2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/45474Study of the production and decay of scalar tau lepton ($\st$) at future $\epem$ colliders helps to determine the value of $\tanβ$ through the measurement of the polarization of $τ$ lepton that arises from $\st$ decay. Key maps of the parameter space of MSSM are presented. (talk presented at the fifth workshop on Japan Linear Collider(JLC) at Kawatabi, Feb 16-17.)9 pages, 6 figures. Complete version with figures available at ftp://ftp.kek.jp/kek/preprints/TH/TH-435High Energy Physics - Phenomenologytext