The proton radius from muonic hydrogen spectroscopy

por Luís M. P. Fernandes

jueves 9 may. 2013 15:30 → 16:30 Europe/Madrid

Sala Seminarios IFIC (Edf. Institutos de Investigación)

From the high precision measurement of the muonic hydrogen Lamb shift, carried out by the CREMA collaboration in 2009, a new estimate of the proton charge radius has been obtained. The results of the experiment have been published in Nature in 2010, generating a scientific controversy due to its deviation (5σ) from the previously accepted value (CODATA). The muonic hydrogen Lamb shift resulting from the data analysis is 206.2949 ± 0.0032 meV and the new estimate for the proton charge radius is 0.84091 (68) fm, as published in Nature 466 (2010) 213-217. This value is 10 times more accurate than the previously accepted value, 0.8768 (69) fm, but is about 5 standard deviations far from it. The origin of this discrepancy is not yet known. The experiment is based on laser spectroscopy of muonic hydrogen. The principle and experimental setup will be described. The proton radius puzzle generated by the Nature publication will be discussed, together with new results recently published in Science 339 (2013) 417-420, resulting from a more exhaustive data analysis.