Colliding ge and gg beams based on the single-pass e ±e − colliders (VLEPP type)

Abstract

We discuss in detail our proposed [1,2] method of obtaining colliding γe and γγ beams with high energies and luminosities using the designed linear accelerators VLEPP and SLC with colliding e +e − beams at the energies 2 E ≳ 100 GeV. The intense γ beams are obtained by backward Compton scattering of laser light which is focused on the electron beams of these accelerators. This paper contains the scheme for conversion of an electron beam into a γ beam, a calculation of the conversion coefficient and of the total and spectral γe and γγ luminosities. To get the luminosity L γe , L γγ ∼ L ee, one needs a laser flash with energy ∼ 15J, and a pulse duration ∼ 30 ps at a repetition rate of 10 or 180 Hz. Such parameters seem to be achievable on the basis of current technology. The luminosity distribution over the γe or γγ invariant mass is broad. A method of monochromatization is described. It demands an increase of the laser flash energy (with a possible increase of pulse duration) and leads to a decrease of luminosity. We also describe a method for calibrating the total and spectral luminosities. Problems concerning the background are shown to be easier than in e +e − collisions. Some examples of interesting physical problems for γe and γγ collisions are enumerated.