Matteo Cremonesi - IN2P3moriond.in2p3.fr/QCD/2015/SundayAfternoon/Cremonesi.pdf · Matteo...
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M Cremonesi - Moriond QCD - March 22, 2015
Recent Top Quark Properties Results from the Tevatron
Matteo Cremonesi FNAL
Accelerator
• Proton-antiproton collider √s = 1.96 GeV
• Two experiments: CDF & D0
• Run II (2001 - 2011) ~10 fb-1/experiment recorded
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Experiments
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Top Discovery
• Discovery announced March 2nd, 1995
• Happy birthday!!!
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Top at Twenty
For more information, visit: http://indico.fnal.gov/event/TopAtTwenty15
Program CommitteeTiziano Camporesi, CERN, SwitzerlandDave Charlton, University of Birmingham, UKMatteo Cremonesi, Fermilab, USADmitri Denisov, Fermilab, USAKeith Ellis, Fermilab, USAPaul Grannis, Stony Brook University, USAAndreas Jung, Fermilab, USAAlison Lister, University of British Columbia, CanadaLuca Malgeri, CERN, SwitzerlandMichelangelo Mangano, CERN, SwitzerlandAndreas Meyer, DESY, Germany
Mark Owen, University of Glasgow, UKDavid Toback, Texas A&M University and Mitchell Institute, USABoris Tuchming, Irfu-CEA Saclay, FranceCostas Vellidis, Fermilab, USAJonathan Wilson, Texas A&M University and Mitchell Institute, USA
Local OrganizersCynthia Sazama, Fermilab, USAMelody Saperston, Fermilab, USASuzanne Weber, Fermilab, USA
Workshop April 9-10, 2015Fermilab, Batavia, IL USA
To celebrate the 20th 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 explorethe indications for physics beyond the standard model.
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Top Quark
• Heaviest know elementary particle
• 174.34 ± 0.76 GeV
• Short lifetime (≈ 5x10-25 s)
• it decays ~ 100% of the times in Wb
• Large Yukawa coupling to the Higgs (~1)
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Properties
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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
τ+τ 1%τ+µ 2%
τ+e 2%
µ+µ 1%
µ+e 2%
e+e 1%
e+jets 15%
µ+jets 15%
τ+jets 15%
"alljets" 46%
"lepton+jets""dileptons"
Top Pair Branching Fractions
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Branching Ratio
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|
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R Dileptons
R = 0.87 ± 0.07 (stat.+syst)
|Vtb| = 0.93 ± 0.04 (stat.+syst)
PRL 112 221801
Number of b-tagged jets0 1 2
Num
ber o
f Eve
nts
020406080
100120140160180200
-1Dilepton final state CDF Run II Preliminary 8.7 fbBackgroundsData , R=0.5tt, R=0.87tt, R=1tt
Wq)→BR(t Wb)→BR(t R =
0.07±R = 0.87
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Top Mass
Measuring Top Mass
• Stringent SM self-consistency test
• Precision is crucial
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JES in situ Calibration
• W boson fully reconstructed
• Constrain to the value of the known W boson mass
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Methods
• Matrix Element method: calculate event probability densities using the matrix element of the hard process
• Template method: compares histograms in data to simulations
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• Data driven QCD model, neural network based event selection
• S/B ~1 after selection
• Template method:
• Mtop and MW templates from kinematic fit
Top Mass Alljets/1
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outNN0.5 0.6 0.7 0.8 0.9 1 1.1 1.2
Even
ts/(0
.01)
0
100
200
300
400
500
600
700
800 Data
JES= 0.0)∆, 2=172.5 GeV/ctop
(Mt Bkg + t
Bkg 2 tags events≥
< 1.50out0.50 < NN
)-1 - Preliminary (9.3 fbtopCDF Run II - All Hadronic M
Top Mass Alljets/2
]2 [GeV/crectm
100 150 200 250 300
)2Ev
ents
/(5.0
GeV
/c
0
100
200
300
400
500 1-tag events≥
)-1 Data (9.3 fb
t Fitted Bkg + t Fitted Bkg
)-1 - Preliminary (9.3 fbtopCDF Run II - All Hadronic M
]2 [GeV/crecWm
20 40 60 80 100 120 140 160 180 200 220
)2Ev
ents
/(5.0
GeV
/c
0
100
200
300
400
500
600
700
800
900 1-tag events≥
)-1 Data (9.3 fb
t Fitted Bkg + t Fitted Bkg
)-1 - Preliminary (9.3 fbtopCDF Run II - All Hadronic M
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Mtop = 175.07±1.58(stat)±1.15(syst) GeV (1.1% rel. unc.)
