B Lifetime Results from CDF and D0

Daria ZieminskaIndiana 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/ψ + X • Exclusive B J/ψ + X channels

- B+ J/ψ + K+

- B0d J/ψ + K*

- B0s J/ψ + φ

- Λ b J/ψ + Λ• Semileptonic B Decays

3

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.

• (NLO) QCD predicted deviations in ≈ agreement with data

Heavy Quark Expansion Experiment• τ(B+)/τ(Bd) = 1.06± 0.02 1.074± 0.014• τ(Bs)/τ(Bd) = 1.00± 0.01 0.948 ± 0.038• ∆Γs / Γs ≈ 0.1 <0.54 (CL=95%)• τ(Λb)/τ(Bd) = 0.90 ± 0.05 0.796 ± 0.052

The main goal is to measure the ratios accurately.

4

B Physics at the Tevatron

Pros• Large BB cross section:

- ~ 100 µbarn total- ~ 3-5 µbarn “reconstructible”

• At 4 x 1031cm-2s-1 ~150 Hz of“reconstructible” B’s

• All B species producedTevatron – world best source of Bs and Λb

• Production is incoherent- reconstruction of both Bs

not needed

Cons• Large background

- B cross section ~10-3 total inelastic- special triggers (leptons, displaced

tracks)- combinatorics in reconstruction

• Typical kinematic cuts:- pT(µ) > 1.5 GeV/c for µ’s from J/ψ- pT(B) > 5 (6) GeV/c

-

5

Run II at the Tevatrondata available by September shutdown

• Analyses presented here based on:- CDF 138 pb -1 (di-µ trig.);

- D0 114 pb -1 (di-µ trig.); 12 pb -1 (single-µ trig.);

6

Triggers for B Lifetime Studies• CDF

Di-muon (J/ψ) pT(µ) > 1.5 GeV/c , |η (µ) | < 0.7

l + displaced track pT(e/µ) > 4 GeV/cpT(trk) > 2 GeV/c , 120 µm < d 0 (trk) < 1 mm

Two displaced tracks pT(trk) > 2 GeV/c , 120 µm < d 0 (trk) < 1 mm

• D0

Di-muon, pT(µ) > 3 GeV/c, |η (µ) | < 2.2 (unprescaled)pT(µ) > 1.5 GeV/c, |η (µ) | < 2.2 (Lum. dependent prescale)

Single µ, pT (µ) > 3-5 GeV/c, |η (µ) | < 2.2 (Lum. dependent prescale)

Displaced tracks – after shutdown

7

List of Analysis Techniques• 1D: bkg template from sideband

(variations: allow LSB ≠ RSB)

• 2D: simultaneous fit to (mass, cτ), free bkgparameters

CDFΛb J/ψ Λ

D0Semileptonic

CDF, D0Bs J/ψ φ

CDF, D0B0d J/ψ K*

CDFD0B+ J/ψ K+

CDF, D0Inclusive B J/ψ X

2D1DChannel

8

Inclusive B J/ψ + X Lifetime (D0)

2GeV/c2 2.2 2.4 2.6 2.8 3 3.2 3.4 3.6 3.8 4

2N

o. E

vts/

12.5

MeV

/c

0

2

4

6

8

10

12

14

16

18

20

22

Invariant Mass-µ+µ3x10

Run 2 Preliminary∅D

Signal = 290,296 eventsψJ/2 0.0002 GeV/c±Mass = 3.0718

2 0.0002 GeV/c± = 0.0741 σ

’ Signal = 8222 eventsψ2 0.0021 GeV/c±Mass = 3.6680 2 0.0022 GeV/c± = 0.0711 σ

PtψJ/2 4 6 8 10 12 14 16

⟩ F

⟨

0.72

0.74

0.76

0.78

0.8

0.82

0.84

0.86

0.88

0.9 / ndf 2χ 32.05 / 32A 0.03737± 0.3357 B 0.04039± -0.4953 C 0.002348± 0.7791

/ ndf 2χ 32.05 / 32A 0.03737± 0.3357 B 0.04039± -0.4953 C 0.002348± 0.7791

+ CΨtBP

) = AeΨtF(P

• Measure: λψ = L xy Mψ /pψT

• Need: λB = L xy MB /pBT

Correction factor:F = λψ / λB = Mψ pB

T / MB pψT

MC provides mean F(pψT) in

slices of pψT

D0 parametrization of F(pψT)

