Speaker
Description
Summary
The in-medium modications of hadron properties have been identied as
one of the key problems in understanding the non-perturbative sector of
QCD. Several theoretical papers discuss the possibility of a partial restora-
tion of chiral symmetry in a strongly interacting environment. However, is
it possible to nd experimental evidence for partial symmetry restoration
by studying the in-medium behaviour of mesons, in particular the meson-
nucleus interaction? Is this interaction suciently strong to allow even the
formation of mesic states only bound by the strong interaction? The an-
swers can be given by studying the meson-nucleus optical potential. What
are the experimental approaches to deduce this potential? In this presen-
tation experimental results from CBELSA/TAPS on the determination of
the meson-nucleus optical potential will be presented and discussed in view
of these questions. Data taken on a C and Nb target at CB/TAPS@ELSA
have been analyzed to deduce the 0- and !-nucleus optical potential. The
data for both mesons are consistent with a weakly attractive potential. The
formation and population of !-nucleus and 0-nucleus bound states will be
discussed. In case of the ! meson the in-medium width is found to be
larger than the potential depth which hampers a successful identication
of !-mesic states. The relatively small in-medium width of the 0 meson
encourages ongoing experiments to search for 0-nucleus bound states.
?Funded by DFG(SFB/TR-16
