First measurements of absolute branching fractions of the Ξ + c baryon at Belle

Abstract

We present the first measurements of the absolute branching fractions of Ξ + c decays into Ξ − π + π + and p K − π + final states. Our analysis is based on a data set of ( 772 ± 11 ) × 10 6

B ¯ B pairs collected at the Υ ( 4 S ) resonance with the Belle detector at the KEKB e + e − collider. We measure the absolute branching fraction of ¯ B 0 → ¯ Λ − c Ξ + c with the Ξ + c recoiling against ¯ Λ − c in ¯ B 0 decays resulting in B ( ¯ B 0 → ¯ Λ − c Ξ + c ) = [ 1.16 ± 0.42 ( stat . ) ± 0.15 ( syst . ) ] × 10 − 3 . We then measure the product branching fractions B ( ¯ B 0 → ¯ Λ − c Ξ + c ) B ( Ξ + c → Ξ − π + π + ) and B ( ¯ B 0 → ¯ Λ − c Ξ + c ) B ( Ξ + c → p K − π + ) . Dividing these product branching fractions by ¯ B 0 → ¯ Λ − c Ξ + c yields B ( Ξ + c → Ξ − π + π + ) = [ 2.86 ± 1.21 ( stat . ) ± 0.38 ( syst . ) ] % and B ( Ξ + c → p K − π + ) = [ 0.45 ± 0.21 ( stat . ) ± 0.07 ( syst . ) ] % . Our result for B ( Ξ + c → Ξ − π + π + ) can be combined with Ξ + c branching fractions measured relative to Ξ + c → Ξ − π + π + to set the absolute scale for many Ξ + c branching fractions.