Recent Top Quark Properties Results from the Tevatron. Matteo Cremonesi FNAL

Transcription

1 Recent Top Quark Properties Results from the Tevatron Matteo Cremonesi FNAL M Cremonesi - Moriond QCD - March 22, 2015

2 Accelerator Proton-antiproton collider s = 1.96 GeV Two experiments: CDF & D0 Run II ( ) ~10 fb -1 /experiment recorded M Cremonesi - Moriond QCD - March 22,

3 Experiments M Cremonesi - Moriond QCD - March 22,

4 Top Discovery Discovery announced March 2nd, 1995 Top at Twenty Happy birthday!!! Workshop April 9-10, 2015 Fermilab, Batavia, IL USA To celebrate the 20 th anniversary of the discovery of the top quark, we will review observations and discoveries made at both the Tevatron and the LHC, the theoretical context and explore the indications for physics beyond the standard model. For more information, visit: Program Committee Tiziano Camporesi, CERN, Switzerland Dave Charlton, University of Birmingham, UK Matteo Cremonesi, Fermilab, USA Dmitri Denisov, Fermilab, USA Keith Ellis, Fermilab, USA Paul Grannis, Stony Brook University, USA Andreas Jung, Fermilab, USA Alison Lister, University of British Columbia, Canada Luca Malgeri, CERN, Switzerland Michelangelo Mangano, CERN, Switzerland Andreas Meyer, DESY, Germany Mark Owen, University of Glasgow, UK David Toback, Texas A&M University and Mitchell Institute, USA Boris Tuchming, Irfu-CEA Saclay, France Costas Vellidis, Fermilab, USA Jonathan Wilson, Texas A&M University and Mitchell Institute, USA Local Organizers Cynthia Sazama, Fermilab, USA Melody Saperston, Fermilab, USA Suzanne Weber, Fermilab, USA M Cremonesi - Moriond QCD - March 22,

5 Top Quark Heaviest know elementary particle ± 0.76 GeV Short lifetime ( 5x10-25 s) it decays ~ 100% of the times in Wb Large Yukawa coupling to the Higgs (~1) M Cremonesi - Moriond QCD - March 22,

6 Properties M Cremonesi - Moriond QCD - March 22,

7 Channels Strong production of top pairs: dominates at the Tevatron distinctive kinematic properties => S/B ~ 1 or larger Channels determined by the W boson decay Top Pair Branching Fractions "alljets" 46% τ+jets 15% τ+τ 1% τ+µ 2% τ+e 2% µ+µ 1% µ+e 2% e+e 1% "dileptons" e+jets 15% µ+jets 15% "lepton+jets" M Cremonesi - Moriond QCD - March 22,

8 Branching Ratio

9 Measuring R In SM R~1 constrained by CKM unitarity In a top-pair production event, 2 b-quarks are expected => technique: comparing cross section vs number of b-tags Measurement of Vtb M Cremonesi - Moriond QCD - March 22,

10 R Dileptons Number of Events Dilepton final state CDF Run II Preliminary 8.7 fb Backgrounds Data tt, R=0.5 tt, R=0.87 tt, R= Number of b-tagged jets R = 0.87 ± 0.07 (stat.+syst) V tb = 0.93 ± 0.04 (stat.+syst) PRL BR(t Wb) R = BR(t Wq) R = 0.87 ± 0.07 M Cremonesi - Moriond QCD - March 22,

11 Top Mass

12 Measuring Top Mass Stringent SM selfconsistency test Precision is crucial M Cremonesi - Moriond QCD - March 22,

13 JES in situ Calibration W boson fully reconstructed Constrain to the value of the known W boson mass M Cremonesi - Moriond QCD - March 22,

14 Methods Matrix Element method: calculate event probability densities using the matrix element of the hard process Template method: compares histograms in data to simulations M Cremonesi - Moriond QCD - March 22,

15 Top Mass Alljets/1 Data driven QCD model, neural network based event selection S/B ~1 after selection Template method: M top and M W templates from kinematic fit Events/(0.01) -1 CDF Run II - All Hadronic M top - Preliminary (9.3 fb ) 800 Data Bkg + tt (M =172.5 GeV/c, JES= 0.0) top Bkg 2 tags events 0.50 < NN out < NN out M Cremonesi - Moriond QCD - March 22,

