# Presentation: 188851

## Measurements of B Rare Decaysat the Tevatron

**Measurements of B Rare Decays****at the Tevatron**

- Fabrizio Scuri a) – I.N.F.N. Pisa
- for the CDF and D0 Collaborations
**Les Rencontres de Moriond – QCD and Hadronic Interactions**
**La Thuile, March 17-24, 2007 **

_***Topics:***_
-   **B ******** h****+****h****-**** (charmless) recent results**
**  ****B ******** ******** search status**
**  ****B ******** ********h updates**

- a) e-mail: fabrizio.scuri@pi.infn.it

- Rare B decays at the Tevatron - Moriond QCD 2007

- F. Scuri

## Why Rare (BR O(10-6) or lower) B Decays are so interesting ?

- Why Rare (BR O(10-6) or lower) B Decays are so interesting ?

## Heavy Flavor physics at the Tevatron 

- Heavy Flavor physics at the Tevatron

-          **Detectors need to have:**
** ****Very good tracking and vertex resolution**
** ****Wide acceptance and good ID for electrons and muons**
** ****Highly selective trigger **

- Rare B decays at the Tevatron - Moriond QCD 2007

- F. Scuri

## B  h+ h’-

- Signal composition is determined with a Likelihood Fit, combining information from
- kinematics (mass and momentum) and particle identification (dE/dx).

- B  h+ h’-

- Rare B decays at the Tevatron - Moriond QCD 2007

- F. Scuri

## B  h+ h’- : BR result summary

- B  h+ h’- : BR result summary

-  **In this talk only highlights on **
**               ****Direct CPV **
**    ****in B****0**** ********  K****+********-**** and B****s**** ******** K****-********+ ****  **

- Rare B decays at the Tevatron - Moriond QCD 2007

- F. Scuri

## Raw DCPV asymmetries

**Raw DCPV asymmetries**

- Plot of pdf(B0)/[pdf(B0)+pdf(B0)]
- shows the good separation
- achieved between B0 and B0 (M, , ptot, dE/dx)

- B0K+-

- Rare B decays at the Tevatron - Moriond QCD 2007

- F. Scuri

## New result on ACP(B0K+-) with 1 fb-1

**New result on A****CP****(B****0********K****+********-****) with 1 fb****-1**

-  CDF competitive with BaBar/Belle
-  Tevatron and B-Factories results agree
-  6-7  effect
-  Difference with ACP(B+K+0)
-   confirmed

- Rare B decays at the Tevatron - Moriond QCD 2007

- F. Scuri

## New results for the Bs  K-+ mode with 1 fb-1

**New results for the B****s**** ******** K****-********+ ****mode with 1 fb****-1**

- In agreement with latest prediction of SCET: (4.9 ± 1.8) 10-6
- Lower than previous predictions of QCDF and pQCD: [6-10] 10-6

- Still marginal but sign and magnitude agree with SM predictions
-  no evidence for exotic sources of CP violation (yet)
**           ****Very interesting to pursue with more data !**

- Rare B decays at the Tevatron - Moriond QCD 2007

- F. Scuri

## B  + -

- B  + -

- Rare B decays at the Tevatron - Moriond QCD 2007

- F. Scuri

## B  + -

**Normalization**
**mode: B****+********J/********K****+**
**(J/****************)**

**Event yield**
**after**
**optimization**

- B  + -

| CDF | 0.99 |
| --- | --- |
| D0 Run IIa | 0.946 |
| D0 Run IIb | 0.986 |

**Optimal L****R**

**(~1250 pb****-1****)**

**Run IIb after Summer ’06**
**insertion of a new inner **
**layer in the SMT**

**(~750 pb****-1****)**

- F. Scuri

## B result summary

|  |  B(Bs)
 90% (95%) C.L. |  B(Bd)
90% (95%) C.L. | Int.Lum.
    pb-1 |
| --- | --- | --- | --- |
| CDF | < 8.0∙10-8(10) | < 2.3∙10-8(3) |   780 |
| D0(combined) | < 7.5∙10-8(9.3) | (*) |  1800 |

- World best limit, compare
- Babar (hep-ex/0408096, 110 fb-1 )
- BR(Bd) < 8.3 ∙ 10-8 @ 90%  C.L.

