37 research outputs found
Measurement of CP observables in B± â D(â)K± and B± â D(â)ϱ decays
Measurements of CP observables in B ± âD (â) K ± and B ± âD (â) Ï Â± decays are presented, where D (â) indicates a neutral D or D â meson that is an admixture of D (â)0 and DÂŻ (â)0 states. Decays of the D â meson to the DÏ 0 and DÎł final states are partially reconstructed without inclusion of the neutral pion or photon, resulting in distinctive shapes in the B candidate invariant mass distribution. Decays of the D meson are fully reconstructed in the K ± Ï â , K + K â and Ï + Ï â final states. The analysis uses a sample of charged B mesons produced in pp collisions collected by the LHCb experiment, corresponding to an integrated luminosity of 2.0, 1.0 and 2.0 fb â1 taken at centre-of-mass energies of s=7, 8 and 13 TeV, respectively. The study of B ± âD â K ± and B ± âD â Ï Â± decays using a partial reconstruction method is the first of its kind, while the measurement of B ± âDK ± and B ± âDÏ Â± decays is an update of previous LHCb measurements. The B ± âDK ± results are the most precise to date
First observation of forward production in collisions at TeV
The decay ZâbbÂŻ is reconstructed in pp collision data, corresponding to 2 fb â1 of integrated luminosity, collected by the LHCb experiment at a centre-of-mass energy of s=8 TeV. The product of the Z production cross-section and the ZâbbÂŻ branching fraction is measured for candidates in the fiducial region defined by two particle-level b -quark jets with pseudorapidities in the range 2.220 GeV and dijet invariant mass in the range 452045 < m_{jj} < 1655462 \pm 763Z \rightarrow b \bar{b}332 \pm 46 \pm 59Z \rightarrow b \bar{b}pp$ collisions
Measurement of the b-quark production cross-section in 7 and 13 TeV pp collisions
See paper for full list of authors - 21 pages, 6 figures - Submitted to Phys. Rev. Lett.International audienceMeasurements of the cross-section for producing \bquark quarks in the reaction ppâbbÂŻÂŻX are reported in 7 and 13 TeV collisions at the LHC as a function of the pseudorapidity η in the range 2<η<5 covered by the acceptance of the LHCb experiment. The measurements are done using semileptonic decays of b-flavored hadrons decaying into a ground-state charmed hadron in association with a muon. The cross-sections in the covered η range are 72.0±0.3±6.8 ÎŒb and 154.3±1.5±14.3 ÎŒb for 7 and 13 TeV. The ratio is 2.14±0.02±0.13, where the quoted uncertainties are statistical and systematic, respectively. The agreement with theoretical expectation is good at 7 TeV, but differs somewhat at 13 TeV. The measured ratio of cross-sections is larger at lower η than the model prediction
Measurements of long-range near-side angular correlations in TeV proton-lead collisions in the forward region
See paper for full list of authors.International audienceTwo-particle angular correlations are studied in proton-lead collisions at a nucleon-nucleon centre-of-mass energy of TeV, collected with the LHCb detector at the LHC. The analysis is based on data recorded in two beam configurations, in which either the direction of the proton or that of the lead ion is analysed. The correlations are measured as a function of relative pseudorapidity, , and relative azimuthal angle, , for events in different classes of event activity and for different bins of particle transverse momentum. In high-activity events a long-range correlation on the near side, , is observed in the pseudorapidity range . This measurement of long-range correlations on the near side in proton-lead collisions extends previous observations into the forward region up to . The correlation increases with growing event activity and is found to be more pronounced in the direction of the lead beam. However, the correlation strengths in the direction of the lead and proton beams are found to be compatible when comparing events with similar absolute activity in the direction analysed
Search for the rare decays and
See paper for full list of authorsInternational audienceA search for the rare decay of a or meson into the final state is performed, using data collected by the LHCb experiment in collisions at and TeV, corresponding to an integrated luminosity of 3 fb. The observed number of signal candidates is consistent with a background-only hypothesis. Branching fraction values larger than for the decay mode are excluded at 90% confidence level. For the decay mode, branching fraction values larger than are excluded at 90% confidence level; this is the first branching fraction limit for this decay
A model-independent confirmation of the state
See paper for full list of authors - Submitted to Phys. Rev. DInternational audienceThe decay is analyzed using of collision data collected with the LHCb detector. A model-independent description of the mass spectrum is obtained, using as input the mass spectrum and angular distribution derived directly from data, without requiring a theoretical description of resonance shapes or their interference. The hypothesis that the mass spectrum can be described in terms of reflections alone is rejected with more than 8 significance. This provides confirmation, in a model-independent way, of the need for an additional resonant component in the mass region of the exotic state
Observation of the decay
Submitted to JHEP. See paper for full list of authors.International audienceThe decay is observed in collision data corresponding to an integrated luminosity of 3 fb recorded by the LHCb detector at centre-of-mass energies of 7 TeV and 8 TeV. This is the first observation of this decay channel, with a statistical significance of 15 standard deviations. The mass of the meson is measured to be MeV/c. The branching fraction ratio is measured to be 0.0115\,\pm\, 0.0012\, ^{+0.0005}_{-0.0009}. In both cases, the first uncertainty is statistical and the second is systematic. No evidence for non-resonant or decays is found