Search for long-lived particles decaying to e± μ∓ ν

Long-lived particles decaying to e±μ∓νe±μ∓ν, with masses between 7 and 50GeV/c250GeV/c2 and lifetimes between 2 and 50ps50ps, are searched for by looking at displaced vertices containing electrons and muons of opposite charges. The search is performed using 5.4fb−15.4fb−1 of pp pp collisions collected with the LHCb detector at a centre-of-mass energy of s√=13TeVs=13TeV. Three mechanisms of production of long-lived particles are considered: the direct pair production from quark interactions, the pair production from the decay of a Standard-Model-like Higgs boson with a mass of 125GeV/c2125GeV/c2, and the charged current production from an on-shell WW boson with an additional lepton. No evidence of these long-lived states is obtained and upper limits on the production cross-section times branching fraction are set on the different production modes

Search for heavy neutral leptons in W+→μ+μ±jet decays

A search is performed for heavy neutrinos in the decay of a W boson into two muons and a jet. The data set corresponds to an integrated luminosity of approximately 3.0fb−13.0fb−1 of proton–proton collision data at centre-of-mass energies of 7 and 8TeV8TeV collected with the LHCb experiment. Both same-sign and opposite-sign muons in the final state are considered. Data are found to be consistent with the expected background. Upper limits on the coupling of a heavy neutrino with the Standard Model neutrino are set at 95%95% confidence level in the heavy-neutrino mass range from 5 to 50GeV/c250GeV/c2. These are of the order of 10−310−3 for lepton-number-conserving decays and of the order of 10−410−4 for lepton-number-violating heavy-neutrino decays

Measurement of the branching fraction of the B0→D+sπ− decay

A branching fraction measurement of the B0→D+sπ−B0→Ds+π− decay is presented using proton–proton collision data collected with the LHCb experiment, corresponding to an integrated luminosity of 5.0fb−15.0fb−1. The branching fraction is found to be B(B0→D+sπ−)=(19.4±B(B0→Ds+π−)=(19.4± 1.8±1.3±1.2)×10−61.8±1.3±1.2)×10−6, where the first uncertainty is statistical, the second systematic and the third is due to the uncertainty on the B0→D−π+B0→D−π+, D+s→K+K−π+Ds+→K+K−π+ and D−→K+π−π−D−→K+π−π− branching fractions. This is the most precise single measurement of this quantity to date. As this decay proceeds through a single amplitude involving a b→ub→u charged-current transition, the result provides information on non-factorisable strong interaction effects and the magnitude of the Cabibbo–Kobayashi–Maskawa matrix element VubVub. Additionally, the collision energy dependence of the hadronisation-fraction ratio fs/fdfs/fd is measured through B¯¯¯¯0s→D+sπ−B¯s0→Ds+π− and B0→D−π+B0→D−π+ decays

Measurement of the CP-violating phase phi(s) from B-s(0) -> J/psi pi(+)pi(-) decays in 13 TeV pp collisions

Decays of B-s(0) and (B) over bar (0)(s) mesons into J/psi pi(+)pi(-) final states are studied in a data sample corresponding to 1.9 fb(-1) of integrated luminosity collected with the LHCb detector in 13 TeV pp collisions. A time-dependent amplitude analysis is used to determine the final-state resonance contributions, the CP-violating phase phi(s) = -0.057 +/- 0.060 +/- 0.011 rad, the decay-width difference between the heavier mass B-s(0) eigenstate and the B-0 meson of -0.050 +/- 0.004 +/- 0.004 ps(-1), and the CP-violating parameter vertical bar lambda vertical bar = 1.01(-0.06)(+0.08) +/- 0.03, where the first uncertainty is statistical and the second systematic. These results are combined with previous LHCb measurements in the same decay channel using 7 TeV and 8 TeV pp collisions obtaining phi(s) = 0.002 +/- 0.044 +/- 0.012 rad, and vertical bar lambda vertical bar = 0.949 +/- 0.036 +/- 0.019. (C) 2019 The Author. Published by Elsevier B.V