**(*) D0 assumes the contribution of B****d************ to **
**B****(B****s************) ****suppressed due to |V****td****/V****ts****|****2**** ~ 0.04**

|  | Rel.Unc.
    [%] |
| --- | --- |
| Background |   ~ 30 |
| fu/fs |   ~ 13 |

**Dominant uncertainty sources**

**B************ result summary**

| Experiment |  | B0s search |  | B0d search |  |
| --- | --- | --- | --- | --- | --- |
|  |  | Expected | Obs. | Expected | Obs. |
| CDF | 780 pb-1 | 1.27±0.37 | 1 | 2.45±0.40 | 2 |
| D0 | Run IIa
(~1300 pb-1) | 0.8±0.2 | 1 |      |  |
|  | Run IIb
(~500 pb-1) | 1.5±0.5 | 2 |  |  |

- Rare B decays at the Tevatron - Moriond QCD 2007

- F. Scuri

## Impact on New Physics

- F. Scuri

## B(+)  +- h(+)

- B(+)  +- h(+)

- (b  s  l+ l-)

**Studied decay modes:**
**CDF: B****+ ******** ********************K****+****, B****0 ******** ********************K****0*******
**CDF & D0: B****s**** ******** **************************

- Rare B decays at the Tevatron - Moriond QCD 2007

- F. Scuri

## Bu,d yields (CDF)

**B****u,d ****yields (CDF)**

**Fit shown only for**
**illustration purpose**

| Mode | B+K+ | B0K*0 |
| --- | --- | --- |
| Nsig.win. |       90 |      35 |
| NBG  | 45.3 ± 5.8 | 16.5 ± 3.6 |
| Significance |       4.5 |       2.9 |

|  |   D0 |  CDF |
| --- | --- | --- |
| Obs. |      0 |     11 |
| Exp. | 1.6±0.6 | 3.5 ±1.5 |
| pb-1 |   450 |   920 |

**2.4 ******** significance**

**B****s**** yields**

- Rare B decays at the Tevatron - Moriond QCD 2007

## BR (Bh) result summary 

**BR (B************h) result summary**

- Good agreement and similar uncertainty for B-Factories & Tevatron:
- Babar PRD 73, 092001 (2006) (208 fb-1   ~10 ****K+, ~15 ****K*0)
- Belle hep-ex/0410006              (250 fb-1   ~40 ****K+, ~40 ****K*0)
_**Tevatron result summary**_
**BR(B****+************K****+****)  = [0.60 ****±**** 0.15(stat.) ****±**** 0.04(sys.)]x10****-6   ****CDF, 45 ev.**
**BR(B****0************K*****0****) = [0.82 ****±**** 0.31(stat.) ****±**** 0.10(sys.)]x10****-6   ****CDF, 45 ev.**
**BR(B****s****************)   < 2.4 x10****-6 ****@ 90% C.L., CDF, 920 pb****-1**** , Bayesian approach**
**                             ****= [1.16 ****±**** 0.56(stat.) ****±**** 0.42(sys.)]x10****-6**
**BR(B****s****************) < 3.3 x 10****-6 ****@ 90% C.L.  D0, 450 pb****-1****, Feldman-Cousins scheme**

- Rare B decays at the Tevatron - Moriond QCD 2007

- F. Scuri

## Impact on New Physics

## Summary

**Summary**

-  **Tevatron is demonstrated to be a good place to study B rare decays offering:**
**  ****- different possibilities to constraint more and more New Physics, B************, b********sl****+****l****-**
**  ****- a physics program complementary to the B-Factories, B****s******** h****+**** h’****-**** **

** ****B********h****+****h’****-****:**
-   - First observation of Bs K-+
-   - First observation of DCPV in Bs: ACP(BsK-+)
-   appears to be large in agreement with expectation

** ****b********sl****+****l****-****:**
-   - CDF/DØ beginning exploration of the bsl+l- field:
-   - New solid B  K signals from CDF;
-     smaller errors on BR and AFB (?) will
-     constrain/rule-out different NP scenarios
-   - A 2.4  excess in the Bsreported from CDF,
-     upper limit close to SM prediction

** ****Now, over 2 fb****-1**** on tape: more significantly improved results coming soon**

- Rare B decays at the Tevatron - Moriond QCD 2007

- F. Scuri

## Back-up slides

- Rare B decays at the Tevatron - Moriond QCD 2007

- F. Scuri

## The Tevatron at Fnal and the running experiments CDF and D0

- CDF Run II

- Main injector
- and recycler

- Tevatron

- Booster

**CDF**

**DØ**

******p source**

- Rare B decays at the Tevatron - Moriond QCD 2007

- F. Scuri

## Two high performance detectors match the requirements... 

- Two high performance detectors match the requirements...

