The quantum numbers of the X(3872) meson are determined to be JPC = 1++ based on angular correlations in B+ to X(3872) K+ decays, where X(3872) to pi+pi- J/psi and J/psi to \mu+\mu-. The data ...correspond to 1.0 fb-1 of pp collisions collected by the LHCb detector. The only alternative assignment allowed by previous measurements, JPC=2-+, is rejected with a confidence level equivalent to more than eight Gaussian standard deviations using the likelihood-ratio test in the full angular phase space. This result favors exotic explanations of the X(3872) state.
An amplitude analysis of the final state structure in the Bs->J/\psi K+K- decay mode is performed using 1.0/fb of data collected by the LHCb experiment in 7 TeV center-of-mass energy pp collisions ...produced by the LHC. A modified Dalitz plot analysis of the final state is performed using both the invariant mass spectra and the decay angular distributions. Resonant structures are observed in the K+K- mass spectrum as well as a significant non-resonant S-wave contribution. The largest resonant component is the \phi(1020), accompanied by f0(980), f'2(1525), and four additional resonances. The overall branching fraction is measured to be B(Bs->J/\psi K+K-)=(7.70 +/-0.08 +/- 0.39 +/- 0.60)x 10^(-4), where the first uncertainty is statistical, the second systematic, and the third due to the ratio of the number of Bs to B- mesons produced. The mass and width of the f'2(1525) are measured to be 1522.2 +/- 2.8^{+5.3}_{-2.0} MeV and 84 +/- 6^{+10}_{-5} MeV, respectively. The final state fractions of the other resonant states are also reported.
We report on a measurement of the flavor-specific \(B^{0}_{s}\) lifetime and of the \(D^{-}_{s}\) lifetime using proton-proton collisions at center-of-mass energies of 7 and 8 TeV, collected by the ...LHCb experiment and corresponding to 3.0 fb\(^{-1}\) of integrated luminosity. Approximately 407 000 \(B^{0}_{s} \rightarrow D^{(*)-}_{s} \mu^{+}\nu_\mu \) decays are partially reconstructed in the \(K^{+}K^{-}\pi^{-}\mu^{+}\) final state. The \(B^{0}_{s}\) and \(D^{-}_{s}\) natural widths are determined using, as a reference, kinematically similar \(B^{0} \rightarrow D^{(*)-}\mu^{+}\nu_\mu\) decays reconstructed in the same final state. The resulting differences between widths of \(B^{0}_{s}\) and \(B^{0}\) mesons and of \(D^{-}_{s}\) and \(D^{-}\) mesons are \(\Delta_\Gamma(B) =-0.0115 \pm 0.0053 (stat) \pm 0.0041 (syst)\) ps\(^{-1}\) and \(\Delta_\Gamma(D) = 1.0131 \pm 0.0117 (stat) \pm 0.0065 (syst)\) ps\(^{-1}\), respectively. Combined with the known \(B^{0}\) and \(D^{-}\) lifetimes, these yield the flavor-specific \(B^{0}_{s}\) lifetime, \(\tau^{\rm fs}_{B^{0}_{s}} = 1.547 \pm 0.013 (stat) \pm 0.010 (syst) \pm 0.004 (\tau_{B})\) ps and the \(D^{-}_{s}\) lifetime, \(\tau_{D^{-}_{s}} = 0.5064 \pm 0.0030 (stat) \pm 0.0017 (syst) \pm 0.0017 (\tau_{D})\) ps The last uncertainties originate from the limited knowledge of the \(B^0\) and \(D^{-}\) lifetimes. The results improve upon current determinations.
A highly significant structure is observed in the \(\Lambda_c^+K^-\pi^+\pi^+\) mass spectrum, where the \(\Lambda_c^+\) baryon is reconstructed in the decay mode \(pK^-\pi^+\). The structure is ...consistent with originating from a weakly decaying particle, identified as the doubly charmed baryon \(\Xi_{cc}^{++}\). The difference between the masses of the \(\Xi_{cc}^{++}\) and \(\Lambda_c^+\) states is measured to be \(1334.94 \pm 0.72 (\mathrm{stat}) \pm 0.27 (\mathrm{syst}~\mathrm{MeV}/c^2\), and the \(\Xi_{cc}^{++}\) mass is then determined to be \(3621.40 \pm 0.72 (\mathrm{stat}) \pm 0.27 (\mathrm{syst} \pm 0.14 \, (\Lambda_c^+)~\mathrm{MeV}/c^2\), where the last uncertainty is due to the limited knowledge of the \(\Lambda_c^+\) mass. The state is observed in a sample of proton-proton collision data collected by the LHCb experiment at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 1.7 \(\mathrm{fb}^{-1}\), and confirmed in an additional sample of data collected at 8 TeV.
The production of J/psi mesons is studied with the LHCb detector using data from pp collisions at sqrt(s)=2.76 TeV corresponding to an integrated luminosity of 71 nb^-1. The differential ...cross-section for inclusive J/psi production is measured as a function of its transverse momentum pT. The cross-section in the fiducial region 0<pT<12 GeV/c and rapidity 2.0<y<4.5 is measured to be 5.6 +/- 0.1(stat) +/- 0.4 (syst) mub, with the assumption of unpolarised J/psi production. The fraction of J/psi production from b-hadron decays is measured to be (7.1 +/- 0.6 (stat) +/- 0.7 (syst)) %.
