Search for time-dependent CPCP violation in D0→π+π−π0D^0 \rightarrow \pi^+ \pi^- \pi^0 decays

International audienceA measurement of time-dependent $CP$ violation in $D^0 \rightarrow \pi^+ \pi^- \pi^0$ decays using a $pp$ collision data sample collected by the LHCb experiment in 2012 and from 2015 to 2018, corresponding to an integrated luminosity of 7.7$\,\mathrm{fb}^{-1}$, is presented. The initial flavour of each $D^0$ candidate is determined from the charge of the pion produced in the $D^*(2010)^+ \rightarrow D^0 \pi^+$ decay. The decay $D^0 \rightarrow K^- \pi^+ \pi^0$ is used as a control channel to validate the measurement procedure. The gradient of the time-dependent $CP$ asymmetry, $\Delta Y$, in $D^0 \rightarrow \pi^+ \pi^- \pi^0$ decays is measured to be \begin{equation*} \Delta Y = (-1.3 \pm 6.3 \pm 2.4) \times 10^{-4}, \end{equation*} where the first uncertainty is statistical and the second is systematic, which is compatible with $CP$ conservation

Study of charmonium production via the decay to ppˉp\bar{p} at s=13 TeV\sqrt{s} = 13\,\rm{TeV}

Charmonium production cross-section in proton-proton collisions is measured at the centre-of-mass energy $\sqrt{s}=13\,\rm{TeV}$ using decays to $p\bar{p}$ final state. The study is performed using a data sample corresponding to an integrated luminosity of $2.2\,\rm{fb}^{-1}$ collected in 2018 with the \mbox{LHCb} detector. The production cross-section of the $\eta_c$ meson is measured in a rapidity range of $2.0 < y < 4.0$ and in a transverse momentum range of $5.0 < p_{\rm{T}} < 20.0\,\rm{GeV\!/\!\it{c}}$, which is extended compared with previous \mbox{LHCb} analyses. The differential cross-section is measured in bins of $p_{\rm{T}}$ and, for the first time, of $y$. Upper limits, at 90% and 95% confidence levels, on the $\eta_c(2S)$ and $h_c(1P)$ prompt production cross-sections are determined for the first time.Charmonium production cross-section in proton-proton collisions is measured at the centre-of-mass energy $\sqrt{s}=13\,TeV$ using decays to $p\bar{p}$ final state. The study is performed using a data sample corresponding to an integrated luminosity of $2.2\,{fb}^{-1}$ collected in 2018 with the $LHCb$ detector. The production cross-section of the $\eta_c$ meson is measured in a rapidity range of $2.0 < y < 4.0$ and in a transverse momentum range of $5.0 < p_{T} < 20.0\,{GeV/\it{c}}$, which is extended compared with previous $LHCb$ analyses. The differential cross-section is measured in bins of $p_{T}$ and, for the first time, of $y$. Upper limits, at 90% and 95% confidence levels, on the $\eta_c(2S)$ and $h_c(1P)$ prompt production cross-sections are determined for the first time

Measurement of exclusive J/ψJ/\psi and ψ(2S)\psi(2S) production at s=13\sqrt{s}=13 TeV

International audienceMeasurements are presented of the cross-section for the central exclusive production of $J/\psi\to\mu^+\mu^-$ and $\psi(2S)\to\mu^+\mu^-$ processes in proton-proton collisions at $\sqrt{s} = 13$ TeV with 2016-2018 data. They are performed by requiring both muons to be in the LHCb acceptance (with pseudorapidity $2<\eta_{\mu^\pm} < 4.5$) and mesons in the rapidity range $2.0 < y < 4.5$. The integrated cross-section results are \begin{equation*} \sigma_{J/\psi\to\mu^+\mu^-}(2.0<y_{J/\psi}<4.5,2.0<\eta_{\mu^\pm} < 4.5) = 400 \pm 2 \pm 5 \pm 12 \,{\rm pb}\,, \end{equation*}\begin{equation*} \sigma_{\psi(2S)\to\mu^+\mu^-}(2.0<y_{\psi(2S)}<4.5,2.0<\eta_{\mu^\pm} < 4.5) = 9.40 \pm 0.15 \pm 0.13 \pm 0.27 \,{\rm pb}\,, \end{equation*} where the uncertainties are statistical, systematic and due to the luminosity determination. In addition, a measurement of the ratio of $\psi(2S)$ and $J/\psi$ cross-sections, at an average photon-proton centre-of-mass energy of 1 TeV, is performed, giving \begin{equation*} \frac{\sigma_{\psi(2S)}}{\sigma_{J/\psi}} = 0.1763 \pm 0.0029 \pm 0.0008 \pm 0.0039 \,, \end{equation*} where the first uncertainty is statistical, the second systematic and the third due to the knowledge of the involved branching fractions. For the first time, the dependence of the $J/\psi$ and $\psi(2S)$ cross-sections on the total transverse momentum transfer is determined in $pp$ collisions and is found consistent with the behaviour observed in electron-proton collisions

