An Isotensor Dibaryon in the $pp \to pp\pi^+\pi^-$ Reaction?

TL;DR

This study investigates the $pp o pp o ext{pions}$ reaction at energies near 1.2 GeV, revealing that an isotensor dibaryon resonance explains discrepancies between measurements and traditional models.

Contribution

The paper provides evidence for an isotensor dibaryon resonance as a key factor in the reaction, challenging existing meson exchange models.

Findings

Measured cross sections deviate from meson exchange predictions.

An isotensor dibaryon resonance explains the observed data.

Resonance with I(J^P)=2(1^+) is identified as significant.

Abstract

Exclusive measurements of the quasi-free $pp \to pp\pi^+\pi^-$ reaction have been carried out at WASA@COSY by means of $pd$ collisions at $T_p$ = 1.2 GeV. Total and differential cross sections have been extracted covering the energy region $T_p = 1.08 - 1.36$ GeV, which is the region of $N^*(1440)$ and $\Delta(1232)\Delta(1232)$ resonance excitations. Calculations describing these excitations by $t$-channel meson exchange are at variance with the measured differential cross sections and underpredict substantially the experimental 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.