LHCb

Abstract:

A search for a manifestly exotic S=-2 baryon state decaying to Ξ-π-, and its neutral partner decaying to Ξ-π+, has been performed using 220pb-1 of pp̄ collisions at s=1.96TeV collected by the Collider Detector at Fermilab. The Ξ- trajectories were measured in a silicon tracker before their decay, resulting in a sample with low background and excellent position resolution. No evidence was found for S=-2 pentaquark candidates in the invariant mass range of 1600-2100MeV/c2. Upper limits on the product of pentaquark production cross section times its branching fraction to Ξ-π+,-, relative to the cross section of the well-established Ξ(1530) resonance, are presented for neutral and doubly negative candidates with pT>2GeV/c and |y|<1 as a function of pentaquark mass. At 1862MeV/c2, these upper limits for neutral and doubly negative final states were found to be 3.2% and 1.7% at the 90% confidence level, respectively. © 2007 The American Physical Society.

Abstract:

Using 65×106 Υ(4S)→BB̄ events collected with the BABAR detector at the PEP-II e+e- storage ring at the Stanford Linear Accelerator Center, we measure the color-favored branching fractions B(B̄0→D+π- )=(2.55±0.05±0.16)×10-3, B(B̄0→D*+π-)=(2. 79±0.08±0.17)×10-3, B(B-→D0π-)=(4.90±0. 07±0.22)×10-3 and B(B-→D*0π-)=(5.52±0. 17±0.42)×10-3, where the first error is statistical and the second is systematic. With these results and the current world average for the branching fraction for the color-suppressed decay B̄0→D(*) 0π0, the cosines of the strong phase difference δ between the I=1/2 and I=3/2 isospin amplitudes are determined to be cos δ=0.872-0.007-0.029+0. 008+0.031 for the B̄→Dπ process and cos δ=0.924-0.017-0. 054+0.019+0.063 for the B̄→D*π process. Under the isospin symmetry, the results for cos δ suggest the presence of final-state interactions in the Dπ system. © 2007 The American Physical Society.

Abstract:

Using 355pb-1 of data collected by the CDF II detector in pp̄ collisions at s=1.96TeV at the Fermilab Tevatron, we study the fully reconstructed hadronic decays B(s)0→D(s)-π+ and B(s)0→D(s)- π+π+π-. We present the first measurement of the ratio of branching fractions B(Bs0→Ds-π+π+π-)/B(B0→D-π+π+π-)=1. 05±0.10(stat)±0.22(syst). We also update our measurement of B(Bs0→Ds-π+)/B(B0→D-π+) to 1.13±0.08(stat)±0. 23(syst), improving the statistical uncertainty by more than a factor of 2. We find B(Bs0→Ds-π+)=[3.8±0.3(stat)±1.3(syst)]×10-3 and B(Bs0→Ds-π+π+π-)=[8.4±0.8(stat)±3.2(syst)] ×10-3. © 2007 The American Physical Society.

Abstract:

We present a measurement of the branching fraction and time-dependent CP asymmetry of B0→ρ0K0. The results are obtained from a data sample of 227×106 Υ(4S)→BB̄ decays collected with the BABAR detector at the PEP-II asymmetric-energy B factory at Stanford Linear Accelerator Center. From a time-dependent maximum likelihood fit yielding 111±19 signal events, we find B(B0→ρ0K0)=(4.9±0.8±0.9)×10-6, where the first error is statistical and the second systematic. We report the measurement of the CP parameters Sρ0KS0=0.20±0.52±0.24 and Cρ0KS0=0.64±0.41±0.20. © 2007 The American Physical Society.

Abstract:

We present an observation of B→η′K*. The data sample corresponds to 232×106 BB̄ pairs collected with the BABAR detector at the PEP-II asymmetric-energy B factory at the Stanford Linear Accelerator Center. We measure the branching fractions (in units of 10-6) B(B0→η′K*0)=3.8±1.1±0.5 and B(B+→η′K*+)=4.9-1.7+1.9±0.8, where the first error is statistical and the second systematic. A simultaneous fit results in the observation of B→η′K* with B(B→η′K*)= 4.1-0.9+1.0±0.5. We also search for B→η′ρ and η′f0(980)(f0→π+π-) with results and 90% confidence level upper limits B(B+→η′ρ+)=8.7-2.8-1.3+3.1+2.3 (<14), B(B0→η′ρ0)<3.7, and B(B0→η′f0(980) (f0→π+π-))<1.5. Charge asymmetries in the channels with significant yields are consistent with zero. © 2007 The American Physical Society.