The first measurements of the forward-backward asymmetry of the dimuon pair $(A_{FB})$, the triple-product asymmetry $(A_{2ϕ})$, and the charge-parity-conjugation asymmetry $(A_{CP})$, in $D^0 → π^+ ...π^- μ^+ μ^-$ and $D^0 → K^+ K^- μ^+ μ^-$ decays are reported. They are performed using data from proton-proton collisions collected with the LHCb experiment from 2011 to 2016, corresponding to a total integrated luminosity of 5 fb$^{-1}$. The asymmetries are measured to be $A_{FB}(D^0 → π^+ π^- μ^+ μ^-)=(3.3±3.7±0.6)\%$, $A_{2ϕ}(D^0 → π^+ π^- μ^+ μ^- )=(-0.6±3.7±0.6)\%$, $A_{CP}(D^0 → π^+ π^- μ^+ μ^-)=(4.9±3.8±0.7)\%, A_{FB}(D^0 → K^+ K^- μ^+ μ^- )=(0±11±2)\%, A_{2ϕ}(D^0 → K^+ K^- μ^+ μ^-)=(9±11±1)\%, A_{CP}(D^0 → K^+ K^- μ^+ μ^- )=(0±11±2)\%$, where the first uncertainty is statistical and the second systematic. The asymmetries are also measured as a function of the dimuon invariant mass. The results are consistent with the standard model predictions.
We report a measurement of the lifetime of the $Ω_c^0$ baryon using proton-proton collision data at center-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of 3.0 fb$^{-1}$ ...collected by the LHCb experiment. The sample consists of about $1000 Ω_b - → Ω_c ^0 μ^- \bar{ν}_μ X$ signal decays, where the $Ω_c^0$ baryon is detected in the $p K^- K^- π^+$ final state and X represents possible additional undetected particles in the decay. The $Ω_c^0$ lifetime is measured to be $τ_{{Ω}_{c}^{0}} = 268±24±10±2 fs$, where the uncertainties are statistical, systematic, and from the uncertainty in the $D^+$ lifetime, respectively. This value is nearly four times larger than, and inconsistent with, the current world-average value.
The cross section for prompt antiproton production in collisions of protons with an energy of 6.5 TeV incident on helium nuclei at rest is measured with the LHCb experiment from a data set ...corresponding to an integrated luminosity of 0.5 nb$^{-1}$. The target is provided by injecting helium gas into the LHC beam line at the LHCb interaction point. The reported results, covering antiproton momenta between 12 and 110 GeV/c, represent the first direct determination of the antiproton production cross section in p-He collisions, and impact the interpretation of recent results on antiproton cosmic rays from space-borne experiments.
The first measurement of the lifetime of the doubly charmed baryon $\Xi_{cc}^{++}$ is presented, with the signal reconstructed in the final state $Λ_c ^+ K^- π^+ π^+$. The data sample used ...corresponds to an integrated luminosity of 1.7 fb$^{-1}$, collected by the LHCb experiment in proton-proton collisions at a center-of-mass energy of 13 TeV. The $\Xi_{cc}^{++}$ lifetime is measured to be $0.256_{-0.022}^{+0.024}(stat)±0.014(syst) ps$.
The $\overline{B_s^0} \rightarrow \chi_{c2} K^+ K^- $ decay mode is observed and its branching fraction relative to the corresponding $\chi_{c1}$ decay mode, in a $\pm 15 \textrm{MeV}/c^2$ window ...around the $\phi$ mass, is found to be $\frac{\mathcal{B}(\overline{B_s^0} \rightarrow \chi_{c2} K^+ K^-) }{ \mathcal{B}(\overline{B_s^0} \rightarrow \chi_{c1} K^+ K^-)} = (17.1 \pm 3.1 \pm 0.4 \pm 0.9)\%,$ where the first uncertainty is statistical, the second systematic and the third due to the knowledge of the branching fractions of radiative $\chi_c$ decays. The decay mode $\overline{B_s^0} \rightarrow \chi_{c1} K^+ K^- $ allows the $ B_s^0$ mass to be measured as $m(B_s^0) = 5366.83 \pm 0.25 \pm 0.27 \, \textrm{MeV}/c^2,$ where the first uncertainty is statistical and the second systematic. A combination of this result with other LHCb determinations of the $B_s^0$ mass is made.
