1. p p interaction in nuclear matter
motivation
experiments
2004/05
conclusion
Ralf Gregor
II.Physikalisches Institut Giessen

2. p p interaction in nuclear matter
motivation
experiments
experiment 2004/05
chiral symmetry = fundamental symmetry of QCD
(in the limit of vanishing quark masses)
if chiral symmetry is valid on hadron level
-> chiral partners (same spin, opposite parity) with the same mass should exist
1232
1535
1520
938
≈ 600
≈ 290
nucleon
chiral symmetry
1260
770
135
600
≈ 470
≈ 490
scalar mesons
vector mesons
in nature chiral symmetry on hadron level broken

3. p p interaction in nuclear matter
motivation
experiments
experiment 2004/05
V. Bernard et al. PRL 59 (1987) 966
T. Hatsuda et al., PRL 82 (1999) 2840
  00, +-
P. Schuck et al., nucl-th/
R. Rapp et al., PRC 59 (1999) 1237
in the chiral limit masses of chiral partners degenerate

4. p p interaction in nuclear matter
motivation
experiments
experiment 2004/05
A(p,p0p0) at 408 MeV/c
A. Starostin et al.,
PRL 85 (2000) 5539
(Crystal Ball Collaboration)
shift of invariant p0p0 - mass towards lower masses with increasing nuclear number
(-> increasing effective nuclear density)

5. p p interaction in nuclear matter
blue curves scaled: (p±p0*0,7)
 ↛ 0±
A (,)
  00
motivation
experiments
experiment 2004/05
Eg = MeV
J. Messchendorp et al.,
PRL 89 (2002)
F.Bloch, S.Janssen, M.Kotulla, S.Schadmand
blue curves:
P. Mühlich et al.
O.Buß
(giessen theory group)

6. p p interaction in nuclear matter
motivation
experiments
experiment 2004/05
difference between
p0p0 and p0p+/-
higher statistic necessary
J. Messchendorp et al.,
PRL 89 (2002)

7. p p interaction in nuclear matter
motivation
experiments
experiment 2004/05
Eg = MeV
red curve: 05
blue points:
99/00
J. Messchendorp et al.,
PRL 89 (2002)
Eg = MeV C
lead/carbon (a.u.) Ca
M(p0p0) (MeV)
counts (a.u.)
shift of 2p0-strength towards 2p0-threshold with increasing nuclear mass Pb
no acceptance correction of the histograms
M(p0p0) (MeV)

8. p p interaction in nuclear matter
motivation
experiments
experiment 2004/05
charged pion identification
protons
PID-Hits
DE [MeV] 
E [MeV]

9. p p interaction in nuclear matter
motivation
experiments
experiment 2004/05
test of p+/p- identification
g + p → h + p
 p+ + p- + p0

10. p p interaction in nuclear matter
motivation
experiments
experiment 2004/05
Eg = MeV
red curve: 05
blue points:
99/00
J. Messchendorp et al.,
PRL 89 (2002)
Eg = MeV C
lead/carbon (a.u.) Ca
M(p0p+/-) (MeV)
counts (a.u.) Pb
no acceptance correction of the histograms

11. p p interaction in nuclear matter
p0p0 (Eg= MeV)
p+/-p0 (Eg= MeV)
Pb/Ca
Ca/C
Pb/Ca
Ca/C
Ratios for neutral channels
Ratios for charged channels
Pb/C
Pb/C

12. p p interaction in nuclear matter
motivation
experiments
experiment 2004/05
Lead-Carbon
Eg = MeV
p0p0
p0p+/-
M(pp) (MeV)
difference between 2p0 und p±p0 channel confirmed

13. p p interaction in nuclear matter
summary
reaction g A p p X measured
high statistic with (improvement about factor 60)
2p0 – channel for C, Ca, Pb shown
first p±p0 – channel results
next steps:
better cuts
D, Li –Targets
simulation (normalisation)
comparison with theory