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

研究核子自旋结构的目的是为了弄清夸克在核子中的作用，验证QCD预言的夸克-胶子行为。我们通过极化μ子与极化质子和极化氘的深度非弹性散射，研究了夸克自旋对核子自旋的影响，检验了QCD求和规则。此外，我们还研制了自旋极化靶，这是实验中最基本的工具。我们将显示分为两个项目的结果。(1)自旋极化靶的发展（a）自旋旋转方法的建立：为了检验深度非弹性散射中的高扭效应，必须将靶的自旋垂直于μ子的自旋，μ子的自旋与其动量方向平行。为此，必须通过偶极磁体将自旋从束轴旋转90度。我们测量了这种旋转的去极化，发现它每旋转1次就会损失1%。我们建立了这种方法， ...更多信息 成功地进行了A_2不对称性的测量。(b)为了更好地测定极化，我们更新了核磁共振系统，并开发了具有多种优点的新材料聚乙烯作为靶材料。我们测试了聚乙烯箔，得到了-66%和+40%的极化。目前聚乙烯薄膜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年质子的数据。结果显示出相当改善的统计学和测量的X区域向下侧的延伸。结果表明，由Ellis-Jaffe求和规则导出的一阶矩G^p_（1/2）与实验值有2个标准偏差。夸克自旋对核子自旋的贡献仅为（20-30）%. (b)1993年，我们还测量了质子的参数g_2（x）。这些数据不足以详细讨论由该参数导出的第三次扭曲，但有4个数据点与第三次扭曲对g_2（x）没有影响一致。此外，该数据对于抑制因忽略g_1（x）而引入的系统误差也是十分有用的。(c)在1994年和1995年，我们测量了氘核的g_1（x）。1995年的数据正在分析中，1994年的数据已经进行了分析，并与1992年的数据进行了比较。Bjorken求和规则已用由氘和质子数据导出的核子g_1（x）进行了检验，符合率在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