Constraints on the diffuse photon flux with energies above 1018 eV using the surface detector of the Telescope Array experiment

We present the results of the search for ultra-high-energy photons with nine years of data from the Telescope Array surface detector. A multivariate classifier is built upon 16 reconstructed parameters of the extensive air shower. These parameters are related to the curvature and the width of the shower front, the steepness of the lateral distribution function, and the timing parameters of the waveforms sensitive to the shower muon content. A total number of two photon candidates found in the search is fully compatible with the expected background. The 95% CL limits on the diffuse flux of the photons with energies greater than 1018.0, 1018.5, 1019.0, 1019.5 and 1020.0 eV are set at the level of 0.067, 0.012, 0.0036, 0.0013, 0.0013km−2yr−1sr−1 correspondingly.