| Abstract |
Laser spectroscopy of muonic hydrogen [1,2] yielded a proton rms charge radius which
is 4% (or ~6 sigmas) smaller than the CODATA value [3]. Also the deuteron charge
radius from muonic deuterium [4] is 6 sigmas smaller than the CODATA value, but
consistent with the smaller proton inside the deuteron. These smaller charge radii,
when combined with precision measurements of the 1S-2S transitions in regular
(electronic) hydrogen [5] and deuterium [6], yield a 6 sigmas smaller value of the
Rydberg constant [7], compared to the CODATA value.
In this talk I will report about a new measurement of the Rydberg constant from the
2S-4P transition in regular hydrogen performed in Garching [8], which supports the
smaller, "muonic" value. I will also discuss the measurements in muonic hydrogen,
deuterium, and helium, and the consequences for the "proton radius puzzle".
[1] Pohl et al. (CREMA Coll.), Nature 466, 213 (2010)
[2] Antognini et al. (CREMA Coll.), Science 339, 417 (2013)
[3] Mohr et al. (CODATA 2014), Rev. Mod. Phys. 88, 035009 (2016)
[4] Pohl et al. (CREMA Coll.), Science 353, 669 (2016)
[5] Parthey et al., PRL 107, 203001 (2011)
[6] Parthey et al., PRL 104, 233001 (2010)
[7] Pohl et al., Metrologia 54, L1 (2017)
[8] Beyer et al., Science, accepted (2017).
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