MASSES OF MAJORANA-LIKE SNEUTRINOS IN NEUTRINOLESS DOUBLE-BETA DECAY AND AT FUTURE COLLIDERS

It has recently been shown that, in the framework of weak-scale softly broken supersymmetry, the existence of a Majorana neutrino inevitably implies a finite (B - L)-violating ''Majorana'' mass (m) over tilde(M ) for scalar neutrinos. This leads to the splitting of the complex sne utrino field into two real fields separated in mass by (m) over tilde( 1)(2)-(m) over tilde(2)(2) = 2\(m) over tilde(M)(2). The existence of a finite Majorana sneutrino mass generates new contributions to neutri noless double beta decay in R-p-conserving models, yielding constraint s on (m) over tilde(M). Furthermore, a nonvanishing (m) over tilde(M) gives rise to new processes potentially observable at future lepton co lliders. In view of the existing low-energy constraints, it will be ve ry difficult, albeit not impossible, to find positive signals for elec tron sneutrinos. For muon and tau sneutrinos, a dedicated search for M ajorana masses has much better prospects. However, high luminosities s eem to be an essential requirement for all accelerator experiments.