# Presentation: 725074

## Sergey Burdin (Fermilab)
for the DØ Collaboration
WIN03 / Lake Geneva, October 6-11, 2003

**for the DØ Collaboration**
**WIN03 / Lake Geneva, October 6-11, 2003**

- B Lifetime and Mixing in

## Detector

- Sergey Burdin (Fermilab): Lifetime & Mixing in D0 / WIN03

- 10/8/03

## Tracker

**Trigger: muon+track covers |****η****|<1.8**

- Sergey Burdin (Fermilab): Lifetime & Mixing in D0 / WIN03

- 10/8/03

## Image of Tracker from γ-conversions

- Sergey Burdin (Fermilab): Lifetime & Mixing in D0 / WIN03

- 10/8/03

## Tracking Performance (1)

- Impact Parameter Resolution

**Is not used yet for PID**

**σ****(DCA)≈53****μ****m @ P****t****=1GeV**
**and better @ higher P****t**

**Can provide**
** ****K/****π**** separation for P****tot****<400 MeV**
** ****p/****π**** separation for P****tot****<700 MeV**

- Sergey Burdin (Fermilab): Lifetime & Mixing in D0 / WIN03

- 10/8/03

## Tracking Performance (2)

- |η| for kaons from D*D0π

- Pt spectrum of soft pion from D*D0π

- Efficient muon system & tracker & tracking give us
- large sample of semileptonic B decays

- Tracks are reconstructed
-  in wide η limits
-  starting from Pt=180 MeV

- Sergey Burdin (Fermilab): Lifetime & Mixing in D0 / WIN03

- 10/8/03

## Large B Semileptonic Sample

***Large B Semileptonic Sample***

**Muon:**
**Pt > 2 GeV/c**
**Ptot > 3 GeV/c**
**nSMT > 1**
**nCFT > 1**

**Charged tracks:**
**Pt > 0.7-1 GeV/c**
**Secondary Vertex**
**L****xy**** / ****σ****L**** > 4**
**cos(****θ****(L,P****D****))>0.95**

**no hadronic PID so far (except for D****±****)**

- Sergey Burdin (Fermilab): Lifetime & Mixing in D0 / WIN03

- 10/8/03

##  History of the B Lifetime Measurements

- τ(Bd)/τ(Bs)=1±0.01
- τ(Ξ0b)≈τ(Λb) < τ(Bd) < τ(Ξ-b) < τ(Ωb)
- Γ(Λb)-Γ(Ξ-b)≈0.11±0.03ps-1
- 0.9< τ(Λb)/τ(Bd) <1

- Predictions

*Report of the B Physics *
*at the Tevatron Workshop (12/2001)*

- Sergey Burdin (Fermilab): Lifetime & Mixing in D0 / WIN03

- 10/8/03

## B Lifetime from Inclusive BJ/ψ+ X

**Method**

- Use J/ψμ+μ-  for tagging, vertex constraint, Pt determination:
- Clean signal
- Large statistics
- Good vertex resolution
- Good momenta resolution

- Large prompt J/ψ contamination
- Need Pt correction factor from MC

- Sergey Burdin (Fermilab): Lifetime & Mixing in D0 / WIN03

- 10/8/03

## B Lifetime from Inclusive BJ/ψ+ X

**Corrections**

-                                              LBxy= **L****B****xy** • **P****B****t** / |PBt|
- cτB=λB= LBxy/(βγ)t= LBxy • MB/PBt = (Lψxy • MψB/Pψt )/<F(Pψt )>

- Sergey Burdin (Fermilab): Lifetime & Mixing in D0 / WIN03

- 10/8/03

## B Lifetime from Inclusive BJ/ψ+ X

**Background (19%):**
**G+Exp(+****τ****0****)+Exp(-****τ****0****)+        Exp(+****τ****1****)+Exp(-****τ****2****)+const**
**Shape from the J/****ψ**** sidebands**
**Signal (81%):**
**Prompt J/****ψ**** (82%): G+Exp(+****τ****0****)+Exp(-****τ****0****)**** **
**J/****ψ**** from b (18%):  Exp(****τ****B****)********G**

**Results**

**<****τ****B****>=1.562±0.013(stat)±0.045(syst) ps**

**BLWG: <****τ****B****>=1.573±0.008 ps**

- Proper Decay Length Shape:

**Correction factor gives one **
**of the major contributions into **
**the systematic errors**

- Sergey Burdin (Fermilab): Lifetime & Mixing in D0 / WIN03

- 10/8/03

## B± Lifetime from B±J/ψK±

***B******±****** Lifetime from B******±************J/******ψ******K******±***

- Background from B-sidebands:
-  G + Exp(+τ1) + Exp(-τ2) +   ExpG (BS contamination)
- Signal:
- ExpG

- Proper Decay Length Shape:

**<****τ****B±****>=1.65±0.083(stat)±0.123(syst) ps**

**BLWG: <****τ****B±****>=1.652±0.014 ps**

**Fully reconstructed → No Correction Factor!**

- Sergey Burdin (Fermilab): Lifetime & Mixing in D0 / WIN03

- 10/8/03

## Bd,S Lifetimes from B  J/ψ+K0*,

- Proper Decay Length Shape:

**Background:    **
** ****G + Exp(+****τ****1****) + Exp(+****τ****2****)  + Exp(-****τ****3****) **
**Signal: **
**Exp(****τ****B****)********G**

**Signal: 105±19**

**Signal: 69±13**

******L****dt****≈114pb****-1**

- Results:

**BLWG: ****τ****Bs****/**** ****τ****Bd****=0.938±0.035**

- Similar kinematics → Some systematic errors  can be cancelled in ratio !

