The Effect of strange Quark Spin and Higher Twist to QCD

本课题组今年在欧洲核子研究中心完成了质子自旋相关结构函数g_1 （chi）的测量。这种测量的动机是在chi=0.02以下的小chi区域中g^P_ （chi, Q^2）的行为。在1993年的上一次测量中，它显示出随chi变小而增加的趋势。测量从4月20日持续到9月17日。日本成员不仅在偏振靶操作和偏振分析方面做出了贡献，而且在mwpc的维护和光谱仪的数据采集方面也做出了贡献。实验条件如下：(1) μ介子束和强度分别为190GeV和4.5*10^7 ppp。梁的重复速率为14.4秒。(2)极化靶材为固体氨（NH_3），平均极化率约为90%。采用NH_3作为靶材，获得的散射数据比丁醇靶材多20-30%。目前正在分析获得的数据。Miya先生…更多的chi和Ogawa参与了这项工作。将目前的数据与1993年的数据相结合，我们可以得到更可靠的下chi区域的g^P_ （chi, Q^2）值。它可以给出夸克自旋对核子自旋的决定性结论，也可以更精确地检验Bjorken和规则和Ellis-Jaffe和规则。在数据采集的同时，我们小组成员还推进了1995年氘靶实验的数据分析。特别是小川先生在SMC集团担任分析的核心人物。通过探测器位置、假不对称、辐射修正、不对称参数A^d_和g^d_ （chi, Q^2）的QCD演化等多种检查，他推导出1995年氘核数据的最终g^d_ （chi, Q^2）值。他总结了1995年的氘核实验，并在1996年9月4日至10日在阿姆斯特丹举行的高能自旋物理国际研讨会上作了报告。并于1997年1月向名古屋大学物理系提出博士论文。1997年3月获博士学位。Iwata与JINR （DUBNA）的人讨论了新型极化靶材料的可能性和DUBNA的极化实验，利用DUBNA的极化氘核束来研究原子核中的夸克结构。少

Our group has achieved this year the measurement of the spin-dependent structure function g_1 (chi) of the proton at CERN.This measurement was motivated by the behavior of g^P_ (chi, Q^2) in the small chi region below chi=0.02. In the previous measurement in 1993, it showed the tendency to increase with smaller chi. The measurement has been done from April 20 to September 17. Japanese members contributed not only in the field of polarized target operation and polarization analysis, but also in the maintenance of the MWPCs and the data acquisition by the spectrometer.The experimental conditions were following. (1) The muon beam and intensity were 190GeV and 4.5*10^7 ppp, respectively. The repitition rate of the beam was 14.4sec.. (2) The polarized target material was solid ammonia (NH_3) with a polarization of about 90% in average. By adopting NH_3 as target material, we could obtain scattering data 20-30% more than the butanol target. The acquired data are now under analysis. Mr.s Miya … More chi and Ogawa are involved in this job.By adding the present data to those obtained in 1993, we can get more reliable values of g^P_ (chi, Q^2) in the lower chi region. It makes possible to give the decisive conclusion on the quark spin contribution to nucleon spin and to test the Bjorken sum rule and Ellis-Jaffe sum rule more precisely.In parallel with the data acquisition, our group members progressed the data analysis for the 1995 deuteron target experiment. Especially, Mr.Ogawa worked as a key person of the analysis in SMC group. By making many kinds of checks, like detector position, false asymmetry, radiative corrections, QCD evolutions to the asymmetry parameter A^d_ and g^d_ (chi, Q^2), etc., he deduced the final g^d_ (chi, Q^2) valuse to 1995 deuteron data. He has summarized the 1995 experiment for the deuteron and reported at the International Symposium on High Energy Spin Physics held in Amsterdam on Sep. 4-10,1996. He has summarized this to Doctor Thesis and proposed to Department of physics, Nagoya University in January, 1997. He was given The Ph.D in March, 1997.Dr.Iwata discussed with JINR (DUBNA) people on the possibility of the new polarized target material and the polarization experiment at DUBNA to investigate the quark structure in nucleus, using the polarized deuteron beam at DUBNA. Less