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Register a new userObservation of the decay Bc+ -> Bs0 pi+
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The result of a search for the decay Bc+ -> Bs0 pi+ is presented, using the Bs0 -> Ds- pi+ and Bs0 -> J/psi Phi channels. The analysis is based on a data sample of pp collisions collected with the LHCb detector, corresponding to an integrated luminosity of 1 fb-1 taken at a center-of-mass energy of 7 TeV, and 2 fb-1 taken at 8 TeV. The decay Bc+ -> Bs0 pi+ is observed with significance in excess of five standard deviations independently in both decay channels. The measured product of the ratio of cross-sections and branching fraction is sigma(Bc+)/sigma(Bs0) x BR(Bc+ -> Bs0 pi+) = (2.37 pm 0.31 (stat) pm 0.11 (syst)^{+0.17}_{-0.13} (tau_Bc)) x 10^-3 in the pseudorapidity range 2 < eta(B) < 5, where the first uncertainty is statistical, the second is systematic and the third is due to the uncertainty on the Bc lifetime. This is the first observation of a B meson decaying to another B meson via the weak interaction.
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The decay Bc+ --> J/psi pi+pi-pi+ is observed for the first time, using 0.8 fb-1 of pp collisions at sqrt{s}=7 TeV collected by the LHCb experiment. The ratio of branching fractions BR(Bc+ --> J/psi pi+pi-pi+)/BR(B_c+ --> J/psi pi+) is measured to be 2.41+-0.30+-0.33, where the first uncertainty is statistical and the second systematic. The result is in agreement with theoretical predictions.
We report the first observation of the decay $Lambda^+_{c}rightarrow Sigma^- pi^+pi^+pi^0$, based on data obtained in $e^+e^-$ annihilations with an integrated luminosity of 567~pb$^{-1}$ at $sqrt{s}=4.6$~GeV. The data were collected with the BESIII detector at the BEPCII storage rings. The absolute branching fraction $mathcal{B}(Lambda^+_{c}rightarrowSigma^-pi^+pi^+pi^0)$ is determined to be $(2.11pm0.33({rm stat.})pm0.14({rm syst.}))%$. In addition, an improved measurement of $mathcal{B}(Lambda^+_{c}rightarrowSigma^-pi^+pi^+)$ is determined as $(1.81pm0.17({rm stat.})pm0.09({rm syst.}))%$.
The first observation of the decay K^+ --> pi^+ gamma gamma is reported. A total of 31 events was observed with an estimated background of 5.1 +- 3.3 events in the pi+ momentum range from 100 MeV/c to 180 MeV/c. The corresponding partial branching ratio, B(K+ -> pi+ gamma gamma, 100 MeV/c < P_pi^+ < 180 MeV/c), is (6.0 +- 1.5 (stat) +- 0.7 (sys)) x 10^{-7}. No K^+ --> pi^+ gamma gamma decay was observed in the pi^+ momentum region greater than 215 MeV/c. The observed pi^+ momentum spectrum is compared with the predictions of chiral perturbation theory.
We have observed the rare decay K+ --> pi+ mu+ mu- and measured the branching ratio Gamma(K+ --> pi+ mu+ mu-)/Gamma(K+ --> all) = (5.0 +/- 0.4 (stat.) +/- 0.7 (sys.) +/- 0.6 (theor.)) x 10^{-8}. We compare this result with predictions from chiral perturbation theory and estimates based on the decay K+ --> pi+ e+ e-.
The decay $B_c^+ to psi(2S)pi^+$ with $psi(2S) to mu^+mu^-$ is observed with a significance of $5.2,sigma$ using $pp$ collision data corresponding to an integrated luminosity of $1.0,invfb$ collected by the LHCb experiment. The branching fraction of $B_c^+ to psi(2S)pi^+$ decays relative to that of the $B_c^+ to J/psipi^+$ mode is measured to be begin{equation*} frac{mathcal{B}(B_c^+ to psi(2S)pi^+)}{mathcal{B}(B_c^+ to J/psipi^+)} = 0.250 pm 0.068 ,text{stat} pm 0.014 ,text{syst} pm 0.006 ,(mathcal{B}). end{equation*} The last term is the uncertainty on the ratio $mathcal{B}(psi(2S) to mu^+mu^-)/mathcal{B}(J/psi to mu^+mu^-)$.
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