The discrepancy between the proton charge radius extracted from the muonic hydrogen Lamb shift measurement and the best present value obtained from the elastic scattering experiments, remains unexplained and represents a burning problem of today’s nuclear physics: after more than 50 years of research the radius of a basic constituent of matter is still not understood. This paper presents a summary of the best existing proton radius measurements, followed by an overview of the possible explanations for the observed inconsistency between the hydrogen and the muonic-hydrogen data. In the last part the upcoming experiments, dedicated to remeasuring the proton radius, are described.
REFERENCES
1.
R. W.
McAllister
and R.
Hofstadter
, Phys. Rev.
102
, 851
(1956
).2.
R.
Pohl
et al, Nature
466
, 213
(2010
).3.
A.
Antognini
et al, Science
339
, 417
(2013
).4.
M. N.
Rosenbluth
, Phys. Rev.
79
, 615
(1950
).5.
J.
Beringer
et al (Particle Data Group
), Phys. Rev. D
86
, 010001
(2012
).6.
M.
Mihovilovič
et al, EPJ Web of Conferences
72
, 00017
(2014
).7.
J. C.
Bernauer
et al, Phys. Rev. Lett.
105
, 242001
(2010
).8.
J. C.
Bernauer
et al, Phys. Rev. C
90
, 015206
(2014
).9.
W.
Lamb
Jr. et al, Phys. Rev.
72
, 241
(1947
).10.
R.
Pohl
et al, Annu. Rev. Nucl. Part. Sci.
63
, 175
(2013
).11.
A.
Antognini
et al, Annals of Physics
331
, 127
(2013
).12.
I.
Kostoulas
et al, Phys. Rev. Lett.
32
, 489
(1974
).13.
H.
Merkel
et al, Phys. Rev. Lett.
112
, 221802
(2014
).14.
G. G.
Simon
et al, Nucl. Phys. A
333
, 381
(1980
).15.
F.
Borkowski
et al., Nucl. Phys. B
93
, 461
(1975
).16.
J. J.
Murphy
et al, Phys. Rev. C
9
, 2125
(1974
).17.
L. E.
Price
et al, Phys. Rev. D
4
, 45
(1971
).18.
M. A.
Belushkin
et al, Phys. Rev. C
75
, 035202
(2007
).19.
M.
Vanderhaeghen
et al, Phys. Rev. C
62
, 025501
(2000
).20.
M.
Meziane
et al, AIP Conf. Proc.
1563
, 183
(2013
).21.
22.
A1-Collaboration
, http://wwwa1.kph.uni-mainz.de/A1/publications/proposals/MAMI-A1-01-2012.pdf (2012
).
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