Diphoton excess through dark mediators

Chien Yi Chen, Michel Lefebvre, Maxim Pospelov, Yi Ming Zhong

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


Abstract: Preliminary ATLAS and CMS results from the first 13 TeV LHC run have encountered an intriguing excess of events in the diphoton channel around the invariant mass of 750 GeV. We investigate a possibility that the current excess is due to a heavy resonance decaying to light metastable states, which in turn give displaced decays to very highly collimated e+e pairs. Such decays may pass the photon selection criteria, and successfully mimic the diphoton events, especially at low counts. We investigate two classes of such models, characterized by the following underlying production and decay chains: gg → S → AA → (e+e)(e+e) and qq¯→Z′→sa→(e+e−)(e+e−), where at the first step a heavy scalar, S, or vector, Z, resonances are produced that decay to light metastable vectors, A, or (pseudo-)scalars, s and a. Setting the parameters of the models to explain the existing excess, and taking the ATLAS detector geometry into account, we marginalize over the properties of heavy resonances in order to derive the expected lifetimes and couplings of metastable light resonances. We observe that in the case of A, the suggested range of masses and mixing angles ϵ is within reach of several new-generation intensity frontier experiments.

Original languageEnglish (US)
Article number63
JournalJournal of High Energy Physics
Issue number7
StatePublished - Jul 1 2016
Externally publishedYes


  • Beyond Standard Model
  • Higgs Physics

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