The ep -->e'p eta reaction at and above the S11(1535) baryon resonance.
New cross sections for the reaction e p-->e p eta are reported for total center of mass energy W = 1.5--1.86 GeV and invariant momentum transfer Q2 = 0.25--1.5 (GeV/c)(2). This large kinematic range allows extraction of important new information about response functions, photocouplings, and eta N coupling strengths of baryon resonances. Newly observed structure at W approximately 1.65 GeV is shown to come from interference between S and P waves and can be interpreted with known resonances. Improved values are derived for the photon coupling amplitude for the S11(1535) resonance.
Thompson
R
R
Department of Physics and Astronomy, University of Pittsburgh, Pennsylvania 15260, USA.
Dytman
S
S
Kim
K Y
KY
Mueller
J
J
Adams
G S
GS
Amaryan
M J
MJ
Anciant
E
E
Anghinolfi
M
M
Asavapibhop
B
B
Auger
T
T
Audit
G
G
Avakian
H
H
Barrow
S
S
Battaglieri
M
M
Beard
K
K
Bektasoglu
M
M
Bertozzi
W
W
Bianchi
N
N
Biselli
A
A
Boiarinov
S
S
Bonner
B E
BE
Briscoe
W J
WJ
Brooks
W
W
Burkert
V D
VD
Calarco
J R
JR
Capitani
G
G
Carman
D S
DS
Carnahan
B
B
Cole
P L
PL
Coleman
A
A
Connelly
J
J
Cords
D
D
Corvisiero
P
P
Crabb
D
D
Crannell
H
H
Cummings
J
J
Day
D
D
Degtyarenko
P V
PV
Demirchyan
R A
RA
Dennis
L C
LC
Deppman
A
A
De Sanctis
E
E
De Vita
R
R
Dhuga
K S
KS
Djalali
C
C
Dodge
G E
GE
Doughty
D
D
Dragovitsch
P
P
Dugger
M
M
Eckhause
M
M
Efremenko
Y V
YV
Egiyan
H
H
Egiyan
K S
KS
Elouadrhiri
L
L
Farhi
L
L
Feuerbach
R J
RJ
Ficenec
J
J
Fissum
K
K
Freyberger
A
A
Funsten
H
H
Gai
M
M
Gavrilov
V B
VB
Gilfoyle
G P
GP
Giovanetti
K
K
Gilad
S
S
Girard
P
P
Griffioen
K A
KA
Guidal
M
M
Guillo
M
M
Gyurjyan
V
V
Hancock
D
D
Hardie
J
J
Heddle
D
D
Heisenberg
J
J
Hersman
F W
FW
Hicks
K
K
Hicks
R S
RS
Holtrop
M
M
Hyde-Wright
C E
CE
Ito
M M
MM
Jenkins
D
D
Joo
K
K
Kane
J
J
Khandaker
M
M
Kim
W
W
Klein
A
A
Klein
F J
FJ
Klusman
M
M
Kossov
M
M
Kuhn
S E
SE
Kuang
Y
Y
Laget
J M
JM
Lawrence
D
D
Leskin
G A
GA
Longhi
A
A
Loukachine
K
K
Lucas
M
M
Magahiz
R
R
Major
R W
RW
Manak
J J
JJ
Marchand
C
C
Matthews
S K
SK
McAleer
S
S
McCarthy
J
J
McNabb
J W
JW
Mecking
B A
BA
Mestayer
M D
MD
Meyer
C A
CA
Minehart
R
R
Mirazita
M
M
Miskimen
R
R
Muccifora
V
V
Mutchler
G S
GS
Napolitano
J
J
Niyazov
R A
RA
Ohandjanyan
M S
MS
O'Brien
J T
JT
Opper
A
A
Patois
Y
Y
Peterson
G A
GA
Philips
S
S
Pivnyuk
N
N
Pocanic
D
D
Pogorelko
O
O
Polli
E
E
Preedom
B M
BM
Price
J W
JW
Qin
L M
LM
Raue
B A
BA
Reolon
A R
AR
Riccardi
G
G
Ricco
G
G
Ripani
M
M
Ritchie
B G
BG
Ronchetti
F
F
Rossi
P
P
Roudot
F
F
Rowntree
D
D
Rubin
P D
PD
Salgado
C W
CW
Sanzone
M
M
Sapunenko
V
V
Sarty
A
A
Sargsyan
M
M
Schumacher
R A
RA
Shafi
A
A
Sharabian
Y G
YG
Shaw
J
J
Shuvalov
S M
SM
Skabelin
A
A
Smith
T
T
Smith
C
C
Smith
E S
ES
Sober
D I
DI
Spraker
M
M
Stepanyan
S
S
Stoler
P
P
Taiuti
M
M
Taylor
S
S
Tedeschi
D
D
Tung
T Y
TY
Vineyard
M F
MF
Vlassov
A
A
Weller
H
H
Weinstein
L B
LB
Welsh
R
R
Weygand
D P
DP
Whisnant
S
S
Witkowski
M
M
Wolin
E
E
Yegneswaran
A
A
Yun
J
J
Zhou
Z
Z
Zhao
J
J