wrochna
Exotic Signals at Hadron Colliders
26/02/03

2. Exotic Signals at Hadron Colliders
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
Exotic Signals at Hadron Colliders
26/02/03

3. Exotic Signals at Hadron Colliders
Extra Dimensions
Why?
Unification of gravitation with other forces.
Hierarchy problem : MEW and MPL
Different models of ED
Exotic Signals at Hadron Colliders
26/02/03

4. Exotic Signals at Hadron Colliders
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 kr≈12
SM brane
Planck brane
bulk
r 
r  = 0
r  = r 
Exotic Signals at Hadron Colliders
26/02/03

5. Exotic Signals at Hadron Colliders
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
Exotic Signals at Hadron Colliders
26/02/03

6. Exotic Signals at Hadron Colliders
Variation of c
0.01 ≤ c ≤ 0.1
c = 0.1
c = 0.05
c = 0.02
c = 0.01
d/dM MG
Exotic Signals at Hadron Colliders
26/02/03

7. Exotic Signals at Hadron Colliders
The CMS detector
pp collider:
14 TeV in cms
Start in 2007
1 low lumi: 10 fb-1
1 high lumi: 100 fb-1
Higgs Discovery
and Search for New Physics
Exotic Signals at Hadron Colliders
26/02/03

8. Exotic Signals at Hadron Colliders
Analysis
Signal:
ffbar, gg  G   (B.R.= 4 %)
ffbar, gg  G  e+e-, +- (B.R.= 2 %)
Generation with PYTHIA
Photon Radiation with PYTHIA or PHOTOS
Detector response with CMSJET (Fast Simulation)
Exotic Signals at Hadron Colliders
26/02/03

9. CMS Performance in CMSJET
ECAL: For electron and  detection
Barrel (||<1.56)  E/E = 3% /√E + 0.2/E %
Endcap (1.65<| |< 3)  E/E = 6% /√E + 0.9/E %
Tracker: For muon detection
p/p = 4% √p
Exotic Signals at Hadron Colliders
26/02/03

10. Exotic Signals at Hadron Colliders
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 e+e-, +-: pp  Z/  l+l- (Drell Yan)
K factor =1.38 from comparison between PYTHIA MC and CDF data
# Events
M (GeV)
Exotic Signals at Hadron Colliders
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11. Exotic Signals at Hadron Colliders
MG= 1500 GeV, c=0.01, Lumi=100 fb-1
CMSJET
G  
# Events
M (GeV)
Exotic Signals at Hadron Colliders
26/02/03

12. Exotic Signals at Hadron Colliders
5  Discovery Limit
CMSJET
100 fb-1
G  
c =0.01
.B (fb)
MG (GeV)
Exotic Signals at Hadron Colliders
26/02/03

13. Exotic Signals at Hadron Colliders
MG= 1000 GeV, c=0.01, Lumi=100 fb-1
CMSJET
Difference in resolution for e (Energy in calo) and  (Momentum
in tracker) => Different mass windows
Exotic Signals at Hadron Colliders
26/02/03

14. Exotic Signals at Hadron Colliders
5  Discovery Limit
CMSJET
G  e+e-
c =0.01
.B (fb)
MG (GeV)
Exotic Signals at Hadron Colliders
26/02/03

15.  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 flag=F, Mass Limits for 5  Discovery:
=> Results in agreement!
Lumi
PYTHIA
PHOTOS
300 fb-1
2300 GeV
2350 GeV
100 fb-1
2000 GeV
2080 GeV
Exotic Signals at Hadron Colliders
26/02/03

16. Exotic Signals at Hadron Colliders
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)
Exotic Signals at Hadron Colliders
26/02/03

17. 5  Discovery Limit with PHOTOS
Theoretical constraint on
curvature c
G  e+e-
Theroretical constraint
for no new hierarchy
CMSJET
MG (GeV)
Exotic Signals at Hadron Colliders
26/02/03

18. Exotic Signals at Hadron Colliders
If there is no signal …
NS: number of expected signal events
NB: number of background events
Nobs:number of “observed” events
95% CL Exclusion Limit
Exotic Signals at Hadron Colliders
26/02/03

19. Exotic Signals at Hadron Colliders
95% CL Exclusion Limit
CMSJET
Excluded
Signal
Exclusion
at 95% CL c
|R5| < M52
 = 10 TeV
Region of
interest
Photons
MG (GeV)
Muons
Electrons
Exotic Signals at Hadron Colliders
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20. Exotic Signals at Hadron Colliders
If there is a signal …
How to be sure it is a RS Graviton?
Graviton? not a Z’?
RS model?
CMSJET
MG=2000 GeV,
c=0.01
Exotic Signals at Hadron Colliders
26/02/03

21. Exotic Signals at Hadron Colliders
Angular Distribution
Graviton = spin 2
CMSJET
pp  G  +-
MG=1000 GeV
c=0.1
After  cut:
( |  | < 3.0 for e
|  | < 2.4 for  )
gg  G  ll:
1-cos4
qqbar  G  ll:
1-3cos2+4cos4
Cos
Exotic Signals at Hadron Colliders
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22. Exotic Signals at Hadron Colliders
How different from Z’?
Kolmogorov-Smirnov Test
Rem: No  mode for Z’
CMSJET
M= 2000 GeV Z’
1+ cos2 G
For G:
number of events corresponding to Lumi, randomly chosen
Cos
Exotic Signals at Hadron Colliders
26/02/03

23. Exotic Signals at Hadron Colliders
95% CL Exclusion Limit
Spin 1 rejection
with 90% probability
at 95% CL
Excluded
CMSJET
Electrons
Leptons c
|R5| < M52
 = 10 TeV
Region of
interest
MG (GeV)
Exotic Signals at Hadron Colliders
26/02/03

24. Exotic Signals at Hadron Colliders
Detector acceptance
|| < 2.4
CMSJET
|| < 1.5
Cos
Importance of the pattern recognition in the endcap regions!
Exotic Signals at Hadron Colliders
26/02/03

25. Exotic Signals at Hadron Colliders
RS model?
Davoudiasl, Hewett, Rizzo
hep-ph/
c=1.
c=0.5
c=0.1
c=0.05
c=0.01
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.
Exotic Signals at Hadron Colliders
26/02/03

26. Exotic Signals at Hadron Colliders
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
Exotic Signals at Hadron Colliders
26/02/03