An analysis of the angular distribution of the decay $\Lambda_b^0 \rightarrow \Lambda \mu^{+} \mu^{-}$ is presented, using data collected with the LHCb detector between 2011 and 2016 and ...corresponding to an integrated luminosity of approximately $5\,fb^{-1}$. Angular observables are determined using a moment analysis of the angular distribution at low hadronic recoil, corresponding to the dimuon invariant mass squared range $15 < q^{2} < 20\, GeV^2/c^4$. The full basis of observables is measured for the first time. The lepton-side, hadron-side and combined forward-backward asymmetries of the decay are determined to be \begin{align} A_{FB}^{l} & = -0.39 \pm 0.04\,\rm{stat} \pm 0.01\, \rm{syst}, \nonumber\\ A_{FB}^{h} & = -0.30 \pm 0.05\,\rm{stat} \pm 0.02\, \rm{syst}, \nonumber\\ A_{FB}^{lh} & = +0.25 \pm 0.04\,\rm{stat} \pm 0.01\, \rm{syst}. \nonumber \end{align} The measurements are consistent with Standard Model predictions.
The ϒ(1S)μ$^{+}$μ$^{−}$ invariant-mass distribution is investigated for a possible exotic meson state composed of two b quarks and two $ \overline{b} $ quarks, $ {X}_{b\overline{b}b\overline{b}} $ . ...The analysis is based on a data sample of pp collisions recorded with the LHCb detector at centre-of-mass energies $ \sqrt{s}=7 $ , 8 and 13 TeV, corresponding to an integrated luminosity of 6.3 fb$^{−1}$. No significant excess is found, and upper limits are set on the product of the production cross-section and the branching fraction as functions of the mass of the $ {X}_{b\overline{b}b\overline{b}} $ state. The limits are set in the fiducial volume where all muons have pseudorapidity in the range 2.0, 5.0, and the $ {X}_{b\overline{b}b\overline{b}} $ state has rapidity in the range 2.0, 4.5 and transverse momentum less than 15 GeV/c.
The Cabibbo-suppressed decay Λ$_{b}^{0}$ → ψ(2S)pπ$^{−}$ is observed for the first time using a data sample collected by the LHCb experiment in proton-proton collisions corresponding to 1.0, 2.0 and ...1.9 fb$^{−1}$ of integrated luminosity at centre-of-mass energies of 7, 8 and 13 TeV, respectively. The ψ(2S) mesons are reconstructed in the μ$^{+}$μ$^{−}$ final state. The branching fraction with respect to that of the Λ$_{b}^{0}$ → ψ(2S)pK$^{−}$ decay mode is measured to be
A search for CP violation in $Λ_{b}^0 → pK^−$ and $Λ_b ^0 → p π^−$ decays is presented using a sample of pp collisions collected with the LHCb detector and corresponding to an integrated luminosity ...of 3.0 fb$^{−1}$ . The $CP$-violating asymmetries are measured to be $A_{CP}^{pK^−} = −0.020±0.013±0.019$ and $A_{CP}^{pπ^−}=−0.035±0.017±0.020$, and their difference $A_{CP}^{pK^−}−A_{CP}^{pπ^−}=0.014±0.022±0.010$, where the first uncertainties are statistical and the second systematic. These are the most precise measurements of such asymmetries to date.
In this paper possibilities of a stabilization of large amplitude
fluctuations in an intracavity-doubled solid-state laser are studied. The
modification of the cross-saturation coefficient by the ...effect of spatial
hole-burning is taken into account. The stabilization of the laser radiation by
an increase of the number of modes, as proposed by James et al. (1990) and
Magni et al. (1993), is analyzed. It is found that when the cross-saturation
coefficient is modulated by the spatial hole-burning the stabilization is not
always possible. We propose a new way of obtaining a stable steady-state
configuration based on an increase of the strength of nonlinearity, which leads
to a strong cancellation of modes, so that during the evolution all of the
modes, but a single one, are canceled. Such a steady-state solution is found to
be stable with respect to small perturbations.
