Abstract
Phenomenological studies of Flavored Dark Matter (FDM) models often have to assume a near-diagonal flavor structure in the coupling matrix in order to remain consistent with bounds from flavor violating processes. In this paper we show that for Lepton FDM, such a structure can naturally arise from an extra dimensional setup. The extra dimension is taken to be flat, with the dark matter and mediator fields confined to a brane on one end of the extra dimension, and the Higgs field to a brane on the other end. The Standard Model fermion and gauge fields are the zero modes of corresponding bulk fields with appropriate boundary conditions. Global flavor symmetries exist in the bulk and on the FDM brane, while they are broken on the Higgs brane. Flavor violating processes arise due to the misalignment of bases for which the interactions on the two branes are diagonalized, and their size can be controlled by a choice of the lepton profiles along the extra dimension. By studying the parameter space for the model, we show that when relic abundance and indirect detection constraints are satisfied, the rates for flavor violating processes such as $\mu\to e\gamma$ remain far below the experimental limits.
Highlights
While the existence of dark matter (DM) is strongly supported by astronomical observations, its microscopic nature remains a mystery
In models that address the naturalness problem of the scalar sector in the Standard Model (SM) by introducing partner particles that are odd under a Z2 symmetry, the DM can be the lightest partner particle, which often leads to its observed relic abundance through thermal production in the early universe
While we have introduced the most general Lagrangian consistent with our 5D setup and the flavor symmetry Glepton, it is not straightforward in this description to calculate the rate of flavor violating processes such as μ → eγ, since both the kinetic terms and the Yukawa terms are nondiagonal in flavor space
Summary
While the existence of dark matter (DM) is strongly supported by astronomical observations, its microscopic nature remains a mystery. In FDM models, the DM is taken to transform nontrivially under lepton, quark, or extended flavor symmetries, and it couples to SM fermions at the renormalizable level via a mediator. The Higgs brane BLKTs cause shifts in the normalization of the lepton kinetic terms in a nonflavor universal way, and the basis transformation necessary to bring the fields back into canonically normalized form involves rescalings, which are not unitary By the time this is done and all interactions on the Higgs brane are brought to diagonal form, the FDM interaction is no longer diagonal.
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