# Presentation: 448780

## B hadrons lifetimes @ Tevatron

- B hadrons lifetimes @ Tevatron

**By Eduard De La Cruz Burelo**
***University of Michigan***
**On behalf of the CDF and D0 collaborations**

**Lancaster University UK,  2-8 July, 2006**

- BEACH 2006

## CDF and DØ Detectors

- Complete description in other talks :
*** ******S. Donati, CDF detector and triggers for B Physics***
*** ******L. Welty, D0 detector and triggers for B Physics***

## Outline

- In this talk
- Bs lifetime in semileptonic decays
- Bc lifetime
- Λb lifetime
- CDF/D0 measurements no presented here
- B+,B0, and Bs lifetime in B→J/ψX decays
- B+,B0, and Bs lifetime in hadronic decays
- B+ and B0 lifetime in semileptonic decays
- Bs lifetime in Bs→K+K-
- Summary, conclusions and future measurements...

## Motivation

- EXPERIMENT

- THEORY

- Testing HQE, where light quarks are included via *1/m**b* perturbative expansions.
- Expect some differences between          lifetimes of different species:
- τ(B**+****) ≥ **τ(B0) **≈ **τ(Bs) > τ(Λb) >> τ(Bc)
- Lifetime ratios are usually reported since it reduces uncertainties
- Currently *b*-baryons are accessible at high statistics at the Tevatron.

- C. Tarantino, hep-ph/0310241

## Current status 

**HFAG**
**hep-ex/0505100**

-  B+,B0 and Bs mesons, excl. reconstructed in hadronic decays (CDF 360 pb-1)
-  τ(B+) = 1.66 ± 0.03(stat) ± 0.01(syst) ps
-  τ(B0) = 1.51 ± 0.02(stat) ± 0.01(syst) ps
-  τ(Bs) = 1.60 ± 0.10(stat) ± 0.02(syst) ps
-  τ(B+)/τ(B0) = 1.10 ± 0.02(stat) ± 0.01(syst)
-  τ(Bs)/τ(B0) = 1.06 ± 0.07(stat) ± 0.01(syst)
- Direct measurement of the lifetime ratio (D0 440 pb-1)
**τ****(B****+****)/****τ****(B****0****) = 1.080 ± 0.016(stat) ± 0.014(syst)**

**Measurements from CDF/D0 no presented in this talk (just to compare):                             **

## Lifetime measure techniques

**Fully reconstructed decay:**
-  Using proper decay length method:

- Transverse component of the boost

- The distribution of  is related to the lifetime of the B

***“******R” *****is the resolution function**

## Lifetime measure techniques

** ****Partially reconstructed decay:**
-  Using pseudo-proper decay length method:

*** ******p******T******(semi)*** : Transverse momentum of the semi-reconstructed decay
*** ******K ***:  factor to account for the momentum of missing particles in the B decay. Extracted from MC

***“******R” *****is the resolution function**

**Signal p.d.f.:**

## Bs system  

*B*s system

- Most general eigenstates:

- Schrödinger equation:

- Heavy (*H*) and light (*L*) *B**s* eigenstates are expected to have different widths

-  Relation of matrix elements to decay and oscillation parameters:

** ****Kin Yip, Measurements of Bs lifetime difference at Tevatron**

** ****J. Walder, *****B******s***** oscillation measurements at D0**
** ****G. Salamanna, *****B******s***** oscillation measurements at CDF**

## Bs lifetime in semileptonic decays

- CDF and D**** have measured the *B*s lifetime in the semileptonic decay ***B******s******→D******s******l************X***, *l*=e, (DØ use only )
- It is a equal mixture of CP states, extra constraint to  ΔΓ/Γ:
- Large statistics from muon triggers

**τ****m****(*****B*****s****) is the mean *****B*****s**** lifetime obtained from a fit assuming a single exponential decay – I. Dunietz et al, Phys. Rev. D63 114015 (2001) -.**

## Bs semileptonic samples

- D0: Muons with pT>2 GeV

- CDF:  8 GeV single lepton trigger (muons and electrons)

*B*s semileptonic samples

## Primary vertex

-  K factor is extracted from MC
-  Charm and bottom background are included in the fit

- Pseudo-proper decay length:

