B Lifetime Results from CDF and D0

1
B Lifetime Results from CDF and D0

• Daria Zieminska
• Indiana University
• (D0 Collaboration)
• Beauty 2003
• See also recent CDF talks Sinead Farrington,
  EPS, July 03
• Kevin
  Pitts, LP03, August 03

2
Outline

• Introduction expectations
• Tevatron Run II B triggers and data
• Inclusive B ? J/? X
• Exclusive B ? J/? X channels
• - B ? J/? K
• - B0d ? J/? K
• - B0s ? J/? f
• - ? b ? J/? ?
• Semileptonic B Decays

3
Run II at the Tevatron data available by
September shutdown

• Analyses presented here based on
• - CDF 138 pb -1 (di-µ trigg)
• - D0 114 pb -1 (di-µ trigg) 12 pb -1
  (single-µ trigg)

4
B Physics at the Tevatron
-

• Large BB cross section
• - 100 µbarn total
• - 3-5 µbarn reconstructible
• At 4 x 1031cm-2s-1 ? 150 Hz of reconstructible
  Bs
• All B species produced
• Tevatron world best source of Bs and ?b
• Production is incoherent
• - reconstruction of both Bs
• not needed

• Large background
• - B cross section 10-3 total inelastic
• - special triggers (leptons, displaced
  tracks)
• - combinatorics in reconstruction
  
• Typical kinematic cuts
• pT(µ) gt 1.5 GeV/c for µs from J/?
• - pT(B) gt 5 (6) GeV/c

5
B Hadron Lifetimes

• SEMILEPTONIC
• ldisplaced track trigger (CDF)
• single ? - prescaled (D0)
• clean
• partially reconstructed
• - need MC to unfold ct
• lifetime biased
• good statistics

• EXCLUSIVE
• J/? trigger
• clean
• fully reconstructed
• lifetime unbiased
• low statistics

B0 ? l?D()- ?b ? l??c B0s? l? D?s
B0 ? J/? K0 B ?J/? K ?b? J/? ? B0s ? J/? ?

• Reconstruct decay length by vertexing
• Measure pT of decay products

6
Index of Fitting Techniques

• 1D bkg template from sideband
• (variations allow LSB ? RSB)
• 2D simulteneous fit to (mass, ct), free bkg
  parameters

Channel 1D 2D
Inclusive B ? J/? X CDF, D0
B ? J/? K D0 CDF
B0d? J/? K CDF, D0
Bs ? J/? f CDF, D0
?b? J/? ? CDF
7
Triggers for B Lifetime Studies

• CDF
• Di-muon (J/?) pT(µ) gt 1.5 GeV/c ,
  ? (µ) lt 1.6
• l displaced track pT(e/µ) gt 4 GeV/c
• pT(trk) gt 2 GeV/c , 120 µm lt d 0
  (trk) lt 1 mm
• Two displaced tracks pT(trk) gt 2 GeV/c ,
  120 µm lt d 0 (trk) lt 1 mm
• D0
• Di-muon, pT(µ) gt 3 GeV/c, ? (µ) lt
  2.2 (unprescaled)
• pT(µ) gt 1.5 GeV/c, ?
  (µ) lt 2.2 (prescaled)
• Single µ, pT (µ) gt 7 GeV/c, ?
  (µ) lt 2.2 (prescaled)
• Displaced tracks after shutdown

8
Inclusive B ? J/? X Lifetime (D0)

• Measure ?? L xy M? /p?T
• Need ?B L xy MB /pBT
• Correction factor
• F ?? / ?B M? pBT / MB p?T
• MC provides mean F(p?T) in
• slices of p?T
• .e.g.
• ? D0 parametrization of F(p?T)

9
Inclusive B ? J/? X Lifetime (D0)Fitting
technique

• Two steps
• - fit the ? distribution of the sidebands to get
  the shape of the background. The bkg
  parametrization gbkg(?)
• Prompt ? taken from MC (the Gaussian plus (?gt0)
  and (?lt0) exponentials)
• (?gt0) and (?lt0) exponentials
• - fit the ? distribution in the signal region
  allowing for
• bkg distribution gbkg(?)
• Prompt J/? (similar to prompt bkg)
• Exponential decay convoluted with Gaussian (b?J/?
  X)

