Abstract
We show that the Cherenkov Telescope Array (CTA) can realistically challenge the Inert Doublet Model, one of the simplest and best known models of dark matter. Specifically, the CTA may exclude its heavy regime up to dark matter masses of 800 GeV and probe a large fraction of the remaining viable parameter space at even higher masses. Two features of the Inert Doublet Model make it particularly suitable for CTA searches. First, the dark matter mass (in the heavy regime) must be larger than 500 GeV. Second, the dark matter annihilation cross section, σ v, is always larger than the thermal one, reaching values as high as 10−25 cm3s−1. This higher value of σv is the result of the unavoidable coannihilation effects that determine the relic density via thermal freeze-out in the early Universe. We find that with 100 hours of Galactic Center exposure, CTA's expected limit widely surpasses, even after the inclusion of systematic errors, current and projected bounds from Fermi-LAT and HESS on this model.
Highlights
The indirect detection of dark matter is one of the most promising alternatives to observe and identify the dark matter particle [1]
A major step forward in gamma-ray astrophysics will be the construction of the Cherenkov Telescope Array (CTA) [5, 6], which should start operating in 2019 and whose sensitivity is expected to be significantly better than currently operating Imaging Air Cherenkov Telescope (IACT)
We demonstrated that the CTA can realistically probe the viable parameter space of the Inert Doublet Model, one of the simplest and best known models of dark matter
Summary
The indirect detection of dark matter is one of the most promising alternatives to observe and identify the dark matter particle [1]. Gamma-ray observations by Fermi-LAT currently provide the most stringent bounds on the dark matter annihilation rate [3] They exclude a thermal cross section (σv = 3 × 10−26cm3s−1) up to dark matter masses of order 100 GeV. Even for a Einasto profile, the CTA will be able to significantly probe the viable parameter space of one of the simplest and best known models of dark matter, the Inert Doublet Model (IDM) [19,20,21] In this model, the Standard Model is extended with a second Higgs doublet that is odd under a Z2 symmetry, ensuring the stability of the dark matter particle –the lightest neutral component of the doublet. Relative Contribution to Relic Density density via freeze-out in the early Universe These coannihilation effects are an unavoidable feature of this model and imply dark matter annihilation rates up to three times larger than the thermal one. 0.3% systematics are achieved, as illustrated in figure 1
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