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

2/25

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

3/25

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- - --

- -

4/25

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)

5/25

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)

6/25

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 ?

7/25

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)

8/25

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

9/25

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)

10/25

No s running With s running

2 contribs: propagator+coupling (s)

Processes 11, 12 only All processes

11/25

No s runnings running

Processes 11, 12 only All processes

s=f() and =f(s) iterative process

12/25

Process 11 Process 12

KK excitation

KK equally spaced spectrum(log scale)

1TeV

Observation of resonance

13/25

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)

14/25

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

15/25

leptons:E=cstt Mandelstam variable (t or u=)

s channel

t channel

16/25

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

17/25

• kinematics with jets: reconstruction of x

protons

x resolution: 6%

Ev.

#

18/25

«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

19/25

s=1 TeV, Cteq6L1, QCD correct^

20/25

gggg interferencenormalised

qgqg

21/25

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

22/25

pdf distributions

Likelihood ratio ponderation using distributions

XD resonance process

Other processes

23/25

After likelihood

S/sqrt(B):2177 ± 17

likelihood

S/sqrt(B):1599±7,9

Sqrt(s)

events lumi=100 fb-1

before likelihood

36 %

24/25

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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