LHCb

Abstract:

We present measurements of the flavor-changing neutral current decays B→K + - and B→K* + -, where + - is either an e+e- or μ+μ- pair. The data sample comprises 229×106Υ(4S)→BB̄ decays collected with the BABAR detector at the PEP-II e+e- storage ring. Flavor-changing neutral current decays are highly suppressed in the standard model and their predicted properties could be significantly modified by new physics at the electroweak scale. We measure the branching fractions B(B→K + -)=(0.34±0.07±0.02)×10-6, B(B→K* + -)=(0.78-0.17+0.19±0.11)×10-6, the direct CP asymmetries of these decays, and the relative abundances of decays to electrons and muons. For two regions in + - mass, above and below mJ/ψ, we measure partial branching fractions and the forward-backward angular asymmetry of the lepton pair. In these same regions we also measure the K* longitudinal polarization in B→K* + - decays. Upper limits are obtained for the lepton-flavor-violating decays B→Keμ and B→K*eμ. All measurements are consistent with standard model expectations. © 2006 The American Physical Society.

Abstract:

We analyze the decay B0→KS0π+π- using a sample of 232×106 Υ(4S)→BB̄ decays collected with the BABAR detector at the SLAC PEP-II asymmetric-energy B factory. A maximum likelihood fit finds the following branching fractions: B(B0→K0π+π-)=(43.0±2.3±2.3) ×10-6,B(B0→f0(→π+π-)K0)=(5.5±0.7±0. 5±0.3)×10-6 and B(B0→K*+π-)=(11.0±1. 5±0.5±0.5)×10-6. For these results, the first uncertainty is statistical, the second is systematic, and the third (if present) is due to the effect of interference from other resonances. We also measure the CP-violating charge asymmetry in the decay B0→K*+π-, AK*π=-0. 11±0.14±0.05. © 2006 The American Physical Society.

Abstract:

We study the two-body decays of B± mesons to K± and a charmonium state Xcc̄ in a sample of 210.5fb-1 of data from the BABAR experiment. We perform measurements of absolute branching fractions B(B±→K±Xcc̄) using a missing mass technique, and report several new or improved results. In particular, the upper limit B(B±→K±X(3872))<3.2×10-4 at 90% C.L. and the inferred lower limit B(X(3872)→J/ψπ+π-)>4.2% will help in understanding the nature of the recently discovered X(3872). © 2006 The American Physical Society.

Abstract:

We present measurements of the branching fraction and time-dependent CP asymmetries in B0→J/ψπ0 decays based on (231.8±2.6) ×106Υ(4S)→BB̄ decays collected with the BABAR detector at the SLAC PEP-II asymmetric-energy B factory. We obtain a branching fraction B(B0→J/ψπ0)=(1.94±0.22(stat)±0.17(syst))×10-5. We also measure the CP asymmetry parameters C=-0.21±0.26(stat)±0. 06(syst) and S=-0.68±0.30(stat)±0.04(syst). © 2006 The American Physical Society.

Abstract:

We present measurements of branching fractions of B0 decays to multibody final states containing protons, based on 232×106 Υ(4S)→BB̄ decays collected with the BABAR detector at the SLAC PEP-II asymmetric-energy B factory. We measure the branching fractions B(B0→D̄0pp̄)=(1. 13±0.06±0.08)×10-4, B(B0→D̄*0pp̄)=(1. 01±0.10±0.09)×10-4, B(B0→D-pp̄π+)=(3. 38±0.14±0.29)×10-4, and B(B0→D*-pp̄π+)= (4.81±0.22±0.44)×10-4 where the first error is statistical and the second systematic. We present a search for the charmed pentaquark state, Θc(3100) observed by H1 and put limits on the branching fraction B(B0→Θcp̄π+)×B(Θc→D*-p) <14×10-6 and B(B0→Θcp̄π+)×B(Θc→D-p) <9×10-6. Upon investigation of the decay structure of the above four B0 decay modes, we see an enhancement at low pp̄ mass and deviations from phase-space in the D̄p̄ and D̄p invariant mass spectra. © 2006 The American Physical Society.