R-parity violation, sneutrino mixing phenomena and CP-violation in p bar p -> sneutrino -> l^+ l^- + X

The sneutrino resonance reactions p \bar p -> sneutrino -> l^+ l^- +X, for l=e,\mu,\tau, in the MSSM without R-parity are considered. We perform a cross-section analysis and show that present limits on some products of R-parity violating couplings in the sneutrino sector can be significantly improved in future upgraded Fermilab Tevatron runs. Furthermore, we introduce CP-violating and CP-conserving \tau-spin asymmetries which are generated already at the TREE-LEVEL in the reaction p \bar p -> sneutrino -> \tau^+ \tau^- +X if there is muon-sneutrino - \bar muon-sneutrino mixing and that vanish in the SM. We find, for example, that for muon-sneutrino masses in the range 150 GeV < m_{muon-sneutrino} < 450 GeV, these spin asymmetries reach ~ 20 - 30% and ~ 10% for mass splitting between the muon-sneutrino CP-odd and CP-even states at the level of \Delta m ~ \Gamma and \Delta m ~ \Gamma/4, respectively, where \Gamma is the muon-sneutrino width. Both the CP-violating and the CP-conserving spin asymmetries should be detectable in future Tevatron runs even for a heavy sneutrino with a mass < 500 GeV. If detected, such asymmetries - being proportional to the mass splitting between the CP-even and CP-odd sneutrino states - may serve as a strong indication for the existence of the sneutrino mixing phenomenon.