Searches at the LHC: Results from first data

Transcription

1 Searches at the LHC: Results from first data 23 March, 2011 Satyaki Bhattacharya SINP, Kolkata

2 Plan of talk CMS Higgs, SUSY, Exotica results from Moriond Higgs SUSY Exotica main emphasis In exotica part data driven techniques One example analysis in detail I have taken all plots, tables (slides also) from Moriond slides

3 Higgs Tevatron limits Diphoton Di-tau Projected limits from CMS and ATLAS

4 Tevatron limits

5 Channels searched

6 Higgs to diphoton: ATLAS Atlas sees good agreement with SM data

7 Higgs to diphoton : ATLAS vs Tevatron

8 Higgs to 2l2b,2l2ν,2l2j

9 Higgs to WW to 2l2ν

10 Higgs to di-tau

11 CMS projection

12 ATLAS projection

13 CMS and ATLAS projection

14 SUSY

15 Signature of LHC

16 Signature of LHC

17 Search strategy Robust object ID e/mu/tau/photon/jet/met Estimate background from data key ingradiant of all searches (examples in exotica part) Well established statistical methods, recommended by LHC statistics committee

18 Two important points for SUSY search

19 Jet + MHT

20 CMSSM exclusion

21 Same sign dilepton search 2 same sign e/mu pt1>20, pt2 > 10 GeV Atleast 2j, ptj1 > 30 GeV, eta < 2.5 MET > 30 GeV (20 GeV for e-mu) Main background tt_bar, lepton from b

22 Other analyses 1 lepton + jet R & MR fully hadronic

23 Exotica Large extra dimension Quark and lepton and compositeness Leptoquarks Z and W primes Others

24 Many new bounds More than 20 searches Most searches use full luminosity (~36 pb-1) of 2010 data at s =7 TeV Results presented at Moriond/published Many more coming up Already better than Tevatron Aaa

25 Excited leptons : motivation The Standard Model s lepton mass hierarchy can be explained by the existence of lepton substructure Æ Leptons can be excited and then decay to ordinary leptons u In this analysis we search for the production of an excited lepton in association with a Standard Model lepton via novel contact interactions (scale determined by parameter L) u Previously, searches performed at LEP, Tevatron and HERA (e* at H1) u U. Baur, M. Spira, and P. M. Zerwas, Excited-quark and -lepton Production at Hadron colliders, Phys. Rev D 42 (1990) 815.

26 Event topology

27 Analysis strategy Z to eeγ main irreducible background Fakes: Z jets + W+jets, qcd Estimate fake from data using fakable objects Estimate efficiency of photon and electron selection from data Use highest e-gamma mass combination Look for excess in counting experiment

28 Counting experiment Count the total number of events above a minimum cut on the discriminating variable (e.g. l-gamma mass in this case) Obtain significance by calculating the probability of seeing the observed number from two competing models This is different from making a mass window, fitting the background and the mass peak to obtain significance Incorporte systematic uncertainty by averaging the significance over the possible values of background expectation and efficiency In this analysis 0 events were observed so probably we are justified.

29 Fake rate from data Take a jet/photon/muon triggered sample Select events satisfying loose photon id but one isolation failed = fakable objects Select events satisfying tight photon id Estimate the ratio of the two = fakerate Apply this fake rate to a ll+loose photon selection on data Systematics from different trigger and difference of gluon and quark jets

30 Excited leptons

31 Excited leptons

32 Upper limit on cross section

33 Excited Leptons

34 Excited quarks

35 ADD graviton search monjet + MET Single jet + MET Non resonant search From data estimate Z-jets from gamma-jet Look for excess in tail of jet pt spectrum Search underway for monophoton

36 Dilepton resonance (Z')

37 Dilepton Resonance ArXiv Submitted to JHEP

38 Massive Long Lived Particles (I) Baseline model: split SUSY Gluinos formr-hadrons (bound state of SUSY particles and quarks/gluons)

39 Massive Long Lived Particle (ii)

40 Leptoquarks

41 Leptoquark bounds

42 Black Holes

43 Summary Detectors at the LHC is running in excellent condition Most detector components operating near full design goal No excess seen so far (actually for many searches no backgroound events seen so far also!) Many new bounds better than Tevatron already 2011 may be the year of discovery