PIRSA:18110037 Scientific Series Particle Physics

DOI10.48660/18110037

Series: Particle Physics

Pohl, R. (2018). Laser spectroscopy of muonic atoms and the proton radius puzzle. Perimeter Institute. https://pirsa.org/18110037

Pohl, Randolf. Laser spectroscopy of muonic atoms and the proton radius puzzle. Perimeter Institute, Nov. 20, 2018, https://pirsa.org/18110037 

@misc{ pirsa_PIRSA:18110037,
  doi = {10.48660/18110037},
  url = {https://pirsa.org/18110037},
  author = {Pohl, Randolf},
  keywords = {Particle Physics},
  language = {en},
  title = {Laser spectroscopy of muonic atoms and the proton radius puzzle},
  publisher = {Perimeter Institute},
  year = {2018},
  month = {nov},
  note = {PIRSA:18110037 see, \url{https://pirsa.org}}
}

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]. This discrepancy is now called the "proton radius puzzle" [4].
Also the deuteron charge radius from muonic deuterium [5] 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 [6] and deuterium [7], yield a 6 sigmas smaller value of the Rydberg constant [8], 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 [9], which supports the smaller, "muonic" value. More recently, however, a new measurement of the 1S-3S transition in Paris confirmed the larger proton radius [10].
Several new measurements, such as hydrogen from Toronto, elastic electron scattering at lower Q², and new results from electronic and muonic helium will help understand the proton radius puzzle.

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