On a possible origin of a resonance-like structure in the two-photon invariant mass spectrum of the reaction pp->ppgg

TL;DR

This paper proposes that a resonance-like feature in the two-photon spectrum of proton-proton collisions is due to an intermediate dibaryon resonance, providing a new interpretation of experimental data.

Contribution

It introduces a dibaryon resonance mechanism as an explanation for the observed resonance-like structure in the two-photon invariant mass spectrum.

Findings

The dibaryon resonance mechanism reproduces the experimental spectrum near the resonance.

The resonance is identified as the $d^_1$(1956) state.

The process involves radiative production and decay of the dibaryon.

Abstract

We show that the resonance-like structure found by the \emph{CELSIUS-WASA Collaboration} in the two-photon invariant mass spectrum of the reaction $pp \to pp \gamma \gamma$ is rather a signature of the $NN$-decoupled dibaryon resonance $d^\star_1$(1956) that is produced in the radiative process $pp \to \gamma d^\star_1$ and then undergoes radiative decay into two protons $d^\star_1 \to pp \gamma$. It is found that a contribution of the dibaryon mechanism $pp \to \gamma d^\star_1 \to pp \gamma \gamma$ of the reaction $pp \to pp \gamma \gamma$ to the invariant mass spectrum of its photon pairs can reasonably well reproduce the experimentally observed spectrum in the vicinity of the resonance-like structure.