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Search for CP Violation in B 0 h decays and B 0 h decays with B A B AR

Search for CP Violation in B 0 h decays and B 0 h decays with B A B AR. Christophe Y èche (CEA-Saclay, DAPNIA/SPP). Outline: CP asymmetries in  +  - and  + K - (PRL, 89, 281802 (2002)) Decay rates for  +  0 and  0  0 (submitted to PRL, hep-ex/0303028)

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Search for CP Violation in B 0 h decays and B 0 h decays with B A B AR

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  1. Search for CP Violation in B0h decays and B0h decays with BABAR Christophe Yèche(CEA-Saclay, DAPNIA/SPP) • Outline: • CP asymmetries in +- and +K- (PRL, 89, 281802 (2002)) • Decay rates for +0 and 00(submitted to PRL, hep-ex/0303028) • CP asymmetries in +- and +K- (submitted to PRL, hep-ex/0306030) • Decay rates for +0, 0+ and 00(BABAR-CONF-03/014) International Europhysics Conference on High Energy Physics, July 17th-23rd, 2003, Aachen, Germany

  2. * VtdVtb * VudVub * VcdVcb CP Violation in Standard Model • 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 = 0.734 ± 0.055 • Next step: “measurement” of sin2 a B0pp, rp  g b  B0DK B0J/yKS 2 Ch. Yèche EPS 2003 Aachen, 18 July, 2003

  3. CP Violation in B0+ - Tree diagram Penguin diagram Vtd * Vub |A(penguin)/A(tree)| ~ 30% For single weak phase With an additional weak phase |  |  1  must fit for direct CP Im ()  sin2  need to relate asymmetry to  Cpp = 0, Spp = Im () =sin2a Cpp  0, Spp = sin2aeff Cpp  0, Spp = sin2aeff 3 Ch. Yèche EPS 2003 Aachen, 18 July, 2003

  4. PEP-2 (SLAC) 0 0 = B B 0 0 rec = flav B B rec CP Experimental technique Exclusive B Meson Reconstruction CP eigenstates Flavor eigenstates Inclusive Reconstruction B-Flavor Tagging (flavor eigenstates) Resolution function and mistags (CP eigenstates) CP analysis 4 Ch. Yèche EPS 2003 Aachen, 18 July, 2003

  5. Background suppression- Discriminating variables E:some separation power for final states with different K/ composition mES:powerful variable to separate signal from light-quark continuum mES and Eare used in the likelihood (DE)  26 MeV s(mES)  2.6 MeV/c2 5 Ch. Yèche EPS 2003 Aachen, 18 July, 2003

  6. Continuum suppression- Discriminating variables  candidate  candidate “Jets” “Rest-Of -Event”  candidate  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 6 Ch. Yèche EPS 2003 Aachen, 18 July, 2003

  7. PID: K/ Separation • 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 hypothesis p hypothesis K/ momentum: 2 4 GeV/c 7 Ch. Yèche EPS 2003 Aachen, 18 July, 2003

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

  9. CP Asymmetry Results for -+ / -K+ No Observation of CP Violation The CP parameters are extracted from a maximum likelihood fit based on the variables: mES, E, F, c and t (for C and S) ACP (K) = -0.102  0.050  0.016 C = -0.30  0.25  0.04 S = 0.02  0.34  0.05 A(B0/B0) Cross-checks: Float t and Dmd B0K+- 9 Ch. Yèche EPS 2003 Aachen, 18 July, 2003

  10. Constraint on : Isospin Analysis • The decays B p+p-, p+p0, p0p0 are related by isospin • Two relations (one for B0, one for B0) • Neglecting EW penguins, B+p+p0 is pure tree diagram • Representation with a triangle with a common side. • Need to measure separate BF for B0/B0 and B+/B- • Triangle relations allow determination of penguin-induced shift in  • Bound on penguin pollution • “Back up” solution if the BF(p0p0) 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, 017504 (1998) 10 Ch. Yèche EPS 2003 Aachen, 18 July, 2003

  11. B 00 /+0 BF Fit region r+p- • B++0 decays • Likelihood fit with mES, E, F and c • Potential +- background suppressed with a tight cut on E • B000 decays • Likelihood fit with mES, E, FT • Potential +0 background suppressed with a cut on M(+0) and on E(+0 0) • Bound on penguin pollution Continuum p0p0 +p0 Continuum e+e- q q 11 Ch. Yèche EPS 2003 Aachen, 18 July, 2003

  12. Interpretation • Isospin Analysis • Large upper limit for BF(B000) • Confidence levels obtained with the BABAR measurements of C, S,, BF(B0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

  13. How to measure  with B0? • Two final states: • Same diagrams as B0- +, related to  angle • Final states are not CP eigenstates • Two parameters (C, S)  Four parameters (C, S, C, S) + charge asymmetry -/+ • Comparison with B0- +: • Larger Branching Fractions (4) • Smaller ratio |A(penguin)/ A(tree)| 13 Ch. Yèche EPS 2003 Aachen, 18 July, 2003

  14. Parameters measured in the the /K analysis • Time probability of the B0/K • 4 CP Violation Parameters: • Direct CP Violation with the charge asymmetries (+/-) ACP0 for K and . • Summing over the charge, we have the “usual” (B0/B0) 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(B0/B0+-)=P(B0 /B0-)) and S=0  no dilution of sin(2eff) when S is measured! Parameterization similar toB0+- 14 Ch. Yèche EPS 2003 Aachen, 18 July, 2003

  15. Overview of /K analysis • 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 mES, E, F/NN, c and t. • Features specific to /K analysis : • Continuum Suppression: NN with L0, L2 and two additional variables •  Mass (mass of the pair (±0)). •  Helicity (angle between 0 and B in  rest frame). • Modeling of true-signal and misreconstructed-signal. • Modeling of charm and charmless B backgrounds. 15 Ch. Yèche EPS 2003 Aachen, 18 July, 2003

  16. B0/K Branching Fractions   Continuum + B background Continuum Continuum Continuum + B background Projection plots K K Continuum + B background Continuum Continuum Continuum + B background 16 Ch. Yèche EPS 2003 Aachen, 18 July, 2003

  17. CP AsymmetryResults for /K   ACP () = -0.18  0.08 0.03 ACP (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  0.03 Continuum + B background B background  • See P-F Giraud’s Talk, about direct CP Violation. • By combining C, C and ACP ()  a little more than a 2 effect for direct CP Violation. 17 Ch. Yèche EPS 2003 Aachen, 18 July, 2003

  18. B 00 /+0/0+ BF • Principle of the analyses • Approach very similar to B0+- • Likelihood fit with mES, 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. B0 00 Continuum + B background Continuum First observation !!! B+ +0 Continuum Continuum + B background 18 Ch. Yèche EPS 2003 Aachen, 18 July, 2003

  19. 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, 094019 (2003) See S. Safir Talk 19 Ch. Yèche EPS 2003 Aachen, 18 July, 2003

  20. Conclusions • BABAR results: • No observation of CP Violation in B0+-. • A “hint” of direct CP Violation in B0+-. • No observation of B000 andB0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 (B0+-, B0+-, and B0+-) may provide a solid framework to test theoretical models and to extract . 20 Ch. Yèche EPS 2003 Aachen, 18 July, 2003

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