Proton structure from the measurement of 2S-2P transition frequencies of muonic hydrogen.
Accurate knowledge of the charge and Zemach radii of the proton is essential, not only for understanding its structure but also as input for tests of bound-state quantum electrodynamics and its predictions for the energy levels of hydrogen. These radii may be extracted from the laser spectroscopy of muonic hydrogen (μp, that is, a proton orbited by a muon). We measured the 2S(1/2)(F=0)-2P(3/2)(F=1) transition frequency in μp to be 54611.16(1.05) gigahertz (numbers in parentheses indicate one standard deviation of uncertainty) and reevaluated the 2S(1/2)(F=1)-2P(3/2)(F=2) transition frequency, yielding 49881.35(65) gigahertz. From the measurements, we determined the Zemach radius, r(Z) = 1.082(37) femtometers, and the magnetic radius, r(M) = 0.87(6) femtometer, of the proton. We also extracted the charge radius, r(E) = 0.84087(39) femtometer, with an order of magnitude more precision than the 2010-CODATA value and at 7σ variance with respect to it, thus reinforcing the proton radius puzzle.
Max-Planck-Institut für Quantenoptik, 85748 Garching, Germany. aldo@phys.ethz.ch
Aldo
A
Antognini
François
F
Nez
Karsten
K
Schuhmann
Fernando D
FD
Amaro
François
F
Biraben
João M R
JM
Cardoso
Daniel S
DS
Covita
Andreas
A
Dax
Satish
S
Dhawan
Marc
M
Diepold
Luis M P
LM
Fernandes
Adolf
A
Giesen
Andrea L
AL
Gouvea
Thomas
T
Graf
Theodor W
TW
Hänsch
Paul
P
Indelicato
Lucile
L
Julien
Cheng-Yang
CY
Kao
Paul
P
Knowles
Franz
F
Kottmann
Eric-Olivier
EO
Le Bigot
Yi-Wei
YW
Liu
José A M
JA
Lopes
Livia
L
Ludhova
Cristina M B
CM
Monteiro
Françoise
F
Mulhauser
Tobias
T
Nebel
Paul
P
Rabinowitz
Joaquim M F
JM
dos Santos
Lukas A
LA
Schaller
Catherine
C
Schwob
David
D
Taqqu
João F C A
JF
Veloso
Jan
J
Vogelsang
Randolf
R
Pohl