Parity-violating vector-meson-exchange potential and asymptotically free theories

Abstract

The parity-violating vector-meson-exchange internucleon potential has been calculated for several gauge-invariant weak-interaction theories. Assuming that strong interactions are described by an asymptotically free field theory, vertex corrections have been calculated up to all orders in strong couplings. Potentials have been deduced by a method which is more general than the standard factorizable approximation. The potentials thus obtained are contrasted with existing experimental data and theoretical analyses for circular $\gamma$ polarization in the $n+p\to d+\gamma$ reaction and for the parity-forbidden $\alpha$ decay of ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$. In the weak-interaction models studied in this work the isotensor part of the weak potential is hindered. The enhancement of the isoscalar part of the weak potential does not seem sufficiently large to upset the apparent agreement between experiment and theory in the case of $\alpha$ decay. There are strong indications that circular $\gamma$ polarization measured in the $n+p\to d+\gamma$ reaction cannot be easily accounted for by any of the weak-interaction models studied. Existing experimental data call for either a new weak-interaction model or a new insight into the nature of nuclear forces.