16 Top Mass Alljets/2 ) -1 CDF Run II - All Hadronic M top - Preliminary (9.3 fb ) ) -1 CDF Run II - All Hadronic M top - Preliminary (9.3 fb ) 2 Events/(5.0 GeV/c tag events Data (9.3 fb ) Fitted Bkg + tt Fitted Bkg 2 Events/(5.0 GeV/c tag events Data (9.3 fb ) Fitted Bkg + tt Fitted Bkg rec m W [GeV/c 2 ] rec m t [GeV/c 2 ] Mtop = ±1.58(stat)±1.15(syst) GeV (1.1% rel. unc.) PRD M Cremonesi - Moriond QCD - March 22,

17 Top Mass Dileptons\1 Template method: M hyb = wmt reco + (1-w)Mlb alt M Cremonesi - Moriond QCD - March 22,

18 Top Mass Dileptons\2 Mtop = ± 1.9 (stat) ± 2.5(syst) GeV (1.9% rel. unc.) CDF Conf. Note M Cremonesi - Moriond QCD - March 22,

19 Top Mass CDF Combination 11 Mass of the Top Quark March 2014 (* CDF preliminary) CDF-I dilepton ± 11.41(±10.30 ± 4.90) CDF-II dilepton * ± 3.25 (±1.83 ± 2.69) CDF-I lepton+jets ± 7.36 (±5.10 ± 5.30) CDF-II lepton+jets ± 1.11 (±0.52 ± 0.98) CDF-I alljets ± 11.51(±10.00 ± 5.70) CDF-II alljets * ± 1.96 (±1.19 ± 1.56) CDF-II track ± 9.46 (±9.00 ± 2.90) CDF-II MET+jets ± 1.85 (±1.26 ± 1.35) 0 CDF combination * ± 0.93 (±0.57 ± 0.74) CDF March 07 χ 2 /dof ± 2.66 = 5.6/7 (±1.50 (58%) ± (GeV/c ) M t ( ± stat ± syst) ) 0.58% rel. unc., CDF Conf. Note M Cremonesi - Moriond QCD - March 22,

20 Top Mass Lepton+jets\1 ME measurement M Cremonesi - Moriond QCD - March 22,

21 Top Mass Lepton+jets\2 Systematic uncertainties: improved object IDs (e, µ, b) new detector calibration Measure ratio of b-jets to light jets => cross-check of b-jes on data increase in MC statistics => statistical component GeV M Cremonesi - Moriond QCD - March 22,

22 Top Mass Lepton+jets\3 2D likelihood fit to extract K JES and m t most precise single measurement (0.43% rel. unc.) PRL (2014) PRL "Editors' Suggestion Nature "News and Views" Long write-up sub. to PRD, arxiv: M Cremonesi - Moriond QCD - March 22,

23 Top Mass Tev Combination 15 Mass of the Top Quark July 2014 (* preliminary) CDF-I dilepton ± (±10.30 ± 4.90) DØ-I dilepton ± (±12.30 ± 3.60) CDF-II dilepton * ± 3.26 (±1.83 ± 2.69) DØ-II dilepton ± 2.80 (±2.36 ± 1.49) CDF-I lepton+jets ± 7.36 (±5.10 ± 5.30) DØ-I lepton+jets ± 5.31 (±3.90 ± 3.60) CDF-II lepton+jets ± 1.12 (±0.52 ± 0.98) DØ-II lepton+jets ± 0.76 (±0.41 ± 0.63) CDF-I alljets ± (±10.00 ± 5.70) CDF-II alljets * ± 1.95 (±1.19 ± 1.55) CDF-II track ± 9.43 (±9.00 ± 2.82) CDF-II MET+Jets ± 1.85 (±1.26 ± 1.36) 0 Tevatron combination * ± 0.64 (±0.37 ± 0.52) CDF March χ 2 /dof ± 2.66 = 10.8/11 (±1.50(46%) ± 2.20) (GeV/c ) M t (± stat ± syst) 0.37% rel. unc., arxiv: M Cremonesi - Moriond QCD - March 22,

24 Summary 20 years of top quark properties measurements at the Tevatron Top quark Tevatron program almost complete M Cremonesi - Moriond QCD - March 22,