Malcolm John

Abstract:

The decays of $B_s^0$ and $\overline{B}_s^0$ mesons into the $J/\psi K^+K^-$ final state are studied in the $K^+K^-$ mass region above the $\phi(1020)$ meson in order to determine the resonant substructure and measure the $CP$-violating phase, $\phi_s$, the decay width, $\Gamma_s$, and the width difference between light and heavy mass eigenstates, $\Delta\Gamma_s$. A decay-time dependent amplitude analysis is employed. The data sample corresponds to an integrated luminosity of $3{\rm fb}^{-1}$ produced in 7 and 8 Tev $pp$ collisions at the LHC, collected by the LHCb experiment. The measurement determines $\phi_s = 119\pm107\pm34 {\rm \, mrad}$. A combination with previous LHCb measurements using similar decays into the $J/\psi \pi^+\pi^-$ and $J/\psi\phi(1020)$ final states gives $\phi_s=1\pm37 {\rm \,mrad}$, consistent with the Standard Model prediction.

Abstract:

We report the first observation of a baryonic Bs0 decay, Bs0→pΛK-, using proton-proton collision data recorded by the LHCb experiment at center-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of 3.0 fb-1. The branching fraction is measured to be B(Bs0→pΛK-)+B(Bs0→pΛK+)=[5.46±0.61±0.57±0.50(B)±0.32(fs/fd)]×10-6, where the first uncertainty is statistical and the second systematic, the third uncertainty accounts for the experimental uncertainty on the branching fraction of the B0→pΛπ- decay used for normalization, and the fourth uncertainty relates to the knowledge of the ratio of b-quark hadronization probabilities fs/fd.

Abstract:

The B+→D∗-K+π+ decay potentially provides an excellent way to investigate charm meson spectroscopy. The decay is searched for in a sample of proton-proton collision data collected with the LHCb detector at center-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of 3 fb-1. A clear signal is observed, and the ratio of its branching fraction to that of the B+→D∗-π+π+ normalization channel is measured to be B(B+→D∗-K+π+)/B(B+→D∗-π+π+)=(6.39±0.27±0.48)×10-2, where the first uncertainty is statistical and the second is systematic. This is the first observation of the B+→D∗-K+π+ decay.

Abstract:

A study of Bs0 → ηcϕ and Bs0 → ηcπ+π− decays is performed using pp collision data corresponding to an integrated luminosity of 3.0 fb^−1 , collected with the LHCb detector in Run 1 of the LHC. The observation of the decay Bs0 → ηcϕ is reported, where the ηc meson is reconstructed in the pp, K+K−π+π−, π+π−π+π− and K+K−K+K decay modes and the ϕ(1020) in the K+K− decay mode. The decay Bs0→J/ψϕ is used as a normalisation channel. Evidence is also reported for the decay Bs0 → ηcπ+π− , where the ηc meson is reconstructed in the pp decay mode, using the decay Bs0 → J/ψπ+π− as a normalisation channel. The measured branching fractions are(Formula Presented.)where in each case the first uncertainty is statistical, the second systematic and the third uncertainty is due to the limited knowledge of the external branching fractions..