10
Inclusive B ? J/? X Lifetime D0 and CDF
results

• D0
• t 1.5620.013(stat)0.045(syst) ps
• main syst uncertainties
• correction factor 1.6
• MC bias 1.9
• ? 82 J/?s prompt
• CDF (2002)
• t 1.5260.034(stat)0.035(syst)
• main syst uncertainties
• correction factor 1.1
• resolution function 1.5
• bkg parametrization 1.1
• ? 83 J/?s prompt

11
B Hadron Lifetimes Expectations and Existing
Data
In the naive quark spectator model, the decay
is a 1 ? 3 process common to all b hadrons.
QCD predicts deviations, in agreement with
experimental data Heavy Quark
Expansion Experiment
t(B)/t(Bs) 1.06 0.02
1.074 0.014 t(Bs)/t(Bd)
1.00 0.01
0.948 0.038 t(?b)/t(Bd) 0.90
0.05 0.796 0.052
12
Exclusive B?J/?X Lifetimes X K,K,f (CDF)
Fit Method Simultaneous fit of M(B) ?
signal fraction, define sidebands c?(B) ?
lifetime
Signal Contribution
Background Parameterisation
13
B ? J/? K Lifetime (D0)Data and Fitting
technique

• Three steps
• - Fit the ? distribution of the right sideband
• Prompt (?gt0) and (?lt0) exponentials
• - Fit the ? distribution in the left sideband
• with an extra term for feeddown from
• multibody B decay channels
• - Fit the signal region
• Norm. of feeddown 0.12 0.01 (MC)

14
B?J/? K Results D0
CDF

• t 1.65 0.083(stat) 0.123(syst) ps

• t 1.630.05(stat) 0.04(syst) ps

15
Bs Lifetime

• Standard Model predicts ??s/?s 0.1
• B0s?J/? f an unknown mixture of CP 1 and CP -1
  states
• The CP-even and CP-odd components have
  distinctly different decay distributions.
• The distribution in transversity variable ?T
  and its time evolution is
• d?(t)/d cos?T 8 (A0(t)2 A(t)2) (1
  cos2?T) A-(t)2 2 sin2?T
• 3 linear polarization states J/? and f
  polarization vectors
• longitudinal (0) to the B direction of
  motion
• 
  transverse and parallel () and (- )
  to each other
• In the case of untagged decay, the CP specific
  terms evolve like
• CP - even ( A0(t)2 A(t)2 ) exp(
  -GLightt)
• CP - odd A-(t)2 exp( -GHeavyt)

16
Bs Lifetime Summary of existing measurements

• Flavor-specific final states
• Gfs Gs - (?Gs)2 / 2Gs ? ( (?Gs)3 / Gs
  2 )
• Gfs Gs ( GLight GHeavy)/2
• CP1 CP-1
• ?Gs GLight - GHeavy
• Unknown mixture of GLight , GHeavy
• (predominantly CP 1)

Value(10-12s) Experiment (channel)
1.420.140.03 DLPH (l)
1.530.160.07 DLPH (Ds)
1.360.090.06 CDF (Ds- l)
1.720.200.18 OPAL (Ds)
1.500.160.04 OPAL (Ds- l)
1.470.140.08 ALEPH (Ds)
1.600.260.14 DLPH (Ds)
1.540.140.04 ALEPH (Ds- l)
1.340.210.05 CDF (J/? f)
1.330.140.02 CDF (J/? f) - prelim
1.190.180.14 D0 (J/? f) - prelim
17
Bs ? J/? f with Bd ? J/? K as a control
channelCDF D0

• 138 pb-1 of data
• 2D fit (Mass, ct)
• Signal events 120 13
• pT(B) gt 6 .5 GeV/c
• pT(f) gt 2 GeV/c
• run averaged beam spot 33µm
• track impact parameter resol 35µm

