ar X iv : n uc l - th / 9 70 80 15 v 1 8 A ug 1 99 7 Nucleon - nucleon partial wave analysis to 2 . 5 GeV

A partial-wave analysis of NN elastic scattering data has been completed. This analysis covers an expanded energy range, from threshold to a laboratory kinetic energy of 2.5 GeV, in order to include recent elastic pp scattering data produced by the EDDA collaboration at COSY. The results of both single-energy and energy-dependent analyses are described. INTRODUCTION This analysis of elastic NN scattering data updates our previous analysis(1) to 1.6 GeV in the laboratory kinetic energy. The present analysis extends to 2.5 GeV, which is the limit for elastic pp differential cross sections measured(2) by the EDDA collaboration using the cooler synchrotron at COSY. Measurements with a laboratory kinetic energy near 2 GeV are particularly interesting as they correspond to a center-of-mass energy (2.7 GeV) which has been suggested(3) for a broad dibaryon resonance. Near this energy, a sharp structure has been recently reported in the polarization observable Ayy(4), and this was taken as support for such a resonance. A resonancelike structure, at about the same energy, has also been reported in a partialwave analysis by Hoshizaki(5). The authors of Ref.(2) have considered this possibility, but find no evidence for a resonant excursion in their unpolarized cross sections. Polarization measurements expected from Saturne II and COSY will certainly help to clarify this issue.