# Presentation: 406698

## B Masses and Lifetimes at the Tevatron

- Satoru Uozumi
- University of Tsukuba

- HCP06 @ Duke University

## In this talk we cover:

- Excited B Mesons
- Bc Meson Mass and Lifetime
- B Hadron Lifetimes :
- Bs flavor specific
- Bs  K+K- (L)
- b

- Results are based on 0.36 ~ 1 fb-1 in Tevatron Run II.

## B Production at pp collider

**B Production at *****pp***** collider**

- Compared to e+e- experiments on (4S), Tevatron have:
- Larger b production rates (~10 b v.s. 1.1 nb )
- Generate not just B-/B0, also Bs0, Bc-, b0
- Sizable Lorentz boost ( ~ 2 - 4)
-  useful for lifetime measurement
- Large QCD background ( ~x1000 larger than b cross-section)
- Collision rate ~1MHz  tape writing limit ~100 Hz         Online triggering and reconstruction is a challenge

- q

- q

- b

- b

- g

- g

- b

- b

- g

- q

- b

- b

- q

- g

- g

- g

- b

- b

- Flavor creation
- (annihilation)

- Flavor creation
- (gluon fusion)

- Flavor excitation

- Gluon splitting

## Tevatron Detectors

- CDF
- Excellent mass and impact parameter measurement
- Good ability of lepton identification

- DØ
- Extended tracking and
-     muon coverage
- Good electron identification

## The B Triggers

-  Lepton triggers
- Single and di-lepton triggers
- Muon trigger is a key for DØ      B physics program
- CDF have 8 GeV lepton triggers  for semileptonic mode,  and    di-muon triggers to capture       B  J/ X or   .
-  Displaced track triggers (CDF only)
- Displaced track + leptons for semileptonic modes
- Two oppositely-charged displaced tracks for hadronic modes
- Workhorse triggers for CDF B physics

## Tevatron performance

**Tevatron performance**

- Tevatron delivered more than 1.5 fb-1 up to Feb 2006
- Recorded 1.4 fb-1(CDF) / 1.2 fb-1 (DØ)
- Now ~ 1.0 fb-1 reconstructed and under analysis

- 2006

- 2005

- 2004

- 2003

- 2002

- 1 fb-1

- 1.5 fb-1

## Excited B Mesons - Overview

|  | Decay | Width |
| --- | --- | --- |
| B0* | B (S-wave) | Broad |
| B1* | B* (S-wave) | Broad |
| B1 | B* (D-wave) | Narrow |
| B2* | B, B*(D-wave) | Narrow |

- There are four L=1 states of (bq) system:

- B0* and B1* have broad width (~100 MeV) and difficult to observe.
- B1 and B2* are narrow (~10 MeV) but not yet well established experimentally.

- Prediction of mass spectra
- M. Pierro, E. Eichten,
- PRD 64 114004 (2001)

- B

- B*

- B0*

- B1*

- B1

- B2*

## Excited B Mesons (B1, B2*)

**Excited B Mesons (B****1****, B****2*********)**

- Data size ~ 370 pb-1 in CDF Run II
- Searched for B+X final state in ~4000 of B+ candidates from J/ K+ and D0  decay modes
- Signal from following states are observed in mass difference Q = M(B+) - M(B+) - M()
-     B1  B*+,  B2*  B*+,  B2*  B+

## Excited B Mesons (B1, B2*)

**Excited B Mesons (B****1****, B****2*********)**

- DØ 1 fb-1

- New result from DØ Run II with 1 fb-1
- Evaluate mass difference     Q = M(B+) - M(B+)
- B1  B*+
- B2*  B*+
- B2*  B+
- Their width is also measured assuming  (B1) = (B2*)

## Excited Bs Meson (Bs2*0)

- JP = 2+ state of (bs) system
- Searched for Bs2*0  B+K- decays followed by
-    B+  J/ K+ from 1 fb-1 at DØ
- First direct observation with 5 significance !

- DØ 1 fb-1

## Bc Meson - Introduction

**B****c**** Meson - Introduction**

- Ground state of two heavy flavors (bc)
- First found in CDF Run I (~20 events), but not yet well studied
- Important check of theoretical predictions given
- Mass prediction from lattice QCD calculation
- Lifetime should be (Bc) = 1/(0.6 + 1.2 + 0.1) ~ 0.5 ps
-    if 3 following diagrams contribute to the decay.
- CDF II results from 365 pb-1 published/submitted to PRL

## Bc Mass

- Fully reconstructed signal with Bc  J/  decay
- New result with ~ 800 pb-1 from CDF Run II
- 38.9 events observed ( >6 significance)
- Best Bc mass measurement !
- Agree with various lattice QCD calculations

## Bc Lifetime

- Measured with high-statistics semileptonic mode,
-    Bc  J/e 
- ~ 203 candidates (5.9 )
-    from ~360 pb-1 in CDF Run II
- World best measurement !!
- Observed lifetime shows consistent value from the         3 expected decay diagrams         ( ~ 0.5 ps)

## B hadron Lifetimes – why important?

- Because (b) is a basic observable
- Test _H_eavy _Q_uark _E_xpansion
- Expand decay width in powers of (1/mb)
- It predict lifetime relations of B hadrons :
- (B+)/(B0) = 1.00 + 0.05 x (fB/200 MeV)2
- (Bs0)/(B0) = 1.00 _+_ 0.01
- (b)/(B0) ~ 0.9
- These predictions should be tested with actual measurements
- The B+/B0 lifetimes are very precisely measured by Belle and Babar
- However Bs and b are original with the Tevatron !