300k J/ψ’s

9

Inclusive B J/ψ + X Lifetime (D0)Fitting technique

Two steps:- fit λ distribution of the sidebands to get the shape of the background. The bkg parametrization gbkg(λ):

Prompt taken from MC (Gaussian plus exponential tails)

(λ>0) and (λ<0) exponentials- fit λ distribution in the signal region allowing for:

bkg distribution gbkg(λ)Prompt J/ψ (similar to prompt bkg)Exponential decay convoluted with Gaussian (b J/ψ +X)

10

Inclusive B J/ψ + X LifetimeD0 and CDF results

• D0 (114 pb -1 )

τ = 1.562±0.013(stat)±0.045(syst) psmain syst uncertainties:

correction factor: 1.6 %MC bias: 1.9 %

82% J/ψ’s prompt

• CDF (18 pb -1 , 2002)

τ = 1.526±0.034(stat)±0.035(syst) psmain syst uncertainties:

correction factor: 1.1 %resolution function: 1.5 %bkg parametrization: 1.1 %

83% J/ψ’s prompt

cmτc-0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 0.5

mµEv

ts/12

.5

1

10

102

103

104

Data

Sideband

B Signal

B Signal + background

Inclusive B Lifetime

mµ 14(syst) ± 4(stat) ± = 468 τc

Run II Preliminary∅D

ct [cm]ψJ/-0.2 -0.1 0.0 0.1 0.2 0.3

mµCa

ndida

tes /

12.

5

1

10

102

103

Total Fit

ContributionψJ/

Background Contribution

CDF Run 2 Preliminary

Signal Region Events

11

B+ J/ψ + K+ Lifetime (D0)Data and Fitting technique

1D fit steps:- Fit λ distribution of the right sideband

Prompt & (λ>0) and (λ<0) exponentials

- Fit λ distribution in the left sideband with an extra term for feeddown frommultibody B decay channels

- Fit the signal regionNorm. of feeddown = 0.12 ± 0.01 (MC)

)2

Mass (GeV/c4.6 4.8 5 5.2 5.4 5.6 5.8 6

Even

ts/ 2

0 M

eV

0

50

100

150

200

250

300

350

400 Run II Preliminary∅D

0.005 (GeV)±Mean=5.272

5 (MeV)± = 48 σ Signal 652 events ±B

0.017 ± = 0.1458 σ 3± fraction in Mean±B

B+ mass

)2

Mass (GeV/c4.6 4.8 5 5.2 5.4 5.6 5.8 6

Even

ts/ 2

0 M

eV

0

10

20

30

40

50

60 Run II Preliminary∅D

0.003 (GeV)±Mean=5.27

3 (MeV)± = 47 σ

Signal 278 events ±B

> 0.03 cm τ B+ mass c

12

B+ J/ψ K+ ; ResultsD0 CDF

cm-0.05 0 0.05 0.1 0.15 0.2 0.25 0.3

mµE

vent

s/ 4

0

1

10

102

103

data∅DTotal Fit B+ signalBackground

Run II Preliminary∅D

m (stat) +29/-37 (syst)µ 25 ± = 495 +Bλ

Lifetime +B

τ =1.65 ±0.08(stat) +0.09-0.12(syst) ps τ =1.63±0.05(stat) ±0.04(syst) ps

13

Fit Method:Simultaneous fit of M(B) → signal fraction, define sidebandscτ(B) → lifetime

( )isig stGct

cF σ

ττ,exp1

⊗

−=

( )

),(

exp

expexp

)(1

ibkg stG

ct

cf

ct

cff

ct

cf

tfff

F σ

ττ

ττττ

δ

⊗

−+

−+

+

−−−

=

++++

++

++

++

−−

−

+++−

Background Parameterisation:

Signal Contribution:

Exclusive B→J/ψX Lifetimes; X= K+, K*, φ (CDF)

