Meson-baryon threshold effects in the light-quark baryon spectrum

Abstract

We argue that selected S wave meson-baryon channels may play a key role to match poor baryon mass predictions from quark models with data. The identification of these channels with effective inelastic channels in data analysis allows to derive a prescription which could improve the extraction and identification of baryon resonances.

Plausible explanation for theΔ5/2+(2000)puzzle

“…In reference [6] it was argued that it could be generated from πN 1/2 − (1650) as it is done here (alternatively π∆ 1/2 − (1620) might be also generating it). It should be remarked that only analyses reproducing the ππN production cross section data extract it as it was the case for ∆ 5/2 + (1740).…”

“…For ∆ 5/2 − (1930) the important role of ρ∆ has been recognized [5]. These are particular examples of a more general situation where a 3q model calculation (providing a reasonable overall description of the whole spectrum) overestimates the mass of a resonance so that a meson-baryon threshold lies in between the calculated 3q value and the experimental data [6].…”

“…[6]. Since the N 5/2 − (1675) has been dynamically generated as a bound state of ρ∆(1232) in the I = 1/2 sector (the same interaction generating the ∆ 5/2 − (1930) for I = 3/2) [5], we shall investigate the three-body π-ρ-∆ system but keeping the strong correlations of the ρ∆ system which generate the N 5/2 − (1675).…”

Hadron physics: a quark-model analysis

“…Among the anomalies we find large-energy-step anomalies, that correspond either to radial excitations as the ∆ P 33 (1600) and the N P 11 (1440) or quark Pauli blocking induced states as the ∆ D 35 (1930) and the ∆ P 31 (1750) [12].…”

Dynamically generated resonances

“…One observes a near degeneracy in the three spins 1/2 − , 3/2 − , 5/2 − , as the theory predicts. It is also very instructive to recall that the case of the ∆(5/2 − ) is highly problematic in quark models since it has a 3 hω excitation and comes out always with a very high mass [50,56] . The association of states found to some reported in the PDG for the case of Λ, Σ and Ξ states looks also equally appealing as one can see from the table.…”