The d ⁎ (2380) dibaryon resonance width and decay branching ratios

Abstract

Attempts to reproduce theoretically the width Γ d * = 80 ± 10 MeV of the I(J P ) = 0(3 + ) d * (2380) dibaryon resonance established by the WASA-at-COSY Collaboration are discussed. The validity of associating the d * (2380) in quark-based models exclusively with a tightly bound ∆∆ configuration is questioned. The d * (2380) width and decay branching ratios into NNππ, NNπ and NN final states are studied within the Gal-Garcilazo hadronic model in which the d * (2380) is a πN∆ resonance embedded in the NNππ continuum some 80 MeV below the ∆∆ threshold. In particular, predictions are made for the branching ratios of the unobserved yet d * (2380) → NNπ decays which are suppressed in a purely-∆∆ dibaryon model. Comments are also made on a possible connection of the ABC effect observed in the pn → d * → dπ 0 π 0 resonance reaction to the d * (2380) dibaryon.

Dibaryons --- Fake or True?

“…[6]. Anyway, since this state has just the width of the ∆, it is believed to be a slightly bound extended molecular-like object, where quark degrees of freedom do not yet play a significant role -in agreement with recent theoretical calculations [7][8][9][10]. This state, for which first indications were already known from experiments in the fifties and early sixties, was associated by Dyson and Xuong [3] with their third predicted state.…”

“…Moreover, the observed decay branchings are not all properly reproduced. In order to cure this deficits, Gal recently proposed a two-configuration model, where the compact hexaquark core is surrounded by a molecular-like ∆N π configuration [9].…”

Form factors of the d*(2380) resonance

“…The result from a compact hexaquark dominated structure model is directly calculated and is consistent with the data. On the other side, a combined α½ΔΔ þ ð1 − αÞ½D 12 π mixing structure was also proposed [17], and the data can be explained as well. Therefore, we need to seek other observable physical quantities to distinguish these two different structures for d à .…”

Scattering of decuplet baryons in chiral effective field theory

“…Table 2) and the fact that the Δ has a sizable width, i.e. there is a coupling to the N Nπ and N Nππ continuum [77]. Both should have a significant influence on the location of the state and certainly on its width.…”