1. The pp→pp  0  0 reaction and 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 M=2360 MeV  =90 MeV  (t-channel) Roper preliminary WASA-at-COSY

3. ABC effect M.Bashkanov et al., Proc. PANIC08, 239 M=2360 MeV  =90 MeV

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

5. “ABC” effect in ANKE data pp→{pp} S X selection: E pp 0.95 1100 MeV1400 MeV final {pp} in asume S-wave in   initial protons in or  only S-wave amplitude only D-wave amplitude S- and D-wave amplitudes S.Dymov et al., PRL 102, 192301 (2009) M x [GeV/c 2 ]

6. Oservation of an “ABC” effect in proton-proton collisions pp→{pp} S X S.Dymov et al., PRL 102, 192301 (2009)  “ If ABC is not a resonance, it does not have to have a definite isospin … ”  “… pp→{pp} S X 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 … ”  “… pp→{pp} S X kinematics are very similar to those of pn→d  0  0 and so a comparison with CELSIUS-WASA data is instructive ”

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

8.      production CELSIUS-WASA N * → N  N * →  L.Alvarez-Ruso et al., Nucl. Phys. A 633 (1998), 519  N * → N  N * →  

9.  0  0 production at T p < 1 GeV Valencia model A(tot)  A(N * →N  )+A(N * →  ) T p =0.795 GeV COSY-TOF At Roper mass M=1440 MeV T p =0.895 GeV All theoretical curves are normalized in area to the data

10.  0  0 production at T p > 1 GeV VC with readjusted N→  branch T p = 1 GeVT p = 1.1 GeVT p = 1.2 GeVT p = 1.3 GeV

11.  0  0 production at T p > 1 GeV VC with readjusted N * →  branch VC with readjusted total N * strength (T. Skorodko et al., Phys.Lett. B 679 (2009) 30) T p = 1 GeVT p = 1.1 GeVT p = 1.2 GeVT p = 1.3 GeV

12.  0  0 production at T p > 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)

13.  0  0 production at T p > 1 GeV VC with readjusted N→  branch VC with readjusted total N * strength VC with readjusted total N * strength and with modified  excitation T p = 1 GeVT p = 1.1 GeVT p = 1.2 GeVT p = 1.3 GeV

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

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

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

17. 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

18. Outlook pn→pn  0  0 p+(np s ) at T p =1.0 GeV p+(np s ) at T p =1.2 GeV TpTp TpTp ABC WASA-at-COSY

19. Thank you