- Theory

- Experiment

- C. Tarantino *et al*.,
- hep-ph/0203089

## Bs and Bs mesons are mixed each other due to 2nd-order weak interaction.
Assuming no CP violation, two CP eigenstates are written as :

- Bs and Bs mesons are mixed each other due to 2nd-order weak interaction.
- Assuming no CP violation, two CP eigenstates are written as :

**B****s**** Lifetime**

- “Flavor-specific” lifetime measurement
-     ... use final state with equal
-          fractions of BsL and BsH at decay
- L (= 1 / L) measurement
-     ... use Bs  K+K- final state (~95% CP even decay)
-  measurement with Bs  J/  mode
-     ... Separate CP - even / odd states by angular analysis
-           Recent DØ result in next talk by S. Burden

- Current approaches to measure L, H, or 

## Bs Lifetime (flavor-specific)

- High-statistics semileptonic modes,
-    Bs  Ds l  ( l = e,  )
- Lepton pT > 8 GeV, high-S/N and non ct-biased sample
- ~1156 partially reconstructed decays from ~ 360 pb-1 inclusive lepton triggers in CDF Run II
- Best measurement for the ratio
-    (Bs)/(B0)
- Update underway with increased statistics

## Bs Lifetime (flavor-specific)

**B****s**** Lifetime (flavor-specific)**

- Fully reconstructed hadronic decays from displaced track trigger
- 360 pb-1 in CDF Run II
- Removing trigger bias is a key
- Fit mass and decay length simultaneously, and extract lifetime
- Update with 1 fb-1 ongoing

- Bs0  Ds- 

- Bs0  Ds- -

## Bs Lifetime (flavor-specific)

- Lifetime measurement with semileptonic decay                  Bs  Ds  
- ~ 0.4 fb-1 of inclusive muon sample in DØ Run II
- Very high statistics thanks to large Br. of semileptonic decays and low muon pT threshold (pT()>2 GeV)
- Current world best measurement of flavor-specific (Bs) !

## Bs lifetime (L, )

**B****s**** lifetime (********L****, ********)**

- Measure “light” lifetime L                    with Bs  K+K- (~95% CP even state)
- Data from displaced track trigger,  ~370 pb-1 in CDF Run II
- Several Bs/Bd  h+h- components resolved by mass, kinematics, and PID information.
- Bd lifetime is fixed to World Average
- Extract  using flavor-specific (Bs) from other measurements

- 

- (average) (ps)

- CDF Bs  K+K-

**Flavor**
**specific**

- B0  K+K-,K-+
- Bs  K+K-
- Background

## b Lifetime

******b**** Lifetime**

- New and hot result from CDF with 1 fb-1!
- Measured with fully reconstructed b  J/ 0 decay
- 542 b candidates found and used for the lifetime measurement
- World best (b) measurement !

## On the (b)/(B0), experimental results show ~2 lower value than theoretical prediction so far.
However the new result sits above the theoretical prediction and world average.
New impact to the theoretical calculation?                    Need more experimental inputs to conclude the issue.

- World Average
- (without this result)

- NLO
- (C.Tarantino et al.,
- hep-ph/0203089)

**CDF New**
**Result**

- On the (b)/(B0), experimental results show ~2 lower value than theoretical prediction so far.
- However the new result sits above the theoretical prediction and world average.
- New impact to the theoretical calculation?                    Need more experimental inputs to conclude the issue.

******b**** Lifetime – Measurement vs Theory**

## Conclusions

- Tevatron is a gold mine of the world largest Bc / Bs / b sample !
- We are entering the stage of precise measurement of the B** and Bc meson.
- Many interesting results with Bs and b lifetime are coming.
-    (More about Bs to come in next talk by S. Burden)
- There results provide very good tests of the various theoretical prediction.
- More precise updates expected toward the summer !

## Backups

## The CDF II detector

- 7 - 8 silicon layers
- 1.6 < *r *< 28 cm,  *|z|*<45 cm
*|**η**|* ≤ 2.0  σ(hit) ~ 15 μm

- time-of-flight
- 110 ps at 150 cm
*p, K, **π* identific.
- 2σ at *p *<1.6 GeV/c

- 96 layer drift chamber
*|**η**|* ≤ 1.0  44 <* r *< 132 cm,      *|z|*<155 cm    30k channels,    σ(hit) ~ 140 μm
- dE/dx for *p, K, **π**,* e identification

-  coverage
*|****|* ≤1.5
- 84% in 

**The CDF II detector**

## D0 Detector

- 2T Solenoid
- forward & central
-    muon detectors
-    with coverage
-    ||<2
- Fiber Tracker
-     8 double layers
- Silicon Detector
-    up to ||<2.5