A bag model calculation of the electroweaks?d? loop

Abstract

We consider the CP-conserving electroweak transitionss→dγ. To include confinement effects below the charm scale, we perform the loop calculations within the bag model. According to the calculation, confinement effects are rather important and give amplitudes three orders of magnitude bigger than that obtained from the free quark loop, which is ∼eG F m c 2 /M W 2 . Moreover, the amplitude is of the same order of magintude as the perturbative two loop amplitude ∼eG F α s ln(m c /μ). For the decay modeΩ−→γΞ− we obtain a branching ratio 4.4·10−5. Other radiative decays of strange baryons are known to be dominated by pole diagrams.