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 Belle

Adachi, Ichiro (author), Borah, Jyotirmoi (author), Bračko, Marko (author), Korpar, Samo (author), Križan, Peter (author), Lozar, Andrej (author), Mrvar, Manca (author), Pestotnik, Rok (author), Podobnik, Tomaž (author), Prudiiev, Ihor (author), Šantelj, Luka (author), Starič, Marko (author), Zhukova, Valentina (author)

We 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.

• Language: English
• Keywords: physics of elementary particles, experimental physics, meson decays
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FMF - Faculty of Mathematics and Physics
• Publication status: Published
• Publication version: Version of Record
• Year: 2025
• Number of pages: Str. L071101-1-L071101-8
• Numbering: Vol. 112, iss. 7
• PID: 20.500.12556/RUL-178835
• UDC: 539.1
• ISSN on article: 2470-0010
• DOI: 10.1103/mkx8-cl23
• COBISS.SI-ID: 266652931
• Publication date in RUL: 30.01.2026

Record is a part of a journal

• Title: Physical review
• Shortened title: Phys. rev., D
• Publisher: American Physical Society
• ISSN: 2470-0010
• COBISS.SI-ID: 29757223

Licences

• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.

Secondary language

• Language: Slovenian
• Keywords: fizika osnovnih delcev, eksperimentalna fizika, razpadi mezonov

Projects

• Funder: ARIS - Slovenian Research and Innovation Agency
• Project number: J1-50010
• Name: Eksperimentalno preverjanje leptonske univerzalnosti in izboljšava metod identifikacije delcev pri eksperimentu Belle II

• Funder: ARIS - Slovenian Research and Innovation Agency
• Project number: P1-0135
• Name: Eksperimentalna fizika osnovnih delcev