Mixed WIMP-axion dark matter

Abstract

We study the experimental constraints on a model of a two-component dark matter, consisting of the QCD axion, and a scalar particle, both contributing to the dark matter relic abundance of the Universe. The global Peccei-Quinn symmetry of the theory can be spontaneously broken down to a residual Z 2 symmetry, thereby identifying this scalar as a stable weakly interacting massive particle, i.e., a dark matter candidate, in addition to the axion. We perform a comprehensive study of the model using the latest data from dark matter direct and indirect detection experiments, as well as new physics searches at the Large Hadron Collider. We find that although the model is mostly constrained by the dark matter detection experiments, it is still viable around a small region of the parameter space where the scalar dark matter is half as heavy as the Standard Model Higgs. In this allowed region, the bounds from these experiments are evaded due to a cancellation mechanism in the dark matter-Higgs coupling. The collider search results, however, are shown to impose weak bounds on the model.

Top-philic Dark Matter in a Hybrid KSVZ axion framework

“…Interestingly such a null outcome in experimental searches can instead be an indication of a much richer dark sector, and the dark sector can possibly be composed of more than one component of DM. In recent times, there have been several proposals for a multicomponent dark matter [43][44][45][46][47][48][49][50][51][52][53][54][55][56] where the dark sector is made up of different DM components. For example, one can think of a scenario with WIMP-WIMP [43][44][45][46][47] dark matter candidates, WIMP-FIMP [48][49][50] dark matter candidates, FIMP-FIMP [51,52] dark matter candidates, WIMP-axion [53,54] dark matter candidates, etc.…”

“…In recent times, there have been several proposals for a multicomponent dark matter [43][44][45][46][47][48][49][50][51][52][53][54][55][56] where the dark sector is made up of different DM components. For example, one can think of a scenario with WIMP-WIMP [43][44][45][46][47] dark matter candidates, WIMP-FIMP [48][49][50] dark matter candidates, FIMP-FIMP [51,52] dark matter candidates, WIMP-axion [53,54] dark matter candidates, etc. In the present work, we aim to explore one such scenario where the dark sector constitutes a WIMP-type dark matter, and the QCD axion plays the role of second dark matter.…”

“…Note that our setup is similar to the one considered in [53,54] but with some crucial differences. For example, the present framework considers an up-type VLQ rather than a down-type VLQ, and it opens up a non-trivial possibility in collider analysis.…”

“…Current construction also aims to explore the possibility of DM effective annihilations (including the DM co-annihilation with the vector-like quark as well as the annihilation of the vectorlike quark to the SM particles) to the SM particles in obtaining the correct relic density of the scalar (WIMP) DM. Next, both [53,54] did not consider the VLQ's contribution to the DM-nucleon spin-independent scattering, which can play a crucial role in the DM phenomenology of WIMP dark matter. This feature of DM effective annihilation to the SM particles, as well as the role of the VLQ in the tree level spin-independent DM-nucleon scattering, was also discussed in [60].…”

Singlet fermion dark matter and Dirac neutrinos from Peccei-Quinn symmetry

“…Concretely, in these scenarios one-loop Dirac neutrino masses are generated through the d = 5 effective operator L HN R S [40,41] once the axionic field S develops a vacuum expectation value, with the contributions arising from the tree-level realizations of such an operator being forbidden thanks to the charge assignment. As a further consequence of the PQ symmetry, the residual discrete symmetry that is left over renders stable the lightest particle mediating the neutrino masses, and since such a particle must be electrically neutral, it turns out that the setup also accommodates a second DM species [26,29,[42][43][44][45].…”