1/25 s with xd & kaluza-klein excitation of gluon at atlas exotic signals at hadron colliders...
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1/25
s with XD & Kaluza-Kleinexcitation of gluon at ATLAS
Exotic signals at Hadron Colliders 04 ,Durham
Exotic signals at Hadron Colliders 04
Marc Escalier, LPNHE Paris
Results within the ATLAS experiment
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XD: the models
• ADD large XD (~mm) Rc>>1 TeV-1
• Small XD (TeV-1) (Antoniadis)• Randal-Sandrum
MSSM
MGUT=1016 GeV MSSM + XD
Hierarchy problem can be solved!
In our model, gauge bosons can propagate in XDmodification of the RGE(E. Dudas, R. Dienes, T. Ghergetta, hep/ph 9803466 and hep/ph9807522)
for (4+2) D and R=1/10 TeV-1
strong MGUT~30 TeV
weakem
i
strong
i em
weak
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Detection of KK excitations of gauge bosonsgluonqq, most abundant ~s
difficult to detect over QCD jet bck• , Z G. Azuelos and G. Polesello – proceedings of the Workshop “Physics at TeV colliders”,Les Houches, May 2001 – hep-ph/0204031, ATL-COM-PHYS-2003-004
• W G. Polesello, M. Prata
• Observation of deviations of • Observation of resonances
Feynman diagrams for dijets production involving KK excitationsqi qi qi qi qi qj qi qj qi qi qi qi
qi qj qi qjqi qi qi qi- - --
- -
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Modification of the coupling constant
• SM :
• MSSM+XD :
Jacobi function :
High Energy theory at (4+)D Effective theory at 4D with Kaluza-Klein excitations of gauge bosons (fermions can also exist but are not considered in the following)
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Data analysis at LHC
Mmin
• What can we measure ? 2 competitive effects:• KK excitations make the cross-section to increase• decrease of s makes decrease at high Mc (counterbalance effect of KK)
Influence of s (dominant for high Mc)
Mmin (pair of jet) (GeV)
Mmax (we’ll take 14
TeV)
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This is NOT a resonance This is NOT a resonance
Accelerator =2 =6Tevatron 940 980LHC 10140 10200
Reachable R-1 (GeV) for different scenarii (Ns
max> 5)
Limits: influence of KK in the propagator ?
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propagator of n-KK resonance cn>0=2 mn=n/Rn=2smnc0=1, n=0: SM gluon
Cross-sections |M|2 (amplitude square)
KK gluon propagator
n=0SM
n=f(s)s=f(n)
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Implementing XD into PythiaXD function from C. Balazs
(done at Les Houches 2003)
m,n=0massless gluon
IF(ISUB.EQ.11.OR.ISUB.EQ.12)THENSQDQQT=EffGluProp(TH,TH,XKKL(1),XKKL(2))
REDQST=EffGluProp(SH,TH,XKKL(1),XKKL(2)) SQDQQU=EffGluProp(UH,UH,XKKL(1),XKKL(2)) REDQTU=EffGluProp(UH,TH,XKKL(1),XKKL(2)) SQDQQS=EffGluProp(SH,SH,XKKL(1),XKKL(2))ENDIF
Mc is compactification scaleMs cutoff scale
Ms/Mc
Only some processes have XDPropagator T, TPropagator S, TPropagator U,UPropagator U,TPropagator S, S
n=2smn
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Us: CTEQ6L1Dicus et al: CTEQ3M
Sigma deviation
Observation up to Mc~15 TeV
Cross-section deviationsNo running of alpha_s hereKK-SM (pb)
Ptmin (GeV)
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No s running With s running
2 contribs: propagator+coupling (s)
Processes 11, 12 only All processes
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Process 11 Process 12
KK excitation
KK equally spaced spectrum(log scale)
1TeV
Observation of resonance
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S/sqrt(B):1599±7,9
Sqrt(s)
events
lumi=100 fb-1
Very large resonance difficult to observe over qcd background
Signif=
s channel (XD resonance)
t channel (SM+XD)
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Search for extra-dimensions : • Kaluza-Klein resonance production in s-channel background• QCD background is t-channel
idea: use (s,t) Mandelstam variables distributions to reject s channel from t channel contributions ?
s(s)̂
s(?)
Strategy : enhance s-channel contribution
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P3
P2P4
t1
P1
t’1
P3P2
P4
t2
t’2
P1
?
Protons: need to reconstruct x1, x2
Take best reconstructed variable t or u
For min{|t1-t’1|;|t2-t’2|}, take:t = (ti+t’i)/2
4-momentum conservation : P1+P2=P3+P4
s = (P1+P2)2=(P3+P4)2 : unambigiuous
t : ambigiuoust1=(P1-P3)2 t’1=(P2-P4)2
t ?t2=(P1-P4)2 t’2=(P2-P3)2
u ?
idea : impose s, look at t
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«S»/«T-U» channelsThe idea is not to separate s channels from t/u, it is just to see if there is special behaviour for s channel and t/u channels
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distributions for s=1TeV
S/sqrt(B)=1690.07± 8.98gain 5,6 %
1,2 105
9,9 105
low cut high cut
Low cut
high cut
Search for optimal cuts
XD resonance processes
Others processes
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pdf distributions
Likelihood ratio ponderation using distributions
XD resonance process
Other processes
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After likelihood
S/sqrt(B):2177 ± 17
likelihood
S/sqrt(B):1599±7,9
Sqrt(s)
events lumi=100 fb-1
before likelihood
36 %
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Conclusion
• Cross-section deviations• Resonancesconsequences on others resonances (KK gravitons ?)
• statistics ~1 106 files to be generated• NLO computation ?• full simulation ?
LES HOUCHES 'PHYSICS AT TEV COLLIDERS 2003' BEYOND THE STANDARD MODEL WORKING GROUP: SUMMARY REPORT.By Beyond the Standard Model Working Group (B.C. Allanach et al.). SLAC-PUB-10365, Mar 2004. 114pp. Contributed to 3rd Les Houches Workshop: Physics at TeV Colliders, Les Houches, France, 26 May - 6 Jun 2003. e-Print Archive: hep-ph/0402295
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