Updated measurement of decay-time-dependent CP asymmetries in $D^0 \to K^+K^-$ and $D^0 \to \pi^+\pi^-$ decays

TL;DR

This paper reports a precise measurement of decay-time-dependent CP asymmetries in D0 meson decays to K+K- and pi+pi- using LHCb data, finding results consistent with CP symmetry and improving previous constraints.

Contribution

The study provides updated measurements of CP asymmetries in D0 decays with larger data sample and refined analysis, enhancing the sensitivity of previous results.

Findings

Measured CP asymmetries consistent with zero

Results improve constraints on CP violation in charm decays

Combined results with previous data reduce uncertainties

Abstract

A search for decay-time-dependent charge-parity ($CP$) asymmetry in $D^0 \to K^+K^-$ and $D^0 \to \pi^+\pi^-$ decays is performed at the LHCb experiment using proton-proton collision data recorded at a center-of-mass energy of 13TeV, and corresponding to an integrated luminosity of 5.4fb$^{-1}$. The $D^0$ mesons are required to originate from semileptonic decays of $b$ hadrons, such that the charge of the muon identifies the flavor of the neutral $D$ meson at production. The asymmetries in the effective decay widths of $D^0$ and $\overline{D}^0$ mesons are determined to be $A_{\Gamma}(K^+K^-) = ( -4.3 \pm 3.6 \pm 0.5 )\times 10^{-4}$ and $A_{\Gamma}(\pi^+\pi^-) = ( 2.2 \pm 7.0 \pm 0.8)\times 10^{-4}$, where the uncertainties are statistical and systematic, respectively. The results are consistent with $CP$ symmetry and, when combined with previous LHCb results, yield $A_{\Gamma}(K^+K^-) = ( -4.4 \pm 2.3 \pm 0.6 )\times 10^{-4}$ and $A_{\Gamma}(\pi^+\pi^-) = ( 2.5 \pm 4.3 \pm 0.7)\times 10^{-4}$.