  The scattering of a charged fermion from an electroweak string is studied.
Owing to an amplification of the wave function at the core radius, the cross
sections for helicity flip processes can be largely enhanced. For $0 <\sin^2
\theta_w < 1/2 $ (where $\theta_w$ is the Weinberg angle), $\omega \sim k \sim
m_e$ and $kR \ll 1$, we show that the helicity flip differential cross section
for electrons is of the order $m_e^{-1}$ and is independent of angle. We
compare our results with those obtained in calculations of rates for baryon
number violating processes in the core of a cosmic string. In that case, while
the enhancement is a general phenomenon, its actual magnitude is extremely
sensitive to the fractional flux carried by the string core. Apart from showing
the existence of a similar enhancement effect for non-topological strings, our
results indicate that in some models the magnitude of enhancement can be
rendered much less sensitive to the value of the parameters in the theories.
Scattering of particles off semi-local strings and axion strings are also
considered.
