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

对核子自旋结构的研究旨在弄清核子内部夸克的作用，并验证预测夸克-胶子行为的QCD。我们研究了夸克自旋含量对核子自旋的影响，验证了QCD求和规则，实现了极化质子和重离子对极化介子的深度非弹性散射。此外，我们还研制了实验中最重要的工具--自旋极化靶。我们将把结果分成两项：(1)自旋极化靶的发展(A)自旋旋转方法的建立：为了测试深度非弹性散射中的高扭转效应，必须垂直于与其动量方向平行的Muon自旋来极化目标自旋。要做到这一点，必须用偶极磁铁将自旋从束轴旋转90度。我们通过这一次旋转测量了去极化，发现它每旋转一次就会损失1%。我们建立了这种方法，并进行了PE…改进了A_2不对称性的测量方法。(2)为了更好地测定A_2的极化，我们更新了核磁共振系统，研制了具有多种优点的新型材料聚乙烯。我们测试了聚乙烯薄膜，得到了-66%和+40%的极化。(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，测量的x区有了较好的统计和向下延伸。结果表明，由Ellis-Jaffe求和规则导出的一阶矩G^p_2与实验有2个标准偏差。因此，夸克自旋对核子自旋的贡献只有(20-30)%。(B)1993年，还测量了质子的参数g_2(X)。由该参数得到的第三次扭转的数据不足以详细讨论，但4个数据点与第三次扭转对G_2(X)的影响是一致的。此外，这些数据对于消除由于忽略这个值而引入g_1(X)的系统误差是很有用的。(C)在1994和1995年，已经测量了氚的g_1(X)。1995年的数据正在进行分析，1994年的数据已经进行了分析，并与1992年的数据进行了很好的统计。Bjorken求和规则已经用由质子和质子数据得到的原子核g_1(X)进行了检验，在10%以内是一致的。较少

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