Decays of an exotic 1?+ hybrid meson resonance in QCD

摘要

We present the first determination of the hadronic decays of the lightest exotic J P C = 1 ? + resonance in lattice QCD. Working with SU(3) flavor symmetry, where the up, down and strange-quark masses approximately match the physical strange-quark mass giving m π ～ 700 ? ? MeV , we compute finite-volume spectra on six lattice volumes which constrain a scattering system featuring eight coupled channels. Analytically continuing the scattering amplitudes into the complex-energy plane, we find a pole singularity corresponding to a narrow resonance which shows relatively weak coupling to the open pseudoscalar–pseudoscalar, vector–pseudoscalar and vector–vector decay channels, but large couplings to at least one kinematically closed axial-vector–pseudoscalar channel. Attempting a simple extrapolation of the couplings to physical light-quark mass suggests a broad π 1 resonance decaying dominantly through the b 1 π mode with much smaller decays into f 1 π , ρ π , η ′ π and η π . A large total width is potentially in agreement with the experimental π 1 ( 1564 ) candidate state observed in η π , η ′ π , which we suggest may be heavily suppressed decay channels.