Search for the Rare Charm Meson Decays D0 → h −h( ′ )+e +e −

Abstract

A search of the rare charm meson decays D⁰ → h ⁻h ^{( ′ )+}e ⁺e ⁻, where hh^(′) = KK, ππ, Kπ is performed using a 942 fb⁻¹ data set collected by the Belle detector at the KEKB asymmetric e ⁺e ⁻ collider. The preliminary results are approved by the Belle (II) collaborations. The branching fraction of the decay D⁰ → K⁻π ⁺e ⁺e ⁻ is measured to be (39.6 ± 4.5 (stat) ± 2.9 (syst)) × 10⁻⁷ , in the ρ/ω mass region 675 < m_ee < 875 MeV/c² . The branching fraction upper limits are set in the range [2.3, 7.7] × 10⁻⁷ for the decays D⁰ → h ⁻h ^{( ′ )+}e ⁺e ⁻ with ee in different mass regions. No beyond standard model contribution is found above than the background predictions. The measured D⁰ → h ⁻h ^{( ′ )+}e ⁺e ⁻ branching fraction upper limits are the tightest to date.