Asymmetries in the time-dependent rates of D^{0}→K^{+}K^{-} and D^{0}→π^{+}π^{-} decays are measured in a pp collision data sample collected with the LHCb detector during LHC Run 1, corresponding to ...an integrated luminosity of 3 fb^{-1}. The asymmetries in effective decay widths between D^{0} and Dover ¯^{0} decays, sensitive to indirect CP violation, are measured to be A_{Γ}(K^{+}K^{-})=(-0.30±0.32±0.10)×10^{-3} and A_{Γ}(π^{+}π^{-})=(0.46±0.58±0.12)×10^{-3}, where the first uncertainty is statistical and the second systematic. These measurements show no evidence for CP violation and improve on the precision of the previous best measurements by nearly a factor of two.
Exclusive J ψ and ψ(2S) vector meson production has been observed in the dimuon channel using the LHCb detector. The cross-section times branching fractions to two muons with pseudorapidities between ...2.0 and 4.5 are measured to be where the first uncertainties are statistical and the second are systematic. The measurements are found to be in good agreement with results from previous experiments and theoretical predictions. The J ψ photoproduction cross-section has been measured as a function of the photon-proton centre-of-mass energy. The results are consistent with measurements obtained at HERA and confirm a similar power law behaviour for the photoproduction cross-section.
A search for the rare decays B_{s}^{0}→τ^{+}τ^{-} and B^{0}→τ^{+}τ^{-} is performed using proton-proton collision data collected with the LHCb detector. The data sample corresponds to an integrated ...luminosity of 3 fb^{-1} collected in 2011 and 2012. The τ leptons are reconstructed through the decay τ^{-}→π^{-}π^{+}π^{-}ν_{τ}. Assuming no contribution from B^{0}→τ^{+}τ^{-} decays, an upper limit is set on the branching fraction B(B_{s}^{0}→τ^{+}τ^{-})<6.8×10^{-3} at the 95% confidence level. If instead no contribution from B_{s}^{0}→τ^{+}τ^{-} decays is assumed, the limit is B(B^{0}→τ^{+}τ^{-})<2.1×10^{-3} at the 95% confidence level. These results correspond to the first direct limit on B(B_{s}^{0}→τ^{+}τ^{-}) and the world's best limit on B(B^{0}→τ^{+}τ^{-}).
The preliminary results of a spin-parity analysis of the annihilation reactions p-barp{yields}{pi}{sup +}{pi}{sup -}{pi}{sup 0}, K{sup +}K{sup -}{pi}{sup 0} and K{sup {+-}}K{sub s}{sup 0}{pi}{sup ...{+-}} are discussed. The availability of different hadronic final states and partial wave mixtures are the peculiar points of the present analysis. The main features of the experimental data selection, the amplitude and the corresponding constraints are discussed.
(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image) The production cross-section of J/ψ pairs is measured using a data sample of pp collisions collected by the LHCb experiment ...at a centre-of-mass energy of ... TeV, corresponding to an integrated luminosity of 279 ±11 pb−1. The measurement is performed for J/ψ mesons with a transverse momentum of less than 10 GeV/c in the rapidity range 2.0 < y < 4.5. The production cross-section is measured to be 15.2 ± 1.0 ± 0.9 nb. The first uncertainty is statistical, and the second is systematic. The differential cross-sections as functions of several kinematic variables of the J/ψ pair are measured and compared to theoretical predictions. Figure not available: see fulltext.
The production of
(1
),
(2
) and
(3
) mesons in proton-proton collisions at the centre-of-mass energy of Formula: see text is studied with the LHCb detector. The analysis is based on a data sample of ...25 pb
collected at the Large Hadron Collider. The
mesons are reconstructed in the decay mode
→
and the signal yields are extracted from a fit to the
invariant mass distributions. The differential production cross-sections times dimuon branching fractions are measured as a function of the
transverse momentum
and rapidity
, over the range
<15 GeV/c and 2.0<
<4.5. The cross-sections times branching fractions, integrated over these kinematic ranges, are measured to be Formula: see text where the first uncertainty is statistical, the second systematic and the third is due to the unknown polarisation of the three
states.
The differential cross-section for the inclusive production of
(2
) mesons in
collisions at Formula: see text has been measured with the LHCb detector. The data sample corresponds to an integrated ...luminosity of 36 pb
. The
(2
) mesons are reconstructed in the decay channels
(2
)→
and
(2
)→
/
, with the
/
meson decaying into two muons. Results are presented both for promptly produced
(2
) mesons and for those originating from
-hadron decays. In the kinematic range
(
(2
))≤16 GeV/
and 2<
(
(2
))≤4.5 we measure Formula: see text where the last uncertainty on the prompt cross-section is due to the unknown
(2
) polarization. Recent QCD calculations are found to be in good agreement with our measurements. Combining the present result with the LHCb
/
measurements we determine the inclusive branching fraction Formula: see text where the last uncertainty is due to the Formula: see text, Formula: see text and Formula: see text branching fraction uncertainties.
Using 34.7 pb-1 of data collected with the LHCb detector, the inclusive production of the X(3872) meson in pp collisions at sqrt(s) = 7 TeV is observed for the first time. Candidates are selected in ...the X(3872) -> J/psi pi+ pi- decay mode, and used to measure sigma(pp -> X(3872) + anything) B(X(3872)-> J/psi pi+ pi-) = 4.7 +- 1.1 (stat) +- 0.7 (syst), where sigma(pp -> X(3872) + anything) is the inclusive production cross-section of X(3872) mesons with rapidity in the range 2.5-4.5 and transverse momentum in the range 5-20 GeV/c. In addition the masses of both the X(3872) and psi(2S) mesons, reconstructed in the J/psi pi+ pi- final state, are measured to be m(X(3872)) = 3871.95 +- 0.48 (stat) +- 0.12 (syst) MeV/c2 and m(psi(2S)) = 3686.12 +- 0.06 (stat) +- 0.10 (syst) MeV/c2
A search for the rare decays B_{s}^{0}→μ^{+}μ^{-} and B^{0}→μ^{+}μ^{-} is performed at the LHCb experiment using data collected in pp collisions corresponding to a total integrated luminosity of 4.4 ...fb^{-1}. An excess of B_{s}^{0}→μ^{+}μ^{-} decays is observed with a significance of 7.8 standard deviations, representing the first observation of this decay in a single experiment. The branching fraction is measured to be B(B_{s}^{0}→μ^{+}μ^{-})=(3.0±0.6_{-0.2}^{+0.3})×10^{-9}, where the first uncertainty is statistical and the second systematic. The first measurement of the B_{s}^{0}→μ^{+}μ^{-} effective lifetime, τ(B_{s}^{0}→μ^{+}μ^{-})=2.04±0.44±0.05 ps, is reported. No significant excess of B^{0}→μ^{+}μ^{-} decays is found, and a 95% confidence level upper limit, B(B^{0}→μ^{+}μ^{-})<3.4×10^{-10}, is determined. All results are in agreement with the standard model expectations.
The $\bar{\Lambda} / \Lambda$ and $\bar{\Lambda} / K^0_\mathrm{S}$ production ratios are measured by the LHCb detector from $0.3\,\mathrm{nb}^{-1}$ of $pp$ collisions delivered by the LHC at ...$\sqrt{s} = 0.9$\,TeV and $1.8\,\mathrm{nb}^{-1}$ at $\sqrt{s} = 7$\,TeV. Both ratios are presented as a function of transverse momentum, $p_\mathrm{T}$, and rapidity, $y$, in the ranges {$0.15 < p_\mathrm{T} < 2.50\,\mathrm{GeV}/c$} and {$2.0
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