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December 15, 1997

UCSC physicists to participate in European-based scientific collaboration

Abraham Seiden, director of UCSC's Santa Cruz Institute for Particle Physics

By Jennifer McNulty

About a dozen physicists, engineers, and technicians from UCSC are among those who will participate in an international scientific collaboration to build a new high-energy particle accelerator and associated detectors near Geneva, Switzerland.

Officials with the U.S. Department of Energy and the National Science Foundation signed an agreement last week to invest more than $500 million over the next eight years in the new particle accelerator, the Large Hadron Collider (LHC), to be built at the European Particle Physics Laboratory, known by its French initials, CERN. The U.S. is one of several non-European nations participating in the project, including Japan, Canada, and Russia. The tab for the project is expected to total more than $6 billion.

Physicists will use the LHC for the next generation of experiments to explore the fundamental nature of matter, said UCSC physics professor Abraham Seiden, who will participate in the project.

The LHC will consist of giant magnets, a circular tunnel 16 miles in circumference, and powerful particle detectors. It will be used to smash together protons to create even tinier particles. Physicists hope to approximate the conditions that existed less than one-billionth of a second after the Big Bang that created the universe.

Seiden, director of UCSC's Santa Cruz Institute for Particle Physics (SCIPP), noted that the LHC will generate higher energy collisions than those produced by any other particle accelerator--about seven times the energy of the U.S. Department of Energy's Fermilab Tevatron near Chicago.

UCSC's physicists, including research physicist Alex Grillo and adjunct professor Hartmut Sadrozinski, will join Seiden as members of one of the two large international collaborations of scientists working on the construction of the two particle detectors, known as the ATLAS (A Toroidal LHC Apparatus) and CMS (Compact Muon Solenoid) detectors. The two detectors are the major particle detectors that will operate at the Large Hadron Collider at CERN. About 20 percent of the physicists involved in the project are from the U.S., noted Seiden, and the collaborations share the common goal of exploring the mysteries that underlie the basic building blocks of matter and the forces acting on them.

The ATLAS and CMS detectors will occupy different locations on the circumference of the 16-mile accelerator ring. At the center of each detector, beams of high-energy protons from the LHC will collide head on, creating about a billion proton-proton collisions each second. The detectors will measure the energies, directions, and identities of the particles that fly off from each of these collisions. Computers will process the resulting information fast enough to select and record only the one-in-10-million collisions that might carry the seeds of a new discovery, said Seiden.

Although the detectors will be the size of five-story buildings, each one will have sensors capable of measuring particle trajectories to better than one-thousandth of an inch, along with other devices that can precisely measure the amounts of energy carried by collision products flying off in every direction. Each detector will have large superconducting magnets to deflect electrically charged collision products and devices to measure their curving tracks. The detectors will be designed to withstand years of exposure to the intense radiation that exists at the center of such particle collisions.

Through SCIPP, the UCSC team will help construct the most precise, innermost particle detection devices for the ATLAS experiment. UCSC physicists have earned an international reputation for their expertise creating detectors made of large, very thin silicon crystals that enable information to be gathered, stored, and distributed via UCSC-designed microchips. "It's kind of like having a little computer on there," said Seiden.

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