Problems in determination of the proton charge radius (aka Proton radius puzzle)

Savely Karshenboim

Institut für Quantenoptik, Garching, Germany
Pulkovo Observatory, Saint Petersburg, Russia

Standard model (of particle physics) is not complete, because it does not predict Dark Matter particles. Due to this incompleteness, any possible failure of the Standard model immediately attract a big attention.

Proton charge radius is determined by means of spectroscopy of ordinary (e-p) and muonic (mu-p) hydrogen and by means of electron-proton scattering. The e-p results are internally consistent and strongly disagree with the muonic value. If one reads the situation literally, the overall e-p to mu-p discrepancy is about 7-8 sigma, which indicates a violation of the lepton universality. I.e., e-p and mu-p interactions are somewhat different.

But that is if one reads the situation literally. In my talk I will review the present situation and will try to respond to the question whether we can really rely on the 7-8-sigma discrepancy.

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