1. Threshold Double Pion Photoproduction from Nuclei
Theorectical Overview
Running Plans

2. Partial chiral symmetry restoration in the nuclear medium
V. Bernard et al. PRL 59 (1987) 966
  00, +-
masses of chiral partners become degenerate in the chiral limit
P. Schuck et al., nucl-th/
T. Hatsuda et al., PRL 82 (1999) 2840
R. Rapp et al., PRC 59 (1999) 1237

3. p0p0 interaction in vacuum and in the nuclear medium
A(p,p0p0) at 408 MeV/c
A. Starostin et al.,
PRL 85 (2000) 5539
(Crystal Ball collaboration)
shift in p0p0 - invariant mass
distribution towards lower masses for increasing nuclear mass

4. p+ g comparison of photon and pion induced two pion production
 p-beam interacts on nuclear surface - p+
l < 1 fm
for Tp= 285 MeV
lp [fm]
Tkin=285MeV p+
study of 2p-correlation at
 photon beam interacts with
full nuclear volume g
pions in final state have
(l  5 fm) at
 small final state interaction
study of 2p0-correlation at   0

5. A (,) E= 400 – 500 MeV p0p0 p±p0 p0p0 RPb/C p±p0
450
p±p0
RPb/C
p0p0
p±p0
mass shift with increasing A
only observed for 00 channel
J. Messchendorp et al.,
PRL 89 (2002)

6. BUU calculation:
in contrast to experiment,
downward shift of
 strength found for
both isospin channels
due to FSI (absorption,
charge exchange)
(P. Mühlich et al.)

7. PAC acknowledged 200 hours 202 hrs
Running Plan:
Target A Xo ρ l
%Xo nT
σ(µb)
hours
statistics
[g/mol]
[cm]
[g/cm3]
[1023/cm2]
7Li 7
155
0.53 5
3.23
2.28
1.68 26
7614
12C 12
18.8
2.27 1
5.32
1.14
2.40
5451
natPb
207
0.56
11.35
0.06
10.72
0.02
16.04
150
3655
PAC acknowledged 200 hours
202 hrs
Additional target could be Ca