Ricerc@Sapienza

A measurement of the time-dependent CP-violating asymmetry in 0→ decays is presented. Using a sample of proton-proton collision data corresponding to an integrated luminosity of 5.0 fb−1 collected by the LHCb experiment at centre-of-mass energies √ = 7 TeV in 2011, 8 TeV in 2012 and 13 TeV in 2015 and 2016, a signal yield of around 9000 0→ decays is obtained. The CP-violating phase ⎯⎯⎯ is measured to be −0.073 ± 0.115(stat) ± 0.027(syst) rad, under the assumption it is independent of the helicity of the ϕϕ decay.

The production fractions of ¯B0s and Λ0b hadrons, normalized to the sum of B− and ¯B0 fractions, are measured in 13 TeV pp collisions using data collected by the LHCb experiment, corresponding to an integrated luminosity of 1.67  fb−1. These ratios, averaged over the b hadron transverse momenta from 4 to 25 GeV and pseudorapidity from 2 to 5, are 0.122±0.006 for ¯B0s, and 0.259±0.018 for Λ0b, where the uncertainties arise from both statistical and systematic sources. The Λ0b ratio depends strongly on transverse momentum, while the ¯B0s ratio shows a mild dependence.

A time-dependent analysis of the B0s→ϕγ decay rate is performed to determine the CP -violating observables Sϕγ and Cϕγ and the mixing-induced observable AΔϕγ. The measurement is based on a sample of pp collision data recorded with the LHCb detector, corresponding to an integrated luminosity of 3  fb−1 at center-of-mass energies of 7 and 8 TeV. The measured values are Sϕγ=0.4±0.30±0.11, Cϕγ=0.11±0.29±0.11, and AΔϕγ=−0.67+0.37−0.41±0.17, where the first uncertainty is statistical and the second systematic. This is the first measurement of the observables S and C in radiative B0s decays.

A new baryon state is observed in the Λ0b+− mass spectrum with high significance using a data sample of pp collisions, collected with the LHCb detector at centre-of-mass energies √ = 7, 8 and 13 TeV, corresponding to an integrated luminosity of 9 fb−1. The mass and natural width of the new state are measured to be

A measurement of the branching fraction of the decay B0s→K0SK0S is performed using proton–proton collision data corresponding to an integrated luminosity of 5  fb−1 collected by the LHCb experiment between 2011 and 2016. The branching fraction is determined to be B(B0s→K0SK0S)=[8.3±1.6(stat)±0.9(syst)±0.8(norm)±0.3(fs/fd)]×10−6, where the first uncertainty is statistical, the second is systematic, and the third and fourth are due to uncertainties on the branching fraction of the normalization mode B0→ϕK0S and the ratio of hadronization fractions fs/fd.

A search is presented for the lepton flavour violating decay B+ → K+µ−τ+using a sample of proton-proton collisions at centre-of-mass energies of 7, 8, and 13 TeV,collected with the LHCb detector and corresponding to a total integrated luminosity of9 fb−1. The τ leptons are selected inclusively, primarily via decays with a single chargedparticle. The four-momentum of the τ lepton is determined by using B+ mesons fromB∗0s2 → B+K− decays.

The Cabibbo-suppressed semileptonic decay +→⎯⎯⎯+ is observed for the first time using a sample of pp collisions corresponding to an integrated luminosity of 1.0, 2.0 and 1.7 fb−1 at centre-of-mass energies of 7, 8 and 13 TeV, respectively. The differential branching fraction is measured as a function of the ⎯⎯⎯ invariant mass using the decay mode B+→ J/ψK+ for normalisation. The total branching fraction is measured to be

(+→⎯⎯⎯+)=(5.27+0.23−0.24±0.21±0.15)×10−6,

Measurements of CP observables in B± → DK± and B± → Dπ± decays are presented, where D represents a superposition of D0 and ⎯⎯⎯⎯⎯0 states. The D meson is reconstructed in the three-body final states 0S±∓ and 0S∓±. The analysis uses samples of B mesons produced in proton-proton collisions, corresponding to an integrated luminosity of 1.0, 2.0, and 6.0 fb−1 collected with the LHCb detector at centre-of-mass energies of √ = 7, 8, and 13 TeV, respectively. These measurements are the most precise to date, and provide important input for the determination of the CKM angle γ.

The ratio of the B0s and B+ fragmentation fractions fs and fu is studied with B0s→J/ψϕ and B+→J/ψK+ decays using data collected by the LHCb experiment in proton-proton collisions at 7, 8, and 13 TeV center-of-mass energies. The analysis is performed in bins of B-meson momentum, longitudinal momentum, transverse momentum, pseudorapidity, and rapidity. The fragmentation-fraction ratio fs/fu is observed to depend on the B-meson transverse momentum with a significance of 6.0σ.

We report four narrow peaks in the Ξ0bK− mass spectrum obtained using pp collisions at center-of-mass energies of 7, 8, and 13 TeV, corresponding to a total integrated luminosity of 9  fb−1 recorded by the LHCb experiment. Referring to these states by their mass, the mass values are m[Ωb(6316)−]=6315.64±0.31±0.07±0.50  MeV, m[Ωb(6330)−]=6330.30±0.28±0.07±0.50  MeV, m[Ωb(6340)−]=6339.71±0.26±0.05±0.50  MeV, m[Ωb(6350)−]=6349.88±0.35±0.05±0.50  MeV, where the uncertainties are statistical, systematic, and the last is due to the knowledge of the Ξ0b mass.