Abstract
We propose a simple model in which dark matter particle exchanges mediate a new quantum force between muons and nucleons, resolving the proton charge radius puzzle. At the same time, the discrepancy between the measured anomalous magnetic moment of the muon and the Standard Model prediction can be accommodated, and thermal relic abundance of the dark matter candidate is consistent with observations. The dark matter particle mass is in the MeV range. We show that the model is consistent with a variety of experimental and observational constraints.
Highlights
Observational evidence for the existence of dark matter (DM) is overwhelming
We show that this shift can account for the observed discrepancy, and demonstrate a set of parameters for which aμ and proton charge puzzles are simultaneously solved, DM particle is a thermal relic with correct relic density, and all experimental and observational constraints are satisfied
We note that if X and X0 were replaced with a single mediator, coupled to both muons and quarks, the dominant new physics effect in muonic hydrogen would come from a tree-level exchange of the mediator, rather than the DMinduced quantum force
Summary
Observational evidence for the existence of dark matter (DM) is overwhelming. While DM comprises most of the matter in today’s Universe, and contributes about 20% of the total energy density, there is no known elementary particle that can account for it. It turns out that in our model, the effect of DM loops on aμ is subdominant to the shift induced by the mediator particles which connect DM and SM sectors We show that this shift can account for the observed discrepancy, and demonstrate a set of parameters for which aμ and proton charge puzzles are simultaneously solved, DM particle is a thermal relic with correct relic density, and all experimental and observational constraints are satisfied. We note that if X and X0 were replaced with a single mediator, coupled to both muons and quarks, the dominant new physics effect in muonic hydrogen would come from a tree-level exchange of the mediator, rather than the DMinduced quantum force To leading order, this model would be identical to that already considered in [14].
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