  We propose an explicitly solvable model for collinear scattering of
photoexcited carriers in intrinsic graphene irradiated by monochromatic light.
We find that the collinear scattering rate is directly proportional to the
photocarrier energy and derive an analytic expression for the corresponding
relaxation time. The result agrees with the recent numerical prediction [Mihnev
et al. Nat. Commun. vol. 7, 11617 (2016)] and is able to describe the
photocarrier evolution at low energies, where scattering on optical phonons is
strongly suppressed.
