CP ASYMMETRIES INDUCED BY PARTICLE WIDTHS - APPLICATION TO TOP-QUARK DECAYS

An on-shell unstable particle produced in a tree-level process, such as W in t --> qW, induces a CP violating signal through its width. This effect arises from an Im(tree) x Re(loop) type of interference. Among t --> qq'qBAR processes (e.g., t --> bcbBAR) proceeding either through the tree-level t --> qW or the one-loop t --> q' + (vitual g) reactions, the CP asymmetry is largest for the case t --> dcdBAR and is of O(eta/lambda-2) in Wolfenstein's parametrization. The resulting effects are found to be small in the standard model, but are much larger than those obtained for radiative top-quark decays. We also briefly discuss B decays where such a mechanism may cause CP violation in, for example, b --> se + e-.