Classical spin contribution to the Tunnel Effect

Since the spin of real particles is of order of $\hbar$, it is difficult to distinguish in a quantum mechanical experiment involving spinning particles what part of the outcome is related to the spin contribution and what part is a pure quantum mechanical effect. We analyze in detail a classical model of a nonrelativistic spinning particle under the action of a potential barrier and compute numerically the crossing for different potentials. In this way it is shown that because of the spin structure there is a nonvanishing contribution to crossing for energies above a certain minimum value, even below the top of the potential barrier. Results are compared with the quantum tunnel effect.