Millicharged atomic dark matter

Abstract

We present a simplified version of the atomic dark matter scenario, in which charged dark constituents are bound into atoms analogous to hydrogen by a massless hidden sector U(1) gauge interaction. Previous studies have assumed that interactions between the dark sector and the standard model are mediated by a second, massive Z ′ gauge boson, but here we consider the case where only a massless γ ′ kinetically mixes with the standard model hypercharge and thereby mediates direct detection. This is therefore the simplest atomic dark matter model that has direct interactions with the standard model, arising from the small electric charge for the dark constituents induced by the kinetic mixing. We map out the parameter space that is consistent with cosmological constraints and direct searches, assuming that some unspecified mechanism creates the asymmetry that gives the right abundance, since the dark matter cannot be a thermal relic in this scenario. In the special case where the dark "electron" and "proton" are degenerate in mass, inelastic hyperfine transitions can explain the CoGeNT excess events. In the more general case, elastic transitions dominate, and can be close to current direct detection limits over a wide range of masses.

Composite millicharged dark matter

“…(28)), the millicharged particle strongly prefers to "hide" in oxygen rather than hydrogen. Our estimate is in accordance with the qualitative argument presented in [17]. For the rest of the ǫ phase space where the reactions (33) are still in thermal equilibrium i.e.…”

“…Composite dark matter (with charged constituents) is an attractive scenario that has been studied extensively [9][10][11][12][13][14]. Recently there has been a revived interest on millicharged dark matter via Stueckelberg Z ′ models [15,16], in the form of millicharged atomic dark mat- * Electronic address: kouvaris@cp3.sdu.dk ter [17], or in the form of MeV particles in order to explain the 511 keV line [18].…”

Scattering, damping, and acoustic oscillations: Simulating the structure of dark matter halos with relativistic force carriers

“…While there are many SIDM scenarios that mediate the self-scattering interaction through a light force carrier, in this paper we will use the dark atom model as a benchmark [34][35][36][37][38][39][40][41][42]48,[50][51][52][53][54][55][56][57][58][59]. In this model, dark matter is composed of two different particles, oppositely charged under a new long-range Abelian gauge group Uð1Þ D , mediated by a dark photon ϕ.…”

“…While it is not required, such a large cross section makes it reasonable to consider the existence of light force carriers in the dark sector. This could occur, for example, in dark atom models interacting through dark photons [34,48,[50][51][52][53][54][55][56][57], in mirror dark matter models [35][36][37][38][39][40][41][42]58,59,85], or dark matter coupled to Standard Model photons [60][61][62][63][64][65][66][67], neutrinos [24][25][26][27][28][29][30][31][32][33], or to some other new light particle [68][69][70][71][72][73][86][87][88].…”

Dissipative dark matter explains rotation curves

“…[22,23,24,25,26,27,28,29,30] (see also [31] for a more detailed bibliography). Such models allow for a very rich dark matter phenomenology, especially if the hidden sector contains unbroken gauge interactions.…”