Radiative corrections to sfermion mass splittings.

We study the one-loop radiative corrections to the SU(2) breaking mass splittings between sfermions in SU(2) doublets in the Minimal Supersymmetric Standard Model. At tree-level, the differences of mass squared m f̃1L −m f̃2L of SU(2) doublet sfermions (f̃1, f̃2)L in the first two generations are determined by tanβ, and are universal to sleptons and squarks. The radiative correction, however, breaks this relation. The typical deviation from the universality between sleptons and squarks is within ±0.05 in terms of the “effective cos 2β”. We also study the SUSY parameter dependence of the deviation. For very heavy sfermions, the relative corrections become large.