TESLA Technical Design Report, Part VI, Chapter 1: The Photon Collider at TESLA

Adelphi University, South Avenue, Garden City, New York 11530 Aomori University, 2-3-1 Kohata, Aomori City, 030 Japan INFN Sezione di Bologna, Via Irnerio 46 I-40126 Bologna, Italy Brunel University, Uxbridge, Middlesex, UB8 3PH United Kingdom Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215 University of Cincinnati, Cincinnati, Ohio 45221 University of Colorado, Campus Box 390, Boulder, Colorado 80309 Columbia University, Nevis Laboratories P. O. Box 137, Irvington, New York 10533 Colorado State University, Ft. Collins, Colorado 80523 INFN Sezione di Ferrara, Via Paradiso, 12, I-44100 Ferrara, Italy Lab. Nazionali di Frascati, Casella Postale, 13 I-00044 Frascati, Italy University of Illinois, 1110 West Green Street, Urbana, Illinois 61801 Lawrence Berkeley Laboratory, Department of Physics, 50B-5211, University of California, Berkeley, California 94720 Louisiana Technical University, Ruston, Louisiana 71272 University of Massachusetts, Amherst, Massachusetts 01003 University of Mississippi, University, Mississippi 38677 Massachusetts Institute of Technology, 77 Massachussetts Avenue Cambridge, Massachusetts 02139 Moscow State University, Institute of Nuclear Physics 119899 Moscow, Russia Nagoya University, Nagoya 464, Japan Department of Physics, University of Oregon, Eugene, Oregon 97403 Oxford University, Oxford, OX1 3RH, United Kingdom Universita di Padova, Via F. Marzolo, 8 I-35100 Padova, Italy Universita di Perugia, Sezione INFN, Via A. Pascoli I-06100 Perugia, Italy

Linear colliders offer a unique opportunity to study γγ and γe interactions. Using the laser backscattering method one can obtain γγ, γe colliding beams with an energy and luminosity comparable to that in e+e− collisions. This work is part of the Conceptual Design of TESLA/SBLC linear colliders considering a second interaction region for γγ and γe collisions. We consider here possible physics in high-energy γγ, γe collisions, e→γ conversion, requirements to lasers, collision schemes, attainable luminosities, backgrounds, possible lasers, optics at the interaction region and other associated problems.

The SLD collaboration completed construction of a new CCD vertex detector (VXD3) in January 1996 and started data taking in April 1996 with the new system. VXD3 is an upgrade of the original CCD vertex detector, VXD2, which had successfully operated in SLD for three years. VXD3 consists of 96 large area CCDs, each having 3.2 million 20 μm × 20 μm pixels. By reducing the detector material and lengthening the lever arm, VXD3 is expected to improve secondary vertex resolution by about a factor of two compared with VXD2. The new three-layered structure enables stand-alone tracking without any ambiguity and its extended size along the beam direction improves the polar-angle coverage to |cos θ| < 0.85. An overview of this detector system and its initial performance are described.

During the past year, the SLD collaboration completed the construction and began the operation of a new vertex detector (VXD3) employing 307 million pixels. This detector, based on 96 CCDs of 13 cm(2) area each, is an upgrade of the original vertex detector of SLD (VXD2), made possible by advances in the technology of CCD detectors. Its improved impact parameter resolution, larger solid angle coverage and virtually error0free track linking will enhance the SLD measurement of the polarization-enhanced forward-backward asymmetry for band c- quarks, increase the precision of the measurement of the b-fraction in hadronic Z decays, and open the possibility to observe B-5(0)-mixing. Full separation of primary, secondary and tertiary vertices is accessible. A description of the mechanics and electronics of VXD3 are presented along with results from the first data.

This report is an overview of the gamma-gamma physics capabilities of LEP2, and covers the following topics: structure functions, equivalent photon approximation, tagging conditions etc, soft and semihard physics, large-$p_t$ processes, heavy-quark physics, and exclusive channels.

The cross sections for processes with the production of Z and pairs of leptons or quarks in the gammagamma collisions are calculated. They re large enough to give an important background for Higgs boson hunting at future photon colliders if the Higgs boson mass is about 100 GeV and they are small for the production of two Z. The equivalent electron approximation for the polarized photon beams is presented.