A couplet from flavored dark matter

Abstract

We show that a couplet, a pair of closely spaced photon lines, in the X-ray spectrum is a distinctive feature of lepton flavored dark matter models for which the mass spectrum is dictated by Minimal Flavor Violation. In such a scenario, mass splittings between different dark matter flavors are determined by Standard Model Yukawa couplings and can naturally be small, allowing all three flavors to be long-lived and contribute to the observed abundance. Then, in the presence of a tiny source of flavor violation, heavier dark matter flavors can decay via a dipole transition on cosmological timescales, giving rise to three photon lines. Two of these lines are closely spaced, and constitute the couplet. Provided the flavor violation is sufficiently small, the ratios of the line energies are determined in terms of the charged lepton masses, and constitute a prediction of this framework. For dark matter masses of order the weak scale, the couplet lies in the keV-MeV region, with a much weaker line in the eV-keV region. This scenario constitutes a potential explanation for the recent claim of the observation of a 3.5 keV line. The next generation of X-ray telescopes may have the necessary resolution to resolve the double line structure of such a couplet.

Naturally large radiative lepton flavor violating Higgs decay mediated by lepton-flavored dark matter

“…In this article we establish a connection between LFV Higgs decay and a type of dark matter (DM), i.e., lepton-flavored DM [32][33][34][35][36][37][38][39][40]. In this scenario, DM interacts merely with the SM lepton sector, whereupon DM-quark interactions arise at loop level.…”

Suppressed flavor violation in lepton flavored dark matter from an extra dimension

“…Relic Abundance: Since the three DM flavors in our model are very nearly degenerate, the relic abundance calculation closely mirrors that considered in ref. [29]. In particular, all three flavors freeze out at the same time, and for purposes of setting the relic abundance, they behave like a single Dirac fermion DM species.…”

“…As mentioned in section 2 (see figure 1 and equation 2.15), the mass splittings between the χ's are induced by loop processes. Specifically, one finds [29] that the dominant decay mode is the one shown in figure 2, with one flavor-preserving coupling λ and one flavor-violating coupling δλ. The width for this decay mode is given by [29]…”

“…This exact mechanism leading to a mass splitting between different DM flavors was studied in ref. [29], with the result that χ e is the lightest flavor, and the mass splittings between flavors i and j are given by…”

Muong−2anomaly and dark leptonic gauge boson

“…Light leptonic gauge bosons, including the flavordependent ones, have been studied in numerous literature [13][14][15][16][17][18][19][20][21][22]. In this paper, we consider the gauged U (1) L with a gauge boson Z ′ of the GeV or sub-GeV scale.…”