Probing slepton mass nonuniversality at e⁺e^- linear colliders

There are many models with nonuniversal soft SUSY breaking sfermion mass parameters at the grand unification scale. Even in the MSUGRA model scalar mass unification might occur at a scale closer to Mpianck' and renormalization effects would cause a mass splitting at MGVT. We identify an experimentally measurable quantity A that correlates strongly with Sm2-m- (MGUT)-in- (MG(jT), and which can be measured at electron-positron colliders provided both selectrons and the chargino are kinemattcally accessible. We show that if these sparticle masses can be measured with a precision of 1% at a 500 GeV linear collider, the resulting precision in the determination of A may allow experiments to distinguish between scalar mass unification at the GUT scale from the corresponding unification at Q~Mpianck Experimental determination of A would also provide a distinction between the MSUGRA model and the recently proposed gaugino-mediation model. Moreover, a measurement of A (or a related quantity A') would allow for a direct determination of Sm2.