Comments on photon colliders for Snowmass 2013

Understand

For more than 30 years [1], gamma-gamma and gamma-electron photon colliders have been considered a natural addition to e+e- linear-collider projects.

• Following the recent discovery of the Higgs boson, the physics community has been actively considering various approaches to building a Higgs factory, a photon collider (with or without e+e-) being one of them.
• In this note, following a brief discuss of photon colliders based on ILC and CLIC, I give a critical overview of the recently proposed photon-collider Higgs factories with no e+e- collision option.