Distinctive signals of spontaneous R-parity breaking at LEP-II

We consider the signals of pair-produced charginos in an e+e− collider, in a scenario where R-parity is spontaneously broken. The possibility of lepton-chargino mixing, together with the presence of a Majoron, opens up the two-body decay channel of a chargino into a tau and a Majoron. We have studied the regions where this is the dominant decay of a chargino, and have shown that over a large region of the parameter space the ensuing signals, namely tau-pairs with missing-pT, may rise well above standard model backgrounds at LEP-II. Such signals can also enable one to distinguish between spontaneous and explicit R-parity breaking.