Is it possible for the Mandelstam variable $t$ to reach positive values in the quasielastic charged current neutrino-neutron scattering?: $$\nu_{\mu} + n \rightarrow \mu^- + p$$
(don't assume that proton and neutron have the same mass.)
I found positive values in my calculations. I always thought that $t$ would always be negative for such processes, and this result surprises me. If my calculations are correct, does this positive region of $t$ have any significance?
There is a plot of my result for a few neutrino energies. At a neutrino energy bigger than approx $2.2$ GeV, positive values of $t$ appear for small scattering angles:
