The production cross-section of \(J/\psi\) pairs is measured using a data sample of \(pp\) collisions collected by the LHCb experiment at a centre-of-mass energy of \(\sqrt{s} = 13 ...\,{\mathrm{TeV}}\), corresponding to an integrated luminosity of \(279 \pm 11 \,{\mathrm{pb^{-1}}}\). The measurement is performed for \(J/\psi\) mesons with a transverse momentum of less than \(10 \,{\mathrm{GeV}}/c\) in the rapidity range \(2.0<y<4.5\). The production cross-section is measured to be \(15.2 \pm 1.0 \pm 0.9 \,{\mathrm{nb}}\). The first uncertainty is statistical, and the second is systematic. The differential cross-sections as functions of several kinematic variables of the \(J/\psi\) pair are measured and compared to theoretical predictions.
Using proton-proton collision data collected by the LHCb experiment at sqrt(s) = 7 TeV, corresponding to an integrated luminosity of 1.0 fb^{-1}, the ratio of branching fractions of the B0 -> D*- pi+ ...pi- pi+ decay relative to the B0 -> D*- pi+ decay is measured to be B(B0 -> D*- pi+ pi- pi+) / B(B0 -> D*- pi+) = 2.64 \pm 0.04 (stat.) \pm 0.13 (syst.). The Cabibbo-suppressed decay B0 -> D*- K+ pi- pi+ is observed for the first time and the measured ratio of branching fractions is B(B0 -> D*- K+ pi- pi+) / B(B0 -> D*- pi+ pi- pi+) = (6.47 \pm 0.37 (stat.) \pm 0.35 (syst.)) x 10^{-2}. A search for orbital excitations of charm mesons contributing to the B0 -> D*- pi+ pi- pi+ final state is also performed, and the first observation of the B0 -> Dbar_{1}(2420)^0 pi+ pi- decay is reported with the ratio of branching fractions B(B0 -> (Dbar_{1}(2420)^0 -> D*- pi+) pi- pi+) / B(B0 -> D*- pi+ pi- pi+) = (2.04 \pm 0.42 (stat.) \pm 0.22 (syst.)) x 10^{-2}, where the numerator represents a product of the branching fractions B(B0 -> Dbar_{1}(2420)^0 pi- pi+) and B(Dbar_{1}(2420)^0 -> D*- pi+).
A search for the decay \(K^0_{\scriptscriptstyle S}\to\mu^+\mu^-\) is performed, based on a data sample of proton-proton collisions corresponding to an integrated luminosity of 3 fb\(^{-1}\), ...collected by the LHCb experiment at centre-of-mass energies of 7 and 8 TeV. The observed yield is consistent with the background-only hypothesis, yielding a limit on the branching fraction of \({\cal B}(K^0_{\scriptscriptstyle S}\to\mu^+\mu^-) < 0.8~(1.0) \times 10^{-9}\) at \(90\%~(95\%)\) confidence level. This result improves the previous upper limit on the branching fraction by an order of magnitude.
This Letter reports a measurement of the CP violation observables S_J/{\psi}KS0 and C_J/{\psi}KS0 in the decay channel B0 -> J/{\psi} KS0 performed with 1.0/fb of pp collisions at sqrt(s) = 7 TeV ...collected by the LHCb experiment. The fit to the data yields S_J/{\psi}KS0 = 0.73 +- 0.07 (stat) +- 0.04 (syst) and C_J/{\psi}KS0 = 0.03 +- 0.09 (stat) +- 0.01 (syst). Both values are consistent with the current world averages and within expectations from the Standard Model.
The decay B0 -> D K*0 and the charge conjugate mode are studied using 1.0fb-1 of pp collision data collected by the LHCb experiment at sqrt(s) = 7TeV in 2011. The CP asymmetry between the B0 -> D K*0 ...and the B0bar -> D K*0bar decay rates, with the neutral D meson in the CP-even final state K+K-, is found to be A_d_KK = -0.45 +- 0.23 +- 0.02, where the first uncertainty is statistical and the second is systematic. In addition, favoured B0 -> D K*0 decays are reconstructed with the D meson in the non-CP eigenstate K+ pi-. The ratio of the B-flavour averaged decay rates in D decays to CP and non-CP eigenstates is measured to be R_d_KK = 1.36 (+0.37) (-0.32) +- 0.07, where the ratio of the branching fractions of D0 -> K- pi+ to D0 -> K+ K- decays is included as multiplicative factor. The CP asymmetries measured with two control channels, the favoured B0 -> DK*0 decay with D -> K+ pi- and the Bs0bar -> D K*0 decay with D K+ K-, are also reported.
Measurements of charm mixing and \(C\!P\) violation parameters from the decay-time-dependent ratio of \( D^0 \to K^+ \pi^- \) to \( D^0 \to K^- \pi^+ \) decay rates and the charge-conjugate ratio are ...reported. The analysis uses \(\overline{B}\to D^{*+} \mu^- X\), and charge-conjugate decays, where \(D^{*+}\to D^0 \pi^+\), and \(D^0\to K^{\mp} \pi^{\pm}\). The \(pp\) collision data are recorded by the LHCb experiment at center-of-mass energies \(\sqrt{s}\) = 7 and 8 TeV, corresponding to an integrated luminosity of 3 fb\(^{-1}\). The data are analyzed under three hypotheses: (i) mixing assuming \(C\!P\) symmetry, (ii) mixing assuming no direct \(C\!P\) violation in the Cabibbo-favored or doubly Cabibbo-suppressed decay amplitudes, and (iii) mixing allowing either direct \(C\!P\) violation and/or \(C\!P\) violation in the superpositions of flavor eigenstates defining the mass eigenstates. The data are also combined with those from a previous LHCb study of \(D^0\to K \pi\) decays from a disjoint set of \( D^{*+} \) candidates produced directly in \(pp\) collisions. In all cases, the data are consistent with the hypothesis of \(C\!P\) symmetry.
