120 research outputs found
Observation of associated production of a boson with a meson in the~forward region
A search for associated production of a boson with an open charm meson is
presented using a data sample, corresponding to an integrated luminosity of
of proton--proton collisions at a centre-of-mass energy
of 7\,TeV, collected by the LHCb experiment. %% Seven candidate events for
associated production of a boson with a meson and four candidate
events for a boson with a meson are observed with a combined
significance of 5.1standard deviations. The production cross-sections in the
forward region are measured to be where the first uncertainty is statistical and the
second systematic.Comment: 18 pages, 2 figure
Measurements of the , , meson and baryon lifetimes
Measurements of -hadron lifetimes are reported using collision data,
corresponding to an integrated luminosity of 1.0fb, collected by the
LHCb detector at a centre-of-mass energy of Tev. Using the exclusive decays
, , ,
and the average decay
times in these modes are measured to be = 0.004 0.003 ps, =
0.006 0.004 ps, = 0.013
0.005 ps, = 0.027
0.006 ps and = 0.011
0.005 ps, where the first uncertainty is statistical and the second is
systematic. These represent the most precise lifetime measurements in these
decay modes. In addition, ratios of these lifetimes, and the ratio of the
decay-width difference, , to the average width, , in
the system, , are
reported. All quantities are found to be consistent with Standard Model
expectations.Comment: 28 pages, 4 figures. Updated reference
Observation of the decay B+câBÂșsÏ+
The result of a search for the decay B+câBÂșsÏ+ is presented, using the BÂșsâDs-Ï+ and BÂșsâJ/ÏÏ channels. The analysis is based on a data sample of pp collisions collected with the LHCb detector, corresponding to an integrated luminosity of 1ââfb-1 taken at a center-of-mass energy of 7 TeV, and 2ââfb-1 taken at 8 TeV. The decay B+câBÂșsÏ+ is observed with significance in excess of 5 standard deviations independently in both decay channels. The measured product of the ratio of cross sections and branching fraction is [Ï(Bc+)/Ï(BÂșs)]ĂB(Bc+âBÂșsÏ+)=[2.37±0.31â(stat)±0.11â(syst)-0.13+0.17(ÏBc+)]Ă10-3, in the pseudorapidity range 2<η(B)<5, where the first uncertainty is statistical, the second is systematic, and the third is due to the uncertainty on the Bc+ lifetime. This is the first observation of a B meson decaying to another B meson via the weak interaction
Measurement of charged particle multiplicities and densities in pp collisions root s=7 TeV in the forward region
Charged particle multiplicities are studied in proton-proton collisions in the forward region at a centre-of-mass energy of TeV with data collected by the LHCb detector. The forward spectrometer allows access to a kinematic range of in pseudorapidity, momenta greater than and transverse momenta greater than . The measurements are performed using events with at least one charged particle in the kinematic acceptance. The results are presented as functions of pseudorapidity and transverse momentum and are compared to predictions from several Monte Carlo event generators
Measurement of the BÂŻs0âDsâDs+ and BÂŻs0âDâDs+ effective lifetimes
The first measurement of the effective lifetime of the BÂŻ0s meson in the decay BÂŻ0sâDâsD+s is reported using a proton-proton collision data set, corresponding to an integrated luminosity of 3ââfbâ1, collected by the LHCb experiment. The measured value of the BÂŻ0sâDâsD+s effective lifetime is 1.379±0.026±0.017ââps, where the uncertainties are statistical and systematic, respectively. This lifetime translates into a measurement of the decay width of the light BÂŻ0s mass eigenstate of ÎL=0.725±0.014±0.009ââpsâ1. The BÂŻ0s lifetime is also measured using the flavor-specific BÂŻ0sâDâD+s decay to be 1.52±0.15±0.01ââps
A study of CP violation in B± â D K ± and B± â Dϱ decays with D â K0S K ±Ïâ final states
A first study of CP Â violation in the decay modes and , where h labels a K or Ï meson and D Â labels a D0 or meson, is performed. The analysis uses the LHCb data set collected in pp collisions, corresponding to an integrated luminosity of 3 fbâ1. The analysis is sensitive to the CP-violating CKM phase Îł through seven observables: one charge asymmetry in each of the four modes and three ratios of the charge-integrated yields. The results are consistent with measurements of Îł using other decay modes
Measurement of the B+c meson lifetime using B+c â J/Ï ÎŒ+ΜΌX decays
The lifetime of the B+
c meson is measured using
semileptonic decays having a J/Ï meson and a muon in the
final state. The data, corresponding to an integrated luminosity
of 2 fbâ1, are collected by the LHCb detector in pp
collisions at a centre-of-mass energy of 8 TeV. The measured
lifetime is
Ï = 509 ± 8 ± 12 fs,
where the first uncertainty is statistical and the second is
systematic
Search for Majorana neutrinos in decays
A search for heavy Majorana neutrinos produced in the decay mode is performed using 3 fb of integrated
luminosity collected with the LHCb detector in collisions at
center-of-mass energies of 7 TeV and 8 TeV at the LHC. Neutrinos with masses in
the range 250-5000 MeV and lifetimes from zero to 1000 ps are probed. In the
absence of a signal, upper limits are set on the branching fraction
as functions of neutrino mass and
lifetime. These limits are on the order of for short neutrino
lifetimes of 1 ps or less. Limits are also set on the coupling between the muon
and a possible fourth-generation neutrino.Comment: 6 pages, 6 figure
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