| Co-Investigator(Kenkyū-buntansha) |
HASEGAWA Takeo Miyazaki University, Faculty of Engineering, Professor, 工学部, 教授 (70025386)
IWATA Takahiro Faculty of Science, Yamagata University, Associate Professor, 理学部, 助教授 (70211761)
DAITO Izuru Center for Integrated Research in Science and Engineering, Assistant Professor, 理工科学総合研究センター, 助手 (90303594)
ISHIMOTO Shigeru Physics Div., KEK, Assistant Professor (50141974)
MATSUDA Tatsuro Miyazaki University, Faculty of Engineering, Associate Professor (20253817)
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| Budget Amount *help |
¥20,400,000 (Direct Cost: ¥20,400,000)
Fiscal Year 2002: ¥7,400,000 (Direct Cost: ¥7,400,000)
Fiscal Year 2001: ¥13,000,000 (Direct Cost: ¥13,000,000)
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| Research Abstract |
The international collaboration research "COMPASS" is now going on as one of the international contributions from Japan to world wide activities in the field of science and engineering. COMPASS beam time has been scheduled on May 27, 2002, and started the measurement from middle July after the installation of the detectors which had not been prepared and the final tuning of all the equipments. The measurement has ended on September 23 after taking the physics data 5x10^9 events. Those data are now on the way of analysis. For the execution of the long term run, we sent two students for full time of the experiment and one student for two months for the start-up of the polarized target system. The staff members visited CERN alternately to take shifts of the experiment and to guide the students during their long term stay.
(1) The construction of the polarized target system for COMPASS experiment :
For the polarizing magnet, we used the old SMC magnet because the COMPASS magnet was not ready
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for the installation. We decided to move the COMPASS magnet to other company called Oxford Danphysik(OD), which is organized by the former Oxford staffs for the rewinding the solenoid coil, after the discussions among Nagoya-group, COMPASS CERN and Oxford Instrument Co. LTD. The solenoid will be reconstructed taking the advices given by the Japanese and French specialists of the superconducting magnet. By the reassemble of the magnet at OD, it has been made clear that there are some problems like insufficient impregnation of the coil and wiring and so on. After the summary of problems found on the coil, the new design will be prepared and the re-fabrication will start. We estimate the completion of the magnet in late autumn of 2003.
(2) The fabrication and utilization of the scintillating fiber tracker :
We constructed four sets of beam tracker detector composed of the scintillating fiber with a diameter of 0.5 mm and the photomultiplier with 16 channel photocathodes(Hamamatsu : H6568). The tracker worked very well under the beam condition of 160GeV and 1.4x10^8/ppp, which gives the counting rate 4MHz to the central one channel. Against this overwhelmingly severe condition, the tracker gave the satisfactory performance like, less than 500ps for time resolution, 130μm for position resolution, more than 96% for the detection efficiency and 1.01 for multiplicity. The reliable performance of the tracker has been used as a reference detector to other detectors for the timing tuning and efficiency tuning etc.
(3) The execution of the measurement
The experimental run started about the middle of July and ended on September 23. During the experiment, we accumulated the data for the longitudinal polarization asymmetry by 57 days and obtained the events for 173kspills. For the transversity measurement, we took the data for 19 days and obtained the data for 52 kspills.
The registered events reached to 5 Gevents.
The D^0 events which contribute to the determination of gluon polarization are estimated to be 29,000 events, and the D^* events are estimated to be 3,800 events. We will report the ΔG/G result, as soon as possible, after the analysis. Less
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