Malcolm John

Abstract:

The measurement of branching fraction for flavor-changing neutral-current process B→XSl+l-, was described. The final state was reconstructed from e+e- or μ+μ- pairs and hadronic system XS, which consists of one K∓ or KS0 and two pions. The systematic uncertainties in signal yield were also evaluated by varying signal gaussian parameters and signal shape. The results show that ratio between generator yield for decay modes which contain KS0 and modes containing a charged kaon was varied within range 0.50∓0.05, allows isospin violation.

Abstract:

We present measurements of the branching fractions and charge asymmetries (where appropriate) of two-body B decays to η(′) K*, η(′) ρ, η(′) π0, ωπ0, and φπ0. The data were recorded with the BABAR detector at PEP-II and correspond to 89×106 BB pairs produced in e +e- annihilation through the Υ (4S) resonance. We find significant signals for two decay modes and measure the branching fractions B(B+→ηK*+)=(25.6 ±4.0±2.4) ×10-6 and B(B0→ηK*0) = (18.6±23±1.2)×10-6, where the first error is statistical and the second systematic. We also find evidence with significance 3,5σ for a third decay mode and measure B(B+ →ηρ+)=(9.2±3.4±1.0)×10 -6. For other channels, we set 90% C.L. upper limits of B(B 0→ηρ0)<1.5 ×10-6, B(B+→η′K*+)<14×10 -6, B(B0→η′K*0)<7. 6×10-6, B(B0→η′K*0) <22×10-6, B(B0 →η′ρ 0)<4.3×10-6, B(B0→ηπ 0)<2.5×10-6, B(B0→η′ π0)<3.7×10-6, B(B0→ωπ 0)<1.2×10-6, and B(B0→φπ 0)<1.0×10-6. For self-flavor-tagging modes with significant signals, the time-integrated charge asymmetries are A ch(ηK*+)=+0.13±0.14±0.02 and Ach(ηK*0)=+0.02±0.11±0.02.

Abstract:

A measurement of the time-dependent CP asymmetry for the neutral B-meson decay B0 → φK0 was discussed. The study was carried by using a sample of B-meson pairs taken at the γ(4S) resonance with the BABAR detector at the PEP-II B-meson factory at SLAC. The CP eigenstates were reconstructed φK0s and φK 0L, where φ K+K-,K 0s → π+ π-, and K 0L was observed. The results show that the values of the CP-violations parameters were SφK = 0.47 ± 0.37(stat) +0.08-0.06.

Abstract:

The branching fraction for the semi-inclusive process B→ήXs, where Xs is a strange hadronic system, was measured. The Xs mass spectrum was also obtained, which fits into models predicting high masses. Two tracking devices, a silicon vertex tracker consisting of five layers of double-sided silicon microstrip detectors and a 40-layer central drift chamber, were used for the detection of charged particles. It was found that the charged-particle identification was provided by the average energy loss in the tracking devices.

Abstract:

The branching fractions and charge asymmeteries in B-meson decays were discussed. The decay amplitudes were evaluated from the measurements of decay rates and CP-violating charge asymmetries. The B-background from charmed and charmless B decays was investigated using MC-simulated events. The uncertainties in the signal MC simulation, which include signal misreconstruction, were evaluated from fully reconstructed B-decays. The misreconstruction signal was due the presence of low momentum pions in the B-decays.