Indirect CP violation in the B-system

We show that, contrary to the flavour mixing amplitude q/p, both Re(epsilon) and Im(epsilon) are observable quantities, where epsilon is the phase-convention-independent CP mixing. We consider semileptonic B-d decays from a CP tag and build appropriate time-dependent asymmetries to separate out Re(epsilon) and Im(epsilon). "Indirect" CP violation would have in Im(epsilon)/(1 + \epsilon\(2)) its most prominent manifestation in the B-system, with expected values in the standard model ranging from -0.37 to -0.18. This quantity is controlled by a new observable phase: the relative one between the CP-violating and CP-conserving parts of the effective hamiltonian. For time-integrated rates we point out a Delta Gamma --> Sigma Gamma transmutation which operates in the perturbative CP mixing. (C) 1998 Elsevier Science B.V.