From CELSIUS to COSY: on the observation of a dibaryon resonance

TL;DR

This paper reports the first observation of a genuine s-channel dibaryon resonance at COSY, identified through detailed two-pion production measurements and neutron-proton scattering data, revealing a narrow resonance about 80 MeV below the ΔΔ system.

Contribution

It presents the discovery of a new dibaryon resonance using exclusive measurements and polarized neutron-proton scattering, advancing understanding of nucleon-nucleon interactions.

Findings

Observation of a narrow dibaryon resonance at 2380 MeV.

Identification of a pole in coupled partial waves.

Confirmation of a genuine s-channel resonance.

Abstract

Using the high-quality beam of storage rings in combination with a pellet target and the hermetic WASA detector covering practically the full solid angle the two-pion production in nucleon-nucleon collisions has been systematically studied by exclusive and kinematically complete measurements -- first at CELSIUS and subsequently at COSY. These measurements resulted in a detailed understanding of the two-pion production mechanism by $t$-channel meson exchange. The investigation of the ABC effect in double-pionic fusion reactions lead the trace to the observation of a narrow dibaryon resonance with $I(J^P) = 0(3^+)$ about 80 MeV below the nominal mass of the conventional $\Delta\Delta$ system. New neutron-proton scattering data, taken with polarized beam at COSY, produce a pole in the coupled $^3D_3$ - $^3G_3$ partial waves at ($2380\pm10~-~i~40\pm5$) MeV establishing thus the first observation of a genuine $s$-channel dibaryon resonance.