# Presentation: 228503

## Rare Decays of B Hadrons at CDF

*Matthew Jones *

- October 3, 2005

## Oh my!

## Rare Decays of B Hadrons at CDF

- Search Bs,Bd μ+μ-
- Charmless B decays
- Bd,Bs,Λb  hh’
- B+  φK+, Bs  φφ
- Not covered
- B masses
- BsDsπ, ΛbΛcπ and kin
- D0  K-π+,K-K+,π-π+

*In this talk, “rare” means branching fractions **≲ 10**-6**.*

## The CDF Detector

- Muon systems:

- Tracking systems:  SVX-II          COT

- CMP CMX CMU

## Heavily suppressed in Standard Model:

Approximately 2 orders of magnitude below current experimental sensitivity
Significant enhancements from contributions of new physics processes

- Approximately 2 orders of magnitude below current experimental sensitivity
- Significant enhancements from contributions of new physics processes

- Search for Bs μ+μ-

## Bs μ+μ- enhancement by SUSY:

Correlation between Br(Bs μ+μ-) and    (g-2)μ measurement
 BNL result could imply a10-100 enhancement compared with SM.
Different behavior for Bs/Bd μ+μ- possible

- Correlation between Br(Bs μ+μ-) and    (g-2)μ measurement
-  BNL result could imply a10-100 enhancement compared with SM.
- Different behavior for Bs/Bd μ+μ- possible

- ~ (tan β)6  up to 3 orders of magnitude enhancement

## Search for Bs μ+μ-

- Di-muon trigger, pT>1.5 or 2 GeV/c
- Limit normalized to B+J/ψK+ signal
- Significant backgrounds from
- Sequential semileptonic
- Double semileptonic decays
- Fake leptons
- Discriminate using multivariate likelihood (isolation, 3D vertex quantities)

## Search for Bs,Bd μ+μ-

- Good mass resolution allows separation of Bs μ+μ- and Bd μ+μ-:

- No events observed in either mass window
- 90% C.L. limits:
- Expected background:

- _[hep-ex/0508036](http://xxx.lanl.gov/abs/hep-ex/0508036)__   submitted to PRL_

- 1.50.2 events

## Example of Constraints on Models

- R. Dermíšek, *et al.,   *_*[hep-ph/0507233](http://xxx.lanl.gov/abs/hep-ph/0507233)*_

- Minimal SO10 SUSY

## Hadronic Decays

- Bππ/Kπ/KK: original motivation for Secondary Vertex Trigger in CDF-II
- Level 1 trigger: require two tracks with requirements on pT and ΔΦ
*   **Dominates level 1 trigger rate!*
- Level 2 trigger: vertex displaced with respect to beam axis  heavy flavor trigger.
- Applications at CDF:
- Two-body B-decays, B0π+π-, B0K+π-, ...
- Non-leptonic B-decays (eg., BsD-s+)
- Semi-leptonic decays (eg. Lepton + displaced track)
- Charm physics

## Charmless Bhh’ Decays

- Charmless Bhh’ Decays

- CDF observes overlapping contributions from B0π+π-, B0K+π-, Bs0K+K-:

- Update of result from Summer 2004:
- Same data sample, uncertainties reduced.

- Separate individual decays using kinematics and particle identification.

- ~ 900 candidates

- Wider than expected for a single channel

## Charmless Bhh’ Decays

- Discriminating variables:
- Invariant mass, m(π+π-),
- “Signed momentum imbalance”, α=Q1(1-p1/p2)
- Energy loss in tracking chamber, dE/dx
- Total momentum
- Corrections applied for relative efficiencies
- Measure relative branching fractions               and ACP in B0K+π-
- Time-dependent asymmetries possible:
-                                          already demonstrated
- In 1 fb-1 we expect of order 50 tagged events
- Γ(BsKK)/Γ(Bdππ) needed for extraction of 

- (_[hep-ph/0404009](http://xxx.lanl.gov/abs/hep-ph/0404009)__)_

## Charmless Bhh’ Decays

- Charmless Bhh’ Decays

- f(BdKπ) = 0.6000.034
- f(BsKK) = 0.2620.035
- f(Bdππ) = 0.1340.030
- f(BsKπ) = 0.0030.028

## Search for Λbpπ-/pK-

- Search for Λbpπ-/pK-

- Charmless Λb decays yet to be observed
- Large ACP expected in baryons
- Branching fraction could be 1-2 x10-6

- Count excess over background in distribution of m(π+π-):

## Search for Λbpπ-/pK-

- Normalize with respect to B0K+π- signal:
- No events observed, set upper limit:
- Significant improvements possible with particle identification and larger data sample.

