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Register a new userMeasurement of the ratio of $B_c^+$ branching fractions to $J/psipi^+$ and $J/psimu^+ u_mu$
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The first measurement that relates semileptonic and hadronic decay rates of the $B_c^+$ meson is performed using proton-proton collision data corresponding to 1.0 fb$^{-1}$ of integrated luminosity collected with the LHCb detector. The measured value of the ratio of branching fractions, ${cal B}(B_c^+ to J/psi pi^+)/{cal B}(B_c^+to J/psimu^+ u_mu)=0.0469 pm 0.0028 (stat.) pm 0.0046 (syst.)$, is at the lower end of available theoretical predictions.
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A measurement is reported of the ratio of branching fractions $mathcal{R}(J/psi)=mathcal{B}(B_c^+,to,J/psitau^+ u_tau)/mathcal{B}(B_c^+,to,J/psi mu^+ u_mu)$, where the $tau^+$ lepton is identified in the decay mode $tau^+,to,mu^+ u_muoverline{ u}_tau$. This analysis uses a sample of proton-proton collision data corresponding to 3.0$mathrm{,fb}^{-1}$ of integrated luminosity recorded with the LHCb experiment at center-of-mass energies $7,mathrm{TeV}$ and $8,mathrm{TeV}$. A signal is found for the decay $B_c^+,to,J/psi tau^+ u_tau$ at a significance of 3 standard deviations, corrected for systematic uncertainty, and the ratio of the branching fractions is measured to be $mathcal{R}(J/psi) = 0.71 pm 0.17 mathrm{,(stat)} pm 0.18mathrm{,(syst)}$. This result lies within 2 standard deviations above the range of existing predictions in the Standard Model.
The ratio of branching fractions $R_{K/pi} equiv mathcal{B}(B_{c}^{+} to J/psi K^{+})/mathcal{B}(B_{c}^{+} to J/psipi^{+})$ is measured with $pp$ collision data collected by the LHCb experiment at centre-of-mass energies of 7 TeV and 8 TeV, corresponding to an integrated luminosity of 3${mbox{fb}^{-1}}$. It is found to be $ R_{K/pi} = 0.079pm0.007pm0.003$, where the first uncertainty is statistical and the second is systematic. This measurement is consistent with the previous LHCb result, while the uncertainties are significantly reduced.
The ratio of branching fractions and the difference in $CP$ asymmetries of the decays $B^+to J/psi pi^+$ and $B^+to J/psi K^+$ are measured using a data sample of $pp$ collisions collected by the LHCb experiment, corresponding to an integrated luminosity of $3~{{,mbox{fb}^{-1}}}$ at centre-of-mass energies of 7 and $8~mathrm{,Tekern -0.1em V}$. The results are begin{equation*} {mathcal{B}(B^+to J/psi pi^+)overmathcal{B}(B^+to J/psi K^+)}=(3.83pm0.03pm0.03)times10^{-2},, end{equation*} begin{equation*} mathcal{A}^{CP}(B^+to J/psi pi^+)-mathcal{A}^{CP}(B^+to J/psi K^+)=(1.82pm0.86pm0.14)times10^{-2}, end{equation*} where the first uncertainties are statistical and the second are systematic. Combining this result with a recent LHCb measurement of $mathcal{A}^{CP}(B^+to J/psi K^+)$ provides the most precise estimate to date of $CP$ violation in the decay $B^+to J/psi pi^+$, begin{equation*} mathcal{A}^{CP}(B^+to J/psi pi^+) =(1.91pm0.89pm0.16)times10^{-2}. end{equation*}
The lifetime of the $B_c^+$ meson is measured using semileptonic decays having a $J!/!psi$ meson and a muon in the final state. The data, corresponding to an integrated luminosity of $2mathrm{~fb^{-1}}$, are collected by the LHCb detector in $pp$ collisions at a centre-of-mass energy of $8,mathrm{TeV}$. The measured lifetime is $$tau = 509 pm 8 pm 12 mathrm{~fs},$$ where the first uncertainty is statistical and the second is systematic.
The difference in total widths between the $B_c^+$ and $B^+$ mesons is measured using 3.0fb$^{-1}$ of data collected by the LHCb experiment in 7 and 8 TeV centre-of-mass energy proton-proton collisions at the LHC. Through the study of the time evolution of $B_c^+ rightarrow J/psi pi^+$ and $B^+rightarrow J/psi K^+$ decays, the width difference is measured to be $$ DeltaGamma equiv Gamma_{B_c^+} - Gamma_{B^+} = 4.46 pm 0.14 pm 0.07mm^{-1}c,$$ where the first uncertainty is statistical and the second systematic. The known lifetime of the $B^+$ meson is used to convert this to a precise measurement of the $B_c^+$ lifetime, $$tau_{B_c^+} = 513.4 pm 11.0 pm 5.7fs,$$ where the first uncertainty is statistical and the second systematic.
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