Münster 2002 – scientific programme
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HK: Physik der Hadronen und Kerne
HK 32: Electromagnetic and Hadronic Probes IV
HK 32.3: Talk
Wednesday, March 13, 2002, 14:45–15:00, D
Photoproduction of pion pairs from nuclei — •Silke Janssen — II. Physikalisches Institut, Heinrich-Buff-Ring 16, 35392 Giessen
The photoproduction of pion pairs from nuclei has been studied in the range of incident photon energies from 400-460 MeV. The experiments were performed with the tagged photon beam at the MAMI electron accelerator facility using the photon spectrometer TAPS for the detection of neutral and charged pion pairs. The invariant mass distribution of the two pions shows a different behaviour as a function of the target mass depending on the isospin of the pion pair. For the π 0 π 0 (I=0) channel a shift in the invariant mass distribution towards the 2π - threshold is observed for increasing nuclear mass number while no change in the shape of the invariant mass distribution is found for the π 0 π ± (I=1) channel. This observation can not be explained by final state interaction but is consistent with theoretical predictions for a partial restoration of chiral symmetry at normal nuclear matter density.
[1] R.Rapp et al., Phys.Rev.C 59(99)1237
[2] M.Lutz et al., NPA 542(92)521
[3] T.Hatsuda et al., Phys.Rev.Lett. 82(99)2840