First Measurement of Charm Production in its Fixed-Target Configuration at the LHC

International audienceThe first measurement of heavy-flavor production by the LHCb experiment in its fixed-target mode is presented. The production of J/ψ and D0 mesons is studied with beams of protons of different energies colliding with gaseous targets of helium and argon with nucleon-nucleon center-of-mass energies of sNN=86.6 and 110.4 GeV, respectively. The J/ψ and D0 production cross sections in pHe collisions in the rapidity range [2, 4.6] are found to be σJ/ψ=652±33(stat)±42(syst)   nb/nucleon and σD0=80.8±2.4(stat)±6.3(syst)  μb/nucleon, where the first uncertainty is statistical and the second is systematic. No evidence for a substantial intrinsic charm content of the nucleon is observed in the large Bjorken-x region

Model-Independent Observation of Exotic Contributions to B0→J/ψK+π−B^0\to J/\psi K^+\pi^- Decays

International audienceAn angular analysis of B0→J/ψK+π- decays is performed, using proton-proton collision data corresponding to an integrated luminosity of 3  fb-1 collected with the LHCb detector. The m(K+π-) spectrum is divided into fine bins. In each m(K+π-) bin, the hypothesis that the three-dimensional angular distribution can be described by structures induced only by K* resonances is examined, making minimal assumptions about the K+π- system. The data reject the K*-only hypothesis with a large significance, implying the observation of exotic contributions in a model-independent fashion. Inspection of the m(J/ψπ-) vs m(K+π-) plane suggests structures near m(J/ψπ-)=4200 and 4600 MeV

Measurement of the branching fraction and CPCP asymmetry in B+→J/ψρ+B^{+}\rightarrow J/\psi \rho^{+} decays

International audienceThe branching fraction and direct $C\!P$ asymmetry of the decay ${{{B} ^+}} \!\rightarrow {{J /\psi }} {{\rho } ^+}$ are measured using proton-proton collision data collected with the LHCb detector at centre-of-mass energies of 7 and 8 TeV, corresponding to a total integrated luminosity of 3 $\,\text{ fb }^{-1}$ . The following results are obtained: $\begin{aligned} \mathcal {B}({{B} ^+} \!\rightarrow {{J /\psi }} {{\rho } ^+} )&= (3.81^{+0.25-0.24} \pm 0.35) \times 10^{-5},\\ \mathcal {A}^{{C\!P}} ({{B} ^+} \!\rightarrow {{J /\psi }} {{\rho } ^+} )&= -0.045^{+0.056-0.057} \pm 0.008, \end{aligned}$ where the first uncertainties are statistical and the second systematic. Both measurements are the most precise to date

Amplitude analysis of the B(s)0→K∗0K‾∗0B^0_{(s)} \to K^{*0} \overline{K}^{*0} decays and measurement of the branching fraction of the B0→K∗0K‾∗0B^0 \to K^{*0} \overline{K}^{*0} decay

International audienceThe ${B}^0\to {K}^{\ast 0}{\overline{K}}^{\ast 0}$ and ${B}_s^0\to {K}^{\ast 0}{\overline{K}}^{\ast 0}$ decays are studied using proton-proton collision data corresponding to an integrated luminosity of 3 fb$^{−1}$. An untagged and timeintegrated amplitude analysis of B_{( s}_{)}^{0}  → (K$^{+}$π$^{−}$)(K$^{−}$π$^{+}$) decays in two-body invariant mass regions of 150 MeV/c$^{2}$ around the K$^{∗0}$ mass is performed. A stronger longitudinal polarisation fraction in the ${B}^0\to {K}^{\ast 0}{\overline{K}}^{\ast 0}$ decay, f$_{L}$ = 0.724 ± 0.051 (stat) ± 0.016 (syst), is observed as compared to f$_{L}$ = 0.240 ± 0.031 (stat) ± 0.025 (syst) in the ${B}_s^0\to {K}^{\ast 0}{\overline{K}}^{\ast 0}$ decay. The ratio of branching fractions of the two decays is measured and used to determine $\mathrm{\mathcal{B}}\left({B}^0\to {K}^{\ast 0}{\overline{K}}^{\ast 0}\right)=\left(8.0\pm 0.9\left(\mathrm{stat}\right)\pm 0.4\left(\mathrm{syst}\right)\right)\times {10}^{-7}$

Measurement of CPCP-violating and mixing-induced observables in Bs0→ϕγB_s^0 \to \phi\gamma decays

International audienceA time-dependent analysis of the Bs0→ϕγ decay rate is performed to determine the CP -violating observables Sϕγ and Cϕγ and the mixing-induced observable AϕγΔ. The measurement is based on a sample of pp collision data recorded with the LHCb detector, corresponding to an integrated luminosity of 3  fb-1 at center-of-mass energies of 7 and 8 TeV. The measured values are Sϕγ=0.43±0.30±0.11, Cϕγ=0.11±0.29±0.11, and AϕγΔ=-0.67-0.41+0.37±0.17, where the first uncertainty is statistical and the second systematic. This is the first measurement of the observables S and C in radiative Bs0 decays. The results are consistent with the standard model predictions

