Towards the establishment of the light $J^{P(C)}=1^{-(+)}$ hybrid nonet

Abstract

The observation of the light hybrid candidate η1(1855) by the BESIII Collaboration brings great opportunities for advancing our knowledges about exotic hadrons in the light flavor sector. We show that this observation provides a crucial clue for establishing the J P (C) = 1 −(+) hybrid nonet. Based on the flux tube model picture, the production and decay mechanisms for the J P (C) = 1 −(+) hybrid nonet in the J/ψ radiative decays into two pseudoscalar mesons are investigated. In the I = 0 sector, we find that the SU(3) flavor octet and singlet mixing is non-negligible and apparently deviates from the flavor ideal mixing. Since only signals for one isoscalar η1(1855) are observed in the ηη channel, we investigate two schemes of the nonet structure in which η1(1855) can be either the higher or lower mass state that strongly couples to ηη . Possible channels for detecting the multiplets are suggested. In particular, a combined analysis of the hybrid production in J/ψ → V H, where V and H stand for the light vector mesons and 1 −(+) hybrid states, may provide further evidence for this nonet structure and finally establish these mysterious exotic species in experiment.

QCD axial anomaly enhances the $ηη^\prime$ decay of the hybrid candidate $η_1(1855)$

“…The η 1 (1855) was interpreted as a hybrid meson in a recent study [44]. There also exist some other possible explanations, e.g., the η 1 (1855) was explained as the K K1 (1400) hadronic molecule using the one-mesonexchange model in Ref.…”

An updated review of the new hadron states

“…Based on the interpretation of the η 1 (1855) as the I G J P C = 0 + 1 −+ hybrid meson, the authors of Ref. [1058] investigated its flavor SU (3) partners using a parametrization method based on the flux tube picture. They examined two schemes for the J P C = 1 −(+) hybrid nonet by assigning the η 1 (1855) to be either the higher or lower state, as shown in Fig.…”

“…The J P C = 1 −(+) hybrid nonet with the η 1 (1855) assigned as either the (a) higher or (b) lower state. Taken from Ref [1058]…”

Hadron spectroscopy at STCF

“…The η 1 (1855) is the first observed candidate of isoscalar 1 −+ hybrid [38,39,61,62]. Further studies with more production mechanisms and decay modes will help clarify the nature of the η 1 (1855).…”