# Presentation: 691855

## B Physics at Tevatron Run II

**Kin Yip**

**     **

**Moriond QCD: La Thuile, Mar. 29****th****, 2004**

**     ****Collider and Detector**
**     ****B Masses & Lifetimes**
**     ****B mixing**
**     ****Exotic states & Rare decays**
- `

## Integrated Luminosities

-  **290 pb****-1**** on tape per experiments**

**CDF**

** ****Data taking efficiency: typically 80-90%**
** ****stable for both experiments**

**Results in this talk:**
**CDF analyses: ~65 - 220 pb****-1**
**D********  analyses : ~115 - 250 pb****-1**

## Detectors

- Silicon microvertex tracker
- Axial solenoid
- Central tracking
- High rate trigger/DAQ
- Calorimeters and muons

- CDF
- L2 trigger on displaced vertexes
- Particle ID (TOF and dE/dx)
- Excellent mass resolution
- DØ
- Excellent muon ID
- Excellent tracking acceptance || < 2-3
- L3 trigger on impact parameter/L2 impact parameter trigger being commissioned

**Detectors**

##  Large production cross section including Bs & b
 Even larger inelastic cross section 
(S/B10-3)  specialized triggers:
Single lepton triggers
Dilepton triggers such as
	J/    +  - 
Track triggers moved to L1 (RunII)
In Run II,  L2 trigger on displaced   tracks using SVX allows CDF to  trigger purely hadronic B decays and study  such as
	B0 +, Bs Ds+ ...
 Precise 2nd vertex reconstruction

** ****Large production cross section including B****s**** ****& ********b**
** ****Even larger inelastic cross section **
**(S/B********10****-3****) ******** specialized triggers:**
**Single lepton triggers**
**Dilepton triggers such as**
**	****J/ ******** ******** ******** ****+ ******** -**** **
**Track triggers moved to L1 (RunII)**
**In Run II,  L2 ****trigger on displaced   tracks using SVX**** allows CDF to  ****trigger purely hadronic B decays and study  such as**
**	****B****0 ********+************, B****s**** ********D****s************+ ****...**
** ****Precise 2****nd**** vertex reconstruction**

-  **Hadron colliders challenge**

**at 2 TeV**

**at ********(4S)**

**at Z****0**

## B Hadron yields for D

**B Hadron yields for D******

**B** mass measurement with 115 pb****-1**

**B****0**

**B****+**

**B****0**

## b and BS masses

******b**** and B****S ****masses**

**M(*****Bs*****) = 5365.50 ******** 1.29 (stat) ******** 0.94 (sys) MeV/c****2**
**M(********B****) = 5620.4 ******** 1.6 (stat) ******** 1.2 (sys) MeV/c****2**
**World’s best measurements from CDF**

**200 pb****-1**

- To be reprocessed with extended tracking  improve yield by 50%

## Bs Lifetime

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

****** ****L**** dt ******** 115 pb****-1**

******Bs****/********0****=****0.79 ******** 0.14**

******Bs****/********0****=****0.89 ******** 0.10**

## (B+)/(B0) from semileptonic decays

******(B****+****)/********(B****0****) from semileptonic decays**

**Preliminary result:**
******(B****+****)/********(B****0****) = 1.093 ******** 0.021 (stat) ******** 0.022 (syst)**
** ****one of the most precise measurements**

**From B****************D*****X and ****B****************D****0****X and sample compositions based on measured branching fraction & isospin relations, one can measure the ratio ********(B****+****)/********(B****0****). **
** **
**Additional inputs include :**
** ****K-factors (from simulation)**
** ****Relative reconstruction efficiencies for different B decay modes (from simulation)**
** ****Decay length resolution (from simulation)**
** ****fixing ********(B****+****) = 1.674 ******** 0.018 ps  [PDG]**

-  **data**
****** ****fit**

- 82% B

- 86% B0

## b Lifetime

- Largest systematic error is from an asymmetric track reconstruction in the COT ~ 26 m
- Work is in progress to add more data and use better track reconstruction
******(********b****) measurement in D******** is in progress**

## B0/B0 mixing: results from D 

**Work in progress:**
-     - other tagging methods:
-           jet charge,
-           same side tagging
-    - add more decay channels