- Rare B decays at the Tevatron - Moriond QCD 2007

- F. Scuri

## B

**Strategy for the B******** h****+**** h’****-**** analysis**

-  Fully exploit the selection power of the CDF L2 SVT trigger for
-   opposite charge track pairs originated form a displaced vertex
-   (a 8500 events B0(s) h+ h’- signal just after trigger selection)
-  Tighten trigger cuts in the offline optimization procedure
-   by minimizing the expected uncertainty on each individual
-   observable (raw asymmetry, event yield); analytical
-   functions used to parameterize signal and background
-   in the pseudo-experiments
-  Add the isolation cut (efficiency measured in the
-   B+ J/ K+ control sample)
-  Evaluate the sample composition with an unbinned
-   Likelihood fit combining kinematics and PID
-  Normalize to the most abundant  B0K+- mode for BRs
-  Only different K+/K- interactions with material matter for correcting ACP

**d = impact parameter**

**Primary **
**Vertex**

**Secondary **
**Vertex**

**B**

**Lxy**

*B*

- R=1 cone
-     in the
- space

- Rare B decays at the Tevatron - Moriond QCD 2007

- F. Scuri

##  invariant mass: offline confirmation

****** ****invariant mass: offline confirmation**
**of the trigger selection**

- L2 trigger selection

- Rare B decays at the Tevatron - Moriond QCD 2007

- F. Scuri

## Separating decays modes

**Separating decays modes**

- Un-binned ML fit using 5 observables (M,ptot,,ID1,ID2)

- Signal shapes:  from MC and analytic formula Background shapes: from data sidebands

- sign and bckg shapes from D0   K-+

- fraction of jth mode, to be determined by the fit

- mass term

- PID term (dE/dx)

- momentum term

***α***

***p******tot***

- Rare B decays at the Tevatron - Moriond QCD 2007

- F. Scuri

## Systematics ACP(B0K+-)

-  dE/dx model (±0.0064);
-  nominal *B*-meson masses input to the fit (±0.005);
-  global mass scale(≈0);
-  momentum background model (±0.001);
-  M background model (±0.003).

- Systematics ACP(B0K+-)

- Contributions to Systematics

***B*****0**** ****→ *****π******+******π******-***

***B*****0**** ****→ *****K******-******π******+***

***B*****0****s**** ****→ *****K******+******K******-***

***other signals***

- Signal composition

- Rare B decays at the Tevatron - Moriond QCD 2007

- F. Scuri

##  BRs small and difficult to predict

-  BRs small and difficult to predict
-  Bs(exp. x3 larger than B0KK)

**Pure annihilation modes**

- Rare B decays at the Tevatron - Moriond QCD 2007

- F. Scuri

## First observation: 0bp- and 0bpK- 

- First observation: 0bp- and 0bpK-

- 0b mass region

- PID variable

** ****11 ******

** ****6 ******

- Ratio of BR in agreement with predictions (0.60-0.62) [Mohanta et al. Phys.Rev. D63 (2001) 074001]

- 0bph- entangled  to B0sK-+
- Large DCPV expected for both modes

- Rare B decays at the Tevatron - Moriond QCD 2007

- F. Scuri

## Bh+h-:  prospects for RunII

- Bh+h-:  prospects for RunII

- Until the beginning of the planned Y(5S) run at Belle and the beginning of  LHCb (at least fall 2008 ) only CDF has
**     ****simultaneous access to B****0****s**** , B****0****d**** (plus B-baryons)**
- ACP(B0K) at ≈ 1% and ACP(B0sK) at ≈ 5%
- High precision measurements for all BRs
- Opportunity to observe annihilation modes B0KK, B0s
- Measurements of BR/ACP  0bpK/p
- Time-dependent ACP(t) for B0, B0sKK, all ingredients are ready Δms,εD2 ≈ 4%

