Observation of in-medium modifications of the omega meson.
The photoproduction of omega mesons on nuclei has been investigated using the Crystal Barrel/TAPS experiment at the ELSA tagged photon facility in Bonn. The aim is to study possible in-medium modifications of the omega meson via the reaction gamma + A --> omega + X --> pi(0)gamma + X('). Results obtained for Nb are compared to a reference measurement on a LH2 target. While for recoiling, long-lived mesons (pi(0), eta, and eta;(')), which decay outside of the nucleus, a difference in the line shape for the two data samples is not observed, we find a significant enhancement towards lower masses for omega mesons produced on the Nb target. For momenta less than 500 MeV/c an in-medium omega meson mass of M(medium) = [722(+4)(-4)(stat)+35-5(syst)] MeV/c(2) has been deduced at an estimated average nuclear density of 0.6rho(0).
Trnka
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II. Physikalisches Institut, Universität Giessen, Germany.
Anton
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Bacelar
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Bartholomy
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O
Bayadilov
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Beloglazov
Y A
YA
Bogendörfer
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R
Castelijns
R
R
Crede
V
V
Dutz
H
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Ehmanns
A
A
Elsner
D
D
Ewald
R
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Fabry
I
I
Fuchs
M
M
Essig
K
K
Funke
Ch
Ch
Gothe
R
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Gregor
R
R
Gridnev
A B
AB
Gutz
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E
Höffgen
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S
Hoffmeister
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P
Horn
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Hössl
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Jaegle
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Junkersfeld
J
J
Kalinowsky
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Klein
Frank
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Klein
Fritz
F
Klempt
E
E
Konrad
M
M
Kopf
B
B
Kotulla
M
M
Krusche
B
B
Langheinrich
J
J
Löhner
H
H
Lopatin
I V
IV
Lotz
J
J
Lugert
S
S
Menze
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Messchendorp
J G
JG
Mertens
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T
Metag
V
V
Morales
C
C
Nanova
M
M
Novotny
R
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Ostrick
M
M
Pant
L M
LM
van Pee
H
H
Pfeiffer
M
M
Roy
A
A
Radkov
A
A
Schadmand
S
S
Schmidt
Ch
Ch
Schmieden
H
H
Schoch
B
B
Shende
S
S
Suft
G
G
Sumachev
V V
VV
Szczepanek
T
T
Süle
A
A
Thoma
U
U
Varma
R
R
Walther
D
D
Weinheimer
Ch
Ch
Wendel
Ch
Ch