**We use our large sample of semileptonic B0/B0 decays to measure ********m****d****:**
-  This analysis uses opposite-side muon tag
-  **Preliminary results:**
**   ********m****d**** = 0.506 ******** 0.055 (stat) ******** 0.049 (syst) ps****-1**
** ****Consistent with world average:**
**          ****	****0.502 ******** 0.007 ps****-1**
-  Tagging efficiency:    4.8  0.2 %
-  Tagging purity:         73.0  2.1 %

## Towards Bs mixing

**Towards B****s**** mixing**

**Semileptonic decays:**
**   ****- Very good statistics but poorer time resolution**
**   ****- If ********m****s**** ******** 15 ps****-1**** expect **
**     ****a 1-2 ******** measurement with 500 pb****-1**

## Towards Bs mixing

**Flavor-tag side**

**Fully reconstructed hadronic decays:**
** ****Poorer statistics**
** ****Excellent time resolution**
** ****need a few fb****-1 ****of data to reach **
******ms ******** 18 ps****-1**** **
** ****CDF “golden channel”: ****B****s**** ******** ****D****s**** ****** **maximum proper time resolution to resolve fast oscillations. **
** ********P****T****(B)****/P****T****(B) ******** 0.5%**
** ****Reconstructed  the signal with  yield / lumi = 0.7/pb****-1****  and  S/B ~ 2 **

**Towards B****s**** mixing**

**BR(Bs ******** Ds******** ) measured :**

- t = 67 fs

## Both CDF & DØ have confirmed BELLE’s  discovery of the X(3872) 

** ****300 ******** 61 candidates**
** ****4.4 ******** effect**

******M = 774.9 ******** 3.1(stat) ******** 3.0 (sys) MeV/c****2**
******M +** **M(J/********)** **= 3871.8 ** ****** 4.3**** ****MeV/****c****2**

** ****730 ******** 90 candidates**
** ****~****12 ******** effect**

**M****X**** = 3871.3 ******** 0.7 (stat) ******** 0.4 (sys) MeV/c****2**

**220 pb****-1**

**Both CDF & DØ have confirmed BELLE’s  discovery of the X(3872)**** **

**Belle: M****X**** = 3872.0 ******** 0.6 (stat) ******** 0.5 (sys) MeV/c****2**

##        X(3872) – (2S) comparison

** ****Is the *****X***** charmonium, or an exotic meson molecule?**
** ****No significant differences between **********(2S) and *****X***** have been observed yet**
** ****From isolation and decay length comparisons, the production of X has the same mixture of prompt and long-lived fractions as the **********(2S)**

## Rare decays – Bd,s  

**BR(B****s**** ******** ********) ~ 10****-9**** suppressed in SM (SUSY physics two orders of magnitude enhancement)**
**Blind analysis optimized for 300-400 pb****-1**** (~ 1 ******** 0.3 expected bkg)**

- Limits at 90% C.L.
- BR(B**s**   ) **** 5.810 7
- BR(B**d**   ) ****** **1.5107

**B****s ****factor 3 better than best published limit (Run I)**
**B****d**** slightly better than Belle’s at LP03: 1.6 E-7@90%CL**
**Still room for improvement: ******** Acceptance & ******** bkgs**

## Rare decays - Bs  

**Optimised cuts using Random Grid Search [Prosper, CHEP’95; Punzi, CSPP’03] based on the mass sidebands.    After optimisation:**
** ****expect 7.3 ******** 1.8 background events in signal region**
** ****signal efficiency: 30 %**

**Expected limit (Feldman/Cousins):**
**    ****Br(B****s**** ******** ********+**** ********-****) < 9.1 ******** 10****-7****  @ 95 % CL    (stat only)**
**    ****Br(B****s**** ******** ********+**** ********-****) < 1.0 ******** 10****-6****  @ 95 % CL    (stat + syst)**
**    ****(expected signal has been normalised to B******** ******** J/******** K******** )**

******180 pb****-1**

**The analysis has not been **
***unblinded***** yet (signal region still hidden).**
**It is still being optimized (without bias) and expected to improve ...**

