Lifetime and mixing
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Lifetime and Mixing. Chunlei Liu / University of Pittsburgh On behalf of CDF and D0 collaborations FPCP 2008 May 5-9. Part I Lifetime Motivation and Experiments B 0 s , B c lifetimes Part II Mixing B 0 s mixing from D0 D 0 mixing from CDF.

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Lifetime and mixing

Lifetime and Mixing

Chunlei Liu / University of Pittsburgh

On behalf of CDF and D0 collaborations

FPCP 2008

May 5-9


Lifetime and mixing

Part I Lifetime

  • Motivation and Experiments

  • B0s , Bc lifetimes

    Part II Mixing

  • B0s mixing from D0

  • D0 mixing from CDF


Lifetime and mixing

Decay of B Hadrons

kinetic and chromomagnetic operator

weak annihilation and Pauli interference

Pauli interference prolongs lifetimes:

+5% for B+, +3% for Lb

Spectator model: all b hadron

lifetimes are equal.

Heavy Quark Expansion (HQE):

Lifetime ratios are better predicted:

t(B+)/t(B0), t(Bs)/t(B0), t(Lb)/t(B0)…

Weak annihilation or scattering

reduces lifetimes -7% Lb


The b c doubly heavy meson

The Bc - Doubly Heavy Meson

• Doubly heavy with band c quark – interesting lab for studying QCD

• Both quarks decay or annihilate, shorter lifetime than light B mesons

theory prediction:

t(Bc):0.47 - 0.59 ps

arXiv:hep-ph/0308214v1

Phy Rev. D 64, 14003 (2001)

Phy Lett. B 452, 129 (1999)

hep-ph/0002127 ( and references within)


B 0 s lifetime and decay width difference

B0s Lifetime and Decay Width Difference

b

s

s

W

W

B0s→J/yf

W

c

s

c

  • Eigenstates: Bslight and Bsheavy => GL and GH

  • Gs= (GL+GH)/2 , DG = GL-GH

  • Two kinds of lifetime measurements:

  • Measure 1/Gs and DG directly (need to identify CP eigenstates)

  • Treat GL and GH together as one exponential, measure t

  • e.g flavor specific channel:


Combine t s and dg

Combine ts and DG

DG: theoretically calculable and sensitive to new Physics

Probe to New Physics : DG= 2|G12|cos(fs)


Latest hfag by 03 08

Latest HFAG (by 03/08)

  • New measurements today:

  • Bs lifetime –direct measurement

  • Bs lifetime – flavor specific

  • Bc lifetime

Theory references:

PRD 68, 114006 (2003)

PRD 70, 094031 (2004)

hep-ph/0705.3802 (2007)


Tevatron

Booster

CDF

Tevatron

p source

Main Injector

& Recycler

Tevatron

  • pp collisions at 1.96 TeV

  • 3.4 fb–1 data on tape (recorded at D0)

  • Initial instantaneous luminosity up to 3x1032cm–2s–1

Apr 2002 – Apr 2008


Cdf ii detector d detector

CDF II DetectorDØ Detector

  • Central tracking: silicon vertex detector drift chamber

  • => dpT/pT = 0.0015 pT

  • excellent vertex resolution

  • Particle identification: dE/dX and TOF

  • Excellent muon coverage

  • Goodtracker coverage

  • Silicon layer 0 installed in 2006 improves track parameter resolution

tracker


Measure t s and dg from b 0 s j y f

q

Measure ts and DG from B0s→J/yf

ct=L/bg

=Lxy/sinq/bg

=LxyM/PT

CP conservation (bs=0)

|BsH> : CP odd eigenstate ~ 25%

|BsL> : CP even eigenstate ~ 75%

S, D waves: CP even

P wave: CP odd

Angular distribution in transversity basis => separate CP eigenstates


Events selection at cdf d0

Events Selection at CDF/D0

  • Di-muon trigger

  • Neural Network selection at CDF ~ 2500 signal events

  • Cuts based selection at D0 ~ 2000 signal events


Measure t s and dg

Measure ts and DG

  • (bs free)

  • =1.52 ± 0.05(stat)±0.01(syst) ps

    DG=0.19±0.07(stat) +0.02-0.01(syst) ps-1

  • (bs=0) t=1.53 ± 0.06(stat) ps DG=0.14 ± 0.07(stat) ps-1

  • (arXiv:/0802.2255[hep-ex])

(bs=0) t=1.52 ± 0.04(stat) ± 0.02(syst) ps DG=0.08 ± 0.06(stat) ± 0.01(syst) ps-1

World’s best measurement!

