Eur. Phys. J. C (2012) 72: 1872
https://doi.org/10.1140/epjc/s10052-012-1872-x

Regular Article - Theoretical Physics

K ⁺→π ⁺ π ⁰ e ⁺ e ⁻: a novel short-distance probe

¹ Dipartimento di Scienze Fisiche, Universitá di Napoli “Federico II”, Via Cintia, 80126, Naples, Italy
² INFN-Sezione di Napoli, Via Cintia, 80126, Naples, Italy
³ Departament de Física Teòrica and IFIC, Universitat de València-CSIC, Apartat de Correus 22085, 46071, València, Spain
⁴ Fakultät für Physik, Arnold Sommerfeld Center for Theoretical Physics, Ludwig-Maximilians-Universität München, 80333, Munich, Germany
⁵ Interdisciplinary Center for Theoretical Study and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui, 230026, China

^* e-mail: giancarlo.dambrosio@na.infn.it

Received: 22 December 2011
Published online: 31 January 2012

Abstract

We study the decay K ⁺→π ⁺ π ⁰ e ⁺ e ⁻, currently under analysis by the NA62 Collaboration at CERN. In particular, we provide a detailed analysis of the Dalitz plot for the long-distance, γ ^∗-mediated, contributions (Bremsstrahlung, direct emission and its interference). We also examine a set of asymmetries to isolate genuine short-distance effects. While we show that charge asymmetries are not required to test short distances, they provide the best environment for its detection. This constitutes by itself a strong motivation for NA62 to study K ⁻ decays in the future. We therefore provide a detailed study of different charge asymmetries and the corresponding estimated signals. Whenever possible, we make contact with the related processes K ⁺→π ⁺ π ⁰ γ and K _L →π ⁺ π ⁻ e ⁺ e ⁻ and discuss the advantages of K ⁺→π ⁺ π ⁰ e ⁺ e ⁻ over them.