CMS Results - PowerPoint PPT Presentation

ivo
cms results n.
Skip this Video
Loading SlideShow in 5 Seconds..
CMS Results PowerPoint Presentation
Download Presentation
CMS Results

play fullscreen
1 / 64
Download Presentation
CMS Results
122 Views
Download Presentation

CMS Results

- - - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

  1. CMS Results XXIX Workshop on Recent Advancements in Particle Physics and Cosmology Patras – April 14-16, 2011 Gervasio Gómez for the CMS Collaboration

  2. LHC: basic parameters • 8 arcs (sectors), ~3 km each • 8 long straight sections (700 m each) • beams cross in 4 points • 2-in-1 magnet design with separate vacuum chambers → p-p collisions Patras 2011

  3. LHC: 2010 and 2011 2010 L≈ 2x1032cm-2s-1 pp@√s = 7 TeV 2011 L≈ 1027cm-2s-1 pp: ~47pb-1 delivered by LHC and ~43pb-1collected by CMS. LHC is performing very well Patras 2011

  4. CMS Detector: basic parameters • Momentum / charge of tracks and secondary vertices (e.g. from b-quark decays) are measured in central tracker (Silicon layers). • Energy and positions of electrons and photons measured in high resolution electromagnetic calorimeters. (~ 0.5% @ ET ~ 50 GeV) • Energy and position of hadrons and jets measured mainly in hadronic calorimeters • Muons identified and momentum measured in external muon spectrometer (+central tracker) dp/p<1% @ 100GeV and <10%@1 TeV • Neutrinos “detected and measured” through measurement of missing transverse energy in calorimeters (hermeticity; good Missing ET resolution) Patras 2011

  5. CMS Physics Results Rich physics program covering processes with production cross sections that span several orders of magnitude over 80 physics analyses and counting cannot cover all results show a (hopefully) representative selection: QCD/jets Heavy Flavor (bottom, charm) Electroweak (W,Z and dibosons) Top Higgs Searches for physics beyond SM First results from HI runs All public results in: https://twiki.cern.ch/twiki/bin/view/CMSPublic/PhysicsResults Patras 2011

  6. CMS Physics Results There are four specialized physics talks from CMS in this workshop: Physics with taus in CMS, by M. Bachtis Tau performance and tau physics completely left out of this talk Recent results on Jets at CMS, by P. Kokkas Measurement of inclusive W and Z boson production at CMS, by S. Kessisoglu W/Z + jets production at CMS, by C. Lazaridis Show just a few highlights in this talk Refer to dedicated talks for details Patras 2011

  7. QCD/jet physics Inclusive jet cross section Dijet cross section vs dijet mass Will not show Dijet angular correlations Jet shapes Ratio of 3J/2J cross-section Very forward jet measurements Patras 2011

  8. Inclusive jet cross-section • Inclusive jet pT spectra in good agreement with NLO QCD • Over wide energy range: 18-1000 GeV • Over ~12 orders of magnitude • JES uncertainties 3-5 % • Using Particle-Flow jets • Reconstruct jet particles • Allows to extend to low pT • Gives best resolution Details in talk by P. Kokkas Patras 2011

  9. Dijet mass • Dijet mass spectra in good agreement with NLO QCD predictions • Exploring new territory • Sensitive to new resonances decaying into jets • Background for “bump hunting” • Overall excellent understanding of jet production Details in talk by P. Kokkas Patras 2011

  10. Heavy Flavor physics b/B differential cross-sections B-hadron angular correlations Will not show J/Y production Fraction of J/Y from b decays Y production Reconstruction of Ks, L, X- Patras 2011

  11. b/B differential cross sections inclusive b  m+X inclusive b jets • Extensive b/B production • studies • Consistent pictures in all • channels: • production rates • between MC@NLO • and PYTHIA • predictions • y distributions flatter • than predictions Bs J/Y f inclusive B0 Patras 2011

  12. BB angular correlations • Sizeable fraction of total BB cross section from collinear B-hadron pairs • Fraction increases with leading jet pT • Excess over PYTHIA at low DR • Very important for upcoming searches with (boosted) bb final states • Such as low mass Higgs! Normalize MC in high DR region Patras 2011

  13. Electroweak physics W and Z production W lepton charge asymmetry W/Z + jets WW cross section Will not show Differential W/Z cross-sections (pT and h distributions) Drell-Yan cross section (but see Z’ searches) Di-boson production (other than WW) W polarization R+/- Patras 2011

  14. W and Z production • Z: fit to mll • W: fit to MET • QCD modeled from data • Excellent agreement between observed and expected spectra • Good agreement with NNLO+PDF theory predictions • Already constraining theory: Details in talk by S. Kessisoglou Patras 2011

  15. W lepton charge asymmetry • More W+ than W- due to excess of u over d in pp collisions • Asymmetry = f(h) since u carries higher fraction of proton momentum • Charge asymmetry in e and m agree with each other • Precision of the measurement good enough to provide new inputs to the PDF global fits Patras 2011

