Ricerc@Sapienza

We report the observation of a new structure in the Λ0
bπþπ− spectrum using the full LHCb data set of pp
collisions, corresponding to an integrated luminosity of 9 fb−1, collected at ffiffi
s p ¼ 7, 8, and 13 TeV. A study
of the structure suggests its interpretation as a superposition of two almost degenerate narrow states. The
masses and widths of these states are measured to be mΛbð6146Þ0 ¼ 6146.17 0.33 0.22 0.16 MeV;
mΛbð6152Þ0 ¼ 6152.51 0.26 0.22 0.16 MeV; ΓΛbð6146Þ0 ¼ 2.9 1.3 0.3 MeV; ΓΛbð6152Þ0 ¼ 2.1

The ratio of branching fractions of the decays Λ0 → pK−e+e− and Λ0 → pK−μ+μ−, −1, is measured for the first time using proton-proton collision data corresponding to an integrated luminosity of 4.7 fb−1 recorded with the LHCb experiment at center-of-mass energies of 7, 8 and 13 TeV. In the dilepton mass-squared range 0.1 < q2 < 6.0 GeV2/c4 and the pK− mass range m(pK−) < 2600 MeV/c2, the ratio of branching fractions is measured to be −1=1.17+0.18−0.16±0.07, where the first uncertainty is statistical and the second systematic.

An angular analysis of the B0 → K0ð→ Kþπ−Þμþμ− decay is presented using a dataset corresponding
to an integrated luminosity of 4.7 fb−1 of pp collision data collected with the LHCb experiment. The full
set of CP-averaged observables are determined in bins of the invariant mass squared of the dimuon system.
Contamination from decays with the Kþπ− system in an S-wave configuration is taken into account. The
tension seen between the previous LHCb results and the standard model predictions persists with the new

The radiative decay Λb0→Λγ is observed for the first time using a data sample of proton-proton collisions corresponding to an integrated luminosity of 1.7 fb-1 collected by the LHCb experiment at a center-of-mass energy of 13 TeV. Its branching fraction is measured exploiting the B0→K∗0γ decay as a normalization mode and is found to be B(Λb0→Λγ)=(7.1±1.5±0.6±0.7)×10-6, where the quoted uncertainties are statistical, systematic, and systematic from external inputs, respectively. This is the first observation of a radiative decay of a beauty baryon.

A flavour-tagged decay-time-dependent amplitude analysis of Bs0 ? (K+??)(K??+) decays is presented in the K±?? mass range from 750 to 1600MeV/c2. The analysis uses pp collision data collected with the LHCb detector at centre-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of 3.0 fb?1. Several quasi-two-body decay modes are considered, corresponding to K±?? combinations with spin 0, 1 and 2, which are dominated by the K0*(800)0 and K0*(1430)0, the K*(892)0 and the K2*(1430)0 resonances, respectively.