Isospin amplitudes in lambda(0)(b) -> J/psi lambda (Sigma(0)) and Xi(0)(b)-> J/psi Xi(0) (Lambda) decays

Abstract

Ratios of isospin amplitudes in hadron decays are a useful probe of the interplay between weak and strong interactions and allow searches for physics beyond the standard model. We present the first results on isospin amplitudes in b -baryon decays, using data corresponding to an integrated luminosity of 8.5     fb − 1 , collected with the LHCb detector in p p collisions at center of mass energies of 7, 8, and 13 TeV. The isospin amplitude ratio | A 1 ( Λ 0 b → J / ψ Σ 0 ) / A 0 ( Λ 0 b → J / ψ Λ ) | , where the subscript on A indicates the final-state isospin, is measured to be less than 1 / 21.8 at 95% confidence level. The Cabibbo suppressed Ξ 0 b → J / ψ Λ decay is observed for the first time, allowing for the measurement | A 0 ( Ξ 0 b → J / ψ Λ ) / A 1 / 2 ( Ξ 0 b → J / ψ Ξ 0 ) | = 0.37 ± 0.06 ± 0.02 , where the uncertainties are statistical and systematic, respectively