Abstract
Axino as the superpartner of axion that solves the strong CP problem can be a good candidate of dark matter. Inspired by the 3.5 keV X-ray line signal found to be originated from galaxy clusters and Andromeda galaxy, we study axino models with R-parity violations, and point out that axino dark matter with trilinear R-parity violations is an attractive scenario that reproduces the X-ray line. The Peccei-Quinn scale is required to be fa ∼ \U0001d4aa(109–1011) GeV for trilinear R-parity violating couplings λ ∼ \U0001d4aa(10−3–10−1) in order to explain the line signal. Moreover, the right-handed stau is predicted to be light, i.e. ∼ \U0001d4aa(100) GeV, and thus can be looked for at the LHC. Cosmological aspects of the model are also discussed in this study.
Highlights
Axion is a product of the Peccei-Quinn (PQ) mechanism introduced to solve the strong CP problem [1]
Axino is neutral and if it is the lightest supersymmetric particle (LSP), it can be a candidate of dark matter (DM) which makes up 27 % of the energy density of the universe [2]
The X-ray line observations have generated interests in interpreting the line signal with axino DM [5, 6]. 1 These studies have been focusing on bilinear R-parity violating (RPV), where axino decays into a photon and a neutrino via gaugino mixing with neutrinos
Summary
Axion is a product of the Peccei-Quinn (PQ) mechanism introduced to solve the strong CP problem [1]. 1 These studies have been focusing on bilinear RPV, where axino decays into a photon and a neutrino via gaugino mixing with neutrinos It is shown in [5] that the PQ scale, fa needs to be ∼ 108 − 109 GeV in order to reproduce the X-ray line. As will be shown fa can be made larger than 109GeV, evading various astrophysical bounds on axion while being consistent with the X-ray line from axino DM decay. Within this framework, sfermions are relatively light, and RPV couplings are predicted to be large, making this model testable using colliders. We describe cosmological and phenomenological consequences and implications of our model
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