e+e- Collisions at the SLC - the Left-Right Asymmetry

Recent progress with the SLC as a prototype linear collider for high energy e+ecollisions is reviewed. Recent advances in the production of high intensity beams of polarized e-s are also discussed. The SLD Collaboration has embarked on a precision measurement of the left-right polarization asymmetry ALR at the Z pole with polarized electrons. Results and future plans are presented. 1. The SLC Performance The SLC was proposed in the early 1980s as a major upgrade of the SLAC linear accelerator to develop ideas and techniques for a e + e linear collider and to conduct experiments at the Z pole. This idea, proposed by Burton Richter, was intended to demonstrate the feasibility of high energy efecolliders using linac technology. In the SLC design, both the electron and positron beams are accelerated in the same linac structure. To bring these bunches into head-on collisions, a dipole magnet at the end of the linac separates the e+ and ebeams, and a pair of transport arcs bring the beams to a collision point. The experimental detector sits at the collision point where the arcs meet. The capability for polarized electron beams was incorporated into the SLC design from the beginning. The layout of the linac-to-damping ring paths was chosen to allow for proper spin manipulation by solenoidal fields so that the spin orientation in the damping ring would be normal to the plane of the ring. Space was included for two more solenoidal rotators after the damping rings to permit pointing of the spin vector in any arbitrary direction. Construction of the SLC commenced in the mid-1980s and the first beams were delivered to the interaction point (IP) in 1988. The detector at the IP was the upgraded Mark II detector which had been running at PEP in preparation for the SLC run. The Mark II detector collected its first physics data at the SLC in 1989 and in 1990 producing a measurement of the mass and width of the Z” along with some other measurements. The physics results for Mark II were based on a total of about 700 Z” decays. In 1991 the Mark II was replaced by the SLD, which conducted an engineering run consisting of 400 Z”s produced. By 1992 the performance of the SLC had improved Invited talk presented at the International Conference on Neutral Currents Twenty Years Later, Paris, France, July 6-9, 1993