Ultimate luminosities and energies of photon colliders

A photon collider luminosity and its energy are determined by the parameters of an electron-electron linear collider (energy, power, beam emittances) and collision effects. The main collision effect is the coherent e+e- pair creation. At low energies (2E < 0.5 - 1 TeV) this process is suppressed due to repulsion of electron beams. In this region gamma-gamma luminosity above 10^{35} cm-2 s-1 is possible (10^{33} is sufficient). At higher energies the limited average beam power and coherent pair creation restrict the maximum energy of photon colliders (with sufficient luminosity) at 2E ~ 5 TeV. Obtaining high luminosities requires the development of new methods of production beams with low emittances such as a laser cooling.Comment: 15 pages, Latex, 6 figures(eps), submitted to Proceedings of the Symposium on Future High Energy Colliders, ITP, UCSB, Santa Barbara, October 1996. AIP Pres

Some problems in plasma suppression of beam-beam interactions at muon colliders

The idea of plasma suppression of beam-beam effects at muon colliders is discussed. It is shown that one should take into account collisions in the plasma that were ignored before. Rough estimates show that this effect leads to a fast ``recovery'' of the beam magnetic field. For beam parameters characteristic for muon colliders the suppression of the magnetic component of the beam field (1/2 of the total force) is almost absent. It is also shown that the presence of the dense plasma (Li jet) at the interaction point leads to enormous hadronic background (due to photo-nuclear reactions) in the detector, about 10^{7} particles per crossing at large angles which creates serious problems for experimentation.Comment: 6 pages, LaTeX, Talk at the Workshop Studies on Colliders and Collider Physics at the Highest Energies: Muon Colliders at 10 TeV to 100 TeV, 27 September - 1 October, 1999 Montauk, New York, USA, be published by the American Institute of Physic

Coherent e^+e^- pair creation at high energy muon colliders

It is shown that at muon colliders with the energy in the region of 100 TeV the process of coherent pair creation by the muon in the field of the opposing beam becomes important and imposes some limitations on collider parameters.Comment: 3 pages, LaTeX, Talk at the Workshop Studies on Colliders and Collider Physics at the Highest Energies: Muon Colliders at 10 TeV to 100 TeV, 27 September - 1 October, 1999 Montauk, New York, USA, be published by the American Institute of Physic

Introduction and recent developments in gamma-gamma, gamma-electron colliders

High energy photon colliders (gamma-gamma, gamma-electron) based on backward Compton scattering of laser light is a very natural addition to e+e- linear colliders. In this report we consider mainly this option for the TESLA project. Recent study has shown that the horizontal emittance in the TESLA damping ring can be further decreased by a factor of four. In this case the gamma-gamma luminosity luminosity in the high energy part of spectrum can reach 0.3--0.5 L_e+e-. Typical cross sections of interesting processes in gamma-gamma collisions are higher than those in e+e- collisions by about one order of magnitude, so the number of events in gamma-gamma collisions will be more that in e+e- collisions. The key new element in photon colliders is a very powerful laser system. The most straightforward solution is ``an optical storage ring (optical trap)'' with diode pumped laser injector which is today technically feasible. This paper briefly review the status of a photon collider based at TESLA, its possible parameters.Comment: 6 pages, Latex, 2 figures(eps), Talk at Intern. Conference on the Structure and Interactions of the Photon: Incl. the 13 Intern. Workshop on Photon-Photon Collisions, PHOTON 2000, 26-31 August, 2000, Ambleside, Englan

Limit on a horizontal emittance in high energy muon colliders due to synchrotron radiation

It is shown that at a 100 TeV muon collider the synchrotron radiation in the ring will determine the minimum horizontal emittance.Comment: 2 pages, LaTeX, Talk at the Workshop Studies on Colliders and Collider Physics at the Highest Energies: Muon Colliders at 10 TeV to 100 TeV, 27 September - 1 October, 1999 Montauk, New York, USA, be published by the American Institute of Physic