Forward Meson Production and Spin Asymmetries at RHIC

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。就像原子由旋转的质子、电子和中子组成一样，质子由旋转的夸克组成，这些夸克由一种类似但神秘的量子色动力学（QCD）力结合在一起。正如原子的动力学与原子轨道壳层内自旋向上和自旋向下的电子配对密切相关一样，质子的动力学与自旋向上和自旋向下的夸克之间的关系密切相关。然而，自旋质子内自旋夸克之间的关系还远未完全被理解。布鲁克海文国家实验室（Brookhaven National Laboratory）是第一个建造质子对撞机加速器的实验室，它允许实验人员在质子对以高达500 GeV的质心高能碰撞之前，准备它们的自旋方向。当自旋与垂直于质子运动的轴对齐时，在非常向前的方向上产生的高能粒子（中性介子，etas和粒子喷流）对这个预先选择的自旋轴的方向很敏感。本研究在较大的STAR探测器的前方区域使用铅-玻璃量热计进行测量，可以区分出这些粒子的产生依赖于我们选择的初始质子自旋方向。这些测量的价值在于对量子cd理论提出的挑战，以解释这些有趣的自旋效应。目前的理论对自由夸克如何相互作用以及这种相互作用如何取决于自旋非常具体。我们希望从这项研究中学到的是关于这些夸克在质子内部环境中的独特相互作用的基本和未解决的问题。最终，我们的目标是了解质子作为复合物体的最基本性质。这项研究需要本科生参与，他们协助制作电子产品并分析实验数据。其中一个部分还将涉及中学生完成的一个项目。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).In the same way that atoms consist of spinning protons, electrons and neutrons, held together by electrical forces, the proton consists of spinning quarks held together by an analogous but mysterious Quantum Chromo Dynamic (QCD) force. Just as the dynamics of atoms are critically tied to the pairing of spin up and spin down electrons within atomic orbital shells, so are the dynamics of protons tied to relationships between spin up and spin down quarks. These relationships between spinning quarks inside a spinning proton are, however, far from fully understood.Brookhaven National Laboratory has been the first to build a proton collider accelerator that allows experimenters to prepare the spin orientation of pairs of protons before they collide at high energy, up to 500 GeV in the center of mass. It is found that when the spins are aligned with an axis perpendicular to the motion of the protons, high energy particles (neutral pions, etas and jets of particles) produced in the very forward directions are sensitive to the orientation of this pre-selected spin axis. This research uses a lead-glass calorimeter in the forward region of the larger STAR detector to make measurements that can sort out the dependence of production of these particles upon our choice of initial proton spin directions. The value of these measurements is in the challenge presented to the theory of QCD to explain these interesting spin effects. Current theory is quite specific about how free quarks would interact and how that interaction depends upon spin. What we hope to learn from this research goes to the fundamental and unresolved questions about the unique interactions of these quarks within their environment inside the proton. Ultimately, the goal is to understand the most basic nature of the proton as a composite object. The research involves participation of undergraduate students who assist in fabrication of electronics and in analysis of data from the experiment. One component will also involve a project done by middle school students.