Amplitude analysis of Bs0→KS0K±π∓B^{0}_{s} \rightarrow K^{0}_{\textrm{S}} K^{\pm}\pi^{\mp} decays

International audienceThe first untagged decay-time-integrated amplitude analysis of B$_{s}^{0}$  → K$_{S}^{0}$ K$^{±}$π$^{∓}$ decays is performed using a sample corresponding to 3.0 fb$^{−1}$ of pp collision data recorded with the LHCb detector during 2011 and 2012. The data are described with an amplitude model that contains contributions from the intermediate resonances K$^{*}$(892)$^{0,+}$, K$_{2}^{*}$ (1430)$^{0,+}$ and K$_{0}^{*}$ (1430)$^{0,+}$, and their charge conjugates. Measurements of the branching fractions of the decay modes B$_{s}^{0}$ → K$^{*}$(892)$^{±}$K$^{∓}$ and ${B}_s^0\to \overset{\left(\hbox{---} \right)}{K^{*}}{(892)}^0\overset{\left(\hbox{---} \right)}{K^0}$ are in agreement with, and more precise than, previous results. The decays B$_{s}^{0}$  → K$_{0}^{*}$ (1430)$^{±}$K$^{∓}$ and ${B}_s^0\to \overset{\left(\hbox{---} \right)}{K_0^{*}}{(1430)}^0\overset{\left(\hbox{---} \right)}{K^0}$ are observed for the first time, each with significance over 10 standard deviations

Measurement of ψ\psi(2SS) production cross-sections in proton-proton collisions at s\sqrt{s} = 7 and 13 TeV

International audienceThe cross-sections of $\psi(2S)$ meson production in proton-proton collisions at $\sqrt{s}=13~\mathrm{TeV}$ are measured with a data sample collected by the LHCb detector corresponding to an integrated luminosity of $275~p\mathrm{b}^{-1}$. The production cross-sections for prompt $\psi(2S)$ mesons and those for $\psi(2S)$ mesons from $b$-hadron decays ($\psi{(2S)}\mathrm{-from-}b$) are determined as functions of the transverse momentum, $p_{\mathrm{T}}$, and the rapidity, $y$, of the $\psi(2S)$ meson in the kinematic range $2<p_{\mathrm{T}}<20~\mathrm{GeV}/c$ and $2.0<y<4.5$. The production cross-sections integrated over this kinematic region are \begin{equation*} \begin{split} \sigma(\mbox{prompt }\psi(2S),13~\mathrm{TeV}) &= {1.430 \pm 0.005(\mathrm{stat}) \pm 0.099 (\mathrm{syst})\mu\mathrm{b}},\\ \sigma(\psi(2S)\mathrm{-from-}b,13~\mathrm{TeV})&={0.426 \pm 0.002(\mathrm{stat}) \pm0.030 (\mathrm{syst})\mu\mathrm{b}}. \end{split} \end{equation*} A new measurement of $\psi(2S)$ production cross-sections in $pp$ collisions at $\sqrt{s}=7~\mathrm{TeV}$ is also performed using data collected in 2011, corresponding to an integrated luminosity of $614~{p\mathrm{b}^{-1}}$.The integrated production cross-sections in the kinematic range $3.5<p_{\mathrm{T}}<14~\mathrm{GeV}/c$ and $2.0<y<4.5$ are \begin{equation*} \begin{split} \sigma(\mbox{prompt }\psi(2S),7~\mathrm{TeV}) &={0.471 \pm0.001 (\mathrm{stat}) \pm 0.025 (\mathrm{syst})\mu\mathrm{b}},\\ \sigma(\psi(2S)\mathrm{-from-}b,7~\mathrm{TeV}) &={0.126\pm0.001 (\mathrm{stat}) \pm0.008 (\mathrm{syst})\mu\mathrm{b}}. \end{split} \end{equation*} All results show reasonable agreement with theoretical calculations

Observation of Several Sources of CPCP Violation in B+→π+π+π−B^+ \to \pi^+ \pi^+ \pi^- Decays

International audienceObservations are reported of different sources of CP violation from an amplitude analysis of B+→π+π+π- decays, based on a data sample corresponding to an integrated luminosity of 3  fb-1 of pp collisions recorded with the LHCb detector. A large CP asymmetry is observed in the decay amplitude involving the tensor f2(1270) resonance, and in addition significant CP violation is found in the π+π-S wave at low invariant mass. The presence of CP violation related to interference between the π+π-S wave and the P wave B+→ρ(770)0π+ amplitude is also established; this causes large local asymmetries but cancels when integrated over the phase space of the decay. The results provide both qualitative and quantitative new insights into CP -violation effects in hadronic B decays