# Presentation: 273326

## CP violation and CKM measurements in Bottom and Charm decays at CDF 

- Saverio D’Auria
*University of Glasgow, UK **and FNAL*
- On behalf of the CDF collaboration
- 6th Int. Conf. on Hyperons, Charm and Beauty Hadrons
-  Chicago, July 1st 2004

## Contents:

- Introduction: b-Physics at the hadron collider
- Charm-less b-decays
- Bu   K±
- Bs   
- Bd,s  h± h (h = K, )
- CP violation in charm decays
- D0   , K K
- Conclusions and perspective

- Moment analysis: see separate talk by R. Miquel,
- Mixing & detector issues have been covered by J. Piedra.

## Introduction

- 3 sources of ACP:
- ACP from mixing: neutral meson oscillate with different phase, mass eigenstates not CP eigenstates.
**A****CP**** direct:                 in SM from interference of weak and strong phases in decay.**
- ACP from the interference of mixing and direct ACP
- Tevatron excellent source of b-hadrons, b = 29.4 ± 0.6 ± 6.2 b (|y| < 1) (CDF)
- New hadronic trigger, based on tracking new channels available.
- Charm-less b-decays
- Bu   K±  Direct ACP
- Bs      mixing & direct ACP (presently BR only)
- Bd,s  h± h (h = K, )  Direct only or  mixing & direct
- CP violation in CKM-suppressed charm decays
- D0   , K K  Search for direct Asymmetry

## Introduction: trigger strategies 

- Introduction: trigger strategies

- Trigger requires:
-  2 opposite charge tracks,
-  each Pt  2 GeV/c,
-  impact parameter (d0) > 120 μm
-  Scalar pt sum > 5.5 GeV/c
-  Projected decay Lxy > 200 μm
-  Polar angle difference 2° <  < 90°

- Select b-events: 1 in 103
- Hadronic trigger (2-track-trigger)
- In addition to
-  soft-lepton trigger (updated!)
-  J/ trigger

- On-line resolution:
- 33 m beam  35m intrinsic

- signal from
- hadronic trigger

## First case: B§ !  K§

- B VP
- Almost pure penguin (annihilation at tree level)

*b*

*s*

- }K

- EW penguin contribution expected ~10%.
- Expect very little asymmetry, probe for new Physics.
- Already measured by Belle and BaBar, proof of principle, bench test
- and measurement with comparable errors (< 2£).

- }

- W

*s*

*b*

## B§ !  K§ : the method 

- Control sample:
-  Bu  J/ K±  same event topology, same trigger,
-  different angular distribution.

- Un-binned maximum likelihood fit
-  3-track invariant mass
-  Two-track invariant mass
-  Helicity angle
-    ( or J/ polarization)
-  Specific ionization (dE/dx)
- Use templates for physical
- background, based on MC
- Fit at the same time for
- CP asymmetry, yield, mass,
- (Background)

- Analysis cuts:
- Lxy > 350m
- Vertex 2 < 8
- Ptsoft > 1.3GeV/c
- d0(B) < 100 m

- Isolation(R < 1.0) > 0.5
- 1 < MKK   < 1.06GeV/c2
- 5 < MKKK < 5.6 GeV/c2
- M< 100MeV/c2

## Signal in B§   K±

- Bu   K±

- K+

- B§

- K-

- “Helicity angle”

- Particle ID: dE/dx in central
- tracking chamber

- mass

- 2/d.o.f = 17.5/14; P=23%

## Signal in B§   K±

- Red: signal template
- Black: combinatorial background
- Physical backgrounds:
- Partially reconstructed B’s
- B§ ! f0 K§
- B§ ! K§ K ̈ K§
- B§! K0* 

- 2/dof = 11.26/14 (P=67%)

## Direct ACP in Bu   K±

- Fit results

- Systematic errors:
- Detector asymmetry: 5% in this analysis from J/ K± ; Can be factor 10 better
- Fit templates and method give 2.5%

- ACP=------------------------- = – 0.07 § 0.17

- B-!  k- - B+!  k+

- B+!  k+ + B-!  k-

- + 0.06

- – 0.05

| Parameter | Bu  J/ K± | Bu   K± |
| --- | --- | --- |
| Signal (evts) | 439 ± 22 | 47.0 ± 8.4 |
| ACP | 0.046 ± 0.050 | -0.07 ± 0.17 |

## Branching fraction measured w.r.t control channel, 

- Measurement limited by statistics:
- with 2fb-1 stat / 3  and sys / 10 on ACP
- ACP (HFAG) =  0.03 § 0.07

- Branching Ratio

- ACP

- Branching fraction measured w.r.t control channel,
- Cancellation of most systematic errors: (abs)  (rel),
- trigger and reconstruction from MC.

