2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/178953We consider the three--body decay stop_1 -> b tau+ tau-sneutrino and propose the asymmetry of the tau polarization perpendicular to the decay plane as a CP sensitive observable. We calculate this asymmetry in the Minimal Supersymmetric Standard Model taking the parameters mu and A_t complex. In the parameter domain where the decay stop_1 -> b tau+ tau-sneutrino is important this asymmetry can go up to 30%. We also estimate the event rates necessary to observe this asymmetry at 90% CL.LaTex, 9 pages, 3 figures, v2, improved treatment of transversal polarized taus, modified table, conclusions unchangedHigh Energy Physics - PhenomenologyHigh Energy Physics - Experimenttext