Measurement of the Top Quark mass using data from CDF experiment at Tevatron

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