**Rare decays -**** B****s**** ******** ******

## CP Violation - Two body charmless decays B  h+h-

**1. Extracting the signal**
**Displaced track trigger at **
**L2 gives CDF accessibility **
**to rare hadronic decays **
**with high S/B.**

**Time dependent asymmetry B****d**** ******** ******** (******** angle)  and B****s**** ******** KK (********angle)**
**Direct CP asymmetry of the self tagging modes B****d**** ******** ********K and B****s**** ******** K******

**2. Separation of the components**
**dE/dx ~ 1.3******** for K/p separation **
**Statistical separation is still possible**
**Unbinned log-likelihood fit defined including kinematical variables & dE/dx**

| Mode | Yield (65 pb-1) |
| --- | --- |
| B0  K | 14817(stat.)  17(syst) |
| B0    | 3914(stat.)  17(syst) |
| Bs  KK | 9017(stat.)  17(syst) |
| Bs  K | 311(stat.)  17(syst) |

## Observation of B    D** X 

**Start from our “B ******** ******** ******** D*****-**** + anything” sample, and “reconstruct another ********+****”. **
**Look at ****mass of D*****-**** ********+**** system****.**

**wrong-sign combinations**

**Excess in right-sign combinations**
**can be interpreted as interfering D****1****0**** and D****2*********0****.**

**From topological analyses at LEP we know:**
**   ****Br(B ******** D*****+**** ********-**** ******** ******** X) = 0.48 ******** 0.10 %**
**D****Ø’s preliminary result constrains the resonant contribution**
**   ****Br(B ******** {D****1****0****,D****2*********0****} ******** ******** X) ******** Br({D****1****0****,D****2*********0****} ******** D*****+**** ********-****) = 0.280 ******** 0.021 (stat) ******** 0.088 (syst)%**

**Work in progress:**
- extract separate
- amplitude, phase
- for each state.

- We study D**1****0**, D**2*********0** produced in semileptonic B decays.  Constrain D spectroscopy; also improve understanding of the sample of semileptonic B decays we use for lifetime, mixing, ... measurements.

## Summary

**Excellent B physics prospects for Run II**** at Tevatron:**
** ****After 2003 fall shutdown, Tevatron has enjoyed substantial improvement and performance is steadily ramping. **
** ****Tevatron offers a broad range of B physics programs.**
** ****Both experiments have confirmed the discovery of X(3872).**
** ****Competitive ****mass & lifetime**** measurements **
** ****eg. ****best in  ********B ****& B****s ****mass measurements**
** ****Both ****expts. are moving to attack B **** ****mixing in semi-leptonic & hadronic decays.**
** ****Rare decays: look for physics beyond the standard model.**
** ****Set best limits in BR(B****s**** ******** ************ ************) & BR(B****d**** ******** ************ ************)**

## BACKUP

## B./B0 Lifetimes

**B********.****/B****0 ****Lifetimes**

**CDF Run II Preliminary**

**B****+****: c******** = 499********12(stat)********6(sys) ********m**
**B****0****: c******** = 446********15(stat)********8(sys) ********m**
******+****/********0****=1.119********0.046(stat)********0.014(sys)**

**B****+****: c******** = 495**** ******** ****25(stat) ****+31****(sys) ********m**
**B****0****: c******** = 4****53**** ****+58****(stat) ******** ****60****(sys) ********m**
******+****/********0****=1.09 ****+0.15**** (stat) ****+0.16 ****(sys)**

** ********37**

** ********51**

******£dt ******** 115 pb****-1**

**  ********0.14**

******0.17**

******£dt ******** 138 pb****-1**

## B Lifetime from Inclusive B  J/+X

**B Lifetime from Inclusive B ******** J/********+X**

**F: correction factor to use the pT(J/ ********) to estimate the ****momentum of the B to find proper time. Obtained from Monte Carlo**

**J/******** from**** B’s = 18%**
**... ****similar % seen at CDF**

**Correction factor leads to the major systematic error**

****** ****= 1.564 ******** 0.014  ps (PDG)**

****** ****= 1.562 ******** 0.013 ******** 0.045  ps**** **

******£dt ******** 114 pb****-1**