# Presentation: 888811

## Charmless B decays at CDF

- Mauro Donegà
- Université de Genève
- on behalf of the CDF collaboration

## Outline

- Lot of Charmless B results...
-    ...in this talk:
- B hh’ (B PP)
- BR and Acp: Bd  Kπ
- BR: Bd  π π Bs  KK
- B VV
- BR _**first evidence**_: Bs   ****** ******
- B PV
- BR and Acp B±  **** K ±

## CDF

**LAYER 00**: 1 layer of radiation-hard silicon at very small radius (1.5 cm)
-                   (expected 50 fs proper time resolution in Bs  Ds )

**COT:** large radius (1.4 m) Drift C.
- 96 layers, 200ns drift time
- Precise PT above 400 MeV/c
- Precise 3D tracking in |****|<1
- (1/PT) ~ 0.1%GeV –1; (hit)~150****m
- dE/dx info provides >1.4 sigma K/****  separation above 2 GeV

**SVX-II + ISL:**  5 + 1 (2) layers of double-side silicon (3cm < R < 30cm)
-  Standalone 3D tracking up to |****|= 2
-  Very good I.P. resolution: ~30****m (~20 ****m with Layer00)

**TIME OF FLIGHT**

- B =1.4 T

**TOF:** ~100ps resolution, 2sigmaK/**** separation for tracks below 1.6 GeV/c
- (significant improvement of Bs flavor tag effectiveness)

## Silicon Vertex Trigger

- B physics @ hadron collider :
- 2 leptons
-               (rare decays, charmonium decays)
- 1 lepton + _1 displaced track_
-               (semileptonic decays)
_**2 displaced tracks**_ :
-               (two-body decays, multibody decays)

- Silicon Vertex Trigger

- Pt(trk) >2 GeV/c
- Pt >5.5 GeV/c
- 100 m<IP(trk)<1 mm
- || <1

## Bhh’ at CDF

- TeVatron all b-hadrons (Bd, Bs, b...)
-   Both Bshh’ processes and Bdhh’

- CDF is the first experiment to be sensitive to Bshh’ decays

- _Physics opportunities:_
**Counting experiments:**
- 	BdK+-
- Branching Ratio
- Direct CP asymmetry
- With higher statistics BsK-+
- Branching Ratio
- Direct CP asymmetry

- Contributions from both:

- tree

- penguin

## Bhh’ at CDF

**More than counting:**
- BsK+K- :
- Lifetime measurement
- sample sensitive to ΓL
- Combined with other lifetime measurements →ΔΓs
**... ****in the future**
- Bd+-       → 
- BdK+-      → 

- Time dependent CP asymmetry
- requires b-flavor tagging and
- more statistics !

##     Bhh’ in 180 pb-1 

- 893±47 Bhh’ events

**Selection cuts**

- The only significant cut
- not already present in the trigger

- B**d**

- B**s**

- Bd k

- Bs kk

- Bd  

- Bs  k

- Invariant mass  hp (GeV/c2)

## Unbinned Maximum Likelihood Fit

- BKG fraction (float)

- BKG Likelihood

- Sum over the 4 channels

- Likelihood variables:

## Likelihood in detail

- Kinematics

- Particle Identification

- =

- fraction of events of the jth mode

- Signal likelihood

- Unbalance
- Momentum
- P(A|B)P(B)

- Background likelihood same structure as the signal

*j*

*j*

*j*

## Kinematics

**M******

- Bd+-

- Bd  K+-

- Bd  K-+

- Bs  K+-

- Bs  K+K-

- Bs  K-+

- 

- Invariant mass ( hypothesis) vs unbalance
- Def:   **=[1–p1/p2] q1**
**Helps to disentangle the **Bd  K+-  **from **Bs  K-+

- 

- 

- 

- 

- 

**M******

## Particle Identification

- K/ separation:
**	****	****1.4******** **@PT>2 GeV/c
- ...no ev/ev PID separation
- This PID performance implies statistical separation of K-pi with resolution 60% of a “perfect” PID
- Background composition:
-   	(ad-hoc study)
- 	kaons            &
- 	pions (muons)&
- 	protons         &
- 	electrons

**Helps to disentangle **Bd+-** from **Bs  K+K-

## Fit Projections

## Bhh’ results BR and Acp

- Analyzed Luminosity =180 pb-1

## Systematic uncertainties 

- ±0.063 ± 0.012 ±0.019 ±0.054

- 0.04755

- 0.0464

- 0.01272

- 0.0033

- Systematic uncertainties

- will decrease with statistics

## Upper Limits

## BVV BPV

- _

- b->sss pure penguin amplitude
- 	Bs   
- 	B±  K ±
- New Physics has a chance to compete!
- 	( BK*: “B K* polarization discrepancy
-        Bs    is the Bs counterpart of Bd K*
- 	  Unexpected result (3 effect) from
- 	  sin(2) measure from penguin
- 	  dominated modes)
- Measuring angular distribution of decay
- 	products determine polarization
- 	amplitudes and their relative phases
- 	through interference effects:
- CP violation
- ΔΓ**s**
- ...

