# Presentation: 177374

## Run II Beauty Physics at CDF and DØ

**. Introduction**
**. Run II Detectors**
**. CP Violation**
**. B****s**** Mixing**

- Wendy Taylor
- SUNY Stony Brook
- on behalf of the CDF and DØ Collaborations

## Introduction

**Why study B physics at the Tevatron?**
**Large rate:****	**

**at 2 TeV**

**at Z****0**

**at ********(4S)**

**All species, including B****s****, B****c****, ********b,**** produced**

## Introduction

**Topics include**
**CP violation and CKM angles**
**sin(2********) (****B°********J/******** K****s****) **
****** ****(B****0******** ********+ ********-****)**
****** ****(B****s****0******** ********+ ********-****)**
**B****s**** mixing**
**Cross sections**
**Spectroscopy and lifetimes**
**Rare and radiative decays**
**Charmonium polarization**

## Run II DØ Detector

## Run II CDF Detector

## Highlights for Run II

**Trigger on tracks at Level 1**
**Trigger on displaced tracks (impact parameter) at Level 2**
**New tracking systems**
**Increased muon coverage**
**DØ has magnet, fiber tracker, silicon vertex detector, EM preshowers**
**CDF has Time-Of-Flight for kaon ID, layer 00 silicon, EM plug calorimeter**

## CKM Matrix

- (**)

- (0,0)

- (1,0)

**

**

**

********is the sine of the Cabibbo angle**
***A***** and ********** have been measured to a few percent **

## CKM Matrix

## CP Violation in B° Decays

**Reconstruct B°********J/******** K****s**** decays to measure sin(2********)**

**Direct and mixed decays yield the same CP eigenstates at different rates**

## B°J/ Ks Reconstruction

**Measure decay length**
**Tag flavour at production **

****** ****+**

****** ****-**

****** ****+**

****** ****-**

****** ****-**

**b**

**b**

**OST - lepton and jet charge**** **

**SST - pion charge **

**J/******

**K****s**

## Flavour Tagging

**Determine production flavour (   vs   )**
**Opposite-side tags (other b)**
**charge of lepton from semileptonic decay**
**charge sum of particles in jet**
**Same-side tags**
**charge of pion produced in fragmentation or B** decay**
**Tagging efficiency**** ********=N****tag****/N****tot**
**Dilution ****D=(N****R****-N****W****)/(N****R****+N****W****)**
**Tag quality=********D****2**

## Flavour Tagging

**CDF uses Run I                                                                                       events to calibrate flavour tagging algorithms **
**Charge of kaon tells you    or**
**Trigger and reconstruction**

**similar to ****B°********J/******** K****s**** **

## Flavour Tagging 

## B°J/ Ks Fitted Mass

**4-track fit**
**m(********)=m(****K****s****)**
**m(********)=m(J/********)**
**K****s ****momentum points back to B vertex**

**B momentum points back to primary vertex**

## CDF Run I sin(2) Result

## Run II sin(2)

**Reconstruct 30K-40K B°********J/******** K****s**** events**
**Expect ********(sin2********)********0.04 due to**
**improved muon acceptance**
**lower muon trigger thresholds**
**improved flavour tagging (K ID (CDF), lepton ID)**
**Forward tracking (DØ)**
**trigger on J/********e****+****e****-**
**Result continues to be statistics limited due to size of tagging calibration samples**

##  and  in B(s) Decays

**Sin(2********) extracted from A****CP****(B****0******** ********+ ********-****)**
**Low branching fraction: (0.5-1)x10****-5**
**Large backgrounds, mostly heavy flavour daughters**
**DØ triggers on opposite-side lepton**
**CDF uses all-hadronic trigger (L1 track + L2 impact parameter)**
**Expect 5000 ****(500)**** events in 2 fb****-1**
**Complicated by ****penguin**** contributions!**

##  and  in B(s) Decays

**Reconstruct**
**B****0******** ********+ **********
**B****0******** ********+ **********
**B****s****0******** ********+ **********
**B****s****0******** ********+ **********
**In********ratios**

**Notes:**
Include figure from Rick’s talk with overlapping mass distributions.

##  and  in B(s) Decays

**Five observables in likelihood fit:**
**A****dir****cp****(********+ **************
**A****dir****cp****(********+ **************
**A****mix****cp****(********+ **************
**A****mix****cp****(********+ **************
**sin(2********)**

**Without penguins, **
**A****mix****cp****(********+ ****************sin2(********+********)=sin(2********) **
**A****mix****cp****(K****+ ****K************sin(2********) **
**A****dir****cp****(********+ ****************A****dir****cp****(********+ **************

**Predict ********(A****CP****(B****0******** ********+ ********-****))********0.15**
**Predict ********(********)=****+5.4****-6.8**** ********3 deg**

**Notes:**
How does alpha figure in here?

## Bs Mixing

**Weak eigenstates ******** mass eigenstates**
**Mixing due to higher order corrections**
******m****q****= m(B****o****heavy****) - m(B****o****light****)**
**Þ****mixed****(t) = ********(1-cos********m****q****t),**** ********m****q ******** |V****tb********V****tq****|****2**
**Mixing parameters x****q****=********m****q****/********q ****and ********q**

## Semileptonic Mode Bs 

**trigger on dilepton events**
**initial flavour tagged by opposite side lepton**
**final flavour tagged by same side lepton**
**require D****s**** daughters kinematically consistent with D****s**
**use amplitude fit method **
**good for x****s****<30**** ****(momentum uncertainty of missing ********)**
**40 000 events in 2 fb****-1**

## Hadronic Mode Bs

**CDF uses 2-track hadronic trigger **
**initial flavour tagged by opposite-side event (3 tags available)**
**final flavour tagged by charge of D****s**
**expect 5K-30K events in 2 fb****-1**
**probe x****s****<60**
**DØ triggers on**** ****opposite side lepton**
**lepton charge tags initial flavour **
**final flavour tagged by charge of D****s**
**expect 1000 events in 2 fb****-1**
**probe x****s****<33**

- *no missing neutrino

## Run II Tevatron Plan

**Run II starts March 2001**
**No ****long**** shutdowns**
**Gradual luminosity improvement over time**
**Start at ****396 ns**** bunch spacing**
**Move to ****132 ns**** bunch spacing  in 2003**
**Reach ****2.0x10****32 ****cm****-1****s****-1**** ****by 2004**
**Collect ****15 fb****-1**** by 2008**
**CDF/DØ make way for ****BTeV ****in 2008**

## Conclusions

**After 2 years/2 fb****-1**** of data we will**
**measure sin(2********) to an accuracy of 0.04**
**probe B****s**** mixing to x****s********30 with semileptonic decays**
**probe Bs mixing to x****s********60 in hadronic mode**
**measure A****CP****(B****0******** ********+ ********-****) to an accuracy of 0.15**** ****and ******** to an accuracy of 8 degrees**
**Full reconstruction of B****c**** decay modes**
**Precision lifetime ratios (B****s****/B****0****, ********b****/B****0****, B****c****/B****0****)**
**Rare decays: B****0****(s)********K****(*)****, K*********, ******