Electron-Positron Collision Experiment with SLAC・SLD Detector

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To proceed a detailed examination of "the standard model" in particle physics, the SLAC Large Detector (SLD) has been constructed and installed in the e^+e^- beam-collision point in the SLAC Linear Collider (SLC). The goal of experiment is to accumulate 10^4 to 10^5 Z^0 events with collision of "polarized electron beam" and "positron beam" at around 92 GeV. Japanese Group took parts in the construction and operation of Central Drift Chamber (CDC) and Crrenkov Ring Imaging Detector (CRID) from 1989 to 1991 under the cooperation with SLAC Group A and Group B.The unique feature of this experiment is that the first utilization of "Polarized electron beam" which provides more than 100 times sensitivity for sin^2rheta_W (rheta_<W'>Weinberg-angle), a key parameter of the electroweak theory, through the forward-backward asymmetry of total crosssections. The vantages of SLD/SLC experiment over other existing detectors are : a smaller beam size at collision point, a precise vertex determination … More by Vertex Detector (VTX), fme track determination by Central Drift Chamber (CDC), good particle identification with Cerenkov Ring Imaging Detector (CRID) and good calorimetry with liquid argon electromagnetic (LAC) and gas-sampling hadron calorimeters (WIC).The detector was completed in the Spring of 1990 and thoroughly tested with cosmic-rays from Summer to Fall in 1990, and was moved into the hewn position in February 1991. First test runs with beam was made from April to July 199 1. In this run, accelerator was tuned to provide higher intensities without polarized beam. After these test runs, some remaining parts of the detector had been installed in the period of Summer shutdown. The engineering runs were successfully done from the middle of October to the end of 1991 with beams of 60 pulses per second operation mode. We obtained total of 363 Z^0 events by net data acquisition time of 103hr., where the total beam on time was 170hr. and detector on time was 130hr.From these experiments, CDC tracking resolutions were turned out to be 97mm in local position resolution and 123mm in overall resolutions. The latter could be tuned up to 35mm by further position calibrations of mini-cells. CRID obtained first Cerenkov ring image for passage of cosmic particles in August 1991 and TAME gas mixing into the complex gas-circulating system was fully successful. We hope correction of 10^4 Z^0s from the high intensity runs at 50 Z^0 s/hour rate (repetition rate of 12OHz) scheduled from March to July 1992 and from October to December 199 1, with the beam polarization of about 35%. Computer setup and preparation for data analysis are ready in Nagoya and Tohoku Universities. Less