  16. W/Z + jets • Important background to top and many searches including Higgs • Simultaneous extraction of W signal and top background • 2D fit to MTWvsNb-jet distributions • VB production in excellent agreement with ME + PS matched Monte Carlo model • X-sec ratios scale as ME Monte Carlo • VB + ≥nj / VB + ≥0j • VB + ≥nj / VB + ≥(n-1)j Details in talk by C. Lazaridis Patras 2011

  17. WW production • Most important background to HWW search • Selection • ee, mm or em • MET>35 GeV (lower to 25 for cleaner em) • Jet veto: no jets with pT>25 GeV/c • Z veto: no events with mll inside MZ 15 GeV/c2 • Top veto: no b-tags, no soft-m • First LHC measurement of WW X-sec: Left: Jet multiplicity for WW selection except Top and jet vetos Right: mll for WW selection except Z veto Patras 2011

  18. Top physics Top pair cross section Single top cross section Top mass Will not show: Charge asymmetry Patras 2011

  19. Top pair cross section Lepton + jets with b-tagging • Divide sample into different categories • Njets, Nbjets, electrons, muons • Binned likelihood fit to secondary vertex mass • Simultaneous fit in e+jets, m+jets with 1/2 b-tagged jets Patras 2011

  20. Top pair cross section Dilepton • Counting experiment • Sample composition studied vsNjet and Nbjet • Data-driven backgrounds for ee, mm and em ee + mm + em Patras 2011

  21. Top pair cross section • All measurements consistent between themselves • Also consistent with theoretical NNLO predictions Patras 2011

  22. Single Top cross section • Select e/m + 2 jets + MET + 1 b-tag • Cut based using angular info • 2D template fit to cosqlj and |hlj| • BDT based on (37!) kinematic observables recoil jet Patras 2011

  23. Single Top cross section Combining 2D e and m and BDT e and m channels: • CMS is able to find very small signals over huge backgrounds • This requires good detector understanding and good control of backgrounds • This shows readiness for challenging searches Patras 2011

  24. Top Mass • Dilepton channel • Shaded areas are background-only shapes • Inserts are Log Likelihood vs. mtop • Method 1: fully kinematic analysis • Select most probable mass for each event and fit mass distribution • Given hypotheses on pZtt and jet energy scale • Method 2: analytical matrix weighting technique • Scan over mt assumptions and choose best • For each mass assumption select best combination given likelihood for lepton energies in top frame • CMS combined: • World: Patras 2011

  25. Higgs Searches SM Higgs searches Current Tevatron limits and prospects HWW LHC prospects Will not show non-SM Higgs searches (ftt, charged Higgs, …) Patras 2011

  26. Constrains on Higgs Mass • MH not predicted by SM, but can be inferred: • From EWK precision data through radiative corrections • Direct searches at LEP • MH>114.4 GeV/c2 @ 95% C.L. • Direct searches at Tevatron • Direct searches at LHC join the game! Non-SM scenarios can weaken both direct and indirect limits Patras 2011

  27. SM Higgs Production & Decay Low Mass High Mass Patras 2011

  28. Tevatron Combination Low mass sensitivity approaching LEP exclusion • High mass 95% C.L. exclusion: • 158<mH<175 GeV/c2 Patras 2011

  29. Tevatron Sensitivity Projections 3-year extension to reach 16/fb was not approved  • By end of 2011: • 10/fb/experiment • >2.4 s expected sensitivity from 100 – 185 GeV/c2 • 3 s sensitivity at 115 GeV/c2 Patras 2011

  30. HWW @ CMS Main challenge: separate H from direct WW production How? Helicity conservation: exploit spin 1 (Z*WW) vs. spin 0 (HWW) For H, charged leptons tend to go in the same direction Same pre-selection as WW analysis S/B poor: rely on MVA techniques (BDT) Patras 2011

  31. CMS Sensitivity Projections @ 1 fb-1 114 Patras 2011

  32. CMS Sensitivity Projections @ 5 fb-1 Patras 2011

  33. CMS Significance of Obs. @ 5 fb-1 Patras 2011

  34. CMS+ATLAS Projections Patras 2011

  35. BSM Searches SUSY Hadronic search with MET Lepton + jets search gg + jets + MET search Non-SUSY (“exotic”) W’ and Z’ Large extra dimensions in gg and mm Microscopic black holes Will not show non-SM Higgs searches (ftt, charged Higgs, …) RPV SUSY leptoquarks microscopic black holes dilepton (SS and OS) and multilepton SUSY searches SUSY searches with single photon and photon+lepton quark and lepton compositeness stopped gluinos extra families Patras 2011