14

Bs J/ψ φwith Bd J/ψ K* as a control channel

CDF D0

138 pb-1 of data2D fit (Mass, cτ)Signal events: 120 ± 13• pT(B) > 6 .5 GeV/c• pT(φ) > 2 GeV/c

• run averaged beam spot: 33µmtrack impact parameter resol: 35µm

114 pb-1 of data2D fit (Mass, cτ)Signal events: 69 ± 14• pT(B) > 6 GeV/c• pT(φ) > 2 GeV/c• pT(K) > 1 GeV/c

• event by event PV• Lxy resolution ≈ 40 µm

15

B0s J/ψ + φ ; Data (D0)

Decay Length resolution

Decay Length Error, cm0 0.004 0.008 0.012 0.016 0.02

0

20

40

60

80

100

120

140

Dots – BLine – J/ψ

16

B0s J/ψ + φ ; Data

D0 CDF

candidate mass, GeV5.1 5.2 5.3 5.4 5.5 5.6 5.7

Even

ts/20

MeV

0

5

10

15

20

25

30

DO Run II Preliminary

φ ψ J/→ sB

candidate mass, GeV5.1 5.2 5.3 5.4 5.5 5.6 5.7

Even

ts/20

MeV

0

2

4

6

8

10

12

14

16DO Run II Preliminary

φ ψ J/→ sB

(ct)>3σct/

69±14cand.

54±10cand.

17

B0d J/ψ + K* ; Data

D0 CDF

candidate mass, GeV5 5.1 5.2 5.3 5.4 5.5 5.6

Even

ts/2

0 M

eV

0

10

20

30

40

50

60

DO Run II Preliminary

* Kψ J/→ dB

2candidate mass, GeV/c5.20 5.25 5.30 5.35 5.40

2can

did

ate

s p

er

5 M

eV

/c

0

50

100

150

200

250

300

350

400 *0 Kψ J/→ 0 B

CDF Run II Preliminary -1 138 pb≈L

37 sig.±805candidates

2candidate mass, GeV/c5.20 5.25 5.30 5.35 5.40

2can

did

ate

s p

er

5 M

eV

/c

0

50

100

150

200

250

300

350

400

Fit prob: 61%

18

B0s J/ψ + φ ; Fit results

D0 CDF

, cmτcandidate c-0.05 0 0.05 0.1 0.15 0.2 0.25

Even

ts/0.0

05 cm

1

10

102

DO Run II Preliminary

φ ψ J/→ sB Data

Total Fit

Signal

Background

τ =1.19 ±0.18(stat) ±0.14(syst) ps τ =1.33 ±0.14(stat) ±0.02(syst) ps

19

B0d J/ψ + K* ; Fit results

D0 CDF

τ =1.51 ±0.18(stat) ±0.20(syst) ps τ =1.51 ±0.06(stat) ±0.02(syst) ps

, cmτcandidate c-0.05 0 0.05 0.1 0.15 0.2 0.25

Even

ts/0.

005 (

cm)

1

10

102

DO Run II Preliminary* Kψ J/→ dB Data

Total Fit

Signal

Background

ct, cm-0.1 0.0 0.1 0.2 0.3

mµ

ca

nd

ida

tes

pe

r 5

0

1

10

102

103

104 *0 Kψ J/→ 0 B

CDF Run II Preliminary -1 138 pb≈L

data

ct (Sig)

) Sct (Bkg

) Lct (Bkg

ct, cm-0.1 0.0 0.1 0.2 0.3

mµ

ca

nd

ida

tes

pe

r 5

0

1

10

102

103

104

Fit prob: 22%

20

Λb→J/ψ Λ Lifetime and Crosscheck (CDF)

CONTROLSAMPLE

Bd→J/ψK0

21

Bs and Λb Lifetimes - Summary

1 1.2 1.4 1.6 1.8 2

τ (Bs) (ps)

LEP average 1.504±0.069 ps

CDF J/ψ φ(92-95)

1.34+0.23 ±0.05 ps1.34 -0.19 ±0.05

CDF J/ψ φ(preliminary)

1.33±0.14±0.02 ps

D0 J/ψ φ(preliminary)

1.19±0.18±0.14 ps

OPAL Ds l(90-95)

1.50+0.16 ±0.04 ps1.50 -0.15 ±0.04

OPAL inclusive Ds(90-95)

1.72+0.20 +0.18 ps1.72 -0.19 -0.17

DELPHI inclusive Ds(91-94)

1.60±0.26+0.13 ps1.60±0.26 -0.15

DELPHI Ds h(91-95 Prel.)

