Search for excited $B_c^{+}$ states

Abstract

A search is performed in the invariant mass spectrum of the $B_c^{+}\ddot{I}{€}^{+}\ddot{I}{€}^{-}$ system for the excited $B_c^{+}$ states $B_c(2^1{S}_0{)}^{+}$ and $B_c(2^3{S}_1{)}^{+}$ using a data sample of $pp$ collisions collected by the LHCb experiment at the centre-of-mass energy of $\sqrt{s}=8\mathrm{TeV}$, corresponding to an integrated luminosity of $2\mathrm{f}{\mathrm{b}}^{-1}$. No evidence is seen for either state. Upper limits on the ratios of the production cross-sections of the $B_c(2^1{S}_0{)}^{+}$ and $B_c(2^3{S}_1{)}^{+}$ states times the branching fractions of $B_c(2^1{S}_0{)}^{+}\to B_c^{+}\ddot{I}{€}^{+}\ddot{I}{€}^{-}$ and $B_c(2^3{S}_1{)}^{+}\to B_c^{\ast +}\ddot{I}{€}^{+}\ddot{I}{€}^{-}$ over the production cross-section of the $B_c^{+}$ state are given as a function of their masses. They are found to be between 0.02 and 0.14 at $95\%$ confidence level for $B_c(2^1{S}_0{)}^{+}$ and $B_c(2^3{S}_1{)}^{+}$ in the mass ranges $[6830,6890]\mathrm{MeV}/c^2$ and $[6795,6890]\mathrm{MeV}/c^2$, respectively.

All figures and tables, along with any supplementary material and additional information, are available at https://lhcbproject.web.cern.ch/lhcbproject/Publications/LHCbProjectPublic/LHCb-PAPER-2017-042.html