The KARMEN anomaly, light neutralinos and supernova SN1987A

The KARMEN experiment observes a time anomaly in events induced by pion decay at rest. This anomaly can be ascribed to the production of a new weakly interacting particle X with mass m_X\sim 34 MeV. We show that a recently proposed identification of the X particle with the lightest neutralino \chi in the frame work of the MSSM with broken R parity is in contradiction to optical observations of SN 1987A.