**BR**** (B****§**** ******** ******** K****§****) / ****BR**** (B****§**** ******** J/******** K****§****) =  (7.2 ****§**** 1.3 ****§**** 0.7 ) ****£**** 10****-3**
**Using PDG value:  ****BR**** (B****§**** ******** ******** K****§****) =  (7.2 ****§**** 1.3 ****§**** 0.7 ) ****£**** 10****-6**

- Main systematic on BR is
- Particle-dependant trigger efficiency

## Motivations:
Penguin diagram decay, never observed before.
Decay to vector-vector, not CP eigenstate, but angular analysis possible in future, other method for s.
Same final state accessible by both initial states.
No or very little direct asymmetry expected in this channel by SM.
Rare penguin Probe for new physics

Method:
Cut-based blind analysis:
Optimize cuts on MC + data background
Establish signal, then fit analysis.
Reference channel: 
	Bs ! J/  

- Penguin diagram decay, never observed before.
- Decay to vector-vector, not CP eigenstate, but angular analysis possible in future, other method for s.
- Same final state accessible by both initial states.
- No or very little direct asymmetry expected in this channel by SM.
- Rare penguin Probe for new physics
- Method:
- Cut-based blind analysis:
- Optimize cuts on MC + data background
- Establish signal, then fit analysis.
- Reference channel:
- 	Bs ! J/ 

-  Second case: Bs   

## Bs    Analysis highlights: 

- Optimize cuts based on MC
- Projection of decay length Lxy,
- Pt(), Pt(2), 2
- pointing constraint d0(Bs),
- impact parameter of reconstructed ,

- Maximize the score function
-  optimization independent on
- MC sample size. Optimized for 3
- significance.

## Bs    results

- Analysis cuts:
- d0(Bs) < 80 μm
-  Pt() > 2.5 GeV/c
-  Lxy > 350 μm
-  2xy < 10
- Cuts slightly depending on
- 	trigger topology

- Bs !  
- Signal:  events,
- Background: 0.75 evts

**BR ****= (1.4 ****± 0.6 ± 0.2 ± 0.5 (BR)) ******** 10****-5**

- From PDG

- From MC

- QCD Factorization: BR =** **3.68 £ 10-5 (Li-Lu-Yang hep-ph/0309136)

## B to 2-body final states

**B****d**** ****!**** ************ **********
**B****d**** ****!**** K******** **********
**B****s**** ****!**** ************ K******
**B****s**** ****!**** K******** K******

****

- (0,0)

- (0,1)

- md/ ms

- 

- 

- Tree and penguin amplitudes
- Weak and strong phases,
- Direct ACP

- Fleischer method: assume U-spin symmetry
- Measure the 4 asymmetries
- Fit the 4 ACP as function of
-   and Penguin / Tree amplitude ratio

- }

- }

- Bd {

- b

- u

- }

- }

- Bd {

- b

- d

- Experimental challenge:
- Disentangle the various decays

**M******

## Bs 

- Specific energy loss: K/ separation
- Recently improved to 1.4 
- Kinematic variables:
- mass, charge and momentum unbalance
- M vs. (1 – pmin / pmax ) Qmin

- MC

- Bd 

- Bs 

- B0 

- B0 

- Bs 

- Bs 

## B h h Results

- B h h Results

- All these results using the first 65 pb-1, update to 190 pb-1 very soon

| B0 ! | 39§ 14 | 14% |
| --- | --- | --- |
| B0 !K | 148§ 17 | 53% |
| Bs !K | 90§ 17 | 32% |
| Bs !K | 3§ 11 | 1% |

- 190 pb-1

- 891±47 evts

## CP Asymmetry in charm decays

- Effect small in standard model (0.1 to 1%) due to small contribution of box diagrams.
- Check direct ACP in Cabibbo-suppressed decays as a test for new physics.
- Large production of charm.
- Very large charm sample
- 	collected to date
- Method:
- Use            from* D**± * D*0 
-      and tag flavour from soft  charge
- Measure relative branching ratios
- final products CP eigenstates
- Take into account slight detector asymmetry

## D0 {

- D0! K+K, D0! +

- High statistics of reconstructed and tagged D0: 2£ 105 candidates
- We measure the relative branching ratio and ACP for the
- suppressed modes

- }

- }

- D0 {

- c

- u

- Relative branching fraction:

- From MC
- including trigger,
- Detector config.,
- nuclear interactions

## Lxy > 350  m

- Lxy > 350  m
- MD = (MD*-MDo) < 3 1⁄4 1.8MeV/c2
- d0(1) d0(2) < 0

- Signal peaks are very well
- separated from background.

- D0! K+K, D0! +

- Physical background for KK

- Asymmetry
- corrections
- at 1% level
- High statistics,
- precise
- measurement

## D0! K+K, D0! +

- Branching ratios:

- Asymmetries:

- Results:

- PDG (0.5 ± 1.6) %
- PDG (2.1 ± 2.6) %

## Conclusions

- CP Asymmetry in hadronic charmless decays measured at CDF , agreement with HFAG, consistent with zero
- New pure penguin decay mode observed for Bs, additional mode for s
- Measurement of  possible with , K,KK decays to charged particles. Measurement update soon.
- Asymmetry in charm decays consistent with zero, in future measurement will be possible at < 0.2 % level
- Looking forward for 2fb-1 (Run-IIa)
- Looking for more channels and developing tag algorithms
- Bs mixing....!