PRD 90 09110116
Top Mass Dileptons\1
• Template method:
Mhyb = wMtreco + (1-w)Mlbalt
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Top Mass Dileptons\2
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Mtop = 171.5 ± 1.9 (stat) ± 2.5(syst) GeV (1.9% rel. unc.)
CDF Conf. Note 1107218
Top Mass CDF Combination
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)2 (GeV/ctM150 160 170 180 190 200
0
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CDF March’07 2.66± 12.40 2.20)±1.50 ±(
CDF combination * 0.93± 173.16 0.74)±0.57 ±( syst)± stat ±(
CDF-II MET+jets 1.85± 173.93 1.35)±1.26 ±(
CDF-II track 9.46± 166.90 2.90)±9.00 ±(
CDF-II alljets * 1.96± 175.07 1.56)±1.19 ±(
CDF-I alljets 11.51± 186.00 5.70)±10.00 ±(
CDF-II lepton+jets 1.11± 172.85 0.98)±0.52 ±(
CDF-I lepton+jets 7.36± 176.10 5.30)±5.10 ±(
CDF-II dilepton * 3.25± 170.80 2.69)±1.83 ±(
CDF-I dilepton 11.41± 167.40 4.90)±10.30 ±(
Mass of the Top Quark(* CDF preliminary)March 2014
/dof = 5.6/7 (58%)2χ
0.58% rel. unc., CDF Conf. Note 1108019
Top Mass Lepton+jets\1
• ME measurement
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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 0.25 → 0.05 GeV
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Top Mass Lepton+jets\3
• 2D likelihood fit to extract KJES and mt
• most precise single measurement (0.43% rel. unc.)
• PRL 113 032002 (2014)
• PRL "Editors' Suggestion”
• Nature "News and Views"
• Long write-up sub. to PRD, arXiv:1501.07912
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Top Mass Tev Combination
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)2 (GeV/ctM150 160 170 180 190 200
0
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CDF March’07 2.66± 12.40 2.20)±1.50 ±(
Tevatron combination * 0.64± 174.34 0.52)±0.37 ±( syst)± stat ±(
CDF-II MET+Jets 1.85± 173.93 1.36)±1.26 ±(
CDF-II track 9.43± 166.90 2.82)±9.00 ±(
CDF-II alljets * 1.95± 175.07 1.55)±1.19 ±(
CDF-I alljets 11.51± 186.00 5.70)±10.00 ±(
DØ-II lepton+jets 0.76± 174.98 0.63)±0.41 ±(
CDF-II lepton+jets 1.12± 172.85 0.98)±0.52 ±(
DØ-I lepton+jets 5.31± 180.10 3.60)±3.90 ±(
CDF-I lepton+jets 7.36± 176.10 5.30)±5.10 ±(
DØ-II dilepton 2.80± 174.00 1.49)±2.36 ±(
CDF-II dilepton * 3.26± 170.80 2.69)±1.83 ±(
DØ-I dilepton 12.82± 168.40 3.60)±12.30 ±(
CDF-I dilepton 11.41± 167.40 4.90)±10.30 ±(
Mass of the Top Quark(* preliminary)July 2014
/dof = 10.8/11 (46%)2χ
0.37% rel. unc., arxiv:1407.2682 23
Summary
• 20 years of top quark properties measurements at the Tevatron
• Top quark Tevatron program almost complete
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