Malcolm John

Abstract:

A search for the lepton-flavor-violating (LFV) decay of the tau into three leptons was performed by using 91.5 fb-1 of data collected at an e+ e- center-of-mass energy around 10.58 GeV with the BABAR detector at the SLAC storage ring PEP-II. It was shown that the most stringent limit on FLV was B(τ → μγ) < 3.1 × 10 -7 at 90% C.L., in tau decays. The efficiency of the selection for signal events was estimated with a Monte Carlo (MC) simulation of LFV ray decays. The simulated tau-pairs events including higher-order radiative corrections were generated using KK2F with one tau decaying to three leptons with a three-body phase space distribution.

Abstract:

We study the decays B+ → ηcK+ and B0 → ηcK0, where the ηc is reconstructed in the KS0K ±π∓ and K+K- π0 decay modes. Results are based on a sample of 86 B B̄ pairs collected with the BABAR detector at the SLAC e+e- B Factory. We measure the product of branching fractions B(B+ → ηcK+) ×B(ηc→KK̄π)= (7.40±0.50±0.70)×10-5 and B(B 0→ηcK0) ×B(ηc→KK̄π)=(6.48±0.85±0.71) ×10-5, where the first error is statistical and the second is systematic, In addition, we search for B → ηcK events with ηc→2(K+K-) and ηc→ φφ and determine the ηc decay branching fraction ratios B(ηc →(K+K-)) /B(ηc→KK̄π)=(2.3±0.7±0.6) ×10-2 and B(ηc→φφ) /B(ηc→KK̄π)=(5.5±1.4±0.5) ×10-2.

Abstract:

Using events in which one of two neutral B mesons from the decay of an Y(4S) resonance is fully reconstructed, we set limits on the difference between the decay rates of the two neutral B mass eigenstates and on CP, T, and CPT violation in B0B̄0 mixing. The reconstructed decays, comprising both CP and flavor eigenstates, are obtained from 88 million Y(4S)→BB̄ decays collected with the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC. We determine six independent parameters governing oscillations (Δm,ΔΓ/Γ), CPT and CP violation (Re z,Im z), and CP and T violation (Im λCP,|q/p|), where λCP characterizes B0 and B̄0 decays to states of charmonium plus KS0 or KL0. The results are sgn(Re λCP)ΔΓ/ Γ=-0.008±0.037(stat.)±0.018(syst.)[-0.084,0.068], |q/p|=1.029±0.013(stat.)±0.011(syst.)[1.001,1.057], (Re λCP|λCP|)Re z=0.014±0.035(stat.) ±0.034(syst.)[-0.072,0.101], Im z=0.038±0.029(stat.)±0.025 (syst.)[-0.028,0.104]. The values inside square brackets indicate the 90% confidence-level intervals. The values of Im λCP and Δm are consistent with previous analyses and are used as cross checks. These measurements are in agreement with standard model expectations.