- Sergey Burdin (Fermilab): Lifetime & Mixing in D0 / WIN03

- 10/8/03

## B Lifetime from Semileptonic Decays B  D0μX

***B Lifetime from Semileptonic Decays ****B** **** D**0**μ**X*

- Proper Decay Length Shape:

- Background:
-  G + G + Exp(+τ1)2G + Exp(-τ2)2G + const
- Signal:
- Exp2G

******L****dt****≈12pb****-1**

- Result:

**     ****τ***B ***=1.460±0.083(stat.) ps**

- cτ** **=** **LxyMbK/Pt(D+μ)

- K = Pt(D+μ) / PtB   *(from MC)*

- Benchmark measurement

- Sergey Burdin (Fermilab): Lifetime & Mixing in D0 / WIN03

- 10/8/03

## B mixing

**Δ****M - *****difference between B******0****** mass eigenstates***** *****gives the oscillation frequency***
**Need for ****Δ****M measurement****:**
**Proper Decay Time**
**Time evolution of flavor**
**or time integrated rate (no CPV): r = N(B****0****)/N(B****0****) ≈ *****x*****2****/(2+*****x*****2****)**
***x***** = ****Δ****M / ****Γ**** = ****Δ****M • ****τ**
**Initial State Flavor Tagging (ISFT):**
**efficiency: ****ε****=(N****corr****+N****wrong****)/(N****corr****+N****wrong****+N****notag****)**
**dilution: D=(N****corr****-N****wrong****)/(N****corr****+N****wrong****)**
**Significance of mixing measurement: S ******** ****ε****D****2**
**Final State Flavor Tagging **
**from decay products**

- .

- Sergey Burdin (Fermilab): Lifetime & Mixing in D0 / WIN03

- 10/8/03

## Bd,S mixing

- ΔMd = 0.502  0.006 ps-1

*The B**d** oscillation frequency is not too high:*
* **Benchmark measurements*
* **Semileptonic B decays can be used for frequency measurements*

*The B**S** oscillation frequency is very high: ***Δ****M****S**** ****> 14.4ps****-1**** (95%CL)**
* **Good proper decay time resolution is needed for    frequency measurements: *
**S ******** ****exp(-(****Δ****M****S**** ****σ****t****)****2****)**
- Semileptonic BS:                          ~6-7k events/200pb-1 ...

- Sergey Burdin (Fermilab): Lifetime & Mixing in D0 / WIN03

- 10/8/03

## ISFT: Opposite Side Muon Tagging

- PTμ > 1.9 GeV
- Qμ – charge of muon with the highest Pt
- Classification:
- Qμ !=  QK : correct tag
- Qμ == QK : wrong tag
- No muon : No tag

**D = (57.0±19.3)%**
** ****ε**** = (5.0±0.7)% **
**ε****D****2**** = (1.6±1.1)%**

***B±************J/******ψ******K±***

-  μ

***D0 RunII preliminary:***

- Sergey Burdin (Fermilab): Lifetime & Mixing in D0 / WIN03

- 10/8/03

## ISFT: Opposite Side Jet Charge Tagging

- Pt> 0.5GeV
- ΔZPV<2cm
- Classifications:
- |Q|>0.2 && sign(Q) !=  QK : correct tag
- |Q|>0.2 && sign(Q) == QK : wrong tag
- |Q|<0.2 : no tag

***B±************J/******ψ******K±***

- Sergey Burdin (Fermilab): Lifetime & Mixing in D0 / WIN03

- 10/8/03

## ISFT: Same Side Tagging

**Excited B** decays into B and pion/kaon which carries the initial state flavor information**

**Example: ****B**********d****→ B****+****π****-**

**+****π****±**

- Sergey Burdin (Fermilab): Lifetime & Mixing in D0 / WIN03

- 10/8/03

## Summary of  Results

- B Lifetime measurements:

| Mode | τ,ps | σstat ,ps | σsyst ,ps | ratios |
| --- | --- | --- | --- | --- |
| Inclusive BJ/ψ+ X | 1.562 | 0.013 | 0.045 |  |
| B±J/ψ+K± | 1.65 | 0.083 | 0.123 |  |
| B  J/ψ+K0* | 1.51 | +0.19-0.17 | 0.20 | τBs/τBd=
0.79±0.14
 |
| BS  J/ψ+ | 1.19 | +0.19-0.16 | 0.14 |  |
| B  D0μX | 1.460 | 0.083 | ------ |  |

| Mode | ε, % | D,% | ε D2,% |
| --- | --- | --- | --- |
| Jet Charge | 46.7±2.7 | 26.7±6.8 | 3.3±1.7 |
| Muon Tag | 5.0±0.7 | 57.0±19.3 | 1.6±1.1 |

- B Flavor Tagging:

- Sergey Burdin (Fermilab): Lifetime & Mixing in D0 / WIN03

- 10/8/03

## Conclusion

- .        has magnetic field and efficient tracker with large coverage
- .        has and continues to collect large samples for B physics
- .        has produced first results on B lifetime & mixing measurements and much more excellent results are ahead

- Sergey Burdin (Fermilab): Lifetime & Mixing in D0 / WIN03

- 10/8/03

## Backup Slides

- Sergey Burdin (Fermilab): Lifetime & Mixing in D0 / WIN03

- 10/8/03

## Bd,S Masses (B  J/ψ+K0*,)

*Cuts are not the same as for LT*

- Sergey Burdin (Fermilab): Lifetime & Mixing in D0 / WIN03

- 10/8/03

## B0  J/ψ+KS

- Sergey Burdin (Fermilab): Lifetime & Mixing in D0 / WIN03

- 10/8/03