Origin of Galactic Sub-PeV Diffuse Gamma-Ray Emission: Constraints from High-energy Neutrino Observations

Very recently, diffuse gamma rays with $0.1\,{\rm PeV}<E_\gamma <1\,\rm PeV$ have been discovered from the Galactic disk by Tibet air shower array and muon detector (Tibet AS+MD array). While measured sub-PeV flux may be compatible hadronic origin in conventional cosmic ray propagation model, we find that it is possible tension non-detection of neutrino emissions IceCube telescope. We further presence an extra component relatively hard spectrum, which probably related to Cygnus Cocoon region other PeV cosmic-ray sources disk, would alleviate tension. This scenario implies existence extreme accelerator either protons or electrons beyond region, predicts continuation gamma-ray spectrum up 1 a hardening $\sim 30-100\,$TeV.