Ricerc@Sapienza

We consider an extension of the Standard Model with two singlet leptons, with masses in the electroweak range, that induce neutrino masses via the see-saw mechanism, plus a generic new physics sector at a higher scale, Λ. We apply the minimal flavor violation (MFV) principle to the corresponding Effective Field Theory (νSMEFT) valid at energy scales E ≪ Λ. We identify the irreducible sources of lepton flavor and lepton number violation at the renormalizable level, and apply the MFV ansätz to derive the scaling of the Wilson coefficients of the νSMEFT operators up to dimension six.

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.

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.

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.

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.