On the Production of an Isotensor Dibaryon in the $pp\to pp\ddot{I}{€}^{+}\ddot{I}{€}^{-}$ Reaction

Abstract

Exclusive measurements of the quasi-free $pp\to pp\ddot{I}{€}^{+}\ddot{I}{€}^{-}$ reaction have been performed by means of $pd$ collisions at $T_p$ = 1.2 GeV using the WASA detector setup at COSY. Total and differential cross sections have been obtained covering the energy region $T_p=1.08-1.36$ GeV ($\sqrt{s}$ = 2.35 - 2.46 GeV), which includes the regions of $N^{\ast }(1440)$ and $\hat{I}”(1232)\hat{I}”(1232)$ resonance excitations. Calculations describing these excitations by $t$-channel meson exchange are at variance with experimental differential cross sections and underpredict substantially the measured total cross section. An isotensor $\hat{I}”N$ dibaryon resonance with $I(J^P)=2(1^{+})$ produced associatedly with a pion is able to overcome these deficiencies. Such a dibaryon was predicted by Dyson and Xuong and more recently calculated by Gal and Garcilazo.