Upper limit on the nu(tau) mass from tau->3h nu(tau) decays

A new technique has been used to determine a limit on the nu tau mass using Z(0) --> tau(+)tau(-) events selected from 140 pb(-1) of data collected with the OPAL detector at LEP during the period 1990-1994. Using Z(0) --> tau(+)tau(-) events in which both tau-leptons decay to three charged particles, a novel likelihood analysis is applied to the 2-dimensional distribution of missing mass squared and missing energy, from which we obtain a limit of M nu(tau) 5 pi nu(tau) decays, we obtain the new 95% confidence level limit of M nu(tau) < 29.9 MeV.