Search for b→u transitions in B±→[K∓π±π0]DK± decays

We present a study of the decays B±→DK± with D mesons reconstructed in the K+π-π0 or K-π+π0 final states, where D indicates a D0 or a D̅ 0 meson. Using a sample of 474×106 BB̅ pairs collected with the BABAR detector at the PEP-II asymmetric-energy e+e- collider at SLAC, we measure the ratios R±≡Γ(B±→[K∓π±π0]DK±)/Γ(B±→[K±π∓π0]DK±). We obtain R+=(5-10+12(stat)-4+2(syst))×10-3 and R-=(12-10+12(stat)-5+3(syst))×10-3, from which we extract the upper limits at 90% probability: R+<23×10-3 and R-<29×10-3. Using these measurements, we obtain an upper limit for the ratio rB of the magnitudes of the b→u and b→c amplitudes rB<0.13 at 90% probability

Observation of the rare decay B+→K+π0π0 and measurement of the quasi-two-body contributions B+→K*(892)+π0, B+→f0(980)K+, and B+→χc0K+

We report an analysis of charmless hadronic decays of charged B mesons to the final state K+π0π0, using a data sample of (470.9±2.8)×106 BB̅ events collected with the BABAR detector at the Υ(4S) resonance. We observe an excess of signal events, with a significance above 10 standard deviations including systematic uncertainties, and measure the branching fraction and CP asymmetry to be B(B+→K+π0π0)=(16.2±1.2±1.5)×10-6 and ACP(B+→K+π0π0)=-0.06±0.06±0.04, where the uncertainties are statistical and systematic, respectively. Additionally, we study the contributions of the B+→K*(892)+π0, B+→f0(980)K+, and B+→χc0K+ quasi-two-body decays. We report the world’s best measurements of the branching fraction and CP asymmetry of the B+→K+π0π0 and B+→K*(892)+π0 channels

Symmetry violations at BABAR

Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Published under licence by IOP Publishing Ltd.2014 J. Phys.: Conf. Ser. 556 012042 (http://iopscience.iop.org/1742-6596/556/1/012042

Observation of time-reversal violation in the B0 meson system

The individually named authors work collectively as The BABAR Collaboration. Copyright @ 2012 American Physical Society.Although CP violation in the B meson system has been well established by the B factories, there has been no direct observation of time-reversal violation. The decays of entangled neutral B mesons into definite flavor states (B0 or B¯¯¯0), and J/ψK0L or cc¯K0S final states (referred to as B+ or B−), allow comparisons between the probabilities of four pairs of T-conjugated transitions, for example, B¯¯¯0→B− and B−→B¯¯¯0, as a function of the time difference between the two B decays. Using 468×106 BB¯¯¯ pairs produced in Υ(4S) decays collected by the BABAR detector at SLAC, we measure T-violating parameters in the time evolution of neutral B mesons, yielding ΔS+T=−1.37±0.14(stat)±0.06(syst) and ΔS−T=1.17±0.18(stat)±0.11(syst). These nonzero results represent the first direct observation of T violation through the exchange of initial and final states in transitions that can only be connected by a T-symmetry transformation.DOE and NSF (USA), NSERC (Canada), CEA and CNRS-IN2P3 (France), BMBF and DFG(Germany), INFN (Italy), FOM (The Netherlands), NFR (Norway), MES (Russia), MINECO (Spain), STFC (United Kingdom). Individuals have received support from the Marie Curie EIF (European Union), the A. P. Sloan Foundation (USA) and the Binational Science Foundation (USA-Israel)