3,866 research outputs found
Search for CP violation in B^0 -> J/psi K^0_S decays with first LHCb data
We report a measurement of the CP violation in B^0 -> J/\psi K^0_S decays. We
perform a time-dependent analysis of the decays reconstructed in 35/pb of LHCb
data that was taken in 2010. We measure the CP asymmetry parameterComment: Presented at the 2011 Hadron Collider Physics symposium (HCP-2011),
Paris, France, November 14-18 2011, 3 pages, 3 figure
Study of coherent charmonium production in ultra-peripheral lead-lead collisions
The cross-sections of coherent and production in
ultra-peripheral PbPb collisions at a nucleon-nucleon centre-of-mass energy of
are measured using a data sample corresponding to an
integrated luminosity of , collected by the LHCb
experiment in 2018. The differential cross-sections are measured separately as
a function of transverse momentum and rapidity in the nucleus-nucleus
centre-of-mass frame for and mesons. The
integrated cross-sections are measured to be and
, where the first listed uncertainty is statistical, the
second systematic and the third due to the luminosity determination. The
cross-section ratio is measured to be
, where the first uncertainty is statistical and the second
is systematic. These results are compatible with theoretical predictions.Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-012.html (LHCb
public pages
A study of violation in the decays () and
The first study of violation in the decay mode
, with , is presented, exploiting
a data sample of proton-proton collisions collected by the LHCb experiment that
corresponds to an integrated luminosity of fb. The analysis is
performed in bins of phase space, which are optimised for sensitivity to local
asymmetries. -violating observables that are sensitive to the
angle of the Unitarity Triangle are determined. The analysis requires
external information on charm-decay parameters, which are currently taken from
an amplitude analysis of LHCb data, but can be updated in the future when
direct measurements become available. Measurements are also performed of
phase-space integrated observables for and
decays.Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-037.html (LHCb
public pages
Model-independent measurement of charm mixing parameters in decays
A measurement of charm mixing and -violating parameters is reported,
using decays reconstructed in proton-proton collisions collected by
the LHCb experiment during the years 2016 to 2018, corresponding to an
integrated luminosity of 5.4 fb. The measured mixing and -violating
parameters are x_{\rm CP} = [ \,\,\,\,\,4.29 \pm 1.48 \mbox{(stat)} \pm 0.26
\mbox{(syst)} ] \times 10^{-3}\,, y_{\rm CP} = [ \,\,12.61 \pm 3.12
\mbox{(stat)} \pm 0.83 \mbox{(syst)} ] \times 10^{-3} \,, \Delta x \,\,= [
-0.77 \pm 0.93 \mbox{(stat)} \pm 0.28 \mbox{(syst)} ] \times 10^{-3} \,,
\Delta y \, = [ \,\,\,\,\,3.01 \pm 1.92 \mbox{(stat)} \pm 0.26 \mbox{(syst)}
] \times 10^{-3} \,. The results are complementary to and consistent with
previous measurements. A combination with the recent LHCb analysis of decays is reported.Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-020.html (LHCb
public pages
Search for the lepton-flavour violating decays
A first search for the lepton-flavour violating decays is presented. The analysis is performed using a sample of
proton-proton collision data, collected with the LHCb detector at
centre-of-mass energies of 7, 8 and 13 TeV between 2011 and 2018, corresponding
to an integrated luminosity of 9 fb. No significant signal is observed,
and upper limits on the branching fractions are determined to be and at the 90% (95%) confidence
level.Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-021.html (LHCb
public pages
Search for rare decays of mesons into two muons
A search for the very rare decay is performed using data
collected by the LHCb experiment in proton-proton collisions at ,
8 and , corresponding to an integrated luminosity of
. The search is optimised for mesons from decays but is also sensitive to mesons from other sources. No
evidence for an excess of events over the expected background is observed. An
upper limit on the branching fraction of this decay is set at at a CL. This represents the
world's most stringent limit, constraining models of physics beyond the
Standard Model.Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-029.html (LHCb
public pages
LHCb: Beam Pipe
The proton beams circulate in the accelerator in Ultra High Vacuum to make them interact only with each other when colliding at the interaction point. A special beam pipe "holds" the vacuum where they pass through the LHCb detector:it has to be mechanically very strong to stand the difference in pressure between the vacuum inside it and the air in the cavern but also be as transparent as possible for the particles originating in the proton−proton collisions
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