Phys. Rev. Lett. 100, 121803 (2008)


B s lifetime measurement from b s d s fp p x cdf

Bs Lifetime Measurement from Bs→ Ds+(fp)p- X - CDF

x2 stats

fully and partially reconstructed channel such as: Bs→ Ds-1r(p+p0)

Double statistics!

“K” factor accounts for missing momentum and mass

Extensive test on B0, B+ control samples


Lifetime and mixing

Events Selection and Fit Strategy

  • Data (1.3 fb-1) collected by displaced-vertex trigger ( 120mm<d0<1mm )

  • ~ 1100 fully reconstructed events

  • ~ 2000 partially reconstructed events

  • => cut on lifetime ( events with ct<d0 removed)

  • modeled with “trigger efficiency curve” from MC

  • Two-step fit, 1)mass fit

  • => relative fraction of various modes and background

  • 2) lifetime fit (shape from MC, fraction from mass fit)

  • => extract lifetime only


Lifetime and mixing

Lifetime Result (CDF)

  • Fix fractions from mass fit

  • t(Bs) only free parameter

  • = 1.518 ± 0.041(stat.) ± 0.025(syst.) ps

    (http://www-cdf.fnal.gov/physics/new/bottom/080207.blessed-bs-lifetime/)

    • Lifetime for control samples:

    • B0→ D-(K+p-p-) p+ B0→ D*-(D0(K+p-)p-) p+ B+ →D0(K+p-) p+

    • Agrees well with PDG

D0 had Bs semileptonic lifetime in 2006 from Bs→Ds-m+nX

t=1.398±0.044(stat)+0.028-0.025(syst) ps

PRL 97, 241801 (2006)


B c semileptonic lifetime

Bc Semileptonic Lifetime

Missing momentum, correct pseudo-lifetime: ct= K x ct*

K= pT(J/y l)/ pT(Bc)

  • Main challenge is multiple backgrounds:

  • real J/Ψ + fake lepton

  • fake J/Ψ + real lepton

  • real J/Ψ + real lepton → from bb events

  • prompt J/Ψ + lepton

  • residual conversion (J/y+e only)


B c j y m x from d0 1 35 fb 1

Bc→J/y+m+X from D0 (1.35 fb-1)

Mass – lifetime simultaneous fit used to

disentangle small signal fraction among

large fraction of backgrounds

http://www-d0.fnal.gov/Run2Physics/WWW/results/prelim/B/B52/


B c j y l x from cdf 1 0 fb 1

Bc→J/y+l+X from CDF (1.0 fb-1)

Lifetime fit only

Muon channel Electron channel

ct=179.1+32.6-27.2(stat) mm ct=121.7+18.0-16.3(stat) mm

combined (by likelihood):

t=0.475+0.052-0.049(stat) ± 0.018(syst) ps(http://www-cdf.fnal.gov/physics/new/bottom/080327.blessed-BC_LT_SemiLeptonic/)


Combine b c lifetime from d0 and cdf

Combine Bc Lifetime from D0 and CDF

Bc lifetime measurements have been exclusive to Tevatron

Weighted average:t=0.459 ± 0.037 ps

Theory prediction:

t=0.47 – 0.59 ps


Lifetime and mixing

Part I Lifetime

  • Motivation and Experiments

  • B0s , Bc lifetimes

    Part II Mixing

  • B0s mixing from D0

  • D0 mixing from CDF


B 0 s mixing

B0s Mixing

  • two eigenstates and

  • Dms mH – mL , Gs( GH+GL)/2,DGGL– GH

  • DmsTheo =19.3 ± 6.4 ± 1.9

  • (arXiv: 0705.3802/hep-ph)

  • Dms/Dmd ∝ |Vts|2/|Vtd|2

  • CDF measured at: 17.77 ± 0.10(stat) ± 0.07(syst) ps

  • Show D0 new result today !


