Direct and indirect limits on the electro-magnetic form factors of WIMPs

TL;DR

This work derives model-independent bounds on the electromagnetic form factors of WIMPs by translating direct-detection recoil limits (from experiments like DAMA and CDMS) into constraints on magnetic and electric dipole moments, anapole, quadrupole, charge radius, and polarizability under standard halo assumptions. It supplements these with indirect bounds from neutrino flux limits associated with WIMP annihilation in the Sun and Earth, though those bounds are more model-dependent. The analysis shows all EM form factors must be very small in nuclear units; for instance, a WIMP magnetic moment is constrained to be well below the proton’s, and the EDM bound is exceptionally tight. The results have implications for non-SUSY WIMP scenarios and self-interacting dark matter, illustrating how EM properties constrain WIMP phenomenology even in a model-independent framework.

Abstract

We use the results of direct and indirect searches for weakly interacting massive particles (WIMPs) to obtain bounds on various electro-magnetic form factors of WIMPs. The limits on the recoil signal in underground dark matter detection experiments, with standard assumptions about the density and r.m.s. velocity of WIMPs in the halo, can be translated into the following model-independent bounds on the magnetic dipole, electric dipole, quadrupole and anapole moments and the polarizability of WIMPs: mu/mu_n < 1.4 10^{-4}, d < 5 10^{-21}e cm, Q < 6 10^{-7}fm^2, a/mu_n < 3 10^{-2} fm, and chi < 5 10^{-8}fm^3 for a WIMP mass of 100 GeV. The limits on fluxes of highly energetic neutrinos produced in the annihilation of WIMPs in the center of the earth and the sun lead to somewhat stronger, but more model dependent bounds.