Determination of the sensitivity of $\Lambda$ and $\Lambda^+_c$ electric dipole moments using a full angular analysis

Abstract

A search for a non-zero Electric Dipole Moment (EDM) of particles, which is a clear signal of a violation of CP symmetry, is one of the unique ways to discover physics beyond the Standard Model. In this paper, we discuss a method for determining the EDM of baryons from the full angular distribution of final particles in electron-positron pair annihilation processes. The question of how accurately the state-of-the-art experiments can determine EDM of $\Lambda$ and $\Lambda_c^+$ baryons is discussed in detail. Investigating the pseudo-statistics that corresponds to the BESIII experiment, the estimated sensitivity for $\Lambda$ EDM is obtained at the level of $10^{-18}$ $e\,$cm. The similar figure for the proposed Super Tau-Charm Facility (STCF) experiment is found to be of the order of $10^{-20}$ $e\,$cm. For the $\Lambda_c^+$ EDM, the calculated sensitivity for the STCF experiment is $10^{-16}$ $e\,$cm. The case of a polarized initial electron is considered separately as such an option is planned at the STCF experiment.