measurement of the top quark mass using data from cdf experiment at tevatron
DESCRIPTION
Measurement of the Top Quark mass using data from CDF experiment at Tevatron. Fedor Prokoshin. Part 2. Tevatron :. Top Production at Tevatron. single top:. top-antitop pairs:. 85%. ~2 pb. 15%. ~1 pb. ~ one top event every 10 BILLION inelastic collisions. Hadronization time. - PowerPoint PPT PresentationTRANSCRIPT
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Measurement of the Top Quark mass
using data from CDF experimentat Tevatron
Fedor Prokoshin
Part 2
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Top Production at Tevatron
15%
Tevatron: TeV96.1@ spp
85%
top-antitop pairs: single top:
~1 pb
~2 pb
pb1.6)( Xttpppb6)(10mb60)( 10 XttppXppinel
~ one top event every 10 BILLION inelastic collisions
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Top quark decay
))(( WbbWtt
( ) ( ) ( )
( ) ( ) ( )
( ) ( ) ( )
e eW W e e
W W
W W
( ) ( )
( ) ( )
W W du ud
W W sc cs
s105.0GeV3.1GeV170M
s10MeV)100(24
ttt
23-11
QCD Hadronization time
NO top hadrons
final state given by W+ W- decays
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Event Classificationqqqqbb hadronic 44%Llbb dilepton 11 (5)%
lqqbb lepton+jets 44 (30)%
tt W bW b qq bq q b
l ltt W bW b qq bl b l bqq b l ltt W bW b l bl b
Events where neither of the W bosons decay by the lepton channel can be referred to as 'all jets‘ or ‘hadronic’ since all the detector sees is hadron jets.
Events in which both the positively charged W boson and the negatively charged W boson decay by the lepton channel can be known as the 'dilepton' channel.
Events in which only one W boson decays by the lepton channel can be known as the single-lepton (or lepton+jets) channel.
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Event selection• 1 energetic (ET>20 GeV)
isolated lepton (e,μ)• 4 energetic (ET>15 GeV)
jets (of which 2 b jets)• Large ET
mis > 20 GeV TE
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Backgrounds• Diboson• Single top• W+multijet
– W+LF jets– W+HF jets
• Non-W (QCD)• EWK 10 %• W+jets 65 %• non-W 23 %
TOTAL BACKGROUND 32 %
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Soft Lepton Taggingsemileptonic B hadron decay
Tagging B-jets
B hadrons are long-livedVertex displaced tracks
Top events contain B hadronsOnly 1-2% of dominant W+jets background contains heavy flavorGreat S/B improvement
Top Event Tagging Efficiency
False Tag Rate (QCD jets)
55%0.5%
15%3.6%
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•Lepton+jets•Undetected neutrino
•Px and Py from Et conservation•2 solutions for Pz from MW=Ml
•Leading 4 jets combinatorics•12 possible jet-parton assignments•6 with 1 b-tag•2 with 2 b-tags
•ISR + FSR
final state:
CDF sees:
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Jet Assignment
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140 200
Mi=160 Mi=200Mi=140 Mi=180
M top
Mass templates
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Signal parameterization
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Background Template
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FINAL FIT
Mtop = 168.9 ± 2.2 (stat) ± 4.2 (syst) GeV/c2
, ,
1
;!
s b N sig reco BG recon n Ns top i top b top ishape s b
topi s b
n P M M n P Me n nM
N n n
L2
12
estb b
estnb
n n
constr e
L
shape constr L L L
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Summary of current resultshttp://www-cdf.fnal.gov/physics/new/top/public_mass.html
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BACKUP SLIDES
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Dilepton
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0 UE t tT T T
t bW
t bW
W l
q qW
p p p
p p p
p p p
p p p
p p p
2
0
80.4t t
W W
M M M
M M GeV c
Equations
Constraints
, , , ,t t W W Unknown
, , Tl jets pObservables:
KINEMATICS
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Ch square fit
2 2, , , ,2
2 2,4 ,
2 22 2
2 2 2 2
i fit i data UE fit UE dataT T j j
i l jets j x yi j
reco recobjj top bl topjj W l W
W W t t
p p p p
M M M MM M M M
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Parametrisation
1 1 1 2 02
1
2 23 51 1
2 24 6
4 6
7 01
1 18 7 82 2
9
;
1
175
recotop
reco recoM Mtop top
Msignal reco recotop top top
i i i top
P M M M e
e e
p p M
1 1 1 2 02
1 01
recoptopp p M ppBG reco reco
top toppP M M p e
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Likehood
, ,
1
;!
s b N sig reco BG recon n Ns top i top b top ishape s b
topi s b
n P M M n P Me n nM
N n n
L
2
12
estb b
estnb
n n
constr e
L
shape constr L L L
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Top pair decay modesDecay mode BR Channel type
36/81 Full-hadronic
12/81 Lepton+jets
12/81 Lepton+jets
12/81 Lepton+jets (τ)
2/81 Dilepton
2/81 Lepton+jets (τ)
2/81 Lepton+jets (τ)
1/81 Dilepton
1/81 Dilepton
1/81 Dilepton (τ)
))(( bqqbqqtt ))(( bebqqtt
))(( bbqqtt ))(( bbqqtt
))(( bbett ))(( bbett
))(( bbtt ))(( bebett
))(( bbtt ))(( bbtt
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