1 CP violation in B → ,  Hiro Sagawa (KEK) FLAVOR PHYSICS & CP VIOLATION, Ecole Polytechnique, Paris, France on June 3-6, 2003

2 Outline CP asymmetries in B 0 →     decayCP asymmetries in B 0 →     decay –CP violating parameters : S  and A  (=  C  ) Belle : hep-ex/ ( to be appeared in PRD ) BaBar : Phys. Rev. Lett –Bound on Penguin Pollution from isospin relation ( B →          and     decays ) CP asymmetries in B 0 →  decay (       )CP asymmetries in B 0 →  decay (       ) –Quasi-two-body analysis BaBar : update at Recontres de Moriond 2003 Belle BaBar

3 Introduction

4 B   Unitarity triangle Quark mixing is described by the 3x3 Cabibbo-Kobayashi-Maskawa (CKM) matrix. (Wolfenstein parametrization) 1()1() 3()3() 2()2() One irreducible complex phase derives CP violation.

5 CP violation in mixing and decay CP violation in neutral B meson results from the interference between decays with and without mixing.

6 Time evolution in B 0  π + π – q= +1 for B 0 tag  1 for B 0 tag  t=  z/(  c) (Belle)

7 CP violation in B 0  π + π – B0B0 b d B0B0 tt d b B0B0 mixing b b d u d B0B0  u d W+W+  Tree(T) b d B0B0 d u u d   g t Penguin(P) decay

8 Analysis Procedure

9 Data sample Event Selection Flavor tagging Vertex and  t Continuum suppression            : charmless B decays BR ~ : rare decays world average (10 -6 ) Need a lot of data Data sample     Belle 85 million BB pairs BaBar 88 million BB pairs  BaBar 89 million BB pairs (HFAG table )

10 Kinematics: Reconstruction of CP side Event Selection Flavor tagging Vertex and  t Continuum suppression Kinematics M bc (GeV/c 2 )  E(GeV) Signal MC

11 Good K/  separation Event Selection Flavor tagging Vertex and  t Continuum suppression Belle ACC(Aerogel Cherenkov Counter) + CDC dE/dx For the tracks in the momentum range that covers the B 0      signal,  effciency = 91% 10.3% of kaons are misidentified as pions  0.2% from K  10.6  0.2% from K + The effect of asymmetry of this misidentification is negligible for the measurement of A  and S . Threshold type

12 Good K/  separation Event Selection Flavor tagging Vertex and  t Continuum suppression BaBar DIRC (Detector of Internally Reflected Cherenkov light)  /K separation Cherenkov angle (, ) is used separately as PDF for maximum likelihood fit. Cherenkov angle for positively and negatively charged tracks

13 Flavor tagging Event Selection Flavor tagging Vertex and  t Continuum suppression Use flavor specific properties and correlations

14 Continuum background Event Selection Flavor tagging Vertex and  t Continuum suppression use kinematics and topology to separate spherical B decays from jetty qq events

15 Continuum suppression B 0      for the case of Belle Cut on a likelihood ratio (LR) that combines an event topology variable (SFW) and B flight direction (cos  B ) SFW: Super Fox Wolfram Fisher discriminant using modified Fox-Wolfram moments SFW cos  B LR

16 Vertex reconstruction Flavor tagging Vertex and  t Continuum suppression The same algorithm as that used for sin2  1 meas. Resolution mostly determined by the tag- side vtx. Example vertices B 0 lifetime of control sample  0.018(stat) ps Time resolution (rms) 1.43ps (PDG02: 1.542±0.016 ps) Event Selection

17 CP asymmetries in B 0     

18 Event reconstruction (Belle) Beam-constrained mass (M bc ) energy difference (  E) (in  E signal region) (in M bc signal region) B-candidate energy – beam energy (CMS)     K   other rare B decays qq continuum

19 Fit results (Belle) Large CP Violation is seen ! B 0 tag sin term cos term hep-ex/ accepted for Phys. Rev. D LR>0.825

20 Confidence Regions (Belle) Feldman-Cousins frequentist approach 1) Evidence for CP violation in B 0  π + π – 2) “Indication” of direct CP Violation (A  >0) CL for CP conservation 3.4 

21 Constraints on the CKM angle  2 (  ) |P/T| (representative) Theory ~0.3  deg (=  ) (Belle & BaBar combined)  2 (=  )  strong phase difference 78 o <  2 <152 o (95.5%C.L.)  <0 favored 22 |P/T|=0.45

22 Constraint on  -   2 =78 o  2 =118 o  2 =152 o 11 22 33 Belle’s results of  1 and  2 are consistent with other measurements. PDG ( Belle  1 &  2 )

23 m ES and  E (BaBar)  -enhanced events Phys Rev Lett 89, (2002) K  -enhanced events m ES EE EE

24 CP asymmetry result (BaBar) Projection in signal  -enhanced events Phys Rev Lett 89, (2002) Asymmetry Events/1ps (A  =+0.30)

25 The difference is at 2.2  level. It’s early to say conclusively for the difference. Fit results (Belle&BaBar) &

26 Comparison with predictions PQCD A  BelleBaBarPQCDQCDF hep-ex/ PRL, (2002) PRD67, (2003) NPB606,245 (2001) (%) Purple regions : PQCD favored Region for each  2 (60 o, 100 o, 150 o )

27 A bound on  =|   eff -   | with an upper limit on     can constrain on   using isospin relation.

28 A bound on  =|   eff -   | Gronau/London/Sinha/Sinha bound (PL B514, 315 (2001))  (deg) HFAV table

29 CP asymmetries in B 0  

30 CP-Violating Asymmetries in B  →    ,      Principle: measure  directly, even with penguins using full Dalitz-plot analysis –difficulty Combinatorics and lower efficiency in three-body topology with  0 Large backgrounds from misreconstructed signal events and other B decays Need large statistics to extract  cleanly “ quasi-two-body ” analysis: –Select the  -dominated region of the        K      Dalitz plane (Rejected when.) –Suppression of qq backgrounds –Simultaneous fit for     and    

31   Final state       : not a CP eigenstate Basically there are four tree amplitudes: CP Violation Study in B 0 →  π decay

32 B 0 →  π Time-dependence Decay rate distribution

33 direct CP violation → A CP and C = 0 indirect CP violation → S = 0  C and  S are insensitive to CP violation Time evolution includes: Time-integrated asymmetry: Q is the  charge  K is self- tagging: Fit for:

34 Preliminary The results with 89 million BB Moriond EW BR of  and  K Charge asymmetry of  and  K B 0 →  π/  K (BaBar) Yields and Charge Asymmetries B 0 →  πB 0 →  K

35 B 0 →  π/  K (BaBar) :  t distributions B+continuum background B-related background 2  (or more) from zero

36 Direct CP violation in B 0 →  (0,0)

37 Comparison with predictions BaBar: A  =  0.08  0.03 C  =  0.15  0.04  C  =  0.19  0.04 QCDF: A  = C  =  C  = w/ Charming Penguin(CP): S  = C  =  C  = Phys. Rev. D67,094019, 2003

38 Prospect ( B 0 →   π - ) L(fb  )  A   S 

39 Prospect ( B 0 →  π ) L(fb -1 )  A   C   S 

40 Summary Measurement of CP asymmetries in B 0 →     Still early to say conclusively for the difference. Measurement of CP asymmetries in B 0 →  –Quasi-two-body analysis was performed by BaBar. –Hint of Direct CPV ? (0,0) 2  lines

41 end