Ricerc@Sapienza

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.

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 time-dependent CP asymmetries in B0→π+π- and Bs0→K+K- decays are measured using a data sample of p p collisions corresponding to an integrated luminosity of 3.0 fb-1, collected with the LHCb detector at center-of-mass energies of 7 and 8 TeV. The same data sample is used to measure the time-integrated CP asymmetries in B0→K+π- and Bs0→π+K- decays.

A search for CP and P violation using triple-product asymmetries is performed with Λb0 → pK−π+π−, Λb0 → pK−K+K− and Ξb0 → pK−K−π+ decays. The data sample corresponds to integrated luminosities of 1.0 fb−1 and 2.0 fb−1, recorded with the LHCb detector at centre-of-mass energies of 7 TeV and 8 TeV, respectively. The CP - and P - violating asymmetries are measured both integrating over all phase space and in specific phase-space regions. No significant deviation from CP or P symmetry is found. The first observation of Λb0 → pK−χc0(1P)(→π+π−, K+K−) decay is also reported.

An analysis of the angular distribution of the decay Λb0 → Λμ+μ− is presented, using data collected with the LHCb detector between 2011 and 2016 and corresponding to an integrated luminosity of approximately 5 fb−1. Angular observables are determined using a moment analysis of the angular distribution at low hadronic recoil, corresponding to the dimuon invariant mass squared range 15 < q2 < 20 GeV2/c4. The full basis of observables is measured for the first time.

The first observation of the Bs0→D̄∗0φ decay is reported, with a significance of more than seven standard deviations, from an analysis of pp collision data corresponding to an integrated luminosity of 3 fb-1, collected with the LHCb detector at center-of-mass energies of 7 and 8 TeV. The branching fraction is measured relative to that of the topologically similar decay B0→D̄0π+π- and is found to be B(Bs0→D̄∗0φ)=(3.7±0.5±0.3±0.2)×10-5, where the first uncertainty is statistical, the second systematic, and the third from the branching fraction of the B0→D̄0π+π- decay.

A measurement of the time-integrated CP asymmetry in D0 → KS0KS0 decays is reported. The data correspond to an integrated luminosity of about 2 fb−1 collected in 2015–2016 by the LHCb collaboration in pp collisions at a centre-of-mass energy of 13 TeV. The D0 candidate is required to originate from a D*+ → D0π+ decay, allowing the determination of the flavour of the D0 meson using the pion charge. The D0 → K+K− decay, which has a well measured CP asymmetry, is used as a calibration channel.

A measurement of the charm-mixing parameter yCP using D0→K+K-, D0→π+π-, and D0→K-π+ decays is reported. The D0 mesons are required to originate from semimuonic decays of B- and B0 mesons. These decays are partially reconstructed in a data set of proton-proton collisions at center-of-mass energies of 7 and 8 TeV collected with the LHCb experiment and corresponding to an integrated luminosity of 3 fb-1. The yCP parameter is measured to be (0.57±0.13(stat)±0.09(syst))%, in agreement with, and as precise as, the current world-average value.

A search for CP violation in the Cabibbo-suppressed D 0 → K + K − π + π − decay mode is performed using an amplitude analysis. The measurement uses a sample of pp collisions recorded by the LHCb experiment during 2011 and 2012, corresponding to an integrated luminosity of 3.0 fb −1 . The D 0 mesons are reconstructed from semileptonic b-hadron decays into D 0 μ − X final states. The selected sample contains more than 160 000 signal decays, allowing the most precise amplitude modelling of this D 0 decay to date. The obtained amplitude model is used to perform the search for CP violation.

Using pp collisions corresponding to 3 fb −1 integrated luminosity, recorded by the LHCb experiment at centre-of-mass energies of 7 and 8 TeV, the ratio of branching fractionsℬ(Λb0→ψ(2S)Λ)/ℬ(Λb0→J/ψΛ)=0.513±0.023(stat)±0.016(syst)±0.011(ℬ)is determined. The first uncertainty is statistical, the second is systematic and the third is due to the external branching fractions used.[Figure not available: see fulltext.]