  It has been recently shown that a chiral molecule accelerates linearly along
a spatially uniform magnetic field, as a result of the parity-time symmetry
breaking induced in its QED self-interaction. In this work we extend this
result to fundamental particles which present EW self-interaction, in which
case parity is violated by the EW interaction itself. In particular, we
demonstrate that, in a spatially uniform and adiabatically time-varying
magnetic field, an unpolarized proton coupled to the leptonic vacuum acquires a
kinetic momentum antiparallel to the magnetic field, whereas virtual leptons
gain an equivalent $Casimir$ $momentum$ in the opposite direction. That
momentum is proportional to the magnetic field and to the square of Fermi's
constant. We prove that the kinetic energy of the proton is a magnetic energy
which forms part of its EW self-energy.
