© 2017 CERN, for the LHCb Collaboration. The decays χc1→J/ψμ+μ- and χc2→J/ψμ+μ- are observed and used to study the resonance parameters of the χc1 and χc2 mesons. The masses of these states are measured to be m(χc1)=3510.71±0.04(stat)±0.09(syst) MeV and m(χc2)=3556.10±0.06(stat)±0.11(syst) MeV, where the knowledge of the momentum scale for charged particles dominates the systematic uncertainty. The momentum-scale uncertainties largely cancel in the mass difference m(χc2)-m(χc1)=45.39±0.07(stat)±0.03(syst) MeV. The natural width of the χc2 meson is measured to be Γ(χc2)=2.10±0.20(stat)±0.02(syst) MeV. These results are in good agreement with and have comparable precision to the current world averages.

© 2016, The Author(s). A measurement of the cross-section for W → eν production in pp collisions is presented using data corresponding to an integrated luminosity of 2 fb−1collected by the LHCb experiment at a centre-of-mass energy of √s=8 TeV. The electrons are required to have more than 20 GeV of transverse momentum and to lie between 2.00 and 4.25 in pseudorapidity. The inclusive W production cross-sections, where the W decays to eν, are measured to be (Formula presented.) where the first uncertainties are statistical, the second are systematic, the third are due to the knowledge of the LHC beam energy and the fourth are due to the luminosity determination. Differential cross-sections as a function of the electron pseudorapidity are measured. The W+/W−cross-section ratio and production charge asymmetry are also reported. Results are compared with theoretical predictions at next-to-next-to-leading order in perturbative quantum chromodynamics. Finally, in a precise test of lepton universality, the ratio of W boson branching fractions is determined to be B(W → eν)=B(W → µν) = 1:020 ± 0:002 ± 0:019 where the first uncertainty is statistical and the second is systematic.[Figure not available: see fulltext.]

© 2016, The Author(s). Measurements of the differential branching fraction and angular moments of the decay B0 → K+π−μ+μ− in the K+π− invariant mass range 1330 < m(K+π−) < 1530 MeV/c2 are presented. Proton-proton collision data are used, corresponding to an integrated luminosity of 3 fb−1 collected by the LHCb experiment. Differential branching fraction measurements are reported in five bins of the invariant mass squared of the dimuon system, q2, between 0.1 and 8.0 GeV2/c4. For the first time, an angular analysis sensitive to the S-, P- and D-wave contributions of this rare decay is performed. The set of 40 normalised angular moments describing the decay is presented for the q2 range 1.1-6.0 GeV2/c4.

© 2016 The Author Using a data set corresponding to an integrated luminosity of 3 fb−1, collected by the LHCb experiment in pp collisions at centre-of-mass energies of 7 and 8 TeV, the effective lifetime in the Bs0→J/ψη decay mode, τeff, is measured to beτeff=1.479±0.034 (stat)±0.011 (syst) ps. Assuming CP conservation, τeff corresponds to the lifetime of the light Bs0 mass eigenstate. This is the first measurement of the effective lifetime in this decay mode.

© 2017 CERN, for the LHCb Collaboration. Published by the American Physical Society under the terms of the «https://creativecommons.org/licenses/by/4.0/» Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. The B± meson production asymmetry in pp collisions is measured using B+→D-0π+ decays. The data were recorded by the LHCb experiment during Run 1 of the LHC at center-of-mass energies of s=7 and 8 TeV. The production asymmetries, integrated over transverse momenta in the range 2

© 2016 CERN. The CP asymmetry in the mixing of Bs0 and Bs0 mesons is measured in proton-proton collision data corresponding to an integrated luminosity of 3.0 fb-1, recorded by the LHCb experiment at center-of-mass energies of 7 and 8 TeV. Semileptonic Bs0 and Bs0 decays are studied in the inclusive mode Dsμ±ν(-)μX with the Ds mesons reconstructed in the Kπ final state. Correcting the observed charge asymmetry for detection and background effects, the CP asymmetry is found to be asls=(0.39±0.26±0.20)%, where the first uncertainty is statistical and the second systematic. This is the most precise measurement of asls to date. It is consistent with the prediction from the standard model and will constrain new models of particle physics.

© 2017 The Author The production of J/ψ mesons is studied in proton-lead collisions at the centre-of-mass energy per nucleon pair sNN=8.16 TeV with the LHCb detector at the LHC. The double differential cross-sections of prompt and nonprompt J/ψ production are measured as a function of the J/ψ transverse momentum and rapidity in the nucleon–nucleon centre-of-mass frame. Forward-to-backward ratios and nuclear modification factors are determined. The results are compared with theoretical calculations based on collinear factorisation using nuclear parton distribution functions, on the colour glass condensate or on coherent energy loss models.

© 2017, CERN for the benefit of the LHCb collaboration. Two new algorithms for use in the analysis of pp collision are developed to identify the flavour of B0mesons at production using pions and protons from the hadronization process. The algorithms are optimized and calibrated on data, using B0→D-π+ decays from pp collision data collected by LHCb at centre-of-mass energies of 7 and 8 TeV . The tagging power of the new pion algorithm is 60% greater than the previously available one; the algorithm using protons to identify the flavour of a B0meson is the first of its kind.

© 2017 CERN. A search for the B0→K+K- decay is performed using pp-collision data collected by LHCb. The data set corresponds to integrated luminosities of 1.0 and 2.0 fb-1 at center-of-mass energies of 7 and 8 TeV, respectively. This decay is observed for the first time, with a significance of more than 5 standard deviations. The analysis also results in an improved measurement of the branching fraction for the Bs0→π+π- decay. The measured branching fractions are B(B0→K+K-)=(7.80±1.27±0.81±0.21)×10-8 and B(Bs0→π+π-)=(6.91±0.54±0.63±0.19±0.40)×10-7. The first uncertainty is statistical, the second is systematic, the third is due to the uncertainty on the B0→K+π- branching fraction used as a normalization. For the Bs0 mode, the fourth accounts for the uncertainty on the ratio of the probabilities for b quarks to hadronize into Bs0 and B0 mesons.

© 2018 CERN. for the LHCb Collaboration. Published by the American Physical Society under the terms of the »https://creativecommons.org/licenses/by/4.0/» Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by SCOAP 3 . The time-integrated untagged Dalitz plot of the three-body hadronic charmless decay B0→KS0π+π- is studied using a pp collision data sample recorded with the LHCb detector, corresponding to an integrated luminosity of 3.0 fb-1. The decay amplitude is described with an isobar model. Relative contributions of the isobar amplitudes to the B0→KS0π+π- decay branching fraction and CP asymmetries of the flavor-specific amplitudes are measured. The CP asymmetry between the conjugate B0→K∗(892)-π+ and B0→K∗(892)+π- decay rates is determined to be -0.308±0.062.