Charm production at the LHC in pp collisions at sqrt(s)=7 TeV is studied with the LHCb detector. The decays D0 -> K- pi+, D+ -> K- pi+ pi+, D*+ -> D0(K- pi+) pi+, D_s+ -> phi(K- K+) pi+, Lambda_c+ -> ...p K- pi+, and their charge conjugates are analysed in a data set corresponding to an integrated luminosity of 15 nb^{-1}. Differential cross-sections dsigma/dp_T are measured for prompt production of the five charmed hadron species in bins of transverse momentum and rapidity in the region 0 < p_T < 8 GeV/c and 2.0 < y < 4.5. Theoretical predictions are compared to the measured differential cross-sections. The integrated cross-sections of the charm hadrons are computed in the above p_T-y range, and their ratios are reported. A combination of the five integrated cross-section measurements gives sigma(c\bar{c})_{p_T < 8 GeV/c, 2.0 < y < 4.5} = 1419 +/- 12 (stat) +/- 116 (syst) +/- 65 (frag) microbarn, where the uncertainties are statistical, systematic, and due to the fragmentation functions.
A search for a long-lived scalar particle \(\chi\) is performed, looking for the decay \({B^+ \to K^+ \chi}\) with \({\chi \to \mu^+\mu^-}\) in \(pp\) collision data corresponding to an integrated ...luminosity of \(3\, {\rm fb}^{-1}\), collected by the LHCb experiment at centre-of-mass energies of \(\sqrt{s}=7\) and 8\(\,\)TeV. This new scalar particle, predicted by Hidden Sector models, is assumed to have a narrow width. The signal would manifest itself as an excess in the dimuon invariant mass distribution over the Standard Model background. No significant excess is observed in the accessible ranges of mass \({250 < m(\chi) < 4700\,\rm MeV/c^2}\) and lifetime \({0.1 < \tau(\chi) < 1000\,\rm ps}\). Upper limits on the branching fraction \(\mathcal{B}(B^+ \to K^+ \chi (\mu^+\mu^-))\) at 95% confidence level are set as a function of \(m(\chi)\) and \(\tau(\chi)\), varying between \(2\times10^{-10}\) and \(10^{-7}\). These are the most stringent limits to date. The limits are interpreted in the context of a model with a light inflaton particle.
The ratio of the \Lambda b baryon lifetime to that of the B0 meson is measured using 1.0/fb of integrated luminosity in 7 TeV center-of-mass energy pp collisions at the LHC. The \Lambda b baryon is ...observed for the first time in the decay mode \Lambda b -> J/\psi pK-, while the B0 meson decay used is the well known B0 -> J/\psi pi+K- mode, where the pi+ K- mass is consistent with that of the K*0(892) meson. The ratio of lifetimes is measured to be 0.976 +/- 0.012 +/- 0.006, in agreement with theoretical expectations based on the heavy quark expansion. Using previous determinations of the B0 meson lifetime, the \Lambda b lifetime is found to be 1.482 +/- 0.018 +/- 0.012 ps. In both cases the first uncertainty is statistical and the second systematic.
Interpretation of CP violation measurements using charmonium decays, in both the B0 and Bs systems, can be subject to changes due to "penguin" type diagrams. These effects can be investigated using ...measurements of the Cabibbo-suppressed B0->J/\psi pi+pi- decays. The final state composition of this channel is investigated using a 1.0/fb sample of data produced in 7 TeV pp collisions at the LHC and collected by the LHCb experiment. A modified Dalitz plot analysis is performed using both the invariant mass spectra and the decay angular distributions. An improved measurement of the B0->J/\psi pi+pi- branching fraction of (3.97 +/-0.09+/- 0.11 +/- 0.16)x10^{-5} is reported where the first uncertainty is statistical, the second is systematic and the third is due to the uncertainty of the branching fraction of the decay B- -> J/\psi K- used as a normalization channel. In the J/\psi pi+pi- final state significant production of f0(500) and rho(770) resonances is found, both of which can be used for CP violation studies. In contrast evidence for the f0(980) resonance is not found, thus establishing the first upper limit on the branching fraction product B(B0->J/\psi f0(980) x B(f0(980)-> pi+ pi-) < 1.1x10^{-6}, leading to an upper limit on the absolute value of the mixing angle of the f0(980)$ with the f0(500) of <31 degrees, both at 90% confidence level.
Bottom baryons decaying to a J/\psi\ meson and a hyperon are reconstructed using 1.0 fb^{-1} of data collected in 2011 with the LHCb detector. Significant \Lambda_b^0 \rightarrow J/\psi \Lambda, ...\Xi_b^-\rightarrow J/\psi \Xi^- and \Omega_b^- \rightarrow J/\psi \Omega^- signals are observed and the corresponding masses are measured to be M(\Lambda_b^0) = 5619.53 \pm 0.13 (stat) \pm 0.45 (syst) MeV/c^2, M(\Xi_b^-) = 5795.8 \pm 0.9 (stat) \pm 0.4 (syst) MeV/c^2, M(\Omega_b^-) = 6046.0 \pm 2.2 (stat) \pm 0.5 (syst) MeV/c^2, while the differences with respect to the \Lambda_b^0 mass are M(\Xi_b^-)-M(\Lambda_b^0) = 176.2 \pm 0.9 (stat) \pm 0.1 (syst) MeV/c^2, M(\Omega_b^-)-M(\Lambda_b^0) = 426.4 \pm 2.2 (stat) \pm 0.4 (syst) MeV/c^2. These are the most precise mass measurements of the \Lambda_b^0, \Xi_b^- and \Omega_b^- baryons to date. Averaging the above \Lambda_b^0 mass measurement with that published by LHCb using 35 pb^{-1} of data collected in 2010 yields M(\Lambda_b^0) = 5619.44 \pm 0.13 (stat) \pm 0.38 (syst) MeV/c^2.
