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STUDY ON THE SPIN STRUCTURE OF NUCLEONS

核子自旋结构的研究

基本信息

批准号：
05044046
负责人：
HORIKAWA Naoaki
金额：
$ 12.8万
依托单位：
Nagoya University
依托单位国家：
日本
项目类别：
Grant-in-Aid for international Scientific Research
财政年份：
1993
资助国家：
日本
起止时间：
1993 至 1994
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-05044046/
关键词：
Spin Nucleon Spin Quark Spin Spin Polarized Target Spin Polarized Muon Beam Ellis-Jaffe Sum Rule Bjorken Sum Rule Spin Crisis 偏極標的偏極核子核子構造

项目摘要

SMC (Spin Muon Collaboration) is now going on the experiment using the high energy polarized muon and polarized proton/deutron targets. This experiment aims at making clear the origin of the nucleon spin and cheking the validity of the QCD which is used for the prediction of the quark-gluon behavior inside hadrons. SMC has performed two experiments in this term (2 years) at CERN.In 1993, the spin dependent structure function of the proton has been measured. In 1994, the same parameter of the deuteron was measured. The former experiment extended the data points to the lowest x region with higher statistics. The latter data are now under analysis.The measurement of the spin-dependent structure function of proton has been achieved under the following conditions. (1) The polarized muon beam had an intensity of 4*10^7ppp with a polarization of 80%. (2) The polarized proton target has a dimension of 50mmphi* 650mmlong. A pair of this target capsuls are installed in a dilution cryostat with opposite direction of the polarization. The value of the polarization was about 45%. The data extended the x-region to 0.003 with fairly better statistical and systematic errors. Whole number of data was 4.4*10^6 events.From the proton data, the following results are derived. (1) The Eliis-Jaffe sum rule which is calculated by the assumption of naive quark model is not valified by the experiment. There is about two standard deviation between the prediction and measurement. (2) The sum of the quark spins inside proton can bring only 22% and the strange quark spin has a contribution of -12%. This requires to look for the origin of nucleon spin. (3) The Bjorken sum rule which is a key relation to check the QCD was tested and guaranteed to be correct within errors.

SMC（自旋μ子协作）目前正在使用高能极化μ子和极化质子/氘核目标进行实验。本实验旨在明确核子自旋的起源，并检验用于预测强子内部夸克-胶子行为的QCD的有效性。SMC在本学期（2年）在CERN进行了两次实验。1993年，测量了质子的自旋相关结构函数。1994年，对氘核的相同参数进行了测量。前一种实验将数据点扩展到最低的x区域，统计量更高。后一项数据目前正在分析中。在以下条件下，实现了质子自旋相关结构函数的测量。(1)极化后的介子束强度为4*10^7ppp，极化率为80%。(2)极化质子靶尺寸为50mmphi* 650mmlong。一对这样的目标胶囊被安装在与极化方向相反的稀释低温恒温器中。极化率约为45%。该数据将x区域扩展到0.003，具有较好的统计和系统误差。数据总数为4.4*10^6个事件。根据质子的数据，得出了以下结果。(1)由朴素夸克模型假设计算的elis - jaffe和规则未被实验验证。预测值与实测值之间约有两个标准差。(2)质子内部夸克自旋的总和只贡献22%，奇夸克自旋的贡献为-12%。这需要寻找核子自旋的起源。(3)对检验QCD的关键关系Bjorken和规则进行了检验，保证了误差范围内的正确性。