Angular analysis of $D^0 \to \pi^+\pi^-\mu^+\mu^-$ and $D^0 \to K^+K^-\mu^+\mu^-$ decays and search for $CP$ violation

TL;DR

This paper presents the first comprehensive angular analysis and updated $CP$ asymmetry measurements for specific $D^0$ meson decays involving muons, using extensive LHCb data, confirming Standard Model predictions and $CP$ symmetry.

Contribution

It provides the first full angular analysis and precise $CP$ asymmetry measurements for these decay modes, utilizing a large dataset from the LHCb experiment.

Findings

Results are consistent with Standard Model expectations.

No evidence of $CP$ violation observed.

Angular observables align with theoretical predictions.

Abstract

The first full angular analysis and an updated measurement of the decay-rate $CP$ asymmetry of the $D^0 \to \pi^+\pi^-\mu^+\mu^-$ and $D^0 \to K^+K^-\mu^+\mu^-$ decays are reported. The analysis uses proton-proton collision data collected with the LHCb detector at centre-of-mass energies of 7, 8 and 13 TeV. The data set corresponds to an integrated luminosity of 9 fb$^{-1}$. The full set of $CP$-averaged angular observables and their $CP$ asymmetries are measured as a function of the dimuon invariant mass. The results are consistent with expectations from the standard model and with $CP$ symmetry.