G.L. Kotkin

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 γ e , 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.

Colliding γe and γγ beams based on single-pass e+e− accelerators II. Polarization effects, monochromatization improvement

Polarization effects are considered in colliding γe and γγ beams, which are proposed to be obtained on the basis of linear e+e− colliders (by backward Compton scattering of laser light on electron beams). It is shown that using electrons and laser photons with helicities λ and Pc, such that λPc<0, essentially improves the monochromatization. The characteristic laser flash energy, A0, which is necessary to obtain a conversion coefficient k ≈ 1 with a definite degree of monochromatization, is considerably less (sometimes by one order of magnitude) in the case 2λPc = −1 in contrast to the case λPc=0. Simultaneously the luminosities Lγe and Lggγ essentially increase. Formulae are obtained which allow one to extract the polarization information about γe → X and γγ → X reactions. Perculiarities connected with the specific scheme of the γ beam preparation are discussed. Problems of the calibration of the γe and γγ collisions for the polarized beams are discussed.

Polarization of high-energy γ-quanta traversing a bunch of polarized laser photons

Abstract The elastic light-light scattering below the threshold of the e + e − pair production leads to a variation in polarization of hard γ-quanta traversing (without loss in intensity) a region where the laser light is focused. This effect can be used to control the γ-quantum polarization. Equations are obtained which determine the variation of Stokes parameters of γ-quanta in this case, and their solutions are given. It is pointed out that this effect can be observed in the experiment of the type of E- 144 at SLAC. It should be taken into account and, perhaps, it can be used in experiments at future γγ colliders.

Effective photon spectra for the photon colliders

The luminosity distribution in the effective

Coherent bremsstrahlung at colliding beams

\gamma\gamma

Polarization of final electrons in the Compton effect

mass at photon collider has usually two peaks which are well separated: high energy peak with mean energy spread 5-7% and wide low energy peak.The low energy peak depends strongly on details of design it is unsuitablefor the study of New Physics phenomena. We find simple approximte form of spectra of collided photons for

Complete description of polarization effects in e + e- pair productionby a photon in the field of a strong laser wave

\gamma\gamma

Electron (positron) beam polarization by Compton scattering on circularly polarized laser photons

and

Coherent bremsstrahlung at the HERA collider

e\gamma

Radiative corrections in charge-exchange and backward hadron scattering

colliders wich convolution describes high energy luminosity peak with good accuracy in the most essential preferable region of parameters.