LHCb

Abstract:

A measurement of the CP-violating parameters in Bs0→Ds∓K± decays is reported, based on the analysis of proton-proton collision data collected by the LHCb experiment corresponding to an integrated luminosity of 6 fb−1 at a centre-of-mass energy of 13 TeV. The measured parameters are obtained with a decay-time dependent analysis yielding Cf = 0.791 ± 0.061 ± 0.022, Af∆Γ = −0.051 ± 0.134 ± 0.058, Af¯∆Γ = −0.303 ± 0.125 ± 0.055, Sf = −0.571 ± 0.084 ± 0.023 and Sf¯ = −0.503 ± 0.084 ± 0.025, where the first uncertainty is statistical and the second systematic. This corresponds to CP violation in the interference between mixing and decay of about 8.6 σ. Together with the value of the Bs0 mixing phase −2βs, these parameters are used to obtain a measurement of the CKM angle γ equal to (74 ± 12)° modulo 180°, where the uncertainty contains both statistical and systematic contributions. This result is combined with the previous LHCb measurement in this channel using 3 fb−1 resulting in a determination of γ=81−11+12∘.

Abstract:

The first measurement of ϕ(1020) meson production in fixed-target pNe collisions at sNN = 68.5 GeV is presented. The ϕ(1020) mesons are reconstructed in their K+K− decay in a data sample consisting of proton collisions on neon nuclei at rest, corresponding to an integrated luminosity of 21.7 ± 1.4 nb−1, collected by the LHCb detector at CERN. The ϕ(1020) production cross-section in the centre-of-mass rapidity range of −1.8 < y*< 0 and transverse momentum range of 800 < pT< 6500 MeV/c is found to be σ = 182.7 ± 2.7 (stat.) ± 14.1 (syst) μb/nucleon. A double-differential measurement of the cross-section is also provided in four regions of rapidity and six regions of transverse momentum of the ϕ(1020) meson and compared with the predictions from Pythia and EPOS4, which are found to underestimate the experimental values.

Abstract:

Based on (2712.4 ± 14.3) × 106ψ(3686) events collected at the BESIII detector operating at the BEPCII collider, we present the first observation of the decay ψ3686→K−Λ1520Ξ¯+ + c.c.. The product branching fraction Bψ3686→K−Λ1520Ξ¯++c.c.×BΛ1520→pK− is measured to be (9.47 ± 0.75 ± 0.97) × 10−7, where the first uncertainty is statistical and the second systematic.

Abstract:

An analysis of the flavour oscillations of the charmed neutral meson is presented. The ratio of D0 → K+π− and D0 → K−π+ decay rates is measured as a function of the decay time of the D0 meson and compared with the charge-conjugated system to search for charge-parity violation. The meson flavour at production is double-tagged by the charges of the muon and pion in the preceding B¯→D∗2010+μ−X and D∗(2010)+ → D0π+ decays, respectively. These decays are selected from proton-proton collision data collected by the LHCb experiment at a centre-of-mass energy of 13 TeV and corresponding to an integrated luminosity of 5.4 fb−1. The flavour oscillation parameters, relating to the differences in mass and width of the mass eigenstates, are found to be y′ = (5.8 ± 1.6) × 10−3 and (x′)2 = (0.0 ± 1.2) × 10−4. No evidence for charge-parity violation is seen either in the flavour oscillations or in the decay, where the direct charge-parity asymmetry is measured to be AD = (2.3 ± 1.7) %.