Physics at Linear Colliders

Much of the success of modern particle physics has hinged on the development of increasingly energetic accelerators which enable the study of fundamental interactions at successively finer scales. In the case of electron-positron accelerators, the excessive amount of synchrotron radiation from circulating electron and positron beams make it necessary to collide beams from opposing linear accelerators in order to achieve center-of-mass energies above 200 GeV or so. In addition, linear collider beams are relatively easy to polarize, leading to an additional, but critically important, tool for exploring the fundamental interactions of matter.

The SLAC Linear Collider (SLC), in operation from 1988-1998 at the Z°-boson resonance (91 GeV), was in some measure a prototype linear collider which demonstrated the feasibility of a higher energy machine. In addition, the SLC was an exacting physics facility, leading to some of the most precise tests of the Standard Model of particle physics performed to date. SCIPP physicists were deeply involved in the SLC (and SLD detector) program, including the design and construction of the tracking, particle identification, and precise electron beam polarimetry systems, as well as software engineering and analysis of SLD detector data.

SCIPP members of the SLC/SLD effort are now part of the international group working towards the proposal for a high energy linear collider, with a center-of-mass collision energy between 500 and 1500 GeV. The physics done at such a machine would complement that of the Large Hadron Collider (currently under construction at CERN) in probing the details of the `electroweak scale' - the precise way in which the electromagnetic and weak nuclear forces coalesce into a single, unified interaction. SCIPP efforts on the Linear Collider include R&D studies of tracking options for the associated detector, the implication of studies of the strong nuclear force on the accelerator and detector design, as well as studies of the advantages obtained by colliding highly polarized e-e- beams. In addition, SCIPP hosts an ongoing series of international workshops on electron-electron interactions at TeV energies. The Linear Collider effort at SCIPP is relatively small (2 faculty, one post-doctoral fellow, one graduate student), but is expected to grow substantially as the international program gains momentum.

SCIPP contact: Bruce Schumm, Clemens A. Heusch