Search for CP Violation in B 0  h decays and B 0  h decays with B A B AR International Europhysics Conference on High Energy Physics, July 17 th -23 rd, 2003, Aachen, Germany Christophe Yèche (CEA-Saclay, DAPNIA/SPP) Outline: CP asymmetries in  +  - and  + K - (PRL, 89, (2002)) Decay rates for  +  0 and  0  0 (submitted to PRL, hep-ex/ ) CP asymmetries in  +  - and  + K - (submitted to PRL, hep-ex/ ) Decay rates for  +  0,  0  + and  0  0 (B A B AR -CONF-03/014)

Ch. Yèche EPS 2003 Aachen, 18 July, 2003 CP Violation in Standard Model 2    V td V tb * V ud V ub * V cd V cb * B  ,  B   J/  K S B   DK CP symmetry can be violated in any field theory with at least one non-trivial phase in the Lagrangian This condition is satisfied in the SM through the three-generation CKM quark-mixing matrix Unitary constraint Representation with Unitary Triangle: The angles ( , ,  ) are related to CP violating asymmetries in specific B decays  is already measured with good precision: Sin2  = ± Next step: “measurement” of sin2   

Ch. Yèche EPS 2003 Aachen, 18 July, 2003 CP Violation in B 0  +  - C   0, S  = Im ( ) =sin2  C   0, S  = sin2  eff For single weak phaseWith an additional weak phase Penguin diagramTree diagram |A(penguin)/A(tree)| ~ 30% | |  1  must fit for direct CP Im ( )  sin2   need to relate asymmetry to  C   0, S  = sin2  eff V ub V td * 3

Ch. Yèche EPS 2003 Aachen, 18 July, 2003 Inclusive Reconstruction B-Flavor Tagging Exclusive B Meson Reconstruction CP eigenstates Flavor eigenstates (flavor eigenstates) Resolution function and mistags (CP eigenstates) CP analysis 00 flavrec BB  00 CPrec BB  PEP-2 (SLAC) Experimental technique 4

Ch. Yèche EPS 2003 Aachen, 18 July, 2003 Background suppression- Discriminating variables 5  (m ES )  2.6 MeV/c 2  (  E)  26 MeV m ES : powerful variable to separate signal from light-quark continuum  E: some separation power for final states with different K/  composition m ES and  E are used in the likelihood

Ch. Yèche EPS 2003 Aachen, 18 July, 2003 Continuum suppression- Discriminating variables 6 “Jets”  candidate Spherical B events vs jet-like continuum:  Techniques exploiting event topology and angular distributions Fisher variable:  Combine two “monomials”, where the sum is over the tracks i of the “Rest-Of-Event”  Use as a discriminating variable in the Likelihood and “Rest-Of -Event”

Ch. Yèche EPS 2003 Aachen, 18 July, 2003 PID: K/  Separation 7 K hypothesis  hypothesis DIRC:  Cherenkov light emitted by the track around a cone with  Photons are captured by internal reflection in the bar and transmitted to a PMT matrix.  Resolution  (  c ) = 2.5 mrad (e + e -  +  - ) Cherenkov angle  c is used in the likelihood to separate ,  K, KK 8  at 2GeV/c 2.5  at 4GeV/c K/  momentum: 2  4 GeV/c

Ch. Yèche EPS 2003 Aachen, 18 July, 2003 B 0  +  - / K +  - / K + K - Branching Fractions 8 The yields are extracted from a maximum likelihood fit based on the variables: m ES,  E, F and  c Continuum e + e -  q q Continuum B 0  +  - B0K+-B0K+- B0K+-B0K+- KK  N(B 0   +  - ) = 157 ± 19 ± 7 N(B 0  K +  - ) = 589 ± 30 ± 17 Projection plots

Ch. Yèche EPS 2003 Aachen, 18 July, 2003 CP Asymmetry Results for  -  + /  - K + A CP (  K) =   C  =  0.25  0.04 S  = 0.02  0.34  The CP parameters are extracted from a maximum likelihood fit based on the variables: m ES,  E, F,  c and  t (for C and S) Cross-checks: Float  and  m d B0K+-B0K+- No Observation of CP Violation A(B 0 /B 0 )

Ch. Yèche EPS 2003 Aachen, 18 July, 2003 Constraint on  : Isospin Analysis The decays B  p + p -, p + p 0, p 0 p 0 are related by isospin  Two relations (one for B 0, one for B 0 )  Neglecting EW penguins, B +  p + p 0 is pure tree diagram  Representation with a triangle with a common side.  Need to measure separate BF for B 0 /B 0 and B + /B -  Triangle relations allow determination of penguin-induced shift in  Bound on penguin pollution  “Back up” solution if the BF( p 0 p 0 ) is too small for isospin analysis!!! M. Gronau and D. London, Phys. Rev. Lett., 65, 3381 (1990) Y. Grossman and H.R. Quinn, Phys. Rev., D58, (1998) 10

Ch. Yèche EPS 2003 Aachen, 18 July, 2003 B   0  0 /  +  0 BF  Fit region  Continuum Continuum e + e -  q q  B +  +  0 decays  Likelihood fit with m ES,  E, F and  c  Potential  +  - background suppressed with a tight cut on  E B 0  0  0 decays  Likelihood fit with m ES,  E, F T  Potential  +  0 background suppressed with a cut on M(  +  0 ) and on  E(  +  0  0 ) Bound on penguin pollution 11

