Nature of $\bm{S}$-wave $\bm{NN}$ interaction and dibaryon production at nucleonic resonance thresholds

Abstract

Phase shifts and inelasticity parameters for N N scattering in the partial-wave channels 3 S 1 -3 D 1 and 1 S 0 at energies T lab from zero to about 1 GeV are described within a unified N N potential model assuming the formation of isoscalar and isovector dibaryon resonances near the N N * (1440) threshold. Evidence for these near-threshold resonances is actually found in the recent WASA experiments on single-and double-pion production in N N collisions. There, the excitation of the Roper resonance N * (1440) exhibits a structure in the energy dependence of the total cross section, which corresponds to the formation of dibaryon states with I(J π ) = 0(1 + ) and 1(0 + ) at the N N * (1440) threshold. These two S-wave dibaryon resonances may provide a new insight into the nature of the strong N N interaction at low and intermediate energies.