Search for the piNN resonance d' at COSY 11 with the reaction pp->pp pi-pi+

R.Bilger, R.Großmann, H.Clement, G.J.Wagner, Physikalisches Institut der Universität Tübingen, Auf der Morgenstelle 14, D-72076 Tübingen, und die COSY-11-Kollaboration

The two-pion production in nucleon-nucleon collisions is the most basic reaction for the hadronic production of resonances in the piNN system which are decoupled from the NN channel. Evidence for such a candidate has recently been found in the pionic double charge exchange (DCX) reaction on nuclei [1,2] as well as in pp->pp pi-pi+ measured at CELSIUS [3]. Since the COSY 11 setup is particularly well suited for the investigation of reactions right at particle production thresholds, we have studied the reaction pp->d'pi+->pp pi-pi+ close to the estimated d' production threshold. In a first test run measurements have been carried out at Tp = 690, 715 and 725 MeV. We report about these measurements and a first analysis of the data.

[1] R. Bilger et al., Phys. Rev. Lett. 71 (1993) 42; 72 (1994) 2972
[2] K. Föhl et al., Phys. Rev. Lett. 79 (1997) 3849
[3] W. Brodowski et al., Z. Phys. A355 (1996) 5
supported by BMBF (06 TU 886), DFG (Mu 705/3) and KFA Jülich (COSY-046)