Ch. Yèche EPS 2003 Aachen, 18 July, 2003 Interpretation Isospin Analysis  Large upper limit for BF(B 0  0  0 )  Confidence levels obtained with the BABAR measurements of C , S ,, BF(B 0  0  0 ) and BF(B +  +  0 )  Independent of models but no constraint in ( ,  ) plane QCD factorization  The phase and the magnitude of the tree and penguin amplitudes are predicted by the QCD factorization.  Confidence levels obtained with the BABAR measurements of C  and S .  Very strong constraint in ( ,  ) plane. BBNS, Nucl. Phys., B606, 245 (2001) 12

Ch. Yèche EPS 2003 Aachen, 18 July, 2003 How to measure  with B 0  ? Two final states:  Same diagrams as B 0  -  +, related to  angle  Final states are not CP eigenstates  Two parameters (C , S  )  Four parameters (C , S ,  C ,  S  ) + charge asymmetry  - /  + Comparison with B 0  -  + :  Larger Branching Fractions (  4)  Smaller ratio |A(penguin)/ A(tree)| 13

Ch. Yèche EPS 2003 Aachen, 18 July, 2003 Time probability of the B 0   /  K Parameters measured in the the  /  K analysis 14 Parameterization similar to B 0  +  - 4 CP Violation Parameters:  Direct CP Violation with the charge asymmetries (  + /  - ) A CP  0 for K and .  Summing over the  charge, we have the “usual” (B 0 /B 0 ) asymmetry:  Direct CP Violation: C   0  CP in interference between decay and mixing: S   0 2 Dilution Parameters:   C  can be different from zero (naïve factorization  C~0.3).   S  can be different from zero, no prediction for this term.  if  C  =0 (P(B 0 /B 0  +  - )=P(B 0 /B 0  -  )) and  S  =0  no dilution of sin(2  eff ) when S  is measured!

Ch. Yèche EPS 2003 Aachen, 18 July, 2003 Overview of  /  K analysis 15 Analysis very similar to  /  K analysis:  Same data set (1999  2002) ~ 81 fb -1.  Tagging and resolution function studied with fully reconstructed events.  Simultaneous fit of  and  K events.  Extraction of a the CP parameters with a maximum Likelihood fit using the same kind of variables m ES,  E, F /NN,  c and  t. Features specific to  /  K analysis :  Continuum Suppression: NN with L 0, L 2 and two additional variables o  Mass (mass of the pair (  ±  0 )). o  Helicity (angle between  0 and B in  rest frame).  Modeling of true-signal and misreconstructed-signal.  Modeling of charm and charmless B backgrounds.

Ch. Yèche EPS 2003 Aachen, 18 July, 2003 B 0  /  K Branching Fractions Continuum Continuum + B background Continuum Continuum + B background 16  Continuum Continuum + B background Continuum Continuum + B background KK KK Projection plots

Ch. Yèche EPS 2003 Aachen, 18 July, 2003 CP Asymmetry Results for  /  K A CP (  ) =  0.08  0.03 A CP (  K) = 0.28  0.17  0.08 C  = 0.36  0.18  0.04  C  = 0.28  0.18  0.04 S  = 0.19  0.24  0.03  S  = 0.15  0.25   Continuum + B background  See P-F Giraud’s Talk, about direct CP Violation.  By combining C ,  C  and A CP (  )  a little more than a 2  effect for direct CP Violation.  

Ch. Yèche EPS 2003 Aachen, 18 July, 2003 B   0  0 /  +  0 /  0  + BF Principle of the analyses  Approach very similar to B 0  +  -  Likelihood fit with m ES,  E, NN and (  t) Next steps  Isospin analysis (more complicated) Two triangles  Two pentagons  Interpretation with QCD factorization For a first attempt, see next slide.  (  0  -  + ) Dalitz plot analysis. First observation !!! Continuum + B background Continuum Continuum + B background B+ +0B+ +0 B0 00B0 00 18

Ch. Yèche EPS 2003 Aachen, 18 July, 2003 Interpretation with QCD factorization Direct CP with QCD factorization  In recent papers, computation of QCD factorization for PV decays ( ,…)  QCD Factorization predicts very small direct CP violation for  +  -, better agreement with charming penguin. Mixing-induced CP Violation  C.L. in ( ,  ) plane the BaBar results for the S  and  S  with the computation of QCD factorization for PV decays R. Aleksan et al., Phys. Rev. D67, (2003) See S. Safir Talk B A B AR QCDF QCDF + Ch. penguin A CP (  ) ± C  0.36 ±  C  0.28 ±

Ch. Yèche EPS 2003 Aachen, 18 July, 2003 Conclusions B A B AR results:  No observation of CP Violation in B 0  +  -.  A “hint” of direct CP Violation in B 0  +  -.  No observation of B 0  0  0 and B 0  0  0 decays.  First observation of B +  +  0 decay. Prospects  The isospin analysis does not constrain  yet.  QCD factorization may give very strong constraint on  but still needs to be validated.  The redundancy in experimental measurements (B 0  +  -, B 0  +  -, and B 0  +  - ) may provide a solid framework to test theoretical models and to extract . 20