##                   Bs                  

- A blind analysis was performed in anticipation of a small signal rate.

- Normalize rate using another BsVV decay: BsJ/  **:**
- NO production ratio of Bs vs Bd
-  (fs/fd)
- one K+K- in the final state
- some systematic on efficiency cancel
- sizeable rate

- Separate optimization for
- Signal and Normalization sample
- Cuts optimized checking which of
- The tracks fired the trigger

## Bs    signal

- Bs   

**BR ****= (14 ****+6 -5 (stat)**** ± 2(syst) ****± 5 (BR)****) ******** 10****-5**

- From PDG *

- Bs    signal

- * BR(needs to be rescaled for fs/fd

- First observation

## Yield and ACP (B±   K±)

- mass

- Extended unbinned maximum likelihood fit to :
- MKKK
- M
- helicity angle
- dE/dx from COT

- Helicity angle

- Measure at the same time:
- N(B± K±)
- ACP(B± K±)

- + disentangle signal from B±f0K±, B± K*0, Bu,dX and combinatorial background

- kaons

- pions

- Bu,dX

- B± K*0

- B±f0K±

- comb

- ID

- Normalization: B±  J/ K±
- Extended unbinned maximum L
- M Mk

## B±   K±  Results

- B±   K±  Results

|  | B±  J/ K± | B±   K± |
| --- | --- | --- |
| NB | 439 ± 22 | 47.0 ± 8.4 |

- PDG 2004

- Babar/Belle results with ~100 fb-1

- Analyzed L =180 pb-1

- +PDG
- BR(B±  J/ K±)

## Bhh’ perspectives

- Bhh’ the future:
- Higher precision BR(BsKK)
- Bs KK lifetime: ΔΓs
- Precision Acp(Bd Kπ)
- 	 (eventually1%)
- Bs  Kπ BR and direct Acp
- Tagged time-dependent measurements further ahead:
-                                            Acp parameters for Bd and Bs

- CDF “_the present_”:
- Next round with ~360 pb-1
- Better tracking
- Improved PID

- 180 pb-1

- 360 pb-1

## B VV perspective

- With dataset now on tape new Bs modes should be visible (BsK*0K*0 , Bs):
- Need significantly more statistics to perform CP measurements
-    (...full Run II)
- Measure “untagged” quantities with Bs and BdK*events:

- And other charmless decays are currently under study:
- Bd(s)K
-  V0    (as b )

## Conclusions

- CDF is giving important contribution in the field of the charmless B decays and remains the only player in the
- 	Bs fully hadronic decays
- New analysis with improved tracking and PID are already in the pipeline
- Significant improvement of the TeVatron performance
-  Mon, 23 May 2005  first fb**-1**  was exceeded
- (delivered luminosity ~600 pb-1on tape)
- Higher level of precision is at the door !

## BACKUP

## TeVatron

- 1 fb-1 delivered

## Imbalance - Momentum

- p

- 

- Monte Carlo

- Binned ML fit

- p

- 

## Systematics 

- a) Mass resolution: the mass resolution is input from MC. It is rescaled to match the D0 resolution on data, vary the  the rescale factor of ±10% and repeat the fit.
- b) dE/dx correlation: repeat the fit using the correlation shape extracted in the sample of kaons and pions from “mixed-events”: e.g. one meson from an event, the other from the subsequent event. Quote the difference wrt the central value.
- c) dE/dx shapes for e and p: repeat the fit assigning to the electrons and protons all 4 combinations of dE/dx shapes (ep)= (/K/KK/K). Quote the maximum difference wrt the central fit.

## Systematics  (cont’d)

- d) input masses: the fit is done on data in which the recipe used for mass measurement at CDF II was applied. Input masses in the kinematics pdf are those measured by CDF II. Repeat the fit varying M(Bd) and M(Bs) within their statistical uncertainties (0.92 and 1.29 MeV/c2).       Quote the differences wrt the central fit
- e) Background model: the fit assumes mass spectrum of bckg = exp + C. Repeat the fit with p1,p2,p3 and quote the difference wrt central value

## Systematics  (cont’d)

- f) Different p-spectra for bckg components: central fit assumes the same momentum distribution for e/pi/K/p of background. Reweight each term of the bckg p.d.f. according to linear fits of populations vs momentum plots.

## Systematics  (cont’d)

- g) B lifetimes: relative kinematics efficiencies depend on the lifetime assumed in MC. Re-evaluate efficiencies after simultaneous shift of  Bs lifetime (+1) and  Bd (-1)  and viceversa.  is the PDG2004 uncertainty. Quote difference wrt central value
- h) Isolation efficiency: has a ~ 10% from measurement on data. Re-evaluate the efficiency at +/- 1  and quote difference wrt central value
- i) MC statistics: kinematics efficiencies have statistical error. Re-evaluate them at +/- 1  and quote difference wrt the central fit.

