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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, 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 (B A B AR -CONF-03/014)
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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 = 0.734 ± 0.055 Next step: “measurement” of sin2
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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
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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
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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
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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”
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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
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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 + - B0K+-B0K+- B0K+-B0K+- KK N(B 0 + - ) = 157 ± 19 ± 7 N(B 0 K + - ) = 589 ± 30 ± 17 Projection plots
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Ch. Yèche EPS 2003 Aachen, 18 July, 2003 CP Asymmetry Results for - + / - K + A CP ( K) = -0.102 0.050 0.016 C = -0.30 0.25 0.04 S = 0.02 0.34 0.05 9 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 B0K+-B0K+- No Observation of CP Violation A(B 0 /B 0 )
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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, 017504 (1998) 10
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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
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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
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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
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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!
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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.
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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 KK KK Projection plots
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Ch. Yèche EPS 2003 Aachen, 18 July, 2003 CP Asymmetry Results for / K A CP ( ) = -0.18 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 0.03 17 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.
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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 00B0 00 18
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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, 094019 (2003) See S. Safir Talk B A B AR QCDF QCDF + Ch. penguin A CP ( ) -0.18 ±0.09-0.015-0.115 C 0.36 ±0.180.0190.092 C 0.28 ±0.180.2500.228 19
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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
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