E-catalog        

The decays Bc+→J/ψDs+ and Bc+→J/ψDs∗+ are studied with the ATLAS detector at the LHC using a dataset corresponding to integrated luminosities of 4.9 and 20.6 fb -1 of pp collisions collected at centre-of-mass energies s=7 TeV and 8 TeV, respectively. Signal candidates are identified through J/ψ→μ+μ- and Ds(∗)+→ϕπ+(γ/π0) decays. With a two-dimensional likelihood fit involving the Bc+ reconstructed invariant mass and an angle between the μ+ and Ds+ candidate momenta in the muon pair rest frame, the yields of Bc+→J/ψDs+ and Bc+→J/ψDs∗+ , and the transverse polarisation fraction in Bc+→J/ψDs∗+ decay are measured. The transverse polarisation fraction is determined to be Γ±±(Bc+→J/ψDs∗+)/Γ(Bc+→J/ψDs∗+)=0.38±0.23±0.07 , and the derived ratio of the branching fractions of the two modes is BBc+→J/ψDs∗+/BBc+→J/ψDs+=2.8-0.8+1.2±0.3 , where the first error is statistical and the second is systematic. Finally, a sample of Bc+→J/ψπ+ decays is used to derive the ratios of branching fractions BBc+→J/ψDs+/BBc+→J/ψπ+=3.8±1.1±0.4±0.2 and BBc+→J/ψDs∗+/BBc+→J/ψπ+=10.4±3.1±1.5±0.6 , where the third error corresponds to the uncertainty of the branching fraction of Ds+→ϕ(K+K-)π+ decay. The available theoretical predictions are generally consistent with the measurement.