• 114 pb-1 of data
• 2D fit (Mass, ct)
• Signal events 69 14
• pT(B) gt 6 GeV/c
• pT(f) gt 2 GeV/c
• pT(K) gt 2 GeV/c
• event by event PV
• Lxy resolution 40 µm

18
B0s ? J/? f DataD0
CDF

19
B0d ? J/? K DataD0
CDF

20
B0s ? J/? f Data (D0) Decay Length
resolution ct all
sideband

Dots B Hist J/?
21
B0s ? J/? f Fit resultsD0
CDF

• t 1.19 0.18(stat) 0.14(syst) ps

• t 1.33 0.14(stat) 0.02(syst) ps

22
B0d ? J/? K Fit resultsD0
CDF

• t 1.51 0.18(stat) 0.20(syst) ps

• t 1.51 0.06(stat) 0.02(syst) ps

23
Systematic uncertainties (CDF)
Systematic effect Uncertainty on ct (B), ?m Uncertainty on ct (B0d), ?m Uncertainty on ct (Bs), ?m Method
Alignment 5 ? same ? same
Resolution function 3 ? same ? same
Fit Model negligible ? same ? same
Event Selection negligible ? same ? same
Fitter Bias negligible ? same ? same
B Pathology 9 n/a n/a
Handling (K?) swap n/a negligible n/a
Total 11 6 6
24
Systematic uncertainties (D0)
Systematic effect Uncertainty on ct (B0d), ?m Uncertainty on ct (Bs), ?m Method
Alignment ? ?
Resolution function negligible ? same data
Fit Model (bkg) 6 ? same data
Fit Model (signal) 5 3 data
Event Selection ( V mass) 7 ? same data
Event Selection (pT) 20 ? same MC
Fitter Reco Bias 56 35 MC
Total 60 42
25
Bs Lifetime transversity variable ?T

• Definition

• MC distributions for CP 1 CP -1 (D0)
• for accepted events.
• ? Fit extension from 2-D to 3-D in progress

26
?b?J/? ? Lifetime and Crosscheck (CDF)
CONTROL SAMPLE
27
Bs and ?b Lifetimes - Summary
28
Semileptonic Lifetimes

• The goal is to extract the Bs and ?b lifetimes
• using lD0 as a control channel
• reconstruct the D decay near lepton
• B decay not fully reconstructed
• ? extract the boost factor from MC
• extract lifetime from decay length
• CDF lepton displaced track trigger
• small statistical uncertainty
  control sample 7 ?m
• trigger bias
• D0 single muon trigger (prescaled)

29
Semileptonic Lifetimes (D0) B ? D0 µ X
benchmark analysis

• Factor K pT(D0µ)/pT(B)
• from MC (generator level, confirmed with
  recoed tracks)
• Bkg model
• - Prompt
• - ve exp,-ve exp
• - additional ve (left side)
• Resolution double Gaussian
• Results ? see next page

30
Semileptonic Lifetimes

• CDF Lifetime statistical error projections for
  70 pb-1

• D0 results for the B ? D0 µ X benchmark analysis

B 0.04 ps
B0d 0.06 ps
B0s 0.07 ps
?b 0.09 ps
31
Summary

• Lifetime measurements for inclusive B ?J/? X
  decays and for exclusive B ?J/? X channels by
  both CDF and D0
• Measurements of polarization states in B0s decay
  and of ??s/?s
• ? in progress
• Lepton displaced vertex trigger has been
  implemented at CDF for the first time
• expects high statistical accuracy for B0s and
  Lb lifetime
• Benchmark measurement of B ? D0 µ X (D0)

CDF D0 World average
B 1.63 0.05 0.04 ps 1.65 0.08 0.12 ps 1.671 0.018 ps
B0d 1.51 0.06 0.02 ps 1.51 0.18 0.20 ps 1.542 0.016 ps
B0s 1.33 0.14 0.02 ps 1.19 0.18 0.14 ps 1.461 0.057 ps
?b 1.25 0.26 0.10 ps ? In progress 1.233 0.077 ps