| Co-Investigator(Kenkyū-buntansha) |
HASEGAWA Takeo Miyazaki Univ., Department of Engineering, 工学部, 教授 (70025386)
MORI Kunikazu Nagoya Univ., School of Science, Professor, 理学研究科, 教授 (70022663)
IWATA Takahiro Nagoya Univ., School of Science, Associate Professor, 理学研究科, 助手 (70211761)
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| Research Abstract |
The nulceon spin structure is one of the most interesting and important problems in high energy physics. By getting support of Grant-in-Aid(Specially Promoted Research), we performed three kinds of research in five years.
The first subject is the research on the quark and gluon spin contributions to the nucleon one. In order to make clear the role of quarks, we performed SMC experiment in 1995 and 1996, using polarized deuteron (deuterated butanol) and polarized proton (solid ammonia) targets. By these experiments, the quark spin contribution to the nucleon spin has been determined as 20%〜30%. The Bjorken sum rule which is thought to beheld is successfully tested. This assured the validity of OPE (Operator Production Expansion) method to the quark-gluon problems in the frame of QCD. The sizable negative spin contribution by s-quark has been again confirmed. Based on those conclusions, the spin contribution of gluon has been an important subject. Our present Grant-in-Aid has stimulated t
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he international collaboration to investigate the role of gluon spin, by proposing the construction of the superconductive magnet, for the polarized target. The magnet has such characteristics as, (i) the maximum field strength of 2.7T with a homogeneity over 3cm in diameter and 130cm inlength, (ii) the dipole coil to produce 0.6T perpendicular to the solenoid field, (iii) the exit aperture of ± 180 mrad. The magnet is now underconstruction and will be transported to CERN from Oxford Co. LTD soon.
The next contribution is the construction of the scintillating fiber beam-tracker detectors which are mounted before and behind the polarized target. This tracker system determined the incoming and outgoing muon in good time and space resolutions. The scintillating fiber has a diameter of 0.5mm. The prototype tracker gave enough time resolution (σ〜300 PS) for the real muon beam. Now, the construction of the tracker for the real experiment is going on.
One more contribution of Japan group is the construction of the off-line analysis program. This job must be prepared before real experiments. Two Japanese members contribute to write programs for data base, histgram display and so on.
Second subject is the research on the test of GDH (Gerasimov, Drell-Hearn) sum rule. This sum rule relates the anomalous magnetic moment to the polarized photon-polarized nucleon reaction cross section. To perform the test of this sum rule, the experiment has to be extended up to the infinite energy. But, the sum rule includes the factor 1/ν (ν : photon energy), the higher energy part is thought to be negligible. So, one should make experiment up to several GeV. As the first experiment in the world, we performed the experiment at Mainz in 1998. The data was taken in the energy range of 200-800 MeV. The data are now being analyzed. To achieve the higher energy region, we are preparing the experiments in Bonn Univ. (up to 2.5 GeV) and in SPring-8 (up to 3 GeV).
Third subject is the development of the polarized target. The study at CERN developed the target for higher polarization, delivation of exact polarization value to spin-1 system. In Nagoya, we tried to polarize the polymer material like polyethylene. This material has a merit to be handled in room temperature. This helps to form very thin target material. We polarized deuterated polyethylene ({CDィイD22ィエD2}n) which is prepared by two methods, i.e. free electron doping method and irradiation one by electron beam. We confirmed the highest polarization P=16.7% to the irradiated d-polyethylene. Less
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