52 research outputs found
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.
Measurement of b hadron fractions in 13 TeV pp collisions
The production fractions of
ÂŻ
B
0
s
and
Î
0
b
hadrons, normalized to the sum of
B
â
and
ÂŻ
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
â
â
fb
â
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
ÂŻ
B
0
s
, and
0.259
±
0.018
for
Î
0
b
, where the uncertainties arise from both statistical and systematic sources. The
Î
0
b
ratio depends strongly on transverse momentum, while the
ÂŻ
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
ÂŻ
B
0
and
B
â
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}âK^{+}K^{-}, D^{0}âÏ^{+}Ï^{-}, and D^{0}âK^{-}Ï^{+} decays is reported. The D^{0} mesons are required to originate from semimuonic decays of B^{-} and B[over ÂŻ]^{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 3ââfb^{-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
Prompt production in collisions at TeV
The production of baryons produced directly at the interacting
point is studied in proton-lead collisions collected with the LHCb detector at
the LHC. The data sample corresponds to an integrated luminosity of
recorded at a nucleon-nucleon centre-of-mass energy of
TeV. Measurements of the differential cross-section and
the forward-backward production ratio are reported for baryons
with transverse momenta in the range GeV/ and rapidities in the
ranges and in the nucleon-nucleon centre-of-mass
system. The ratio of cross-sections of baryons and mesons
is also reported. The results are compared with next-to-leading order
calculations that use nuclear parton distribution functions.Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://lhcbproject.web.cern.ch/lhcbproject/Publications/LHCbProjectPublic/LHCb-PAPER-2018-021.htm
Study of the decay with an amplitude analysis of decays
International audienceAn amplitude analysis of B â (ÏÏ)(KÏ) decays is performed in the two-body invariant mass regions 300 < m(ÏÏ) < 1100 MeV/c, accounting for the Ï, Ï, f(500), f(980) and f(1370) resonances, and 750 < m(KÏ) < 1200 MeV/c, which is dominated by the K(892) meson. The analysis uses 3 fb 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 = 0.164 ± 0.015 ± 0.022 and = 0.68 ± 0.17 ± 0.16, and their CP asymmetries, = â0.62 ± 0.09 ± 0.09 and = â0.13 ± 0.27 ± 0.13, where the first uncertainty is statistical and the second systematic
Observation of Two Resonances in the Î_{b}^{0}Ï^{±} Systems and Precise Measurement of ÎŁ_{b}^{±} and ÎŁ_{b}^{*±} Properties.
The first observation of two structures consistent with resonances in the final states Î_{b}^{0}Ï^{-} and Î_{b}^{0}Ï^{+} 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 3ââfb^{-1}. The ground states ÎŁ_{b}^{±} and ÎŁ_{b}^{*±} are also confirmed and their masses and widths are precisely measured
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