Some of the few loopholes allowing one to avoid the Lee-Weinberg bound without introducing new forces below the electroweak scale have been ruled out by accelerator experiments (i.e. CERN, Tevatron), and in decays of B mesons.
This increases the annihilation cross section and reduces the coupling of dark matter particles to the Standard Model making them consistent with accelerator experiments.
[4][5][6] Current methods to search for light dark matter particles include direct detection through electron recoil.
It has also been suggested that light dark matter may explain a small discrepancy in the measured value of the fine structure constant in different experiments.
[8] Furthermore, the lack of dark matter signals in higher energy ranges in direct detection experiments incentivizes sub-GeV searches.
[4] The thermal freeze in model proposes that dark matter particles were very weakly interacting shortly after the Big Bang such that they were essentially decoupled from the plasma.
The greatest difficulty in using this method is creating a detector with a low enough threshold energy for detection while also minimizing background signals.
[13] XENON10 is a liquid xenon detector that searches for and places limits on the mass of dark matter by directly detecting electron recoil.
[14] SENSEI is a silicon detector capable of measuring the electronic recoil of a dark matter particle between 500 keV and 4 MeV using CCD technology.
[15] The experiment has been working to place further rule out possible mass ranges of dark matter below 1 GeV, with its most recent results being published in October 2020.