Evidence for the decay $ \mathrm{B}_{\mathrm{c}}^{+}\to {{\mathrm{J}} \left/ {{\uppsi\;3{\uppi^{+}}2{\uppi^{-}}}} \right.} $

Evidence is presented for the decay $ \mathrm{B}_{\mathrm{c}}^{+}\to {{\mathrm{J}} \left/ {{\uppsi\;3{\uppi^{+}}2{\uppi^{-}}}} \right.} $ using proton-proton collision data, corresponding to an integrated luminosity of 3 fb −1 , collected with the LHCb detector. A signal yield of 32 ± 8 decays is found with a significance of 4.5 standard deviations. The ratio of the branching fraction of the $ \mathrm{B}_{\mathrm{c}}^{+}\to {{\mathrm{J}} \left/ {{\uppsi\;3{\uppi^{+}}2{\uppi^{-}}}} \right.} $ decay to that of the $ \mathrm{B}_{\mathrm{c}}^{+}\to {{\mathrm{J}} \left/ {{\uppsi\;{\uppi^{+}}}} \right.} $ decay is measured to be $ \frac{{\mathcal{B}\left( {\mathrm{B}_{\mathrm{c}}^{+}\to {{\mathrm{J}} \left/ {{\uppsi\;3{\uppi^{+}}2{\uppi^{-}}}} \right.}} \right)}}{{\mathcal{B}\left( {\mathrm{B}_{\mathrm{c}}^{+}\to {{\mathrm{J}} \left/ {{\uppsi\;{\uppi^{+}}}} \right.}} \right)}}=1.74\pm 0.44\pm 0.24, $ where the first uncertainty is statistical and the second is systematic.