Evidence for the Strangeness-Changing Weak Decay Ξ−b→Λ0bπ−

Abstract

Using a p p collision data sample corresponding to an integrated luminosity of 3.0 fb − 1 , collected by the LHCb detector, we present the first search for the strangeness-changing weak decay Ξ − b → Λ 0 b π − . No b hadron decay of this type has been seen before. A signal for this decay, corresponding to a significance of 3.2 standard deviations, is reported. The relative rate is measured to be f Ξ − b f Λ 0 b B ( Ξ − b → Λ 0 b π − ) = ( 5.7 ± 1. 8 + 0.8 − 0.9 ) × 10 − 4 , where f Ξ − b and f Λ 0 b are the b → Ξ − b and b → Λ 0 b fragmentation fractions, and B ( Ξ − b → Λ 0 b π − ) is the branching fraction. Assuming f Ξ − b / f Λ 0 b is bounded between 0.1 and 0.3, the branching fraction B ( Ξ − b → Λ 0 b π − ) would lie in the range from ( 0.57 ± 0.21 ) % to ( 0.19 ± 0.07 ) % .