Abstract
We provide an updated assessment of the power of the Cherenkov Telescope Array (CTA) to search for thermally produced dark matter at the TeV scale, via the associated gamma-ray signal from pair-annihilating dark matter particles in the region around the Galactic centre. We find that CTA will open a new window of discovery potential, significantly extending the range of robustly testable models given a standard cuspy profile of the dark matter density distribution. Importantly, even for a cored profile, the projected sensitivity of CTA will be sufficient to probe various well-motivated models of thermally produced dark matter at the TeV scale. This is due to CTA's unprecedented sensitivity, angular and energy resolutions, and the planned observational strategy. The survey of the inner Galaxy will cover a much larger region than corresponding previous observational campaigns with imaging atmospheric Cherenkov telescopes. CTA will map with unprecedented precision the large-scale diffuse emission in high-energy gamma rays, constituting a background for dark matter searches for which we adopt state-of-the-art models based on current data. Throughout our analysis, we use up-to-date event reconstruction Monte Carlo tools developed by the CTA consortium, and pay special attention to quantifying the level of instrumental systematic uncertainties, as well as background template systematic errors, required to probe thermally produced dark matter at these energies.
Highlights
The Cherenkov Telescope Array (CTA) [11] is close to entering the production phase and will be the world’s most sensitive gamma-ray telescope for a window of photon energies stretching more than three orders of magnitude, from a few tens of GeV to above 300 TeV, with an angular resolution that is better than any existing instrument observing at frequencies higher than the X-ray band
Given the imminent start of the telescope construction, and the strong science case outlined above, it is timely to move beyond existing analyses and provide more realistic sensitivity estimates to a DM signal from Galactic centre (GC) observations with CTA that fully take into account the current best estimates for the expected telescope characteristics as well as recent developments in understanding the Galactic diffuse emission (GDE) components in that region
A major motivation of this work is to study in detail the applicability of a full template fitting approach in the analysis of imaging atmospheric Cherenkov telescopes (IACT) data, a field which has traditionally mostly relied on separate ‘ON’ and ‘OFF’ regions to extract the DM signal and background, respectively
Summary
Even if increasingly pressured by lack of experimental evidence [6], weakly interacting massive particles (WIMPs) remain one of the best-motivated candidates [7]. Such particles with masses and couplings at the electroweak scale would be a compelling solution to the DM puzzle because their existence could point to a way of addressing the naturalness problems in the standard model of particle physics (SM), and because it would allow us to understand the presently measured DM abundance as a result of the standard thermal history of the Universe [8]. A major motivation of this work is to study in detail the applicability of a full template fitting approach in the analysis of imaging atmospheric Cherenkov telescopes (IACT) data, a field which has traditionally mostly relied on separate ‘ON’ and ‘OFF’ regions to extract the DM signal and background, respectively (though first studies indicate the advantages of moving beyond that method [14])
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