Reanalysis of CP Violation in K_L -> pi^+ pi^- gamma

Abstract

We present a reanalysis of direct CP violation in the decay K_L -> pi^+ pi^- gamma. We point out an existing discrepancy between the theoretical and experimental definitions of epsilon'_{+-gamma}. Adopting the experimental definition of epsilon'_{+-gamma}, we estimate that epsilon'_{+-gamma}/epsilon could be as large as a few times 10^{-4} both within the standard model and beyond. We discuss these estimates in detail and we also show how a judicious choice of E_gamma cuts can increase the sensitivity of the observable epsilon'_{+-\gamma} to the underlying CP violation.