- Rare B decays at the Tevatron - Moriond QCD 2007

- F. Scuri

## Discriminating observables: (almost) the same in the two experiments

**Discriminating observables: (almost) the same in the two experiments**

- 1) B vertex displacement:
- CDF 
-  D0  

- 2) “pointing angle ()”:

**P********

**P********

**P********

**L****3D**

**********

***x***

***y***

*******R***** < 1 **
**(**********<**** ****57****o****)**

- 

- 

- 

- 

***z***

- 3) Isolation (Iso):

- (fraction of tracks with *p**T** *within the
- R=(2+2)1/2=1 cone of the B cand.)

**CDF II  (780 pb****-1****)**

**(300 pb****-1****)**

## Search optimization: similar methods

**Search optimization: similar methods**

-  construct a likelihood ratio LR
-    using 3D proper dec. len. , , Iso

-  Optimize LR cut on the expected
*   **a-priori* 90% C.L. limit; 0.99 is the
-    optimal value

-  Background PDF from data sidebands

-  Define two search regions in the (****)
-    inv. mass spectrum around the nominal
-    Bd and Bs masses, 120 MeV/c2 wide
-    (±2.5 M measured in the Bhh analysis)

- Define a single signal region around
- the Bs nominal mass, 180 MeV/c2 wide
- B from linear extrapolation of the sidebands
- Construct a likelihood ratio LR on six
- discriminating observables
-     Pointing angle
-     2D decay length significance
-     Isolation
-     B impact parameter
-     minimal muon impact param.
-     2 vertex probability
-  Optimize LR on:

- CDF

-  Evaluate the fake Bhh rate

- D0

- a):   / <nup.lim.(nexp.bkg.)>
-                                             same optimal
- b):   /(1+sqrt(B))                       values

- Extraction of the upper limit

- Bayesian approach assuming flat prior for **B**(B) and Gaussian uncertainties

## Likelihood Ratio

**Likelihood Ratio**

- Rare B decays at the Tevatron - Moriond QCD 2007

- F. Scuri

## B event yield after optimization 

**B************ event yield after optimization**

- Rare B decays at the Tevatron - Moriond QCD 2007

- F. Scuri

## B  : area of improvement

- B  : area of improvement

- Improved muon selection based on additional information:
- Energy deposition in the calorimeter
- dE/dx in the drift chamber
- significant reduction in fakes expected.
- Neural Net based final discriminant with additional background suppression power
- use the 2-dimensional dimuon mass-discriminant plane to evaluate signal/limit

- Rare B decays at the Tevatron - Moriond QCD 2007

- F. Scuri

## Bs   h (bs l+l-) status

**B****s**** ******** ******** h (b********s l****+****l****-****) status**

-  Bd and B+ modes established at B-factories:
- BR(B+ **** K+)  = 0.34+0.19-0.14 x 10-6 (PDG 06)
- BR(Bd **** K*0) = 1.22+0.38-0.32 x 10-6  (PDG 06)
-  Tevatron goals: re-establish B-factories observations and look for the unseen Bs**** mode; predicted BR(Bs ********)=1.6x10-6 C. Geng and C. Liu, J. Phys. G 29, 1103 (2003)

- Strategy

-  Normalize signal to analogous BJ/****h (J/********) decays
-  Exclude J/ and ’ regions in the (****) inv. mass spectrum
-  Blind optimization, sideband data used for optimization and background estimate
-  Monte Carlo for efficiency ratios with normalization mode
-   (To estimate signal efficiency for the B+, Bd modes, CDF uses data yields of Bd, B+
-     in the normalization modes, scaled using the w.a. of measured BR(B+(d) ****K+(*)) )

- Rare B decays at the Tevatron - Moriond QCD 2007

- F. Scuri

## B(+) + - h(+) Normalization modes

**B****(+)******** ********+**** ********-**** h****(+)**** Normalization modes**

- Rare B decays at the Tevatron - Moriond QCD 2007

- F. Scuri

## Signal Selection Optimization

**Signal Selection Optimization**

- Discriminating observables (after pre-selection cuts):

- Rare B decays at the Tevatron - Moriond QCD 2007

- F. Scuri