Re-opening dark matter windows compatible with a diphoton excess

Abstract

We investigate a simple setup in which an excess in the di-photon invariant mass distribution around 750 GeV, as seen by the ATLAS and CMS collaborations, is originated through a pair of collimated photon pairs. In this framework a scalar state s decays into two light pseudo-Goldstone bosons a, each of which subsequently decays into a pair of collimated photons which are misidentified as a single photon. In a minimal context of spontaneous symmetry breaking, we show that coupling a complex scalar field Φ = (s + ia)/ √ 2 to a fermionic dark matter candidate χ, also responsible for generating its mass, allows for the correct relic density in a large region of the parameter space, while not being excluded by the direct or indirect detection experiments. Moreover, the correct relic abundance can naturally co-exist with a relatively large width for the resonant field s.

The waning of the WIMP? A review of models, searches, and constraints

“…(77). In this kind of setup it is rather natural to identify the pseudoscalar component with a pseudo-Goldstone boson associated to a U (1) global symmetry carried by the complex scalar Φ and then assumes that m a m S [298][299][300]. We further assume that after the EWSB it is possible to write interaction terms of the fields S and a both with the SM fermions and a fermionic DM candidate as follows:…”

“…As pointed out in Refs. [299,302,303] the annihilation into Sa can lead to box shaped gamma-ray signals which could be probed in the near future by CTA. However, our choice for m a , implies a too suppressed decay branching ratio for a → γ γ process.…”

Precision tools and models to narrow in on the 750 GeV diphoton resonance

“…To keep all scalar masses positive, it is necessary to choose a rather large B E as well. Therefore, we are going to choose always 28) in our numerical study to circumvent tachyonic scalars.…”

Diphotons at the Z-pole in models of the 750 GeV resonance decaying to axion-like particles

“…We consider a scenario in which this field has a renormalizable potential invariant under a discrete symmetry Φ → −Φ, but breaking explicitly an U(1) a symmetry only through quadratic terms δm 2 [Φ 2 +(Φ * ) 2 ]. This potential was proposed recently in [43] as part of a model of the 750 GeV resonance which also communicates with a dark sector. We also assumed that the interaction between Φ and the SM is negligible, implying that there is no significant mixing of S with the SM Higgs boson, so the potential is…”

“…We take R γγ = 1 as in ref. [43], i.e., the ALP contribution accounts for the entire diphoton signal. In figure 7 we show, in the left panel, the 95% CL allowed region in the √ λ Φ k BB vs. m a plane in the wide scenario and, in the right panel, the points on the k GG vs. λ Φ plane which explain the diphoton rate for fixed widths Γ.…”