Search for the dark photon in B 0 → A′A′, A′ → e + e , μ + μ , and π + π decays at Belle

The Belle Collaboration

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We present a search for the dark photon A′ in the B0 → A′A′ decays, where A′ subsequently decays to e+e, μ+μ, and π+π. The search is performed by analyzing 772 × 106BB¯ events collected by the Belle detector at the KEKB e+e energy-asymmetric collider at the ϒ(4S) resonance. No signal is found in the dark photon mass range 0.01 GeV/c2 ≤ mA′ ≤ 2.62 GeV/c2, and we set upper limits of the branching fraction of B0 → A′A′ at the 90% confidence level. The products of branching fractions, ℬ(B0→A′A′)×ℬ(A′→e+e−)2 and ℬ(B0→A′A′)×ℬ(A′→μ+μ−)2, have limits of the order of 10−8 depending on the A′ mass. Furthermore, considering A′ decay rate to each pair of charged particles, the upper limits of ℬ (B→ A′ A′) are of the order of 10−8–10−5. From the upper limits of ℬ (B→ A′ A′) , we obtain the Higgs portal coupling for each assumed dark photon and dark Higgs mass. The Higgs portal couplings are of the order of 10−2–10−1 at mh′≃mB0 ± 40 MeV/c2 and 10−1–1 at mh′≃mB0 ± 3 GeV/c2. [Figure not available: see fulltext.]

Original languageEnglish
Article number191
JournalJournal of High Energy Physics
Issue number4
Publication statusPublished - 2021 Apr

Bibliographical note

Publisher Copyright:
© 2021, The Author(s).


  • B physics
  • Beyond Standard Model
  • Rare decay
  • e+-e- Experiments

ASJC Scopus subject areas

  • Nuclear and High Energy Physics


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