Parity violating asymmetry in inclusive $\pi^0$ or $\pi^+$ meson production
by longitudinally polarized electrons on unpolarized protons, is
calculated as a function of the momentum transfer square $k^2$ and the total
energy $W$ of the $\pi N$-system. We
consider the $\Delta$-contribution in the s-channel, the standard
Born contributions and the vector mesons ($\rho$ and $\omega$) exchanges in
the $t-$channel. The parity-odd term is the sum of
two contributions. The main term (found to be linear in $k^2$) comes from the
isovector component of the electromagnetic currents. It is model
independent and can be calculated exactly in terms of fundamental constants.
The second term is isoscalar in nature. Near threshold and in the
$\Delta$-region, it is found to be much
smaller (in absolute value) than the isovector one. |
