Study of Beauty Hadron Decays into Pairs of Charm Hadrons

Abstract

First observations of the decays Λ 0 b → Λ + c D − ( s ) are reported using data corresponding to an integrated luminosity 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 B ( B 0 s → D + D − s ) is made and a search is performed for the decays B 0 ( s ) → Λ + c Λ − c . The results obtained are B ( Λ 0 b → Λ + c D − ) / B ( Λ 0 b → Λ + c D − s ) = 0.042 ± 0.003 ( stat) ± 0.003 ( syst ) , [ B ( Λ 0 b → Λ + c D − s ) B ( ¯ B 0 → D + D − s ) ] / [ B ( Λ 0 b → Λ + c π − ) B ( ¯ B 0 → D + π − ) ] = 0.96 ± 0.02 ( stat) ± 0.06 ( syst) , B ( B 0 s → D + D − s ) / B ( ¯ B 0 → D + D − s ) = 0.038 ± 0.004 ( stat) ± 0.003 ( syst) , B ( ¯ B 0 → Λ + c Λ − c ) / B ( ¯ B 0 → D + D − s ) < 0.0022 [ 95 % C . L . ] , B ( B 0 s → Λ + c Λ − c ) / B ( B 0 s → D + D − s ) < 0.30 [ 95 % C . L . ] . Measurement of the mass of the Λ 0 b baryon relative to the ¯ B 0 meson gives M ( Λ 0 b ) − M ( ¯ B 0 ) = 339.72 ± 0.24 ( stat ) ± 0.18 ( syst) MeV / c 2 . This result provides the most precise measurement of the mass of the Λ 0 b baryon to date.