Ricerc@Sapienza

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.

The CP asymmetry in B? ? Ds?D0 and B? ? D?D0 decays is measured using LHCb data corresponding to an integrated luminosity of 3.0 fb?1, collected in pp collisions at centre-of-mass energies of 7 and 8 TeV. The results are ACP(B??Ds?D0)=(?0.4±0.5±0.5)%andACP(B??D?D0)=(2.3±2.7±0.4)%, where the first uncertainties are statistical and the second systematic. This is the first measurement of ACP(B??Ds?D0) and the most precise determination of ACP(B?? D?D0). Neither result shows evidence of CP violation.

A measurement of the CP asymmetries Sf and Sf¯ in B0 ? D??± decays is reported. The decays are reconstructed in a dataset collected with the LHCb experiment in proton-proton collisions at centre-of-mass energies of 7 and 8 TeV and corresponding to an integrated luminosity of 3.0 fb?1. The CP asymmetries are measured to be Sf = 0.058 ± 0.020(stat) ± 0.011(syst) and Sf¯=0.038±0.020(stat)±0.007(syst). These results are in agreement with, and more precise than, previous determinations. They are used to constrain angles of the unitarity triangle, | sin (2?

The cross-section for inelastic proton-proton collisions at a centre-of-mass energy of 13TeV is measured with the LHCb detector. The fiducial cross-section for inelastic interactions producing at least one prompt long-lived charged particle with momentum p > 2 GeV/c in the pseudorapidity range 2 < ? < 5 is determined to be ? acc = 62:2 ± 0:2 ± 2:5mb. The first uncertainty is the intrinsic systematic uncertainty of the measurement, the second is due to the uncertainty on the integrated luminosity. The statistical uncertainty is negligible.

A search for the decay B-s(0) -> (K) over bar (*0) mu(+) mu(-) is presented using data sets corresponding to 1.0, 2.0 and 1.6 fb(-1) of integrated luminosity collected during pp collisions with the LHCb experiment at centre-of-mass energies of 7, 8 and 13TeV, respectively. An excess is found over the background-only hypothesis with a significance of 3.4 standard deviations.

The production cross-sections of ?(1S), ?(2S) and ?(3S) mesons in proton-proton collisions at s=13 TeV are measured with a data sample corresponding to an integrated luminosity of 277 ± 11 pb ?1 recorded by the LHCb experiment in 2015. The ? mesons are reconstructed in the decay mode ? ? ? + ? ? . The differential production cross-sections times the dimuon branching fractions are measured as a function of the ? transverse momentum, p T , and rapidity, y, over the range 0 < p T < 30 GeV/c and 2.0 < y < 4.5.

The Cabibbo-suppressed decay ?b0 ? ?(2S)p?? is observed for the first time using a data sample collected by the LHCb experiment in proton-proton collisions corresponding to 1.0, 2.0 and 1.9 fb?1 of integrated luminosity at centre-of-mass energies of 7, 8 and 13 TeV, respectively. The ?(2S) mesons are reconstructed in the ?+?? final state. The branching fraction with respect to that of the ?b0 ? ?(2S)pK? decay mode is measured to be ?(?b0??(2S)p??)?(?b0??(2S)pK?)=(11.4±1.3±0.2)%, where the first uncertainty is statistical and the second is systematic. The ?(2S)p and ?(2S)??

The B¯s0??c2K+K? decay mode is observed and its branching fraction relative to the corresponding ?c1 decay mode, in a ±15 MeV/c2 window around the ? mass, is found to be ?(B¯s0??c2K+K?)?(B¯s0??c1K+K?)=(17.1±3.1±0.4±0.9)%, where the first uncertainty is statistical, the second systematic and the third due to the knowledge of the branching fractions of radiative ?c decays. The decay mode B¯s0??c1K+K? allows the Bs0 mass to be measured as m(Bs0)=5366.83±0.25±0.27MeV/c2, where the first uncertainty is statistical and the second systematic.