Decays of the lightest top squark

We analyze higher order decay modes of the lightest top squark $t_1$ in the minimal supersymmetric (SUSY) extension of the standard model (MSSM), where the lightest SUSY particle (LSP) is assumed to be the neutralino ${\chi }_1^0.$ For small $t_1$ masses accessible at CERN LEP2 and the Fermilab Tevatron, we show that the four-body decay mode into the LSP, a bottom quark and two massless fermions, $t_1\to b{\chi }_1^{0}f{f}^{\prime },$ can dominate in a wide range of the MSSM parameter space over the loop-induced decay into a charm quark and the LSP, $t_1\to c{\chi }_1^0.$ This result might affect the experimental searches on this particle, since only the later signal has been considered so far.