Studying Hadronic Structure of the Photon in Lattice QCD

We show that the matrix element of a local quark-gluon operator in the photon state, $〈\gamma \left(k\lambda \right)|\hat{O}|\gamma \left(k\lambda \right)〉$, can be calculated in lattice QCD. The result is generalized to other quantities involving spacelike photons, including the transition form factor $\gamma {\gamma }^{*}\to {\pi }^0$ and the virtual-photon-nucleon Compton amplitude $〈{\gamma }^{*}N|{\gamma }^{*}N〉$ which can be used to define the generalized Drell-Hearn-Gerasimov and Bjorken sum rules.