The differential branching fraction of the decay $\Lambda_b^0\rightarrow\Lambda\mu^+\mu^-$ is measured as a function of the square of the dimuon invariant mass, $q^2$. A yield of $78\pm12$ ...$\Lambda_b^0\rightarrow\Lambda\mu^+\mu^-$ decays is observed using data, corresponding to an integrated luminosity of 1.0\,fb$^{-1}$, collected by the LHCb experiment at a centre-of-mass energy of 7\,TeV. A significant signal is found in the $q^2$ region above the square of the $J/\psi$ mass, while at lower-$q^2$ values upper limits are set on the differential branching fraction. Integrating the differential branching fraction over $q^2$, while excluding the $J/\psi$ and $\psi(2S)$ regions, gives a branching fraction of $\BF($\Lambda_b^0\rightarrow\Lambda\mu^+\mu^-$)=(0.96\pm 0.16\stat\pm 0.13\syst\pm 0.21 (\mathrm{norm}))\times 10^{-6}$, where the uncertainties are statistical, systematic and due to the normalisation mode, $$\Lambda_b^0\rightarrow J/psi\Lambda$, respectively.
Prompt production of charmonium $\chi_{c0}$, $\chi_{c1} and $\chi_{c2}$ mesons is studied using proton-proton collisions at the LHC at a centre-of-mass energy of $\sqrt{s}=7$TeV. The $\chi_{c}$ ...mesons are identified through their decay to $J/\psi\gamma$, with $J/\psi\to\mu^+\mu^-$ using photons that converted in the detector. A data sample, corresponding to an integrated luminosity of $1.0\mathrm{fb}^{-1}$ collected by the LHCb detector, is used to measure the relative prompt production rate of $\chi_{c1}$ and $\chi_{c2}$ in the rapidity range $2.0
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 charmless three-body decays of B0 and B0s mesons with a KS0 meson in the final state is performed using the pp collision data, corresponding to an integrated luminosity of 1.0 /fb, ...collected at a centre-of-mass energy of 7 TeV recorded by the LHCb experiment. Branching fractions of the B0(s) -> KS0 h+ h'- decay modes (h(') = \pi, K), relative to the well measured B0 -> KS0 \pi+ \pi- decay, are obtained. First observation of the decay modes B0s -> KS0 K+/- \pi-/+ and B0s -> KS0 \pi+ \pi- and confirmation of the decay B0 -> KS0 K+/- \pi-/+ are reported. The following relative branching fraction measurements or limits are obtained BF(B0 -> KS0 K+/- \pi-/+) / BF(B0 -> KS0 \pi+ \pi-) = 0.128 +/- 0.017 (stat.) +/- 0.009 (syst.), BF(B0 -> KS0 K+ K-) / BF(B0 -> KS0 \pi+ \pi-) = 0.385 +/- 0.031 (stat.) +/- 0.023 (syst.), BF(B0s -> KS0 \pi+ \pi-) / BF(B0 -> KS0 \pi+ \pi-) = 0.29 \pm 0.06 (stat.) +/- 0.03 (syst.) +/- 0.02 (f_s/f_d), BF(B0s -> KS0 K+/- \pi-/+) / BF(B0 -> KS0 \pi+ \pi-) = 1.48 +/- 0.12 (stat.) +/- 0.08 (syst.) +/- 0.12 (f_s/f_d), BF(B0s -> KS0 K+ K-) / BF(B0 -> KS0 \pi+ \pi-) E 0.004;0.068 at 90% CL.
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