Upper limit on the flux of photons with energies above 1019 eV using the Telescope Array surface detector

We search for ultra-high energy photons by analyzing geometrical properties of shower fronts of events registered by the Telescope Array surface detector. By making use of an event-by-event statistical method, we derive upper limits on the absolute flux of primary photons with energies above 1019, 1019.5, and 1020 eV based on the first three years of data taken. © 2013 American Physical Society.