CP Violation in Charm: a New Method

TL;DR

This paper introduces a novel method for analyzing time-dependent CP asymmetries in charm mesons using both correlated and uncorrelated $D^0$ mesons, enabling potential measurements of the charm unitarity triangle angle $eta_c$ and mixing phase with high precision.

Contribution

The paper presents the first method to analyze CP asymmetries in charm using both correlated and uncorrelated $D^0$ mesons, facilitating the measurement of $eta_c$ and mixing phases.

Findings

Super$B$ can measure $eta_{c,eff}$ with 1.3° precision.

LHCb can measure $eta_{c,eff}$ with 1.4° precision.

Super$B$ can measure $ heta_{MIX}$ with 1.3° precision.

Abstract

We propose for the first time a method to perform analysis of time-dependent CP asymmetries in charm by using both, correlated and un-correlated $D^0$ mesons. Here we consider the decay channels $D^0\to K^+ K^-$ and $D^0\to \pi^+ \pi^-$. The channel $D^0\to K^+ K^-$ will be used to measure the mixing phase, and the difference between the measured phase $D^0\to K^+ K^-$ and $D^0\to \pi^+ \pi^-$ will open the door to the first measurement of $\beta_c$, one of the angle of the charm unitarity triangle. Since in the standard model CP asymmetries in charm are expected to be small, any observation of large time dependent asymmetries or mismatch between predicted and observed value for $ \beta_c$ could signify new physics. We perform and show results of numerical analysis made considering Super$B$ running at charm threshold, Super$B$ running at $\Upsilon(4S)$ and LHCb and find that Super$B$ and LHCb will be able to measure $\beta_{c,eff}$ with a precision of $1.3^\circ$ and $1.4^\circ$ respectively. The same analysis shows that $\phi_{MIX}$ could be measured at Super$B$ with a precision of $1.3^\circ$.