Study of Beauty Hadron Decays into Pairs of Charm Hadrons

First observations of the decays Λ0b → Λþc D−ðsÞ are reported using data corresponding to an integratedluminosity of 3 fb−1 collected at 7 and 8 TeV center-of-mass energies in proton-proton collisions with the LHCb detector. In addition, the most precise measurement of the branching fraction BðB0s → DþD−s Þ is made and a search is performed for the decays B0ðsÞ → Λþc Λ−c . The results obtained are BðΛ0b → Λþc D−Þ=BðΛ0b → Λþc D−s Þ ¼ 0.042 0.003ðstatÞ 0.003ðsystÞ; BðΛ0b → Λþc D−s ÞBðB¯ 0 → DþD−s Þ=BðΛ0b → Λþc π−ÞBðB¯ 0 → Dþπ−Þ¼ 0.96 0.02ðstatÞ 0.06ðsystÞ; BðB0s → DþD−s Þ=BðB¯ 0 → DþD−s Þ ¼ 0.038 0.004ðstatÞ 0.003ðsystÞ; BðB¯ 0 → Λþc Λ−c Þ=BðB¯ 0 → DþD−s Þ < 0.0022½95% C.L.; BðB0s → Λþc Λ−c Þ=BðB0s → DþD−s Þ < 0.30½95% C.L.: Measurement of the mass of the Λ0b baryon relative to the B¯ 0 meson gives MðΛ0bÞ − MðB¯ 0Þ ¼ 339.72 0.24ðstatÞ 0.18ðsystÞ MeV=c2. This result provides the most precise measurement of the mass of the Λ0b baryon to date.