1.49+0.16 +0.07 ps1.49 -0.15 -0.08

DELPHI Ds l(91-95 Prel.)

1.42+0.14 ±0.03 ps1.42 -0.13 ±0.03

ALEPH Ds h(91-95)

1.47±0.14±0.08 ps

ALEPH Ds l(91-95)

1.54+0.14 ±0.04 ps1.54 -0.13 ±0.04

0.8 0.9 1 1.1 1.2 1.3 1.4 1.5 1.6 1.7

τ (Λb) (ps)

World average 1.233+0.078 ps1.233 -0.076

OPAL Λc l(90-95)

1.29+0.24 ±0.06 ps1.29 -0.22 ±0.06

DELPHI Λc l(91-95)

1.11+0.19 ±0.05 ps1.11 -0.18 ±0.05

CDF Λc l(92-95)

1.32±0.15±0.06 ps

CDF J/ψΛ(01-02, Run 2, prel.)

1.25±0.26±0.10 ps

ALEPH Λ l+l-(91-95)

1.30+0.26 ±0.04 ps1.30 -0.21 ±0.04

ALEPH Λc l(91-95)

1.18+0.13 ±0.03 ps1.18 -0.12 ±0.03

22

Bs CP =+1 & CP = -1 Lifetimes • B0

s→J/ψ φ unknown mixture of CP =+1 & CP = -1 states

Standard Model predicts ∆Γs/Γs ~ 0.1Γs = ( ΓLight + ΓHeavy)/2 ; ∆Γs = ΓLight - ΓHeavy

CP=+1 CP=-1

In the case of untagged decay, the CP – specific terms evolve like:

CP - even: ( |A0(0)|2 + |A||(0)|2 ) exp( -ΓLightt)

CP - odd: |A┴(0)|2 exp( -ΓHeavyt)

• Flavor specific final states (e.g. B0s→lνDs ) provide:

Γfs = Γs - (∆Γs)2 / 2Γs + Ό ( (∆Γs)3 / Γs 2 )

23

Bs Lifetimes, transversity variable θTThe CP-even and CP-odd components have distinctly different decay

distributions.

The distribution in transversity variable θT and its time evolution is:

dΓ(t)/d cosθT ∞ (|A0(t)|2 + |A||(t)|2) (1 + cos2θT) + |A┴(t)|2 2 sin2θT

3 linear polarization states: J/ψ and φ polarization vectors:longitudinal (0) to the B direction of motion; transverse and parallel (||) and (┴ ) to each other

• MC distributions for CP = +1 & CP= -1 for accepted events (D0)

Fit extension from 2-D to 3-D in progress

candidate transversity0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Even

ts/0

.01

0

50

100

150

200

250

candidate transversity0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Even

ts/0

.01

0

50

100

150

200

250

300

350

400

450

24

Semileptonic Lifetimes

• The goal is to extract the Bs and Λb lifetimesusing lepton + D0 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 triggersmall statistical uncertainty

D0: single muon trigger (prescaled at high luminosity)

25

Semileptonic Lifetimes (D0)B D0 µ X benchmark analysis

1D Analysis• Factor K = pT(D0+µ)/pT(B)

from MC (generator level, confirmed with reco’ed tracks)

• Bkg model:- Prompt & - +ve exp,-ve exp & - additional +ve (left side)

• Resolution: double Gaussian • Results see next page

]2

) [GeV/cπMass(K 1.65 1.7 1.75 1.8 1.85 1.9 1.95 2 2.05 2.1

)2Ev

ents/

(18 G

eV/c

0

200

400

600

800

1000

Mass0D / ndf 2χ 16.68 / 20

Prob 0.6739

Nevents 102.9± 1276

Mean 0.002202± 1.857

Sigma 0.002627± 0.02937

Norm 6.659± 616.6

Slope 0.064± 1.439

Run II Preliminary∅D

Signal fraction = 0.155

Mass0D

[cm]τc-0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 0.5

Eve

nts

/(0.

