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Register a new userMeasurement of the CP Violation Parameters in B0 -> pi+ pi- Decays
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We present a measurement of the time-dependent charge-parity (CP) violation parameters in B0 -> pi+ pi- decays. The results are obtained from the final data sample containing 772 million BBbar pairs collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider. We obtain the CP violation parameters Acp = +0.33 +/- 0.06 (stat) +/- 0.03 (syst) and Scp = -0.64 +/- 0.08 (stat) +/- 0.03 (syst), where Acp and Scp represent the direct and mixing-induced CP asymmetry, respectively. Using an isospin analysis including results from other Belle measurements, we find 23.8 < phi2 < 66.8 degrees is disfavored at the 1 sigma level, where phi2 is one of the three interior angles of the CKM unitarity triangle related to B_{u,d} decays.
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An analysis of B0->D K*0 decays is presented, where D represents an admixture of D0 and D0b mesons reconstructed in four separate final states: K-pi+, pi-K+, K+K- and pi+pi-. The data sample corresponds to 3.0fb-1 of proton-proton collision, collected by the LHCb experiment. Measurements of several observables are performed, including CP asymmetries. The most precise determination is presented of rB(DK*0), the magnitude of the ratio of the amplitudes of the decay B0->D K+ pi- with a b->u or a b->c transition, in a K pi mass region of +/-50 MeV/c2 around the K*(892) mass and for an absolute value of the cosine of the K*0 helicity angle larger than 0.4.
Using proton-proton collision data collected by the LHCb experiment at sqrt(s) = 7 TeV, corresponding to an integrated luminosity of 1.0 fb^{-1}, the ratio of branching fractions of the B0 -> D*- pi+ pi- pi+ decay relative to the B0 -> D*- pi+ decay is measured to be B(B0 -> D*- pi+ pi- pi+) / B(B0 -> D*- pi+) = 2.64 pm 0.04 (stat.) pm 0.13 (syst.). The Cabibbo-suppressed decay B0 -> D*- K+ pi- pi+ is observed for the first time and the measured ratio of branching fractions is B(B0 -> D*- K+ pi- pi+) / B(B0 -> D*- pi+ pi- pi+) = (6.47 pm 0.37 (stat.) pm 0.35 (syst.)) x 10^{-2}. A search for orbital excitations of charm mesons contributing to the B0 -> D*- pi+ pi- pi+ final state is also performed, and the first observation of the B0 -> Dbar_{1}(2420)^0 pi+ pi- decay is reported with the ratio of branching fractions B(B0 -> (Dbar_{1}(2420)^0 -> D*- pi+) pi- pi+) / B(B0 -> D*- pi+ pi- pi+) = (2.04 pm 0.42 (stat.) pm 0.22 (syst.)) x 10^{-2}, where the numerator represents a product of the branching fractions B(B0 -> Dbar_{1}(2420)^0 pi- pi+) and B(Dbar_{1}(2420)^0 -> D*- pi+).
Observations are reported of different sources of $CP$ violation from an amplitude analysis of $B^+ to pi^+ pi^+ pi^-$ decays, based on a data sample corresponding to an integrated luminosity of $3 ; {rm fb}^{-1}$ of $pp$ collisions recorded with the LHCb detector. A large $CP$ asymmetry is observed in the decay amplitude involving the tensor $f_2(1270)$ resonance, and in addition significant $CP$ violation is found in the $pi^+ pi^-$ S-wave at low invariant mass. The presence of $CP$ violation related to interference between the $pi^+ pi^-$ S-wave and the P-wave $B^+ to rho(770)^0 pi^+$ amplitude is also established; this causes large local asymmetries but cancels when integrated over the phase space of the decay. The results provide both qualitative and quantitative new insights into $CP$-violation effects in hadronic $B$ decays.
A search for time-integrated $CP$ violation in the Cabibbo-suppressed decay $mbox{$D^0rightarrowpi^+pi^-pi^+pi^-$}$ is performed using an unbinned, model-independent technique known as the energy test. This is the first application of the energy test in four-body decays. The search is performed for $P$-even $CP$ asymmetries and, for the first time, is extended to probe the $P$-odd case. Using proton-proton collision data corresponding to an integrated luminosity of 3.0 fb$^{-1}$ collected by the LHCb detector at centre-of-mass energies of $sqrt{s}=$7 TeV and 8 TeV, the worlds best sensitivity to $CP$ violation in this decay is obtained. The data are found to be consistent with the hypothesis of $CP$ symmetry with a $p$-value of $(4.6pm0.5)%$ in the $P$-even case, and marginally consistent with a $p$-value of $(0.6pm0.2)%$ in the $P$-odd case, corresponding to a significance for $CP$ non-conservation of 2.7 standard deviations.
We present updated measurements of branching fractions and CP-violating asymmetries for neutral B meson decays to two-body final states of charged pions and kaons. The results are obtained from a data sample of about 60 million Y(4S) --> B-anti-B decays collected between 1999 and 2001 by the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC. The sample contains 124^{+16}_{-15} pi-pi, 403+/-24 K-pi, and 0.6^{+8.0}_{-7.4} K-K candidates, from which we measure the following quantities: BF(B0 --> pi+pi-) = (5.4+/-0.7+/-0.4) x 10^{-6}, BF(B0 --> K+pi-) = (17.8+/-1.1+/-0.8) x 10^{-6}, BF(B0 --> K+K-) < 1.1 x 10^{-6} (90% C.L.} A_Kpi = -0.05+/-0.06+/-0.01 [-0.14,+0.05], S_pipi = -0.01+/-0.37+/-0.07 [-0.66,+0.62], C_pipi = -0.02+/-0.29+/-0.07 [-0.54,+0.48], where the errors are statistical and systematic, respectively, and the asymmetry limits correspond to the 90% confidence level. These results are preliminary.
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