Measurement of the differential branching fraction of the decay $\hat{I}{›}_b^0\to \hat{I}›\hat{I}{¼}^{+}\hat{I}{¼}^{-}$

Abstract

The differential branching fraction of the decay $\hat{I}{›}_b^0\to \hat{I}›\hat{I}{¼}^{+}\hat{I}{¼}^{-}$ is measured as a function of the square of the dimuon invariant mass, $q^2$. A yield of $78\pm 12$ $\hat{I}{›}_b^0\to \hat{I}›\hat{I}{¼}^{+}\hat{I}{¼}^{-}$ 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 $J/\ddot{I}ˆ$ 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 $J/\ddot{I}ˆ$ and $\ddot{I}ˆ(2S)$ regions, gives a branching fraction of $\BF($Λ_b^0\rightarrowΛμ^+μ^-$)=(0.96\pm 0.16\stat\pm 0.13\syst\pm 0.21 (\mathrm{norm}))\times 10^{-6}$, where the uncertainties are statistical, systematic and due to the normalisation mode, $$Λ_b^0\rightarrow J/psiΛ$, respectively.

Submitted to PLB