  36. SUSY SM extension: each boson(fermion) gets a fermion(boson) “superpartner” which differs only in spin Gauginos mix to form charginos and neutralinos Some advantages: • Removes fine-tuning problem (large radiative corrections cancel) • Offers dark-matter candidate (assuming LSP is stable) • Offers possibility of force unification Popular SUSY model: mSUGRA (Minimal Supergravity) • SUSY broken via gravitational interactions • Assuming mass unification at GUT scale reduces vast parameter space to just 5: • mo, m1/2, A0, tanb, sign(m) Patras 2011

  37. SUSY Signatures Missing energy leptons jets Another cascade Strong production of squarks and gluinos Production rate depends on masses, ~ SUSY model independent Decay chain details depend on SUSY model (BRs, mass spectrum, ...) Long decay chains Signature has MET from LSPs (and ns), energetic jets, leptons Many gauge-mediated models also predict photons in final state Patras 2011

  38. SUSY Search Strategy • Basic analysis strategy: • Focus on topology using different kinematic observables • Generic MET signatures • Categorize by number of leptons, photons or jets • All counting experiments so far • not optimal for best exclusion limits • but easy and sharp for discovery • Look for excess production of these signatures w.r.t. SM predictions • No significant excess? Set limits to production rate • Set model-dependent limits on parameters upon which production*decay rate • depends (such as masses) Patras 2011

  39. Hadronic search with MET 95% C.L. in CMSSM extend Tevatron limits • ≥3 jets with ET>50 GeV and |h|<2.5 • HT>300 GeV and MHT>150 GeV • No electrons or muons • Backgrounds from data-driven techniques • QCD, Znn, W+jets and top Patras 2011

  40. Single lepton + MET • Exactly one isolated e or m with pT>20 GeV/c • HT>500 GeV and MHT>250 GeV • ≥4 jets with ET>30 GeV and |h|<2.4 • Backgrounds from data-driven techniques • Exploit fact that in W+jets events l and n have similar pT spectra • Use muon pT spectrum (cleaner than e) to predict MET spectrum Patras 2011

  41. CMS Combined Exclusion Plot Limits extend well beyond Tevatron reach Patras 2011

  42. gg + jets + MET • General Gauge Mediated SUSY breaking (GGM) • Neutralino (NLSP)  Gravitino (LSP) + g • ≥2 g with ET>30 GeV and |h|<1.4 • ≥1 jet with ET>30 GeV and |h|<2.6 • DRjg > 0.9 • MET > 50 GeV • Backgrounds from data-driven techniques • QCD dominant background Patras 2011

  43. W’ search MW’>1.58TeV W’ heavy analogue of SM W with same couplings 1 m (e) with pT>30 GeV and large MET MT spectra consistent with SM Combined e+m channels: MW’ > 1.58 TeV Patras 2011

  44. Signal region Signal region Z’ search Z’/GKK • Z’ with SM like couplings • excluded below 1140 GeV • Superstring-inspired Z’x • excluded below 887 GeV • RS Kaluza-Klein gravitons excluded • below 855–1079 GeV • for couplings of 0.05–0.1 2 m (e) with pT>20 (25) GeV Dilepton mass spectrum consistent with SM Best limits to date Patras 2011

  45. LED in ggand mm g,m g,m sxBR < 0.11 pb for Mgg > 500 GeV Ms > 1.6 – 2.3 TeV depending on n Extends Tevatron limits for all n>2 • Theory parameters • Ms = UV cuttoff in s • n = number of ED • Look for excess in invariant mass spectrum • Spectra consistent with SM • No events observed with Mgg (Mmm) > 500 (600) GeV • Set lower limits on Ms vs. n Patras 2011

  46. Microscopic Black Holes • Spectacular signature: BH decays via Hawking radiation to all SM particles • Events with large number of energetic final state particles (mostly q and g but also leptons, photons) • Look for excess in ST distributions in bins of particle multiplicity N • ST = scalar sum of PT of all jets, e, m, g with Pt>50 GeV and MET • Agreement with SM backgrounds (dominated by QCD multijet production) • Set lower limits on MBH vs. number of extra dimensions Patras 2011

  47. Pb-Pb collisions in LHC Jet quenching Will not show Z production in HI collisions di-hadron correlations Charged particle multiplicity spectacular events! Patras 2011

  48. Jet Quenching • Systematic study of dijet properties in Pb-Pb collisions • pT,1 > 120 GeV/c ; pT,2 > 50 GeV/c • Df12 > 2p/3 • |h1,2| < 2 Striking imbalance in dijet transverse momentum First direct evidence of strong jet quenching observed in LHC HI collisions (by CMS and ATLAS) Patras 2011

  49. Jet Quenching: dijet imbalance pp Increasing jet energy asymmetry Aj with increasing “centrality”… Patras 2011

  50. From CAL to TK: overall p balance Project missing pT of reconstructed charged tracks onto leading jet axis • Underlying HI background cancels • Over full TK acceptance, central • and peripheral events are balanced • even for events with large Aj • Leading jet has more high • pT tracks than away jet • Away jet E carried by low pT tracks Patras 2011