A framework for PDFs at a photon collider

We introduce a resolved photon PDF framework for photon colliders and set of photon PDFs. The energy of a photon-photon collider whose beams are created from gamma-electron backscatter will vary between ~0 and 400 GeV at a 500 GeV $e^-e^-$ collider. While fits to the probability to find a quark or gluon from a photon exist in CJK2 and GRV PDF sets, a photon collider requires the convolution of the probability to have a beam photon with a given energy with the probability to find the parton for each event. To accomplish this convolution during event production in a Monte Carlo generator is computationally prohibitively expensive (several minutes per integral). Hence, we create a table-based photon PDF with interpolation in an offline step, and provide an interface to LHAPDF to read in the results. This new general-purpose PDF makes possible fast phenomenological studies at photon-photon colliders, such as $b\bar b$ production, a major background to precision Higgs physics at a photon collider.