1. 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

2. Marc M. Baarmand – Florida Tech 2 p p t b WW q q’ t b W+W+ ll 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

3. 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 2000-004

4. 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

5. 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

6. Marc M. Baarmand – Florida Tech 6 D  : PRL 79 1203 (1997); CDF: PRL 80 2773 (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. 4.7 - 6.2 pb Tevatron t  t Cross Section RUN 1

7. 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!

8. PDF: ±10% scale: ±6% Theoretical Uncertainties

9. Marc M. Baarmand – Florida Tech 9  Fundamental parameter of Standard Model Tevatron Run 1: 174.3  5.1 GeV  Affects predictions of SM via radiative corrections Measurements of M W = 80.398±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 !

10. 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

11. 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 !

12. 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 = 0.332 for LHC using CTEQ4L L. Sonnenchein CMS PhD thesis

13. Marc M. Baarmand – Florida Tech 13 CMS Study Fit  C = -0.021 ± 0.022 C = 0.331 ± 0.023 ISR, FSR, multiple int., detector response included, corrected for selection cuts PYTHIA 6.1 + M.E. by S. Slabospitsky

14. 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%

15. Marc M. Baarmand – Florida Tech 15 FCNC in Top Decays  t  t pair production  Background processes

16. 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

17. 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

18. 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, 151803 (2002) H +  W bb H +   H +  c s B(t  H + b) < 0.36 @ 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, 012004 (2000)

19. 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!

20. 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

21. 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

22. 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  10 -3 - 10 -6  Lots of work and fun ahead… Summary