Isospin Amplitudes in Lambda(0)(b) -> J/psi Lambda (Sigma(0)) and Xi(0)(b)-> J/psi Xi(0) (Lambda) Decays

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 pp collisions at center of mass energies of 7, 8, and 13 TeV. The isospin amplitude ratio |A1(Λb0→J/ψς0)/A0(Λb0→J/ψΛ)|, 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 Ξb0→J/ψΛ decay is observed for the first time, allowing for the measurement |A0(Ξb0→J/ψΛ)/A1/2(Ξb0→J/ψΞ0)|=0.37±0.06±0.02, where the uncertainties are statistical and systematic, respectively.