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 sneutrino 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 neutrinoless double beta decay in R-p-conserving models, yielding constraints on (m) over tilde(M). Furthermore, a nonvanishing (m) over tilde(M) gives rise to new processes potentially observable at future lepton colliders. In view of the existing low-energy constraints, it will be very difficult, albeit not impossible, to find positive signals for electron sneutrinos. For muon and tau sneutrinos, a dedicated search for Majorana masses has much better prospects. However, high luminosities seem to be an essential requirement for all accelerator experiments.