The high-intensity hyperon beam at CERN

A high-intensity hyperon beam was constructed at CERN to deliver Sigma- to experiment WA89 at the Omega facility and operated from 1989 to 1994. The setup allowed rapid changeover between hyperon and conventional hadron beam configurations. The beam provided a Sigma-flux of 1.4 x 10^5 per burst at mean momenta between 330 and 345 Gev/c, produced by about 3 x 10^10 protons of 450 GeV/c . At the experiment target the beam had a Sigma-/pi- ratio close to 0.4 and a size of 1.6 x 3.7 cm^2. The beam particle trajectories and their momenta were measured with a scintillating fibre hodoscope in the beam channel and a silicon microstrip detector at the exit of the channel. A fast transition radiation detector was used to identify the pion component of the beam.Comment: 20 pages, 13 figures. Submitted to Nucl. Instr. Meth.

Erratum to: Measurement of ϒ production in pp collisions at s√ = 13 TeV

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Measurement of b hadron fractions in 13 TeV pp collisions

The production fractions of ¯ B 0 s and Λ 0 b hadrons, normalized to the sum of B − and ¯ B 0 fractions, are measured in 13 TeV p p collisions using data collected by the LHCb experiment, corresponding to an integrated luminosity of 1.67     fb − 1 . These ratios, averaged over the b hadron transverse momenta from 4 to 25 GeV and pseudorapidity from 2 to 5, are 0.122 ± 0.006 for ¯ B 0 s , and 0.259 ± 0.018 for Λ 0 b , where the uncertainties arise from both statistical and systematic sources. The Λ 0 b ratio depends strongly on transverse momentum, while the ¯ B 0 s ratio shows a mild dependence. Neither ratio shows variations with pseudorapidity. The measurements are made using semileptonic decays to minimize theoretical uncertainties. In addition, the ratio of D + to D 0 mesons produced in the sum of ¯ B 0 and B − semileptonic decays is determined as 0.359 ± 0.006 ± 0.009 , where the uncertainties are statistical and systematic

Measurement of the Charm-Mixing Parameter yCP

A measurement of the charm-mixing parameter y_{CP} using D^{0}→K^{+}K^{-}, D^{0}→π^{+}π^{-}, and D^{0}→K^{-}π^{+} decays is reported. The D^{0} mesons are required to originate from semimuonic decays of B^{-} and B[over ¯]^{0} mesons. These decays are partially reconstructed in a data set of proton-proton collisions at center-of-mass energies of 7 and 8 TeV collected with the LHCb experiment and corresponding to an integrated luminosity of 3  fb^{-1}. The y_{CP} parameter is measured to be (0.57±0.13(stat)±0.09(syst))%, in agreement with, and as precise as, the current world-average value

Study of the B0→ρ(770)0K∗(892)0B^0\to \rho(770)^0 K^*(892)^0 decay with an amplitude analysis of B0→(π+π−)(K+π−)B^0\to (\pi^+\pi^-) (K^+\pi^-) decays

International audienceAn amplitude analysis of B$^{0}$ → (π$^{+}$π$^{−}$)(K$^{+}$π$^{−}$) decays is performed in the two-body invariant mass regions 300 < m(π$^{+}$π$^{−}$) < 1100 MeV/c$^{2}$, accounting for the ρ$^{0}$, ω, f$_{0}$(500), f$_{0}$(980) and f$_{0}$(1370) resonances, and 750 < m(K$^{+}$π$^{−}$) < 1200 MeV/c$^{2}$, which is dominated by the K$^{*}$(892)$^{0}$ meson. The analysis uses 3 fb$^{−1}$ of proton-proton collision data collected by the LHCb experiment at centre-of-mass energies of 7 and 8 TeV. The CP averages and asymmetries are measured for the magnitudes and phase differences of the con- tributing amplitudes. The CP-averaged longitudinal polarisation fractions of the vector-vector modes are found to be ${\tilde{f}}_{\rho {K}^{*}}^0$ = 0.164 ± 0.015 ± 0.022 and ${\tilde{f}}_{\omega {K}^{*}}^0$ = 0.68 ± 0.17 ± 0.16, and their CP asymmetries, ${\mathcal{A}}_{\rho {K}^{*}}^0$ = −0.62 ± 0.09 ± 0.09 and ${\mathcal{A}}_{\omega {K}^{*}}^0$ = −0.13 ± 0.27 ± 0.13, where the first uncertainty is statistical and the second systematic

Observation of Two Resonances in the Λ_{b}^{0}π^{±} Systems and Precise Measurement of Σ_{b}^{±} and Σ_{b}^{*±} Properties.

The first observation of two structures consistent with resonances in the final states Λ_{b}^{0}π^{-} and Λ_{b}^{0}π^{+} is reported using samples of pp collision data collected by the LHCb experiment at sqrt[s]=7 and 8 TeV, corresponding to an integrated luminosity of 3  fb^{-1}. The ground states Σ_{b}^{±} and Σ_{b}^{*±} are also confirmed and their masses and widths are precisely measured

First Measurement of Charm Production in its Fixed-Target Configuration at the LHC

The first measurement of heavy-flavor production by the LHCb experiment in its fixed-target mode is presented. The production of J/ψ and D0 mesons is studied with beams of protons of different energies colliding with gaseous targets of helium and argon with nucleon-nucleon center-of-mass energies of sNN=86.6 and 110.4 GeV, respectively. The J/ψ and D0 production cross sections in pHe collisions in the rapidity range [2, 4.6] are found to be σJ/ψ=652±33(stat)±42(syst) nb/nucleon and σD0=80.8±2.4(stat)±6.3(syst) μb/nucleon, where the first uncertainty is statistical and the second is systematic. No evidence for a substantial intrinsic charm content of the nucleon is observed in the large Bjorken-x region