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 -baryon decays, using data corresponding to an integrated luminosity of 8.5 fb, collected with the LHCb detector in collisions at center of mass energies of 7, 8 and 13 TeV. The isospin amplitude ratio , where the subscript on indicates the final-state isospin, is measured to be less than at 95% confidence level. The Cabibbo suppressed decay is observed for the first time, allowing for the measurement , where the uncertainties are statistical and systematic, respectively.
Alessandro Mapelli, Radoslav Marchevski, Alina Kleimenova