In-medium modifications of the pipi interaction in photon-induced reactions.
Differential cross sections of the reactions (gamma,pi(0)pi(0)) and (gamma,pi(0)pi(+/-)) have been measured for several nuclei (1H,12C, and (nat)Pb) at an incident-photon energy of E(gamma)=400-460 MeV at the tagged-photon facility at MAMI-B using the TAPS spectrometer. A significant nuclear-mass dependence of the pipi invariant-mass distribution is found in the pi(0)pi(0) channel. This dependence is not observed in the pi(0)pi(+/-) channel and is consistent with an in-medium modification of the pipi interaction in the I=J=0 channel. The data are compared to pi-induced measurements and to calculations within a chiral-unitary approach.
Messchendorp
J G
JG
II. Physikalisches Institut, University of Giessen, Germany.
Janssen
S
S
Kotulla
M
M
Ahrens
J
J
Annand
J R H
JR
Beck
R
R
Bloch
F
F
Caselotti
G
G
Fog
L
L
Hornidge
D
D
Krusche
B
B
Langgärtner
W
W
McGeorge
J C
JC
MacGregor
I J D
IJ
Mengel
K
K
Metag
V
V
Novotny
R
R
Owens
R O
RO
Pfeiffer
M
M
Sack
S
S
Sanderson
R
R
Schadmand
S
S