Isospin amplitudes in Λ0b→J/ψΛ(Σ0) and Ξ0b→J/ψΞ0(Λ) 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 pp collisions at center of mass energies of 7, 8, and 13 TeV. The isospin amplitude ratio |A[subscript 1](Λ[superscript 0 over subscript b]→J/ψΣ[superscript 0])/A[subscript 0](Λ[superscript 0 over subscript b]→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 Ξ[superscript 0 over subscript b]→J/ψΛ decay is observed for the first time, allowing for the measurement |A[subscript 0](Ξ[superscript 0 over subscript b]→J/ψΛ)/A[subscript 1/2](Ξ[superscript 0 over subscript b]→J/ψΞ[superscript 0])|=0.37±0.06±0.02, where the uncertainties are statistical and systematic, respectively.