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 $m_{\tilde{f}_{1L}}^2-m_{\tilde{f}_{2L}}^2$ of SU(2) doublet sfermions $(\tilde{f}_1, \tilde{f}_2)_L$ in the first two generations are determined by $\tan\beta$, 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 $\pm0.05$ in terms of the ``effective $\cos2\beta$''. We also study the SUSY parameter dependence of the deviation. For very heavy sfermions, the relative corrections become large.