- (90% C.L.)

## B+φK+ and Bsφφ

- More examples of charmless B decays selected using secondary vertex trigger
- Pure penguin                  transitions may differ from SM expectations
- ACP can be measured in B+φK+
- In principle, CP composition in BsVV obtained from angular analysis
- B+φK+ already seen but this is the first observation of Bsφφ

## B+φK+ Analysis

- Candidates are 3-track vertices containing two trigger tracks
- Discriminating variables:
- M(K+K-K+): signal and physics backgrounds
- M(K+K-): φK+K- signal
- φ decay helicity angle, Hφ
- dE/dx: kaon identification
- Likelihood fit to determine yield of B+φK+ and CP asymmetry.

## B+φK+ Analysis

- B+φK+ Analysis

- Physics backgrounds:

- B+K+K-K+X
- B+f0K+
- B+K*0+
- B+K+K-K+
- B+K++-

- Signal:

- B+ φK+

## B+φK+ CP Asymmetry

- B+φK+ CP Asymmetry

- Br(B+φK+) x 10-6

- ACP(B+φK+)

## Observation of Bsφφ

- Angular analysis possible with 1 fb-1.

- 179 pb-1

- _[hep-ex/0502044](http://xxx.lanl.gov/abs/hep-ex/0502044)__ and PRL 95, 031801 (2005)_

- 8 events in search window
- 0.750.41 BG expected

## 2005

**2005**

**2004**

**2003**

**2002**

- Bsμ+μ-

- Bhh’, B+φK+, Bsφφ

- 1 fb-1 of data for analysis by 2006 spring shutdown.

## What to do with 1 fb-1

- Expected limit on Br(Bsμ+μ-):  <10-7   Ultimate sensitivity in Run-II could reach 3x10-8
- Resolution on ACP(B0K+π-) should approach 0.025 with 1 fb-1
-    Ultimate precision of ~1%
- Bsφφ background free – 120 events      in 1 fb-1  *angular analysis*.
- Good prospects for observing Λbpπ/pK

## Additional Material

## CDF Triggers for B Physics

- Beam crossings every 396 ns
- Level 1 trigger:
- Axial tracks from segments found in COT
- Association with hits in muon chambers
- Level 2 trigger:
- Silicon hits added to tracks found at level 1
- Finer granularity in muon systems
- Level 3 trigger:
- Full event reconstruction

## CDF Detector Performance

- J/ψ trigger:
- 8x106 J/ψ with hits in SVX-II in 1 fb-1
- B+J/ψK+:

- Includes          c>60 μm

## J/ψ Trigger at CDF

- Level 1 – Two muons with pT >1.5 GeV
- Level 2 – Opposite charge
- Level 3 – Full event reconstruction

## Charmless Bhh’ Decays

- Contributions to systematic uncertainty:
- m(π+π-) resolution from Monte Carlo
- Shapes of dE/dx *p.d.f.*’s, dE/dx correlations
- Electron/proton backgrounds
- B meson masses
- Background shape, momentum spectrum
-  (B), s through decay length requirements
- Isolation requirement used in reconstruction
- Track trigger K/π bias
- Proton/anti-proton asymmetry in background
- Correlations between discriminating variables
- Final state radiation (_[Cirigliano](http://xxx.lanl.gov/abs/hep-ph/0008290)__[, et al.](http://xxx.lanl.gov/abs/hep-ph/0008290)_)

- not fundamental limitations

- Bhh’ systematics

## dE/dx Calibration at CDF

- High statistics calibration samples:
- D*+D0+
-    p-
- K0S+-
- J/ψμ+μ-
- 1.4σ K/π separation for p>2 GeV/c

## The Future