Effective photon spectra for the photon colliders

The luminosity distribution in the effective \(\gamma\gamma\) mass at a photon collider usually has two peaks which are well separated: a high energy peak with mean energy spread about 5–7% and a wide low energy peak. The low energy peak strongly depends on the details of the design and is unsuitable for the study of new physics phenomena. We find a simple approximate form for the spectra of colliding photons for \(\gamma \gamma\) and \(e\gamma \) colliders, whose convolution describes the high energy luminosity peak with a good accuracy in most of the essential preferable region of the parameters.