Abstract
Dark photons (DP) are interesting as potential mediators between the dark matter (DM) sector and the fields of the Standard Model (SM). The interaction of the DP, described by a broken $U(1)_D$ gauge symmetry, with the SM is usually generated at the one-loop level via kinetic mixing through the existence of portal matter (PM), here assumed to be fermionic, which carries both a dark charge as well as a SM $U(1)_Y$ hypercharge. For theoretical consistency, as well as for many phenomenological reasons, this PM must be vector-like with respect to the SM and dark gauge groups and, in particular, is shown to be allowed only to transform as vector-like copies of the usual SM fields. The dark Higgs that is responsible for the breaking of $U(1)_D$ can then generate a mixing between the PM and SM fields with the same electric charge thus altering the DP interactions with (at least some of) the SM fields and also providing a path for the PM fields to decay. In this paper we briefly explore the phenomenology of some specific simple models of this PM including, for the case where the PM is leptonic in nature, their potential impact on experiments probing low energy parity-violation and the g-2 of the muon. In the case of color-triplet, bottom quark-like PM, their direct pair- and single-production at the LHC is shown to be observable in final states that include missing $E_T$ and/or very highly boosted lepton-jets together with pairs of high $p_T$ b-jets that can be used to trigger on such events. These signatures are quite distinct from those usually employed in the search for vector-like quarks at the LHC and, furthermore, we demonstrate that the conventional signal channels for vector-like quarks involving the SM Higgs and gauge fields are essentially closed in the case of PM.
Highlights
The nature of dark matter (DM) remains as one of the great mysteries facing particle physics
As will be further discussed below, assuming that the kinetic mixing (KM) is generated only at oneloop to have a phenomenologically interesting strength, in order to obtain a nonzero and yet finite result several, nondegenerate portal matter fields are required, tPhe product of whose charges must satisfy the condition iQYi QDi 1⁄4 0. What are these portal matter states and how do they impact nonDM phenomenology? These portal matter fields which form a necessary ingredient of this setup have so far received very little attention much less detailed study in the literature [8] in the case where they carry nontrivial Standard Model (SM) SUð3Þc charges. It is the nature of these portal matter fields, their interactions with the dark photon, as well as with the familiar SM particles that will be of interest to us below
We have briefly summarized the usual development of the dark photon/KM scenario to establish notation and basic assumptions; let us return to a discussion of the portal matter part of the action
Summary
The nature of dark matter (DM) remains as one of the great mysteries facing particle physics. What are these portal matter states and how do they impact nonDM phenomenology? These portal matter fields which form a necessary ingredient of this setup have so far received very little attention much less detailed study in the literature [8] in the case where they carry nontrivial SM SUð3Þc charges To rectify this situation, it is the nature of these portal matter fields, their interactions with the dark photon, as well as with the familiar SM particles that will be of interest to us below. An appendix summarizes the most important couplings appearing in the present analysis
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