KaluzaKlein excitation of gluon膠子的卡魯克萊因激勵(lì)

1、1/25as with xd & kaluza-kleinexcitation of gluon at atlasexotic signals at hadron colliders 04 ,durhamexotic signals at hadron colliders 04marc escalier, lpnhe parisresults within the atlas experiment2/25xd: the models add large xd (mm) rc1 tev-1 small xd (tev-1) (antoniadis) randal-sandrummssmm

2、gut=1016 gevmssm + xdhierarchy 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-1strongmgut30 tevweakema a-1-1istronga a-1-1iemweak3/25detection of kk excitations

3、 of gauge bosonsgluonqq, most abundant g ga asdifficult to detect over qcd jet bck g, 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 wg. polesello, m. prata observation of deviations of s observation of

4、 resonancesfeynman diagrams for dijets production involving kk excitationsqi qi qi qiqi qj qi qjqi qi qi qiqi qj qi qjqi qi qi qi-4/25modification of the coupling constant sm : mssm+xd :jacobi function :high energy theory at (4+d d)d effective theory at 4d with kaluza-klein excitations of gauge boso

5、ns (fermions can also exist but are not considered in the following)5/25data analysis at lhcmmin what can we measure ? 2 competitive effects: kk excitations make the cross-section to increase decrease of as makes s decrease at high mc (counterbalance effect of kk)influence of a as (dominant for high

6、 mc)mmin (pair of jet) (gev)mmax (well take 14 tev)6/25this is not a resonancethis is not a resonanceacceleratord=2d=6tevatron940980lhc10140 10200reachable r-1 (gev) for different scenarii (nsmax 5)limits: influence of kk in the propagator ?7/25propagator of n-kk resonancecn0=2mn=n/rgn=2asmnc0=1, n=

7、0: sm gluoncross-sections |m|2 (amplitude square)kk gluon propagatorn=0smgn=f(as)as=f(gn)8/25implementing xd into pythiaxd function from c. balazs(done at les houches 2003)m,n=0massless gluonif(isub.eq.11.or.isub.eq.12)thensqdqqt=effgluprop(th,th,xkkl(1),xkkl(2) redqst=effgluprop(sh,th,xkkl(1),xkkl(

8、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)endifmc is compactification scalems cutoff scalems/mconly some processes have xdpropagator t, tpropagator s, tpropagator u,upropagator u,tpropagator s, sgn=2asmn9/25us: cteq6l1di

9、cus et al: cteq3msigma deviationobservation up to mc15 tevcross-section deviationsno running of alpha_s hereskk-ssm (pb)ptmin (gev)10/25no as runningwith as running2 contribs: propagator+coupling (as)processes 11, 12 onlyall processes11/25no as runningas runningprocesses 11, 12 onlyall processesas=f

10、(g) and g=f(as) iterative process12/25process 11process 12kk excitationkk equally spaced spectrum(log scale)1tevobservation of resonance13/25s/sqrt(b):15997,9 ssqrt(s)eventslumi=100 fb-1very large resonance difficult to observe over qcd backgroundsignif=s channel (xd resonance)t channel (sm+xd)14/25

11、search for extra-dimensions : kaluza-klein resonance production in s-channel background qcd background is t-channelidea: use (s,t) mandelstam variables distributions to reject s channel from t channel contributions ?as(s)as(?)strategy : enhance s-channel contribution15/25leptons:e=cstt mandelstam va

12、riable (t or u=k)s channelt channel16/25p3p2p4t1p1t1p3p2p4t2t2p1?protons: need to reconstruct x1, x2take best reconstructed variable t or ufor min|t1-t1|;|t2-t2|, take:t = (ti+ti)/24-momentum conservation : p1+p2=p3+p4s = (p1+p2)2=(p3+p4)2 : unambigiuoust : ambigiuoust1=(p1-p3)2t1=(p2-p4)2t ?t2=(p1-

13、p4)2t2=(p2-p3)2u ?idea : impose s, look at t17/25 kinematics with jets: reconstruction of xprotonsx resolution: 6%ev. #18/25s/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 channels19/25s=1 tev, cteq6l1, lqcd correct

14、20/25gggginterferencenormalisedqgqg21/25k distributions for s=1tevs/sqrt(b)=1690.07 8.98gain 5,6 %1,2 1059,9 105low cuthigh cutlow cuthigh cutsearch for optimal cutsxd resonance processesothers processes22/25k pdf distributionslikelihood ratio ponderation using k distributionsxd resonance processoth

15、er processes23/25after likelihoods/sqrt(b):2177 17likelihoods/sqrt(b):15997,9 ssqrt(s)eventslumi=100 fb-1before likelihood36 %24/25conclusion 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 s