Indirect $\boldsymbol{CP}$ Violation in $\boldsymbol{D^0 \rightarrow h^+ h^-}$ Decays at LHCb

TL;DR

This paper reports the most precise measurements to date of indirect CP violation in D0 decays to K+K- and pi+pi- using LHCb data, finding no evidence of CP violation and constraining new physics effects.

Contribution

First precise measurements of AΓ in D0→K+K- and π+π- decays from LHCb, providing stringent tests of CP violation beyond the Standard Model.

Findings

No evidence of CP violation observed.

Results are the most precise to date.

Constraints on new physics contributions.

Abstract

Indirect CP violation in the $D^0$ system can be probed by measuring the parameter $A_{\Gamma}$, defined as the CP asymmetry of the effective lifetime of the $D^0$ meson decaying to a CP eigenstate. This can be significantly enhanced beyond Standard Model predictions by new physics. Measurements of $A_{\Gamma}$ using $D^0 \rightarrow K^+K^-$ and $D^0\rightarrow \pi^+\pi^-$ decays reconstructed from pp collisions collected by the LHCb experiment, corresponding to an integrated luminosity of 1.0 fb$^{-1}$, are presented. The results are \begin{align*} A_{\Gamma} (\pi\pi) = (+0.33 \pm 1.06 \pm 0.14) \times 10^{-3},\quad A_{\Gamma} (KK) = (-0.35 \pm 0.62 \pm 0.12) \times 10^{-3}, \end{align*} where the uncertainties are statistical and systematic, respectively. These are the most precise measurements of their kind to date, and show no evidence of CP violation.