On the Production of an Isotensor Dibaryon in the $pp \to pp\pi^+\pi^-$ Reaction

TL;DR

This study investigates the production of an isotensor dibaryon resonance in proton-proton collisions leading to a two-pion final state, providing experimental evidence that supports the existence of this predicted exotic state.

Contribution

First experimental measurement of the $pp o pp o ext{dibaryon}+ ext{pion}$ reaction, demonstrating the role of an isotensor dibaryon in explaining cross section discrepancies.

Findings

Measured total and differential cross sections across energy range.

Observed data inconsistent with meson exchange models.

Supported the existence of an isotensor dibaryon resonance.

Abstract

Exclusive measurements of the quasi-free $pp \to pp\pi^+\pi^-$ 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 $N^*(1440)$ and $\Delta(1232)\Delta(1232)$ 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 $\Delta N$ 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.