CP violation analysis of $D^0\to M^0 K \to M^0(\pi^\pm \ell^\mp \nu)$

TL;DR

This paper investigates CP violation in a specific charm meson decay process, finding that interference effects dominate and could be experimentally measurable without flavor tagging, with potential implications for new physics detection.

Contribution

It introduces a novel analysis of CP violation in cascade $D^0$ decays, highlighting the dominance of interference effects and proposing an experimentally feasible measurement method.

Findings

CP violation peaks at about 5 x 10^{-3} due to interference.

CP violation in semileptonic channels is 10-100 times larger than in non-leptonic channels.

Proposed measurement method avoids flavor tagging, simplifying experimental detection.

Abstract

CP violation in the charm sector is highly sensitive to new physics due to its small predicted value within the standard model. By this work, we investigated the CP violation in the cascade decay process $D^0(t_1) \to \pi^0 K(t_2) \to \pi^0(\pi^\pm \ell^\mp \nu)$. Our results indicate that the CP violation induced by the interference of unmixed $D$-meson decay amplitudes dominates, with a peak value reaching $5 \times 10^{-3}$. This is one order of magnitude larger than the sub-leading contribution, namely the double-mixing CP violation. Furthermore, the CP violation in the decay channel with the semileptonic final state $\pi^- \ell^+ \nu_\ell$ is one to two orders of magnitude larger than that in the channel with $ \pi^+ \ell^- \bar{\nu}_\ell$. We propose that the CP asymmetry of the combined two decay channels can be measured experimentally. The resulting value is approximately half of the CP violation observed in the $\pi^- \ell^+ \nu_\ell$ channel, with the dominant contribution still reaching the order of $10^{-3}$. This approach offers the advantage of eliminating the need for flavor tagging of the initial $D$ meson, thereby avoiding associated efficiency losses.