Ricerc@Sapienza

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.

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

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.

Using a data sample corresponding to an integrated luminosity of 2.0 fb−1, collected by the LHCb experiment, the production of the (1) state in proton–proton collisions at a centre-of-mass energy of √=13 TeV is studied in the rapidity range 2.0<<4.5 and in the transverse momentum range 6.5<T<14.0GeV. The cross-section for prompt production of (1) mesons relative to that of the / meson is measured using the ⎯⎯⎯ decay mode and is found to be (1)//=1.69±0.15±0.10±0.18.

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 ϒ(1S)μ+μ− invariant-mass distribution is investigated for a possible exotic meson state composed of two b quarks and two b¯ quarks, Xbb¯bb¯. The analysis is based on a data sample of pp collisions recorded with the LHCb detector at centre-of-mass energies s=7, 8 and 13 TeV, corresponding to an integrated luminosity of 6.3 fb−1. No significant excess is found, and upper limits are set on the product of the production cross-section and the branching fraction as functions of the mass of the Xbb¯bb¯ state.

The first observation of the Bs0→D̄0K+K- decay is reported, together with the most precise branching fraction measurement of the mode B0→D̄0K+K-. The results are obtained from an analysis of pp collision data corresponding to an integrated luminosity of 3.0 fb-1. The data were collected with the LHCb detector at center-of-mass energies of 7 and 8 TeV. The branching fraction of the B0→D̄0K+K- decay is measured relative to that of the decay B0→D̄0π+π- to be B(B0→D̄0K+K-)B(B0→D̄0π+π-)=(6.9±0.4±0.3)%, where the first uncertainty is statistical and the second is systematic.

The doubly charmed baryon decay Ξcc++→Ξc+π+ is observed for the first time, with a statistical significance of 5.9σ, confirming a recent observation of the baryon in the Λc+K-π+π+ final state. The data sample used corresponds to an integrated luminosity of 1.7 fb-1, collected by the LHCb experiment in pp collisions at a center-of-mass energy of 13 TeV. The Ξcc++ mass is measured to be 3620.6±1.5(stat)±0.4(syst)±0.3(Ξc+) MeV/c2 and is consistent with the previous result.