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New parity-violating muonic forces and the proton charge radius
Brian Batell1, David McKeen, Maxim Pospelov
1Perimeter Institute for Theoretical Physics, Waterloo, ON, Canada.
Physical Review Letters
|July 30, 2011
Summary
A new force differentiating between electron and muon interactions may explain proton radius discrepancies. This force, mediated by new particles, could enhance parity-violating asymmetries in muon-nucleus scattering, enabling new tests.
Area of Science:
- Particle Physics
- Nuclear Physics
- Lepton Physics
Background:
- Discrepancies exist in proton charge radius measurements from electron-proton and muon-proton scattering.
- These discrepancies suggest potential differences in how electrons and muons interact with protons, possibly indicating new physics.
Purpose of the Study:
- To investigate a class of models that could explain the observed proton charge radius discrepancy.
- To explore the implications of such models for lepton-nucleus scattering and parity violation.
Main Methods:
- Identification of theoretical models featuring gauged right-handed muon number.
- Analysis of the predicted properties of new vector and scalar force carriers.
- Calculation of parity-violating asymmetries in low-energy muon-nucleus scattering.
Main Results:
- A class of models with gauged right-handed muon number, involving new light force carriers (∼100 MeV or lighter), is consistent with current observations.
- These models predict a significant enhancement (several orders of magnitude) of parity-violating asymmetries in low-energy muon-nucleus scattering.
Conclusions:
- The identified models offer a potential explanation for the proton radius puzzle by introducing lepton-flavor-dependent forces.
- The predicted large parity-violating asymmetries present a promising avenue for new experimental tests of parity violation in neutral currents using existing low-energy muon beams.
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