Abstract
The e difference in proton radii measured with µp atoms and with ep atoms and scattering
remains an unexplained puzzle. The PSI MUSE proposal is to measure µp and ep scattering
in the same experiment at the same time. The experiment will determine cross sections,
two-photon effects, form factors, and radii independently for the two reactions, and will
allow µp and ep results to be compared with reduced systematic uncertainties. These data
should provide the best test of lepton universality in a scattering experiment to date, about
an order of magnitude improvement over previous tests. Measuring scattering with both
particle polarities will allow a test of two-photon exchange at the sub-percent level, about a
factor of four improvement on uncertainties and over an order of magnitude more data points
than previous low momentum transfer determinations, and similar to the current generation
of higher momentum transfer electron experiments. The experiment has the potential to
demonstrate whether the µp and ep interactions are consistent or different, and whether any
difference results from novel physics or two-photon exchange. The uncertainties are such
that if the discrepancy is real it should be confirmed with ≈5σ significance, similar to that
already established between the regular and muonic hydrogen Lamb shift.
remains an unexplained puzzle. The PSI MUSE proposal is to measure µp and ep scattering
in the same experiment at the same time. The experiment will determine cross sections,
two-photon effects, form factors, and radii independently for the two reactions, and will
allow µp and ep results to be compared with reduced systematic uncertainties. These data
should provide the best test of lepton universality in a scattering experiment to date, about
an order of magnitude improvement over previous tests. Measuring scattering with both
particle polarities will allow a test of two-photon exchange at the sub-percent level, about a
factor of four improvement on uncertainties and over an order of magnitude more data points
than previous low momentum transfer determinations, and similar to the current generation
of higher momentum transfer electron experiments. The experiment has the potential to
demonstrate whether the µp and ep interactions are consistent or different, and whether any
difference results from novel physics or two-photon exchange. The uncertainties are such
that if the discrepancy is real it should be confirmed with ≈5σ significance, similar to that
already established between the regular and muonic hydrogen Lamb shift.
| Original language | American English |
|---|---|
| Publisher | arXiv |
| Pages | 1-105 |
| Number of pages | 105 |
| Volume | 1709.09753 |
| State | Published - 2017 |