Accidental scale-invariant Majorana dark matter in leptoquark-Higgs portals

Abstract

We study a classically accidental scale-invariant extension of the Standard Model (SM) containing three additional fields, a vector leptoquark ($ V_{\mu} $), a real scalar ($ \phi $), and a neutral Majorana fermion ($ \chi $) as a dark matter (DM) candidate. The scalar $ \phi $ (scalon) and Majorana fermion $ \chi $ are both singlets under the SM gauge group, while $ V_{\mu} $ has (\textbf{3}, \textbf{1}, 2/3) quantum numbers under the $ SU(3)_{c} \times SU(2)_{L} \times U(1)_{Y} $. The Majorana DM couples to the SM sector via both Higgs and leptoquark portals. We perform a scan over the independent parameters to determine the viable parameter space consistent with the Planck data for DM relic density, and with the PandaX-II and LUX direct detection limits for the spin-independent (SI) and spin-dependent (SD) DM-nucleon cross section. The model generally evades indirect detection constraints while being consistent with collider data.