Forward Spin Physics at STAR

该项目涉及在布鲁克海文相对论重离子对撞机上测量极化质子之间的碰撞。散射截面的测量与初态自旋方向的依赖关系，使我们得以深入了解构成质子的夸克和胶子的自旋构型，本项目的近期目标是测量前向中性π介子产生对初态质子自旋横向分量的依赖关系。为了实现这一目标，量热仪将安装在星星探测器的最前方。这组测量有望在RHIC质子-质子碰撞中产生最大的自旋依赖性，自然是我们的第一个目标，因为新的极化设施上线。最近的理论进展增加了这个运动区域的重要性。在星星中，用纵向和横向极化的质子束，用量热法和跟踪法在很宽的散射角范围内进行完整的测量，有可能表征质子的夸克和胶子自旋结构。

This project involves measurements of collisions between polarized protons at the Brookhaven Relativistic Heavy Ion Collider. The measurement of scattering cross sections, with thedependence upon initial state spin orientation, yields insight into the spin configurations of thequarks and gluons that make up the proton.The immediate goal for this project will be measurement of the dependence of forward neutral pionproduction on the transverse components of the initial state proton spins. Toward this goal,calorimetry is to be installed in the very forward directions of the STAR detector. This set ofmeasurements is expected to produce the largest spin dependence in proton-proton collisions atRHIC and is naturally our first objective as the new polarized facility comes on- line. Recenttheoretical progress has increased the importance of this kinematic region. Completemeasurements in STAR, with both longitudinally and transversely polarized proton beams and withcalorimetry and tracking covering a wide range of scattering angles, have the potential tocharacterize the quark and gluon spin structure of the proton.