On the η1(1855), π1(1400) and π1(1600) as Dynamically Generated States and Their SU(3) Partners

Abstract

In this work, we interpret the newly observed η1(1855) resonance with exotic JPC=1−+ quantum numbers in the I=0 sector, reported by the BESIII Collaboration, as a dynamically generated state from the interaction between the lightest pseudoscalar mesons and axial-vector mesons. The interaction is derived from the lowest order chiral Lagrangian from which the Weinberg–Tomozawa term is obtained, describing the transition amplitudes among the relevant channels, which are then unitarized using the Bethe–Salpeter equation, according to the chiral unitary approach. We evaluate the η1(1855) decays into the ηη′ and KK¯*π channels and find that the latter has a larger branching fraction. We also investigate its SU(3) partners, and according to our findings, the π1(1400) and π1(1600) structures may correspond to dynamically generated states, with the former one coupled mostly to the b1π component and the latter one coupled to the K1(1270)K¯ channel. In particular, our result for the ratio Γ(π1(1600)→f1(1285)π)/Γ(π1(1600)→η′π) is consistent with the measured value, which supports our interpretation for the higher π1 state. We also report two poles with a mass about 1.7 GeV in the I=1/2 sector, which may be responsible for the K*(1680). We suggest searching for two additional η1 exotic mesons with masses around 1.4 and 1.7 GeV. In particular, the predicted η1(1700) is expected to have a width around 0.1 GeV and can decay easily into KK¯ππ.