## Bs lifetime results:

- CDF 360 pb-1
- D0 400 pb-1
- World average(2006):

- Best world measurement !!!. Hep-ex/0604046

## Constraining ΔΓ/Γ 

- Constraining ΔΓ/Γ

- R. Van Kooten: _[hep-ex/0606005](http://arxiv.org/abs/hep-ex/0606005)_

**One sigma contours of flavor-specific decays lifetime, including D0 measurement**.

**For ****ΔΓ****/****Γ**** and Bs→K****+****K****-**** lifetime see:**** **
** ****Kin Yip, Measurements of B****s**** lifetime difference at Tevatron**

## Λb lifetime in the fully reconstructed decay Λb→J/ψΛ

- Lightest b baryon (udb)
- World average lifetime dominated by measurements in semileptonic decay channels, where Λb is not fully reconstructed.
- Currently produced in high statistics only at Tevatron, (no produced in B factories)
- Testing Heavy Quark Expansion theory in three quarks system.

## R is the detector resolution

****

****

**Λ**

**π**

**p**

**Beam line**

****** ****distribution related to the ****Λ****b**** lifetime:**

## Measurement method

-  λ + mass distribution
- (signal + bkg)

- Models for
-  λ + mass distribution

- Simultaneous Mass & lifetime likelihood fit

- Signal selection

**Fitting procedure**

**B****0********J/******** K****S ****is used as a control sample due to its similar topology, lifetime measured at the same time. It can be used to compute the lifetime ratio ****τ****(****Λ****b****)/ ****τ****(B****0****) **

**Background p.d.f.:**
** ****Resolution for zero lifetime component**
** ****Exponential decays for short and long-lived bkg.**

**Signal p.d.f.:**
** ****Exponential decay convoluted with the resolution function**

## Λb mass signal

***PRL 94, 102001 (2005)***

**L=250 pb****-1**

## D0 Λb lifetime measurement

***V.M Abazov et al, PRL 94, 100201 (2005)***

**Measurement in 250 pb****-1**** of data, in the decay:**

## New CDF’s Λb lifetime measurement

- New CDF’s Λb lifetime measurement

**First time the ****Λ****b**** lifetime is measured as large as to the B****0**** lifetime. New precision is at the level of the world average.**

**World average:**
**τ****(****Λ****b****)=1.23 ± 0.08 ps**

## Cross check for lifetime measurement (CDF)

## Slide 21

## Slide 22

## Bc lifetime

-  Bound state of two heavy quarks (b and c)
-  Bc is the only meson with different heavy flavors
-  Only weak decays possible
-  Low production rate B0:B+:Bs:Λb ≈ 40:40:10:10, Bc~0.5%
-  Difficult to select due to its short lifetime

- See dedicated talk to Bc:
-  **A. Rahaman, New results on B****c**** in Tevatron**

## Lifetime extracted from Bc → J/Ψ l ν samples

- CDF in J/Ψe channel (360 pb-1 )
- DØ in J/Ψμ channel (210 pb-1 )

## Bc lifetime measurement

- CDF: lifetime measured in J/Ψe channel (360 pb-1 )

- DØ: lifetime measured in J/Ψμ channel (210 pb-1 )

- Prediction:
- 0.55 ±0.15 ps
- V. Kiselev, hep-ph/0308214

- Lifetime measurement using pseudo-proper decay length, K factor from MC

## Summary

- A lot of lifetime measurements from the Run II of Tevatron. No possible to cover all of them in this talk.
- New CDF Λb lifetime is surprising high compare to the world average. New measurements in complementary channels to come to support or cross check this.
- Best world measurement of Bs lifetime in semileptonic decay, an extra constraint to ΔΓ/Γ and the possibility of new physics in the Bs system.
- Bc lifetime measurement consistent with prediction. Measurements in fully reconstructed decay channels in the future will help to improve the precision.

## Future measurements...

- More results in the future:
- DØ
- Updated b J/ Lifetime with 1 fb-1
- Measurement of b Lifetime in semileptonic decays using 1 fb-1
- CDF
- Lifetime measurement in b c
- Update of lifetime of B hadrons in B J/ X channels using 1 fb-1

- This measurements will cross check the CDF lifetime measurement what is 3σ away from the world average.