The measurement of the spin-dependent structure function g_2 (x, Q^2) and test of QCD higher twist effect

核子自旋结构的研究旨在明确夸克在核子内部的作用，并验证预测夸克-胶子行为的QCD。研究了夸克自旋对核子自旋的含量，并对极化质子和极化氘核的极化介子进行深度非弹性散射的QCD求和规则进行了测试。此外，我们还开发了自旋极化靶，这是实验中最重要的工具。我们将显示结果分为两项。(1)自旋极化目标的发展(a)自旋旋转方法的建立：为了测试深度非弹性散射中较高的扭转效应，必须使目标自旋垂直于与其动量方向平行的μ子自旋极化。为此，必须用偶极磁体将自旋从光束轴旋转90度。我们通过这个旋转测量去极化发现它每旋转1次就损失1%建立了该方法，成功地改进了A_2不对称的测量方法。(b)为了更好地测定极化，我们更新了核磁共振系统，并开发了聚乙烯作为靶材料。我们对聚乙烯箔进行了测试，得到了-66%和+40%的极化率。目前聚乙烯箔的极化值仍是世界上最大的。(2)核子自旋结构的测定(a)我们总结了1994年的质子数据。结果表明，统计数据得到了相当大的改善，测量的x区域向下侧延伸。结果表明，由Ellis-Jaffe求和规则导出的一阶矩G^p_与实验结果有2个标准差。随后，夸克自旋对核子自旋的贡献只有（20-30）%。(b) 1993年也测量了质子的参数g_2 (x)。数据不足以详细讨论由该参数导出的第三捻度，但有4个数据点与第三捻度对g_2 (x)没有影响一致。此外，该数据对于抑制由于忽略该值而引入g_1 (x)的系统误差非常有用。(c) 1994年和1995年测量了氘核的g_1 (x)。目前正在分析1995年的数据，1994年的数据已经分析过，并与1992年的数据相结合，得出了很好的统计数字。由氘核数据和质子1得到的中子g_1 (x)对比约肯和规则进行了检验，二者的一致性在10%以内。少

The study of the nucleon spin structure aims to make clear the role of quarks inside nucleon and to verify the QCD which predicts the quark-gluon behavior. We made the research work to investigate the quark spin content to the nucleon spin and test the QCD sum rule performing the deep-inelastic scattering of polarized muon of polarized proton and deuteron. Morever, we developed the spin polarized target which is the most essential tool for the experiment. We will show the resuts dividing into two items.(1) The development of the spin polarized target(a) The establishment of the spin rotation method : In order to test the higher twist effect in the deep-inelastic scattering, one has to polarize the target spin perpendicular to the muon spin which has a parallel direction to its momentum. For that, one has to rotate the spin 90 degree by a dipole magnet from beam axis. We measured the depolarization by this rotation and found it looses 1% per 1 rotation. We established this method and pe … More rformed the measurement of A_2 asymmetry successfully.(b) For the better determination of the polarization, we renewed the NMR system and developed the new material polyethylene which has several merits as target material. We tested polyethylene foil and got the polarization of -66% and +40%. The value of the polarization is still the maximum in the world for the polyethylene foil at present.(2) The determination of the nucleon spin structure(a) We summarized the data taken in 1994 for the proton. the results showed fairly improved statistics and extension of the measured x region to the lower side. As a result, it has been made clear that the 1st moment G^p_ derived from Ellis-Jaffe sum rule has 2 standard deviation from the experiment. Followingly, the quark spin has only (20-30)% conribution to the nucleon spin.(b) In 1993, the parameter g_2 (x) for the proton has been also measured. The data is not enough to discuss on detail about the 3rd twist derived from this parameter, but 4 data points are consistent with no effect of the 3rd twist to g_2 (x). Moreovere, the data was quite usuful for the suppression of the systematic error brought into g_1 (x) from the neglect of this value.(c) In 1994 and 1995, the g_1 (x) for the deuteron has been measured. The data taken in 1995 is now being analyzed, The data in 1994 has been already analyzed and gave a good statistics mixing with the data in 1992. The Bjorken sum rule has been tested by the nuetron g_1 (x) derived from the deuteron data and proton one and showed the agreement within 10%. Less