  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 type II supernovae.