0085

cm

)

1

10

102

103

X Lifetime RSBµ0B->D X Lifetime RSBµ0B->D

[cm]τc-0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 0.5

Even

ts/(

0.0

085 c

m)

1

10

102

103

X Lifetime LSBµ0B->D X Lifetime LSBµ0B->D

26

Semileptonic LifetimesD0 results for the B D0 µ X benchmark analysis

[cm]τc-0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 0.5

Even

ts/(0.

0085

cm)

10-1

1

10

102

103

data∅D

Total Fit

Signal

Background

Run II Preliminary∅D

m (stat) µ 25 ±(B) = 438 τc

X Lifetimeµ0B->D

τ =1.46 ± 0.083(stat) ps - to be compared withτ =1.60 ± 0.02 ps WA for this channel

27

Summary• Lifetime measurements for inclusive B →J/ψ X decays and for

exclusive B →J/ψ X channels by both CDF and D0:

• Measurements of polarization states in B0s decay and of ∆Γs/Γs

in progress• Lepton + displaced vertex trigger has been implemented at

CDF for the first time– expects high statistical accuracy for B0

s and Λb lifetime• Benchmark measurement of B D0 µ X (D0)

In progress1.19 ± 0.18 ± 0.14 ps

1.51 ± 0.18 ± 0.20 ps

1.65 ± 0.08 ± 0.12 ps

D0

1.233 ± 0.077 ps1.25 ± 0.26 ± 0.10 psΛb

1.461 ± 0.057 ps1.33 ± 0.14± 0.02 psB0s

1.542 ± 0.016 ps1.51 ± 0.06 ± 0.02 psB0d

1.671 ± 0.018 ps1.63 ± 0.05 ± 0.04 psB+

World averageCDF

28

Backup slides

29

Bs Lifetime Summary of existing measurements

Flavor-specific final states:Γfs = Γs - (∆Γs)2 / 2Γs + Ό ( (∆Γs)3 / Γs

2 )

Γfs ≈ Γs = ( ΓLight + ΓHeavy)/2CP=+1 CP=-1

∆Γs = ΓLight - ΓHeavy

Unknown mixture of ΓLight , ΓHeavy

(predominantly CP = +1)

ALEPH (Ds- l+)1.54±0.14±0.04

DLPH (Ds)1.60±0.26±0.14

ALEPH (Ds)1.47±0.14±0.08

OPAL (Ds- l+)1.50±0.16±0.04

OPAL (Ds)1.72±0.20±0.18

CDF (Ds- l+)1.36±0.09±0.06

DLPH (Ds)1.53±0.16±0.07

DLPH (l+)1.42±0.14±0.03

Experiment (channel)Value(10-12s)

D0 (J/ψ φ) - prelim1.19±0.18±0.14

CDF (J/ψ φ) - prelim1.33±0.14±0.02

CDF – (J/ψ φ)1.34±0.21±0.05

30

Systematic uncertainties (CDF)

± 6± 6± 11Totaln/anegligiblen/aHandling (Kπ) swapn/an/a± 9B+ PathologysamesamenegligibleFitter BiassamesamenegligibleEvent SelectionsamesamenegligibleFit Modelsamesame± 3Resolution functionsamesame± 5Alignment

Uncertainty oncτ (Bs), µm

Uncertainty oncτ (B0

d), µmUncertainty oncτ (B+), µm

Systematic effect

31

Systematic uncertainties (D0)

datasame± 7Event Selection ( V mass)

datasame± 6Fit Model (bkg)

± 42± 60TotalMC± 35± 56Fitter & Reco BiasMCsame± 20Event Selection (pT)

data± 3± 5Fit Model (signal)

datasamenegligibleResolution functiondatasame ± 5Alignment

MethodUncertainty oncτ (Bs), µm

Uncertainty oncτ (B0

d), µmSystematic effect