1−+ hybrid meson in J/ψ radiative decays from lattice QCD

Revealing the inner structure of the newly observed η 1(1855) via photoproduction

“…Indeed, many works at present can naturally interpret the η 1 (1855) as a hybrid meson. In particular, the QCD axial anomaly supports the interpretation of the η 1 (1855) as the ssg hybrid meson [26], which was also supported by the Lattice QCD [27] and the flux tube model picture [28]. An additional hybrid meson explanation of the η 1 (1855) can be found in [29].…”

“…The observed resonance masses, spin-parity, and widths indicate that the newly observed state η 1 (1855) is most likely to be a ssg ¯hybrid meson. Indeed, the authors in [26][27][28][29] support its interpretations as a ssg ¯hybrid meson of J PC = 1 −+ . However, a completely different conclusion was drawn from [32,33] that the η 1 (1855) can be explained as S-wave KK 1400 1 ¯( ) molecular state.…”

“…Based on the theoretical studies in [26][27][28][29][30][31][32][33], η 1 (1855) can be interpreted as a ssg ¯hybrid meson, a compact tetraquark state, and a KK 1 ¯molecular state, respectively. Since the photoproduction processes are very helpful to distinguish which inner structure of η 1 (1855) state is possible, we suggest experimentally searching for η 1 (1855) in the γp → η 1 (1855)p reaction.…”

“…It can only be determined by the theoretical calculation. Fortunately, the branching fraction Br(J/ψ → γη 1 (1855)) is estimated to be about 6.2 × 10 −5 [27]. And the decay width of J/ψ into γη 1 (1855) is G = q q F q u p s g q q m q q m p g p g p s p s i ,…”