Measurements of the proton elastic-form-factor ratio mu pG p E/G p M at low momentum transfer.
High-precision measurements of the proton elastic form-factor ratio, mu pG p E/G p M, have been made at four-momentum transfer, Q2, values between 0.2 and 0.5 GeV2. The new data, while consistent with previous results, clearly show a ratio less than unity and significant differences from the central values of several recent phenomenological fits. By combining the new form-factor ratio data with an existing cross-section measurement, one finds that in this Q2 range the deviation from unity is primarily due to G p E being smaller than expected.
Ron
G
G
Tel Aviv University, Tel Aviv 69978, Israel.
Glister
J
J
Lee
B
B
Allada
K
K
Armstrong
W
W
Arrington
J
J
Beck
A
A
Benmokhtar
F
F
Berman
B L
BL
Boeglin
W
W
Brash
E
E
Camsonne
A
A
Calarco
J
J
Chen
J P
JP
Choi
Seonho
S
Chudakov
E
E
Coman
L
L
Craver
B
B
Cusanno
F
F
Dumas
J
J
Dutta
C
C
Feuerbach
R
R
Freyberger
A
A
Frullani
S
S
Garibaldi
F
F
Gilman
R
R
Hansen
O
O
Higinbotham
D W
DW
Holmstrom
T
T
Hyde
C E
CE
Ibrahim
H
H
Ilieva
Y
Y
de Jager
C W
CW
Jiang
X
X
Jones
M K
MK
Kang
H
H
Kelleher
A
A
Khrosinkova
E
E
Kuchina
E
E
Kumbartzki
G
G
LeRose
J J
JJ
Lindgren
R
R
Markowitz
P
P
May-Tal Beck
S
S
McCullough
E
E
Meekins
D
D
Meziane
M
M
Meziani
Z-E
ZE
Michaels
R
R
Moffit
B
B
Norum
B E
BE
Oh
Y
Y
Olson
M
M
Paolone
M
M
Paschke
K
K
Perdrisat
C F
CF
Piasetzky
E
E
Potokar
M
M
Pomatsalyuk
R
R
Pomerantz
I
I
Puckett
A
A
Punjabi
V
V
Qian
X
X
Qiang
Y
Y
Ransome
R
R
Reyhan
M
M
Roche
J
J
Rousseau
Y
Y
Saha
A
A
Sarty
A J
AJ
Sawatzky
B
B
Schulte
E
E
Shabestari
M
M
Shahinyan
A
A
Shneor
R
R
Sirca
S
S
Slifer
K
K
Solvignon
P
P
Song
J
J
Sparks
R
R
Subedi
R
R
Strauch
S
S
Urciuoli
G M
GM
Wang
K
K
Wojtsekhowski
B
B
Yan
X
X
Yao
H
H
Zhan
X
X
Zhu
X
X