The $d^{\ast}$(2380) dibaryon resonance width and decay branching ratios

Abstract

Attempts to reproduce theoretically the relatively small width, $\Gamma_{d^{\ast}}=80\pm 10$ MeV, of the $I(J^P)=0(3^+)$ $d^{\ast}$(2380) dibaryon resonance established by the WASA-at-COSY Collaboration are discussed. The validity of associating the $d^{\ast}$(2380) in quark-based models primarily with a tightly bound $\Delta\Delta$ configuration is questioned. The $d^{\ast}$(2380) width and decay branching ratios into $NN\pi\pi$, $NN\pi$ and $NN$ final states are studied within the Gal-Garcilazo hadronic model in which the $d^{\ast}$(2380) is a $\pi N\Delta$ resonance embedded in the $NN\pi\pi$ continuum some 80 MeV below the $\Delta\Delta$ threshold. In particular, predictions are made for the branching ratios of the unobserved yet $d^{\ast}(2380)\to NN\pi$ decays which are suppressed in a purely-$\Delta\Delta$ dibaryon model. Comments are also made on a possible connection of the ABC effect observed in the $pn\to d^{\ast}\to d\pi^0\pi^0$ resonance reaction to the $d^{\ast}$(2380) dibaryon.