Colliding positrons, polarized electrons.The Stanford Linear Collider The Stanford Linear Collider was a linear accelerator that collided electrons and positrons at the Stanford Linear Accelerator Center. The center of mass energy was about 90 GeV, equal to the mass of the Z boson, which the accelerator was designed to study. (SLC (Subscriber Loop Carrier) Lucent's designation for its digital loop carrier (DLC) products. See digital loop carrier. See also 386SLC. ) is back in business. Since June, researchers at the facility have been collecting data generated by high-energy collisions between beams of polarized A one-way direction of a signal or the molecules within a material pointing in one direction. electrons and unpolarized positrons (the antimatter antimatter: see antiparticle.
Substance composed of elementary particles having the mass and electric charge of ordinary matter (such as electrons and protons) but for which the charge and related magnetic properties are opposite in sign. counterparts of electrons).
So far, the international team of more than 150 physicists working with the Stanford Large Detector The Stanford Large Detector (SLD) was the main detector for the Stanford Linear Collider at the Stanford Linear Accelerator Center. It was designed primarily to detect Z bosons produced by the accelerator's electron-positron collisions, but the observations made were overshadowed has observed and recorded more than 10,000 collisions that produced Z particles. These elementary particles are among those carrying the so-called weak force, which is responsible for radioactive decay radioactive decay
1. Spontaneous disintegration of a radionuclide accompanied by the emission of ionizing radiation in the form of alpha or beta particles or gamma rays.
2. An instance of such disintegration. .
Earlier this month, at the International Conference on High-Energy Physics, held in Dallas, the researchers reported the results of analyses based on data from roughly 5,000 of these events. Their findings yielded a new measurement of a key parameter in the standard model of particle physics, which describes how the fundamental particles of matter interact with one another.
This achievement represents a belated victory for the innovative but trouble-plagued SLC, whose technical glitches cost it the race in 1989 with the 17-mile Large Electron-Positron ring at the European Center for Particle Physics in Geneva Geneva, canton and city, Switzerland
Geneva (jənē`və), Fr. Genève, canton (1990 pop. 373,019), 109 sq mi (282 sq km), SW Switzerland, surrounding the southwest tip of the Lake of Geneva. , Switzerland, to generate large numbers of Z particles (SN: 9/10/88, p.167; 9/2/89, p.159).
Upgraded in April to produce polarized electrons, whose spins are aligned in the direction of the beam, the SLC now allows researchers to probe more precisely certain kinds of interactions between elementary particles. No other high-energy accelerator in the world has this capability.
Polarized electrons are created by shining a powerful beam of polarized laser light on a specially prepared gallium arsenide surface. The ejected electrons gather into compact bunches and reach an energy of 46 billion electron-volts as they race down the SLC's 2-mile track to crash head-on into high-energy, unpolarized positrons traveling at the same speed.
Researchers can switch the electrons' direction of polarization back and forth between clockwise and anticlockwise by changing the polarization of the laser light. By comparing what happens when electrons "rotate" clockwise versus anticlockwise along the beam axis, Charles Baltay of Yale University, Martin Breidenbach of the Stanford Linear Accelerator Center
The Stanford Linear Accelerator Center (SLAC) is a United States Department of Energy National Laboratory operated by Stanford University under the programmatic direction of the U.S. , and their collaborators could for the first time study how this difference affects the production rate of Z particles.
From these data, they obtained a new measurement of the so-called Weinberg angle. In the standard model, this quantity determines the degree of "mixing" between the electromagnetic and weak forces.