Measurement of the $D^0 \to K^-\pi^+e^+e^-$ branching fraction and search for $D^0 \to \pi^+\pi^-e^+e^-$ and $D^0 \to K^+K^-e^+e^-$ decays at BelleAdachi, Ichiro (Avtor) Borah, Jyotirmoi (Avtor) Bračko, Marko (Avtor) Korpar, Samo (Avtor) Križan, Peter (Avtor) Lozar, Andrej (Avtor) Mrvar, Manca (Avtor) Pestotnik, Rok (Avtor) Podobnik, Tomaž (Avtor) Prudiiev, Ihor (Avtor) Šantelj, Luka (Avtor) Starič, Marko (Avtor) Zhukova, Valentina (Avtor) physics of elementary particlesexperimental physicsmeson decaysWe present a study of the rare charm meson decays $D^0 \to K^+K^-e^+e^-, \pi^+\pi^-e^+e^-$, and $K^-\pi^+e^+e^-$ using a 942 fb$^{-1}$ dataset collected by the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider. We identify $D^0$ candidates via the charge of the pion from $D^{\ast +} \to D^0\pi^+$ decays and normalize the branching fractions to $D^0 \to K^-\pi^+\pi^-\pi^+$ decays. The branching fraction for decay $D^0 \to K^-\pi^+e^+e^-$ is measured to be (39.6 $\pm$ 4.5 (stat) $\pm$ 2.9 (syst))×10$^{-7}$, with the dielectron mass in the $\rho/\omega$ mass region 675 < $m_{ee}$ < 875  MeV/c$^2$. We also search for $D^0 \to h^-h^{(\prime)+}e^+e^-(h^{(\prime)}=K, \pi)$ decays with the dielectron mass near the $\eta$ and $\phi$ resonances, and away from these resonances for the $K^+K^-e^+e^-$ and $\pi^+\pi^-e^+e^-$ modes. For these modes, we find no significant signals and set 90% confidence level upper limits on their branching fractions at the $\mathcal{O}⁡(10^{-7})$ level.20252026-01-30 11:10:28Članek v reviji178835UDK: 539.1ISSN pri članku: 2470-0010DOI: 10.1103/mkx8-cl23COBISS_ID: 266652931sl