A 'known' CP asymmetry in τ decays

We point out that dynamics known from the observed CP violation in K-L -> pi(-/+)l +/- v coupled with CPT invariance generate a CP asymmetry of 3.3 x 10(-3) in tau(+/-) -> vKS pi(+/-) -> v[pi(+) pi(-)](K)(pi +/-). The equality of the tau(+) and tau(-) lifetimes required by CPT symmetry is restored in an intriguing way as the combined effect of long-lived K -> pi(+) pi(-) as well as contributions from K-L-K-S interference. While little new can be learnt from this CP asymmetry, the latter has to be accounted for, since CP asymmetries in T -> vK pi channels are prime candidates for revealing the intervention of New Physics. This 'known' CP asymmetry provides a very useful calibration point in such searches. It also provides a test of CPT symmetry (as well as the Delta Q = Delta S selection rule). (c) 2005 Elsevier B.V. All rights reserved.