# Presentation: 352580

## Selected B-physics at DØ 

**Selected B-physics at D****Ø**

- for the DØ Collaboration
- 09 nov 2005 Flavour in the era of the LHC
- CERN

- Tevatron and DØ
- Results and Prospects
-  s/s
-  Bs Mixing
-  Bs
- Summary

## Tevatron

- Highest Luminosity at DØ:
- 1.6ּ1032 cm-2s-1
- Recorded Luminosity:
- 1.04 fb-1
- Delivered Luminosity:
- 1.24 fb-1
- Integrated Luminosity
- per Experiment:
-  ~2 fb-1 until 2006
-  ~8 fb-1 until 2009

- Flavour in the era of the LHC , Cano Ay

- 09 nov 2005

## DØ Detector

- Muon system:
- Coverage: ||<2
- Good shielding
- 2T Toroid Field

- Tracking system:
- Coverage: ||<3.2
- 2T Solenoid Field

- 1m

- Flavour in the era of the LHC , Cano Ay

- 09 nov 2005

## Muon triggers

-  single inclusive muons,
-     ||<2.0, pT>3,4,5 GeV
-  Muon + track match at Level 1 and a muon at Level 2
-  Unbiased; prescaled or turned off depending on inst. Lumi.
-  At Level 3 also invariant mass track selections (imply impact parameter bias)
-  Dimuons

- Flavour in the era of the LHC , Cano Ay

- 09 nov 2005

## Motivation 

-  ms/md constrain unitarity triangle

- larger uncertainties!

- smaller uncertainties!

-  SM predicts a ms0 and s0

- Tevatron currently only place to study Bs Meson

- Flavour in the era of the LHC , Cano Ay

- 09 nov 2005

## Motivation 

-  Expectation for lifetime difference s/s (with experimental input)
-  Discrepancies to SM Expectation  new physics

-  decay Bs   : example indirect search for New physics
-  FCNC process  highly suppressed in SM
-  Observing the decay  would indicate new physics (SUSY, MSSM, etc)

- Flavour in the era of the LHC , Cano Ay

- 09 nov 2005

## B-physics program at DØ

-  Reconstruction of BsDsX decays
-  Reconstruction of B Hadron Signals at D0
-  Evidence of BsDs(2536)X
-  Observation of the Bc Meson and study of ist properties
-  Study of exited B Mesons (B**)
-  A high statistics measurement of the Bs0 lifetime
-  Observation of Bs(2s) and a measurement of B(Bs(2s) ))/B( Bs(2s) )
** ****Search for B****s******** rare decays**
-  FCNC charm decays and Observation of Ds 
** ****B****s**** mixing with B****s**** ********D****s********X, D****s************ and opposite-side flavor tagging**
** ****B****s**** mixing with B****s**** ********D****s********X, D****s********K*K and opposite-side flavor tagging**
-  Flavor oscillations in Bd Mesons with 3 combined Taggers
-  Measurement of upsilon differential cross section
-  Measurement of the ratio B+ and B0 meson lifetimes
-  Measurement of the b lifetime in the decay J decays
-  Measurement of the Bs lifetime in the exclusive decay channel BsJ/
-  **Measurement of the lifetime difference in the B****s**** system**
-  Measurement of the semileptonic branching fractions of B mesons to narrow D** states
-  Observation and Properties of the X(3872) Decayoing to J/+-

- B-physics program at DØ

- Flavour in the era of the LHC , Cano Ay

- 09 nov 2005

##  s/s 

-  ___s__/____s_
-  Bs Mixing
-  Bs

- Flavour in the era of the LHC , Cano Ay

- 09 nov 2005

## ss Analysis

-  the polarisation state of the vector mesons in the final states are different for CP eigenstates
-  Simultaneous fit to

- ss Analysis

- Flavour in the era of the LHC , Cano Ay

- 09 nov 2005

## ss Results

- DØ : 450pb-1

- Flavour in the era of the LHC , Cano Ay

- 09 nov 2005

## Prospects s/s

-  Analysis improvement
-  Fit all 3 angles in transversity, not only 1 angle
-  update silicon Layer 0
-  extrapolate forwards to higher luminositiy

- Prospects s/s

- Flavour in the era of the LHC , Cano Ay

- 09 nov 2005

##  ss

-  ss
-  _B__s__ Mixing_
-  Bs

- Flavour in the era of the LHC , Cano Ay

- 09 nov 2005

## Bs Mixing: Analysis

- Semileptonic decays:
- (trigger on )

- Bs Mixing: Analysis

- Proper decay time:

- Flavour in the era of the LHC , Cano Ay

- 09 nov 2005

## DØ Bs Mixing Limit

**Limit for both channels **

-  very large semileptonically decaying sample (~34k) in 610pb-1

-  after flavour tagging (~4.2k)

- Flavour in the era of the LHC , Cano Ay

- 09 nov 2005

## Prospects ms

-  more data
-  General Analysis improvements
-  hadronic channel, other semileptonic channels
-  Event-by-event fit, not binned likelihood
-  improved flavour tagging
-  Upgrades
-  layer 0 silicon, improved vertex resolution
-  L3 bandwidth 50Hz to 100Hz

- ms sensitivity

- Flavour in the era of the LHC , Cano Ay

- 09 nov 2005

##  Bs Mixing

-  Bs Mixing
-  ss
- _ __B__s___

- Flavour in the era of the LHC , Cano Ay

- 09 nov 2005

## Search for rare decays

-  ‘blind’ analysis with 300 pb-1
-  Signal selection was optimized with random grid search

- Flavour in the era of the LHC , Cano Ay

- 09 nov 2005

## Search for rare decays

-  Calculate BR Limit using the B+J/K+ as normalisation channel

-  After selection 4.31.2 background events were expected and 4 events were found in the signal region

- Flavour in the era of the LHC , Cano Ay

- 09 nov 2005

## Prospects Bs 

-  Based on DØ results at ~300pb-1
-  Scale to higher luminositiy
-  Bands indicate 10% variation of events

- Flavour in the era of the LHC , Cano Ay

- 09 nov 2005

## Summary

-  Presented three preliminary results (only fraction of B-physics program at DØ )
-  Lifetime difference s/s
-  Mass difference ms (only semileptonic)
-  rare decay Bs

- with more statistics error will be reduced by a factor ~10

- With improved analysis, upgrades and more data push sensitivity above the SM expectation

- Not sensitiv for SM Prediction, but maybe for new physics

- Flavour in the era of the LHC , Cano Ay

- 09 nov 2005

## Backup

- Flavour in the era of the LHC , Cano Ay

- 09 nov 2005

## Transversity

- Flavour in the era of the LHC , Cano Ay

- 09 nov 2005

## Combined Likelihood

- Flavour in the era of the LHC , Cano Ay

- 09 nov 2005

## Proper decay length

- Flavour in the era of the LHC , Cano Ay

- 09 nov 2005

## K*K data sample

- untagged

- tagged

- Flavour in the era of the LHC , Cano Ay

- 09 nov 2005

## Limits , K*K

- Limit only for

- Flavour in the era of the LHC , Cano Ay

- 09 nov 2005

## Disciminating variables Bs

- Disciminating variables Bs

- Flavour in the era of the LHC , Cano Ay

- 09 nov 2005