The \(B^+ \to D^{*-}K^+\pi^+\) decay potentially provides an excellent way to investigate charm meson spectroscopy. The decay is searched for in a sample of proton-proton collision data collected ...with the LHCb detector at centre-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of \(3~{\rm fb}^{-1}\). A clear signal is observed, and the ratio of its branching fraction to that of the \(B^+ \to D^{*-}\pi^+\pi^+\) normalisation channel is measured to be \begin{equation*} \frac{\mathcal{B}(B^+ \to D^{*-}K^+\pi^+)}{\mathcal{B}(B^+ \to D^{*-}\pi^+\pi^+)} = \left( 6.39 \pm 0.27 \pm 0.48 \right) \times 10^{-2} \, , \end{equation*} where the first uncertainty is statistical and the second is systematic. This is the first observation of the \(B^+ \to D^{*-}K^+\pi^+\) decay.
We report a measurement of the time-dependent ratio of D0->K+pi- to D0->K-pi+ decay rates in D*+-tagged events using 1.0 fb^{-1} of integrated luminosity recorded by the LHCb experiment. We measure ...the mixing parameters x'2=(-0.9+-1.3)x10^{-4}, y'=(7.2+-2.4)x10^{-3} and the ratio of doubly-Cabibbo-suppressed to Cabibbo-favored decay rates R_D=(3.52+-0.15)x10^{-3}, where the uncertainties include statistical and systematic sources. The result excludes the no-mixing hypothesis with a probability corresponding to 9.1 standard deviations and represents the first observation of D0-D0bar oscillations from a single measurement.
Using decays to \(\phi\)-meson pairs, the inclusive production of charmonium states in \(b\)-hadron decays is studied with \(pp\) collision data corresponding to an integrated luminosity of ...\(3.0fb^{-1}\), collected by the LHCb experiment at centre-of-mass energies of 7 and 8 TeV. Denoting by \(B_C\equiv B(b\to CX)\times B(C\to\phi\phi)\) the inclusive branching fraction of a \(b\) hadron to a charmonium state \(C\) that decays into a pair of \(\phi\) mesons, ratios \(R^{C1}_{C2}\equiv B_{C1}/B_{C2}\) are determined as \(R^{\chi_{c0}}_{\eta_c(1S)}=0.147\pm0.023\pm0.011\), \(R^{\chi_{c1}}_{\eta_c (1S)}=0.073\pm0.016\pm0.006\), \(R^{\chi_{c2}}_{\eta_c (1S)}=0.081\pm0.013\pm0.005\), \(R^{\chi_{c1}}_{\chi_{c0}}=0.50\pm0.11\pm0.01\), \(R^{\chi_{c2}}_{\chi_{c0}}=0.56\pm0.10\pm0.01\) and \(R^{\eta_c (2S)}_{\eta_c(1S)}=0.040\pm0.011\pm0.004\). Here and below the first uncertainties are statistical and the second systematic. Upper limits at \(90\%\) confidence level for the inclusive production of \(X(3872)\), \(X(3915)\) and \(\chi_{c2}(2P)\) states are obtained as \(R^{X(3872)}_{\chi_{c1}}<0.34\), \(R^{X(3915)}_{\chi_{c0}}<0.12\) and \(R^{\chi_{c2}(2P)}_{\chi_{c2}}<0.16\). Differential cross-sections as a function of transverse momentum are measured for the \(\eta_c(1S)\) and \(\chi_c\) states. The branching fraction of the decay \(B_s^0\rightarrow\phi\phi\phi\) is measured for the first time, \(B(B_s^0\to\phi\phi\phi)=(2.15\pm0.54\pm0.28\pm0.21_{B})\times 10^{-6}\). Here the third uncertainty is due to the branching fraction of the decay \(B_s^0\to\phi\phi\), which is used for normalization. No evidence for intermediate resonances is seen. A preferentially transverse \(\phi\) polarization is observed. The measurements allow the determination of the ratio of the branching fractions for the \(\eta_c(1S)\) decays to \(\phi\phi\) and \(p\bar{p}\) as \(B(\eta_c(1S)\to\phi\phi)/B(\eta_c(1S)\to p\bar{p})=1.79\pm0.14\pm0.32\).
Decays of \(B^0\) and \(B_{s}^0\) mesons to the charmless baryonic final states \(p \overline{p} h^+ h^{\prime-}\), where \(h\) and \(h^\prime\) each denote a kaon or a pion, are searched for using ...the LHCb detector. The analysis is based on a sample of proton-proton collision data collected at center-of-mass energies of \(7\) and \(8\,\)TeV, corresponding to an integrated luminosity of \(3\,\)fb\(^{-1}\). Four-body charmless baryonic \(B_{s}^0\) decays are observed for the first time. The decays \(B^0_{s}\to p \overline{p} K^+ K^-\), \(B^0_{s}\to p \overline{p} K^\pm \pi^\mp\), \(B^0\to p \overline{p} K^\pm \pi^\mp\) and \(B^0\to p \overline{p} \pi^+\pi^-\) are observed with a significance greater than \(5\) standard deviations; evidence at \(4.1\) standard deviations is found for the \(B^0\to p \overline{p} K^+ K^-\) decay and an upper limit is set on the branching fraction for \(B^0_{s}\to p \overline{p} \pi^+ \pi^-\). Branching fractions in the kinematic region \(m(p \overline{p})<2850\,\)MeV\(/c^2\) are measured relative to the \(B^0 \to J/\psi (\to p \overline{p}) K^*(892)^0\) channel.
