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

p p interaction in nuclear matter motivation experiments CB@MAMI 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

p p interaction in nuclear matter motivation experiments CB@MAMI 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/0002031 R. Rapp et al., PRC 59 (1999) 1237 in the chiral limit masses of chiral partners degenerate

p p interaction in nuclear matter motivation experiments CB@MAMI 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)

p p interaction in nuclear matter blue curves scaled: (p±p0*0,7)  ↛ 0± A (,)   00 motivation experiments CB@MAMI experiment 2004/05 Eg = 400-500 MeV J. Messchendorp et al., PRL 89 (2002) 222302 F.Bloch, S.Janssen, M.Kotulla, S.Schadmand blue curves: P. Mühlich et al. O.Buß (giessen theory group)

p p interaction in nuclear matter motivation experiments CB@MAMI experiment 2004/05 difference between p0p0 and p0p+/- higher statistic necessary J. Messchendorp et al., PRL 89 (2002) 222302

p p interaction in nuclear matter motivation experiments CB@MAMI experiment 2004/05 Eg = 400-450 MeV red curve: CB/TAPS@MAMI 05 blue points: TAPS@MAMI 99/00 J. Messchendorp et al., PRL 89 (2002) 222302 Eg = 400-450 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)

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

p p interaction in nuclear matter motivation experiments CB/TAPS@MAMI experiment 2004/05 test of p+/p- identification g + p → h + p  p+ + p- + p0

p p interaction in nuclear matter motivation experiments CB@MAMI experiment 2004/05 Eg = 400-450 MeV red curve: CB/TAPS@MAMI 05 blue points: TAPS@MAMI 99/00 J. Messchendorp et al., PRL 89 (2002) 222302 Eg = 400-450 MeV C lead/carbon (a.u.) Ca M(p0p+/-) (MeV) counts (a.u.) Pb no acceptance correction of the histograms

p p interaction in nuclear matter p0p0 (Eg=400-450MeV) p+/-p0 (Eg=400-450MeV) Pb/Ca Ca/C Pb/Ca Ca/C Ratios for neutral channels Ratios for charged channels Pb/C Pb/C

p p interaction in nuclear matter motivation experiments CB@MAMI experiment 2004/05 Lead-Carbon Eg = 400-450 MeV p0p0 p0p+/- M(pp) (MeV) difference between 2p0 und p±p0 channel confirmed

p p interaction in nuclear matter summary reaction g A p p X measured high statistic with CB@MAMI (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