Ricerc@Sapienza

A search for charmless four-body decays of ?b0 and ?b0 baryons with a proton and three charged mesons (either kaons or pions) in the final state is performed. The data sample used was recorded in 2011 and 2012 with the LHCb experiment and corresponds to an integrated luminosity of 3 fb?1. Six decay modes are observed, among which ?b0 ? pK??+??,?b0 ? pK?K+K?,?b0 ? pK??+?? and ?b0 ? pK??+K? are established for the first time. Their branching fractions (including the ratio of hadronisation fractions in the case of the ?b0 baryon) are determined relative to the ?b0 ? ?c+??

A search for the lepton-flavour violating decays Bs0 ? e±?? and B0 ? e±?? is performed based on a sample of proton-proton collision data corresponding to an integrated luminosity of 3 fb?1, collected with the LHCb experiment at centre-of-mass energies of 7 and 8 TeV. The observed yields are consistent with the background-only hypothesis. Upper limits on the branching fraction of the Bs0 ? e±?? decays are evaluated both in the hypotheses of an amplitude completely dominated by the heavy eigenstate and by the light eigenstate.

The ratios of the branching fractions of the decays ?c+ ? p???+, ?c+ ? pK?K+, and ?c+ ? p??K+ with respect to the Cabibbo-favoured ?c+ ? pK??+ decay are measured using proton-proton collision data collected with the LHCb experiment at a 7 TeV centre-of-mass energy and corresponding to an integrated luminosity of 1.0 fb?1:?(?c+?p+)?(?c+?pK??+)=(7.44±0.08±0.18)%,?(?c+?pK?K+)?(?c+?pK??+)=(1.70±0.03±0.03)%?(?c+?p??K+)?(?c+?pK??+)=(0.165±0.015±0.005)%,where the uncertainties are statistical and systematic, respectively.

A measurement is reported of the ratio of branching fractions R(J/?)=B(Bc+?J/??+??)/B(Bc+?J/??+??), where the ?+ lepton is identified in the decay mode ?+??+????. This analysis uses a sample of proton-proton collision data corresponding to 3.0 fb-1 of integrated luminosity recorded with the LHCb experiment at center-of-mass energies of 7 and 8 TeV. A signal is found for the decay Bc+?J/??+?? at a significance of 3 standard deviations corrected for systematic uncertainty, and the ratio of the branching fractions is measured to be R(J/?)=0.71±0.17(stat)±0.18(syst).

The ratio of branching fractions R(D?-)?B(B0?D?-?+??)/B(B0?D?-?+??) is measured using a data sample of proton-proton collisions collected with the LHCb detector at center-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of 3 fb-1. The ? lepton is reconstructed with three charged pions in the final state. A novel method is used that exploits the different vertex topologies of signal and backgrounds to isolate samples of semitauonic decays of b hadrons with high purity.

The ratio of branching fractions R(D?-)?B(B0?D?-?+??)/B(B0?D?-?+??) is measured using a data sample of proton-proton collisions collected with the LHCb detector at center-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of 3 fb-1. For the first time, R(D?-) is determined using the ?-lepton decays with three charged pions in the final state. The B0?D?-?+?? yield is normalized to that of the B0?D?-?+?-?+ mode, providing a measurement of B(B0?D?-?+??)/B(B0?D?-?+?-?+)=1.97±0.13±0.18, where the first uncertainty is statistical and the second systematic.

A search for decays of Bc+ mesons to two charm mesons is performed for the first time using data corresponding to an integrated luminosity of 3.0fb?1, collected by the LHCb experiment in pp collisions at centre-of-mass energies of 7 and 8 TeV. The decays considered are Bc+?D(s)(?)+D?(?)0 and Bc+?D(s)(?)+D(?)0, which are normalised to high-yield B+?D(s)+D?0 decays. No evidence for a signal is found and limits are set on twelve Bc+ decay modes.