title: Confronting dark matter with the diphoton excess from a parent resonance decay.
abstract: A diphoton excess with an invariant mass of about 750 GeV has been recently reported by both ATLAS and CMS experiments at LHC. While the simplest interpretation requires the resonant production of a 750 GeV (pseudo)scalar, here we consider an alternative setup, with an additional heavy parent particle which decays into a pair of 750 GeV resonances. This configuration improves the agreement between the 8 and 13 TeV data. Moreover, we include a dark matter candidate in the form of a Majorana fermion which interacts through the 750 GeV portal. The invisible decays of the light resonance help to suppress additional decay channels into Standard Model particles in association with the diphoton signal. We realise our hierarchical framework in the context of an effective theory, and we analyse the diphoton signal as well as the consistency with other LHC searches. We finally address the interplay of the LHC results with the dark matter phenomenology, namely the compatibility with the relic density abundance and the indirect detection bounds.
authors.affiliation: Instituto de Física Teórica UAM/CSIC, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain ; Departamento de Física Teórica, Universidad Autónoma de Madrid, 28049 Madrid, Spain.
authors.forename: Valentina
authors.initials: V
authors.lastname: De Romeri
authors.affiliation: Instituto de Física Teórica UAM/CSIC, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain.
authors.forename: Jong Soo
authors.initials: JS
authors.lastname: Kim
authors.affiliation: Instituto de Física Teórica UAM/CSIC, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain ; Departamento de Física Teórica, Universidad Autónoma de Madrid, 28049 Madrid, Spain.
authors.forename: Víctor
authors.initials: V
authors.lastname: Martín-Lozano
authors.affiliation: Instituto de Física Teórica UAM/CSIC, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain ; Institute of Theoretical Physics, University of Warsaw, 02093 Warsaw, Poland.
authors.forename: Krzysztof
authors.initials: K
authors.lastname: Rolbiecki
authors.affiliation: Instituto de Física Corpuscular, IFIC/CSIC, Valencia, Spain.
authors.forename: Roberto Ruiz
authors.initials: RR
authors.lastname: de Austri