D m s measurement strategy

Dms Measurement Strategy

Opposite Side

Same Side


Final states reconstruction at d0

Final States Reconstruction at D0

Data collected by inclusive single and di-muon triggers, 2.4 fb-1

Final cuts maximizing S/ sqrt(S+B)

D0 Run IIa

D0 Run IIb innermost layer of silicon added resolution improved


Measure d m s at d0

Measure Dms at D0

  • Introduce amplitude, P(t) ~ 1AD cos(Dmst)

  • Fitfor A at different Dms

Δms = 18.53± 0.93(stat) ± 0.30(syst) ps-1

2.9 s significance

( DO conference note 5618)

Agrees with what CDF measured in 2006:

Δms = 17.77 ± 0.10(stat) ± 0.07(syst) ps-1


D 0 mixing

DM/GDG/G discovered

K0 0.474 0.9971964

B0 0.77 <0.01 1987

Bs 27 0.15 2006

D0 < 0.01< 0.01 2007

D0 Mixing

D0 mixing in SM occurs through either:

‘short range’ processes ‘long range’ processes

(negligible in SM)

  • Recent D0 mixing evidence :

  • Compare D0 → ππ, KK (CP eigenstates) with D0 → Kπ(Belle)

  • 2) Comparedoubly Cabibbo suppressed (DCS) D0 →K+π- with Cabibbo favored (CF) D0 →K-π+(Babar )

Lifetime ratio:

where x=DM/DG , y=DG/2G, d is strong phase between DCS and CF modes


Evidence for d 0 mixing at cdf 1 5 fb 1

Evidence for D0 Mixing at CDF (1.5 fb-1)

CDF : probe longer D0 lifetime than B factories

3.8s significance comparing DCS D0 →K+π- to CF D0 →K-π+

RD (10-3)=3.04±0.55 x’2(10-3)=-0.12±0.35 y’(10-3)= 8.5±7.6

(Phys.Rev.Lett.100:121802,2008 )

Lifetime ratio fit

Bayesian probability 1-4s contour: closed circle: best fit value open diamond: highest probability point physically allowed (x’2≥0) cross : no mixing point 3.8s


Conclusion

Conclusion

  • Best Bst and DG measurement in the world

  • Bc lifetime provide better constraint for theory

  • Bs mixing from D0 confirms CDF measurement

  • D0 mixing evidence from hadron collider

  • Expect new Lb lifetime result for the summer


Back up

Back Up


Angular analysis in transversity basis

Angular Analysis in Transversity Basis

●Bs->J/yf is P -> VV decay

➔ 3 possible angular momenta:

S, D wave: CP even

P wave : CP odd

● Separation by angular

distribution

➢ Transversity angles q, f,y 


B 0 s systematics and cross check

B0s Systematics and Cross Check

Systematics at CDF: 1) Background angular distribution 2) Mass model 3) Lifetime resolution function 4) B0 cross feed 5) Detector acceptance 6) Silicon detector alignment

Cross check sample at CDF:

B0→J/y K*0 for angular analyis

Lifetime: td= 1.52 ± 0.02(stat) ± 0.02(syst) ps

Systematics at D0: 1) Procedure test 2) Acceptance 3) Reconstruction algorithm 4) Background model 5) Detector alignment


B s j y f angular distribution

Bs→ J/yf angular distribution


B 0 j y k 0

B0 → J/y K*0

ctd = 456 +/- 6 (stat) +/- 6 (syst) μm

|A0|2 = 0.569 +/- 0.009 (stat) +/- 0.009 (syst) |A|||2 = 0.211 +/- 0.012 (stat) +/- 0.006 (syst) δ|| = -2.97 +/- 0.08 (stat) +/- 0.03 (syst) δ⊥ = 2.97 +/- 0.06 (stat) +/- 0.01 (syst)


Lifetime and mixing

Mass components:

Single B templates (MC): (signal): Bs→ Ds(fp) X (bkgd): B0, B+, Lb

Real D + track (background): template comes from fit to wrong-sign sampleDs-p-

Fake D + track (background): template comes from D sidebands


B c background summary at cdf

Bc Background Summary at CDF


One word about b lifetime status

decay mode CDF lifetime (ps), 1 fb-1 DØ lifetime (ps), 1.3 fb-1

x

expected soon x

updateexpected soon x

One word about Λb LifetimeStatus

  • DØ measurements are in agreement with the theoretical predictions and with

  • the world average

  • CDF measurement in is ~3s highw.r.t world average

  • Expect CDF measurement updates very soon


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