Study of charmonium production via the decay to ppˉp\bar{p} at s=13TeV\sqrt{s} = 13 TeV

International audienceCharmonium production cross-section in proton-proton collisions is measured at the centre-of-mass energy $\sqrt{s}=13\,TeV$ using decays to $p\bar{p}$ final state. The study is performed using a data sample corresponding to an integrated luminosity of $2.2\,{fb}^{-1}$ collected in 2018 with the $LHCb$ detector. The production cross-section of the $\eta_c$ meson is measured in a rapidity range of $2.0 < y < 4.0$ and in a transverse momentum range of $5.0 < p_{T} < 20.0\,{GeV/\it{c}}$, which is extended compared with previous $LHCb$ analyses. The differential cross-section is measured in bins of $p_{T}$ and, for the first time, of $y$. Upper limits, at 90% and 95% confidence levels, on the $\eta_c(2S)$ and $h_c(1P)$ prompt production cross-sections are determined for the first time

Study of charmonium production via the decay to ppˉp\bar{p} at s=13TeV\sqrt{s} = 13 TeV

International audienceCharmonium production cross-section in proton-proton collisions is measured at the centre-of-mass energy $\sqrt{s}=13\,TeV$ using decays to $p\bar{p}$ final state. The study is performed using a data sample corresponding to an integrated luminosity of $2.2\,{fb}^{-1}$ collected in 2018 with the $LHCb$ detector. The production cross-section of the $\eta_c$ meson is measured in a rapidity range of $2.0 < y < 4.0$ and in a transverse momentum range of $5.0 < p_{T} < 20.0\,{GeV/\it{c}}$, which is extended compared with previous $LHCb$ analyses. The differential cross-section is measured in bins of $p_{T}$ and, for the first time, of $y$. Upper limits, at 90% and 95% confidence levels, on the $\eta_c(2S)$ and $h_c(1P)$ prompt production cross-sections are determined for the first time

Study of charmonium production via the decay to ppˉp\bar{p} at s=13TeV\sqrt{s} = 13 TeV

International audienceCharmonium production cross-section in proton-proton collisions is measured at the centre-of-mass energy $\sqrt{s}=13\,TeV$ using decays to $p\bar{p}$ final state. The study is performed using a data sample corresponding to an integrated luminosity of $2.2\,{fb}^{-1}$ collected in 2018 with the $LHCb$ detector. The production cross-section of the $\eta_c$ meson is measured in a rapidity range of $2.0 < y < 4.0$ and in a transverse momentum range of $5.0 < p_{T} < 20.0\,{GeV/\it{c}}$, which is extended compared with previous $LHCb$ analyses. The differential cross-section is measured in bins of $p_{T}$ and, for the first time, of $y$. Upper limits, at 90% and 95% confidence levels, on the $\eta_c(2S)$ and $h_c(1P)$ prompt production cross-sections are determined for the first time

Study of the rare decay J/ψ→μ+μ−μ+μ−J/\psi \to \mu^+\mu^-\mu^+\mu^-

International audienceThe rare electromagnetic $J/\psi \to \mu^+\mu^-\mu^+\mu^-$ decay is observed with a significance greatly exceeding the discovery threshold, using proton-proton collision data collected by the LHCb experiment during 2016-2018 at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of $5.4\,\text{fb}^{-1}$. The rate of this decay is measured relative to that of the $J/\psi \to \mu^+\mu^-$ mode. Using the QED model for the four-muon decay in the efficiency estimation, its branching fraction is determined to be \begin{equation*} {\mathcal{B}}(J/\psi \to \mu^+\mu^-\mu^+\mu^-) = (1.13\pm0.10\pm0.05\pm0.01)\times 10^{-6}, \end{equation*} where the uncertainties are statistical, systematic and due to the uncertainty on the branching fraction of the $J/\psi \to \mu^+\mu^-$ decay

Tracking of charged particles with nanosecond lifetimes at LHCb

International audienceA method is presented to reconstruct charged particles with lifetimes between 10 ps and 10 ns, which considers a combination of their decay products and the partial tracks created by the initial charged particle. Using the $\Xi^-$ baryon as a benchmark, the method is demonstrated with simulated events and proton-proton collision data at $\sqrt{s}=13$ TeV, corresponding to an integrated luminosity of 2.0 fb${}^{-1}$ collected with the LHCb detector in 2018. Significant improvements in the angular resolution and the signal purity are obtained. The method is implemented as part of the LHCb Run 3 event trigger in a set of requirements to select detached hyperons. This is the first demonstration of the applicability of this approach at the LHC, and the first to show its scaling with instantaneous luminosity