Search for low-mass exotic mesonic structures: II. Attempts to understand the results

Our previous paper, part I of the same study, shows the different experimental spectra used to draw a conclusion on the genuine existence of narrow, weakly excited mesonic structures having masses below and a little above the pion (M = 139.56 MeV) mass. This study [1] was instigated by the observation, in the Σ⁺ disintegration—Σ⁺ → pP⁰, P⁰ → μ^-μ⁺ [2]—of a narrow range of dimuon masses. The authors make a conclusion on the existence of a neutral intermediate state P₀ with a mass M = (214.3 ± 0.5) MeV. We present here some attempts to understand the possible nature of the structures observed in part I.