The proton radius puzzle, originally published by Randolf Pohl et
al. in Nature
in July 2010 is a recent high profile issue - the
proton size appears to be different when measured with electons vs.
when measured with muonic hydrogen, a result for which we have no explanations.
Experts in the field think the likely explanation is either new
physics or issues with electron experiments. Novel aspects of
proton structure / QCD are not entirely ruled out, although almost
every suggestion made to date in this area has been.
The puzzle has been confirmed with a second paper
by Aldo Antognini et al. with new muonic hydrogen results.
The muonic hydrogen measurements were done at the Paul Scherrer Institut.
A press release from PSI can be found here.
Here we propose a simultaneous measurement of μ+ p and e+ p scattering, as well as μ- p and e- p scattering, which will allow a determination of the consistency of the μp interaction with the ep interaction. Preliminary tests are currently being done at the PiM1 secondary beam line of the PSI proton accelerator. Data taking is foreseen starting from the year 2016.
Here we propose a simultaneous measurement of μ+ p and e+ p scattering, as well as μ- p and e- p scattering, which will allow a determination of the consistency of the μp interaction with the ep interaction. Preliminary tests are currently being done at the PiM1 secondary beam line of the PSI proton accelerator. Data taking is foreseen starting from the year 2016.