New parity-violating muonic forces and the proton charge radius

Brian Batell, David McKeen, Maxim Pospelov

Research output: Contribution to journalArticlepeer-review

114 Scopus citations


The recent discrepancy between proton charge radius measurements extracted from electron-proton versus muon-proton systems is suggestive of a new force that differentiates between lepton species. We identify a class of models with gauged right-handed muon number, which contains new vector and scalar force carriers at the ∼100MeV scale or lighter, that is consistent with observations. Such forces would lead to an enhancement by several orders-of-magnitude of the parity-violating asymmetries in the scattering of low-energy muons on nuclei. The relatively large size of such asymmetries, O(10-4), opens up the possibility for new tests of parity violation in neutral currents with existing low-energy muon beams.

Original languageEnglish (US)
Article number011803
JournalPhysical review letters
Issue number1
StatePublished - Jun 30 2011
Externally publishedYes


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