Slepton Production as a Probe of the Squark Mass Scale

We investigate an important radiative correction to the slepton and chargino production processes. We consider a supersymmetric spectrum with a large splitting between the squark and slepton masses. In this case, in the effective theory below the squark mass threshold, the supersymmetric Slavnov-Taylor identities which enforce the equality of the gauge and gaugino couplings are violated. The gaugino propagators receive potentially large corrections due to virtual quark/squark loop effects. We compute the full one-loop (s)quark corrected slepton production cross-sections. The t-channel one-loop scattering amplitudes are factorized into an effective chargino/neutralino mass matrix and an effective fermion-sfermion-gaugino coupling. The difference between the effective gaugino coupling and the gauge coupling is proportional to log(Msq/msl) in the large squark mass limit. We find that the one-loop corrected slepton production cross-sections can depend on the squark mass strongly, up to 9% times log(Msq/msl). We investigate the squark mass sensitivity of the slepton cross-section measurements at a future linear collider. For sneutrino production accessible at sqrt{s}= 500 GeV there can be sensitivity to squark masses at or larger than 1 TeV.