Item

Abstract

It is well-known that the determination of indirect CP-violation in models
with highly mixed and unstable gauge-singlet neutrinos requires a careful
analysis of the matrix of propagators in the vicinity of its poles. In this
paper, in a system with an arbitrary number of unstable mixed Majorana or Dirac
particles, a simple prescription is given for obtaining, roughly speaking,
"square-rooted residues" of propagators, i.e. for obtaining the matrices
$\zeta^{a}_{\ b}$ that (in a special case of stable particles) together with
the ordinary $u$ and $v$ spinors convert the amputated Green's functions in the
$\overline{{\rm MS}}$ scheme (or any other scheme for that matter) into the
$S$-matrix elements. Corresponding prescription for the scalar case is provided
as well.