Marc M. Baarmand – Florida Tech 1 TOP QUARK STUDIES FROM CMS AT LHC Marc M. Baarmand Florida Institute of Technology PHYSICS AT LHC Prague, Czech Republic, July 6-12, 2003
Marc M. Baarmand – Florida Tech 2 p p t b WW q q’ t b W+W+ ll X Production cross-section Resonance production Production kinematics Top Mass W Helicity |V tb | ; Single top production Branching Ratios Rare/non SM Decays Anomalous Couplings CP Violation Top Spin Top Charge Top Width _ _ _ _ Top Quark Physics
Marc M. Baarmand – Florida Tech 3 Topics in This Talk Top production properties Top cross section Top mass Top spin effects Top-antitop spin correlations Anomalous couplings FCNC in top physics Non-Standard-Model decays of top Search for charged Higgs Single top production; top partial width, V tb and spin effects… see talk by Sherstnev More in proceedings of “SM physics (and more) at the LHC” CERN
Marc M. Baarmand – Florida Tech 4 Top Quark Production and Decay Strong t t pair production EW single top quark production Standard Model: t Wb dominates, BR for t t final states (Drell-Yan) (W-g fusion) 21% 15% 1% 3% 1% 44% + X + jets e + jets e + e e + + all - hadronic
Marc M. Baarmand – Florida Tech 5 Motivation t t cross section is a test of QCD predictions Inclusive and differential cross sections A discrepancy may indicate possible new physics Production via a high mass intermediate state Non Wb decay model Measurements performed using various final states Dilepton channels ee, e and Lepton + jets channels e+jets, +jets: topological analysis and b-tagging All hadronic channel Topological variables and b-tagging Neural networks techniques Trilepton channels t t Production Cross Section
Marc M. Baarmand – Florida Tech 6 D : PRL (1997); CDF: PRL (1998)(+updates) theory CDF dilepton DØ dilepton DØ topological CDF lepton-tag DØ lepton-tag CDF SVX-tag CDF hadronic DØ hadronic DØ combined CDF combined Berger et al. Bonciani et al. Laenen et al. Nason et al pb Tevatron t t Cross Section RUN 1
Marc M. Baarmand – Florida Tech 7 t t Production at LHC t t cross section at LHC (√s = 14 TeV) 830 pb LHC is a Top factory: 10 8 t t in 100 fb -1 Measurement of with high statistical precision Measurement of d /p T up to TeV in p T Full understanding of top needed for evaluation of backgrounds to Higgs, SUSY, etc. Challenge is to control systematics Experiment: a few percent?! Theory: currently 12% but expect improvements (next slide) Relation to top mass: Within SM expect m t /m t 0.2 (t t)/ (t t) If 5% precision in cross section is achieved Indirect determination of m t with m t 1.8 GeV!
PDF: ±10% scale: ±6% Theoretical Uncertainties
Marc M. Baarmand – Florida Tech 9 Fundamental parameter of Standard Model Tevatron Run 1: 5.1 GeV Affects predictions of SM via radiative corrections Measurements of M W = ±0.041 GeV and m t constrain M H Large mass of top quark Yukawa coupling 1 Clues about electroweak symmetry breaking! WW t b WW H Top Quark Mass Light Higgs !
Marc M. Baarmand – Florida Tech 10 CMS Top Mass Studies Lepton + jets m t = 1.0 – 1.5 GeV depending on p T modeling and calibration precision W-jj, b-jet resolution, combinatorics… Dilepton m t ≤ 2 GeV obtained from correlation between M(e ) and m t
Marc M. Baarmand – Florida Tech 11 Promising Channel l + J/ channel m t ≤ 1 GeV strong correlation between M(l J/ ) and m t Sensitivity to b fragmentation function Small BR (5x10 -5 ) Suitable for high luminosity data !
Marc M. Baarmand – Florida Tech 12 t t Spin Correlations t t → l + l’ - X (l=e, ) with pure V-A top decays Expect C = for LHC using CTEQ4L L. Sonnenchein CMS PhD thesis
Marc M. Baarmand – Florida Tech 13 CMS Study Fit C = ± C = ± ISR, FSR, multiple int., detector response included, corrected for selection cuts PYTHIA M.E. by S. Slabospitsky
Marc M. Baarmand – Florida Tech 14 FCNC in Top Quark Physics Flavor Changing Neutral Current couplings tVc and tVu; V = g, , Z Absent at tree-level and highly suppressed in SM Present through loop contributions Observation of top quark FCNC processes New Physics! CDF & LEP2 Present Limits BR < 17% BR < 3.2% BR < 18%
Marc M. Baarmand – Florida Tech 15 FCNC in Top Decays t t pair production Background processes
Marc M. Baarmand – Florida Tech 16 Branching Ratios Expected constraints on “BR” = Г(tVq) / Г(SM) Tevatron Run 2 LHC – CMS Linear e + e - collider BR’s significantly constrained – allowing test of SUSY scenarios
Marc M. Baarmand – Florida Tech 17 Supersymmetry Presently observed bosons and fermions would have more massive superpartners (SUSY is a broken symmetry) SUSY Higgs sector – two Higgs doublets (MSSM) 5 states (h 0,H 0,A 0,H +,H - ) survive after giving W & Z masses H LEP limit 77.4 GeV (LEP Working Group 2000) Decay t H + b can compete with t W + b H couples to heaviest fermions detection through breakdown of e / / universality in t t production Non-SM Decays of Top
Marc M. Baarmand – Florida Tech 18 Tevatron Search - Run 1 DØ Indirect search for t H + b; disappearance of SM t W + b Direct search for t H + b; with H + for large tan PRL 88, (2002) H + W bb H + H + c s B(t H + b) < 95% CL if B(H + ) 1 and M H < 160 GeV CDF Direct search for t H + b; with H + for large tan PRD 62, (2000)
Marc M. Baarmand – Florida Tech 19 Expectation from Tevatron Run 2 Excluded regions expected from Run 2 Large regions of parameter space for M H < m t remain to be searched!
Marc M. Baarmand – Florida Tech 20 CMS Search One CMS study searches for excess of jets in t t events jets identified as narrow hadronic jets dilepton deficit used to enhance the search min L to exclude tWb (2 )min L to discover tHb (5 ) Possible to explore M H < 160 GeV and 2<tan <40 with 30 fb -1
Marc M. Baarmand – Florida Tech 21 Charged Higgs Boson 5 discovery reach for light and heavy Higgs See talks by A. Nikitenko R. Kinnunen Search in top quark decays
Marc M. Baarmand – Florida Tech 22 Top quark physics is rich, exciting and doable at low luminosity LHC SM: EW and QCD tests BSM: probe SUSY Today’s signal, tomorrow’s background Top quark (pair and single) production is the main background to processes with multi lepton + jets in final state, e.g. SUSY Although top will be explored at Tevatron, it will have to be re-visited at LHC for high statistics studies m t ≤ 1 GeV BR for FCNC tVq Lots of work and fun ahead… Summary