# Presentation: 258121

## Rare B Decays at the Tevatron

- Jason Rieger,
- Indiana University
- On behalf of the DØ and CDF collaborations
- BEACH 2006

## A Myriad of Rare Decays

- Those which require large data sets
- Measurement of Br(BsDs1(2536)X) at D
- Those which are Cabibo suppressed
- Br(BD K)/Br(BD π)  at CDF
- FCNC at the Tevatron, still room for factor 10+ SUSY effects
- Bs +-

## The DØ Detector

- 2 Tesla Magnetic Field
- Excellent Coverage
- Muon system: ||<2
- Tracking System: ||<3
- Robust Muon triggers
- High semi-leptonic yields

## The CDF Detector

- New Silicon vertex detecor
- Inner layer at 1.35 cm
- New central tracker
- Excellent mass resolution
- Extended  coverage
- TOF and dE/dx particle ID
- Second level impact parameter trigger
- Allows all hadronic B decay triggers

## Medium RareBr(BsDs1(2536)X)

- Important for testing HQET
- Semileptonic decay to heavy excited state, mostly in phase space close to zero recoil, where most of the correction action is!
- The B0s Ds1(2536) is a significant fraction of B0s semileptonic decays making it important for:
- Comparing inclusive/exclusive decay rates
- Extracting CKM matrix elements
- Using semileptonic decays in B0s mixing
- More info on Ds** doublets

##  Bs  Ds1(2536) X Decay

- Bs

- Ds**  

## Data Sample and Signal

- D* Candidates

- 82130±463 D* Candidates

- Ds** Candidates

- 43.8±8.3 Ds** signal events
- ~5 significance

- DØ RunII Preliminary

- DØ RunII Preliminary

## The Measurement

***Normalize to the known branching ratio:***

***We can use the equation***

***Giving a final result of***

- 1

- 2

- 3

***First ***
***Measurement!!!***

## Comparison With Theory

- Using
- And assuming **Br(D****s1****(2536)********D*********K****s****0****)=0.25**
- Ds1(2536) decays half the time into D*K0 by isospin arguments
- K0 decays half the time in Ks0
- We get the following

| Source | Br(Bs0Ds1(2536)X |
| --- | --- |
| This Result | (0.86±0.16(stat)±0.13(syst)±0.09(prod.frac))% |
| ISGW2 | 0.53% |
| RQM | 0.39% |
| HQET & QCD sum rules | 0.195% |

*H.B. Mayorga,A.Moreno*
*Briceno and J.H.Munoz*
*J.Phys G 29(2003) 2059*

- from PDG

## RareBr(BDK)/Br(BD)

***Can use partial widths of B************D******0******K to ***
***Obtain measurement of ***

- Belle, Babar and CLEO have advanced measurements in this channel
- Before the Tevatron can contribute with the Bs channel we first have to understand B+

- This is the Tevatron’s first
- step in the measurement
- of gamma

*See talk by A. Garmash for a more detailed discussion*

## The Data Sample

- Use :
-  small kinematic differences between modes
- Particle ID (dE/dx) to differentiate between the two modes
- Calibrate dE/dx using sample of kaons and pions from :
- D*D0K
- 1.5 sigma separation

*Unbinned Likelihood fit was *
*used, combining kinematic **information & dE/dx*

## Br(BDK)/Br(BD) results

- World Average for this measurement:
- 0.0830±0.0035
- Coming from combined results of Belle, Babar and Cleo

- Br(BDK)/Br(BD) =
- 0.065±0.007 (stat.)±0.004(syst.)

- Mass fit projection

- PID fit projection

## (Very) RareFlavor Changing Neutral Currents

- FCNC’s are forbidden at tree level.
- B*l*+*l*- decays are also helicity supressed
- Standard Model
- BR(Bs +-)~3.4 x10-9
- Depends only on one SM operator in effective Hamiltonian,
- hadronic uncertainties are small

## New Physics in Flavor Physics?

- bs penguins
- bs, bs *l**+**l*-, bs sbar rate, and asymmetry measurements at Belle, Babar, and Cleo are all consistent with theory
- B
- Measured at Belle and again, consistent with theory
- Bs mixing
- First double-sided limit by D limited hope for new physics, the later measurement by CDF confirmed that ms within theory errors, no new physics there
- All great measurements, but...

- Is there any hope for new physics in flavor physics?

## Annihilation Topologies

- Initial state:
*q=s* better than *q=d* since Vts>>Vtd : factor ~40 gain
- Final state :
- Rate proportional to m*l*2
*l= **** *versus* l=e : *factor ~40000 gain
*l=****  *versus* l=**** : *factor ~200 gain

- Internal SM is
- the same
- regardless of
*q* or *l*

*l**-*

- Much harder to do experimentally

- This is why we use Bs+-

## Annihilation Topologies

- Pick up several powers of
- tan , once you introduce
- SUSY Higgs

*M. Carena et al.*
*hep-ph/0603106*

## Annihilation Topologies

- Pick up several powers of
- tan , once you introduce
- SUSY Higgs

*M. Carena et al.*
*hep-ph/0603106*

- Given agreement between Tevatron ms and CKM fit on order of 5 ps-1

- Bs+- still unbounded!

## Bs+- analysis variables used

*Isolation*
- Fraction of momentum in jet carried by B meson
- Expect majority of momentum from b to be carried by Bs meson

*Pointing angle*
- Angle between dimuon momentum vector and decay length vector
- Angle should be small between these two vectors

***Decay Length Significance***
- Since the B meson has lifetime one can require decay
- length to be greater than error on decay length

## B+- experimental search

***CDF***
- 780 pb-1 di-muon triggered data
- Two separate seach channels
- central/central muons
- central/forward muons
- Extract Bs & Bd limit
***D*********
- 300 pb-1 di-muon triggered data
- Study done for sensitivity out to 700 pb-1
- Bd & Bs overlap

***Both Experiments***
- Blind analysis
- Side bands for background determination
- Use B+J/K+ as normalization mode

## Normalization

- Normalization done to BJ/ K+
- Advantages:
- +- selection efficiency the same
- High statistics
- Well known branching ratio
- Disadvantages:
- bBs and bBd fragmentations both needed

## B+- Cut Optimization at D

***Optimize cuts on three ***
***Discriminating variables:***
- Pointing angle
- Decay length significance
- Isolation

## B+- Cut Optimization at CDF

***Discriminating Variables***
- Pointing Angle
- Proper Decay Length
- Isolation

## Bs+- at D

- D waiting for full RunIIa dataset to open the box
- Preliminary sensitivity for 700pb-1 : 2.3x10-7

**Expect 2.2 ±0.7 background events**

## Latest Bs+- Results

- Effect of old ~0.4fb-1 Tev.
- Limit on a favorable corner
- Of parameter space

**Minimal **
**SO(10)**

## Latest Bs+- Results

- One less corner of
- Parameter space!

**Minimal **
**SO(10)**

- BF(Bs+-) < 1x10-7@ 95% CL

## Conclusions

- B physics at the Tevatron is great for exploring many different types of rare decays
- Bs+- remains the best current probe for SUSY effects in B physics
- One of the last places to find order 10 SUSY effects!