The pp→pp 0  0 reaction and its limiting case, the fusion to quasibound ,

1. The pp→pp00 reactionand its limiting case, the fusion to quasibound , in search of ABC effect T. Skorodko, University Tuebingen for CELSIUS-WASA ► motivation and detector setup ► results and discussions ► summary and outlook

2. ABC effect WASA-at-COSY M=2360 MeV =90 MeV preliminary  (t-channel) Roper

3. “ABC” effect in ANKE data S.Dymov et al., PRL 102, 192301 (2009) 0.8 GeV pp→{pp}SX 1.1 GeV phase space selection: Epp < 3 MeV, cosθpp > 0.95 1.4 GeV 2 GeV

4. “ABC” effect in ANKE data pp→{pp}SX S.Dymov et al., PRL 102, 192301 (2009) selection: Epp < 3 MeV, cosθpp > 0.95 1100 MeV 1400 MeV Mx [GeV/c2] only S-wave amplitude • final {pp} in • asume S-wave in  •  initial protons in or  only D-wave amplitude S- and D-wave amplitudes

5. Oservation of an “ABC” effect in proton-proton collisions S.Dymov et al., PRL 102, 192301 (2009) pp→{pp}SX  “If ABC is not a resonance, it does not have to have a definite isospin …”  “… pp→{pp}SX kinematics are very similar to those of pn→d00 and so a comparison with CELSIUS-WASA data is instructive”  “… pp→{pp}SX kinematics are very similar to those of pn→d00 and so a comparison with CELSIUS-WASA data is instructive”  “… we certainly have no evidence for an I=1 dibaryon …”

6. pp→pp00 at 4 CELSIUS-WASA detector Tp = 775, 895, 1000, 1100, 1200, 1300, 1360 MeV γ γ p p γ γ

7. p0p0production  N* →Ns CELSIUS-WASA N* →Dp N* →Dp N* →Ns  L.Alvarez-Ruso et al., Nucl. Phys. A 633 (1998), 519

8. 00 production at Tp < 1 GeV A(tot)  A(N*→N)+A(N*→) Valencia model Tp=0.795 GeV COSY-TOF All theoretical curves are normalized in area to the data Tp=0.895 GeV At Roper mass M=1440 MeV

9. 00 production at Tp > 1 GeV Tp = 1 GeV Tp = 1.1 GeV Tp = 1.2 GeV Tp = 1.3 GeV VC with readjusted N→ branch

10. 00 production at Tp > 1 GeV Tp = 1 GeV Tp = 1.1 GeV Tp = 1.2 GeV Tp = 1.3 GeV VC with readjusted N*→ branch VC with readjusted total N* strength (T. Skorodko et al., Phys.Lett. B 679 (2009) 30)

11. 00 production at Tp > 1 GeV modification of the  excitation  include relativistic corrections • reduce the contribution from ρ-exchange in  excitation by an order of magnitude (Xu Cao et al., nucl-th:1004.0140, today plenary session)

12. 00 production at Tp > 1 GeV Tp = 1 GeV Tp = 1.1 GeV Tp = 1.2 GeV Tp = 1.3 GeV VC with readjusted N→ branch VC with readjusted total N* strength and with modified  excitation VC with readjusted total N* strength

13. Total pp→pp00 cross section original VC VC with readjusted N→ branch VC with readjusted total N* strength VC with readjusted total N* strength and with modified  excitation

14. Comparison ANKE data with modified VC VC with readjusted total N* strength and with modified  excitation (ANKE cuts)

15. CELSIUS-WASA data with Mpp < 10 MeV cut VC with readjusted total N* strength and with modified  excitation (Mpp < 10 MeV cut)

16. Conclusions pp00 production can be described by a conventional t-channel  calculations with small contribution from ρ-exchange no evidence is found for a significant ABC effect (no low mass enhancement in M) since pp00 is isospin I=1 channel, it is not instructive to compare these data with isospin I=0 pn→d00 data

17. Outlook ABC pn→pn00 WASA-at-COSY p+(nps) at Tp=1.0 GeV Tp Tp p+(nps) at Tp=1.2 GeV

18. Thank you