## Systematics  (cont’d)

- l) Charge asymmetry:  assess +/-25% of the 10% charge-asymmetry effect studied in the published D0 analysis
- m) XFT bias correction:  the correction function have uncertainties. Stretch (push) K/ discrepancy shifting simultaneously the correction coefficients by 1 , reevaluate the correction, and quote differences wrt the central fit
- n) pT(B) spectrum: Bs and Bd spectra are different, in principle, but use MC with an “average” spectrum. Created an additional  “shrunk” spectrum by shifting by –1% each entry in the pT(B) histogram used in central fit. Extract weights from the ratio of the two spectra, apply to MC events; re-evaluate the relative efficiencies.

## Systematics  (cont’d)

- o) ΔΓs/Γs : Standard Model predicts ~ 0.12±0.06 and          Bs →K+K- to be dominated by the short-lived component. We derive the systematic uncertainties from these assumptions by varying ΔΓs/Γs from 0.06 to 0.18 , re-evaluating the relative efficiencies and quoting the differences wrt the central fit.

## Systematic uncertainties 

- Systematic uncertainties

- will decrease with statistics

## Measure sin(2) using golden charmonium modes                         (i.e. BdJ/KS0)from mixing induced time dependent CP asymmetry

- Hint of discrepancy with SM in bs penguin decays

- Unexpected result (3 effect) when measuring sin(2) from penguin dominated modes

- B0K0 and B0’K0 theorethically clean!

## B background

**Due to the large width of K* and to**
**its value close to m**φ **we get in our**
**Bs signal window a reflection from **
**Bd****J/**ψ **K* for Bs****J/**ψ φ **and from Bd**φ **K* for Bs**φφ
**We get an estimate of this contribution by evaluating from MC the efficiency of reconstructing a Bd****J/**ψ **K* event as Bs****J/**ψ φ **and from the measured BRs and fs/fd.**
**As a cross-check we can evaluate the**
**contribution from the sidebands**
**subtracted mass spectrum of the **φ
**meson, in which the only remaining**
**source of background comes from the**
**Bd****J/**ψ **K* reflection that doesn’t enter**
**the Bs sidebands region**

## BR(Bs   )  systematics

- Systematic error dominated by normalization mode BR uncertainty and already similar in size to the statistical error
- Theory uncertainty on polarization very conservative (vary longitudinal fraction in 20 % to 80% range as suggested by A. Kagan)
-  s uncertainty based on the preferred theory value of: s/s = 0.12 ± 0.06
- BR is rather on the low side respect to QCDF (2.5 ) 1.4 vs 3.7 E-5

| Source | Relative error on BR |
| --- | --- |
| Trigger efficiency | 3.3 % |
| J/ yield and efficiency | 8.4% |
| Background subtraction | 5.4% |
| Bs polarization | 3.8% |
| BsJ/ polarization | 1.4% |
| s uncertainty | 0.6% |
| J/ and  BR | 2.1% |
| Sub Total  | 11 % |
| BR(J/ )  | 35% |
| Total | 37% |

## BR(B±   K±) systematics

- Systematic error on BR dominated by fit uncertainty and acceptance correction, largely below statistical uncertainty
- ACP  systematic is largely statistical in nature, intrinsic systematic below 0.01
- Comparable to B-factory experiments

| Source | Relative error on BR |
| --- | --- |
| Trigger efficiency | 3.3 % |
| J/ yield and eff. | 4.0% |
| Efficiency Ratio | 3.6% |
| B±   K±  fit syst. | 3.0% |
| J/ and  BR | 2.1% |
| B±   K±  BR | 0.4% |
| Total  | 7.4 % |

| Source | error on Acp |
| --- | --- |
| B±   K±  fit syst. | +0.034  
-0.020 |
| Charge asymmetry | ±0.005 |

## Further Bs modes

- Rich harvest of interesting Bs VV decays
-     (Li,Lu,Yang hep-ph/0309136)
- Only the 0-less shown in the table here
- Measure them all!
- K*+K*-/K*0anti-K*0 untagged angular analysis gives  (with SU(2) assumptions)
- (Fleisher,Duniets)
-   dominated by Electro Weak Penguin (insight in to the BK puzzle!)

| Decay | BR(10-6) | BR/BR()
(including daugher BR) |
| --- | --- | --- |
| K* | 0.53 | 0.11 |
| K*+K*- | 1.94 | 0.008 |
|  | 1.03 | 0.16 |
| K*0 anti-K*0 | 2.61 | 0.35 |
| K* | 0.14 | 0.014 |
|  | 13.1 | 1 |

- Pure penguin

- bs

- bd

- Trigger efficiency not included
- (but expected very similar)