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

Abstract

Phase shifts and inelasticity parameters for $NN$ scattering in the partial-wave channels ${}^3{S}_1$--${}^3{D}_1$ and ${}^1{S}_0$ at energies $T_{\mathrm{lab}}$ from zero to about 1 GeV are described within a unified $NN$ potential model assuming the formation of isoscalar and isovector dibaryon resonances near the $N{N}^{\ast }(1440)$ threshold. Evidence for these near-threshold resonances is actually found in the recent WASA experiments on single- and double-pion production in $NN$ collisions. There, the excitation of the Roper resonance $N^{\ast }(1440)$ exhibits a structure in the energy dependence of the total cross section, which corresponds to the formation of dibaryon states with $I(J^{\pi })=0(1^{+})$ and $1(0^{+})$ at the $N{N}^{\ast }(1440)$ threshold. These two $S$-wave dibaryon resonances may provide a new insight into the nature of the strong $NN$ interaction at low and intermediate energies.

Comments: 10 pages, 8 figures