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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 Presentation
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Measurement of the Top Quark mass
using data from CDF experimentat Tevatron
Fedor Prokoshin
Part 2
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
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
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.
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
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 %
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%
•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:
Jet Assignment
140 200
Mi=160 Mi=200Mi=140 Mi=180
M top
Mass templates
Signal parameterization
Background Template
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
Summary of current resultshttp://www-cdf.fnal.gov/physics/new/top/public_mass.html
BACKUP SLIDES
Dilepton
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
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
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
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
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
