Geneva University - Measurement of the Lamb shift in muonic hydrogen: the proton radius puzzle

GENEVA UNIVERSITY
École de physique
Département de physique nucléaire et corspusculaire
24, quai Ernest-Ansermet
1211 GENEVA 4
Tel: (022) 379 62 73
Fax: (022) 379 69 92
Wednesday 12 May 2010
PARTICLE PHYSICS SEMINAR
at 17.00 hrs – Stückelberg Auditorium

Measurement of the Lamb shift in muonic hydrogen: the proton radius puzzle
Dr Aldo Antogninia , CREMA Collaboration, Max Planck Institute, Germany

At the Paul Scherrer Institut, Switzerland, we have measured several 2S-2P transition frequencies in muonic hydrogen (µp) and deuterium (µd) by means of laser spectroscopy. This results in an order of magnitude improvement on the rms charge radius values of the proton and the deuteron. Additionally the Zemach radii and the deuteron polarizability are also inferred. The new proton radius value is deduced with a relative accuracy of 0.1% but strongly disagrees from CODATA.

The origin of this discrepancy is not yet known. It may come from theory of the muonic hydrogen energy levels (used to deduce the new value), or from problems in hydrogen spectroscopy experiments or hydrogen energy level theory (both used to deduce the CODATA value). The decrease of the proton value uncertainty opens the way to compare the hydrogen energy levels predictions with high-precision (ur = 10-12 ...-14) measurements to an unprecedented accuracy. This will stimulate progress in the understanding of the simplest atom and its related bound-state QED theory.

Experimental setup, measurements and results will be presented. Additionally the key issues regarding the observed discrepancy will be given together with the impact of these measurements on bound-state QED test and fundamental constants.


Information : http://dpnc.unige.ch/seminaire/annonce.html
Organizer : J.-S. Graulich