Collaborative Research: Development of a Fast Muon Trigger to Study the Quark-Gluon Structure of the Proton

我们知道核子--质子和中子--作为原子和中子星中原子核的基本构件。核子本身是一个复合体，具有复杂的子结构，夸克和胶子束缚在质子或中子内部。核子中夸克和胶子之间的相互作用用强核力的量子场论：量子色动力学(QCD)来描述。自从1969年Friedman，Kendall和Taylor在斯坦福直线加速器上首次实验观测到深度非弹性电子-质子散射中的夸克亚结构以来，在理解核子的夸克和胶子结构方面取得了重大进展。然而，许多重要的问题仍然悬而未决；特别是我们对质子自旋的起源仍然只有初步的了解。我们提议使用一种真正新颖的科学技术来研究质子自旋结构：在布鲁克海文国家实验室的相对论重离子对撞机(RHIC)上使用PHENIX探测器观测高能极化质子-质子碰撞中的W玻色子。破坏W产生的宇称将导致分别测量上夸克和下夸克及其对应的反夸克对质子自旋的自旋贡献。该测量将以极高的统计精度和系统精度将夸克和反夸克的自旋分布解析为相对于质子的夸克动量的函数。PHENIX的快速Muon触发器将基于阻性平板计数器(RPC)、用于读出的前端电子设备和大型快速可编程门阵列来实施算法，这些算法可以在p+p碰撞中发出罕见的W玻色子形成的信号。由于W信号预计大约每10亿次p+p碰撞才出现一次，触发允许选择和存储这些有趣的罕见事件，并拒绝大量的背景事件。RPC是一种紧凑、相对便宜的设备，当电离粒子穿过它们的块状物体时，它会产生电子脉冲。W玻色子产生的电子学由定制设计的电路板组成，电路板放大和处理来自RPC所有单个元素的原始电脉冲，然后是分析来自各个元素的信号以确定它们是否与W玻色子的创建一致的电子学。拟议中的项目为研究生、本科生和年轻研究人员提供了一个出色的培训基础，他们将在核物理前沿进行分析，并将在最先进的探测器和读出电子学的设计、建造和测试方面获得经验。目前有13名本科生、8名研究生和9名博士后研究员参与了该项目。未来，该项目将强烈依赖本科生团队在BNL进行RPC探测器的组装。BNL为16名本科生提供的暑期支持已列入预算。来自13个国家的80多名研究生和67名博士后研究人员目前正在研究PHENIX，其中很大一部分将在完成后使用新设备。从历史上看，大量女性作为本科生和研究生参与了PHENIX的研究，为科学和工程工作人员的多样性做出了贡献。PHENIX Muon Trigger小组由伊利诺伊大学厄巴纳香槟分校的核物理实验室领导，合作人员来自阿比林基督教大学、科罗拉多大学博尔德分校、纽约哥伦比亚大学、爱荷华州立大学艾姆斯分校、日本京都大学、北京北京大学、中国、布鲁克海文国家实验室的美日联合核子研究中心和加州大学河滨分校。

We know the nucleon - proton and neutron - as the fundamental building blocks of nuclei in atoms and neutron stars. The nucleon itself is a composite object having complex sub-structure with quarks and gluons bound inside the proton or neutron. The interactions between quarks and gluons in the nucleon are described by the quantum field theory of the strong nuclear force: quantum chromo dynamics (QCD). Since Friedman, Kendall and Taylor's first experimental observation of quark sub-structure in deep inelastic electron-proton scattering at the Stanford Linear Accelerator in 1969 significant progress in understanding the quark and gluon structure of the nucleon has been made. However, many important questions remain open; in particular we are still left with only rudimentary understanding of the origin of the proton spin.We propose to study proton spin structure using a truly novel scientific technique: the observation of W-bosons in high energetic polarized proton-proton collisions with the PHENIX detector at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL). Parity violating W production will lead to separate measurements of the spin contributions from up- and down-quarks and their corresponding anti-quarks to the proton spin. The proposed measurement will resolve the quark and anti-quark spin-distributions as a function of the relative quark momentum to the proton with excellent statistical precision and systematic accuracy.The fast muon trigger for PHENIX will be based on resistive plate counter stations (RPCs), their front-end electronics for read-out, and large fast programmable gate arrays for the implementation of algorithms that can signal the rare formation of a W-boson in a p+p collision. Since a W signal is expected to occur only about once per billion p+p collisions, the trigger allows selection and storage of these interesting rare events and rejection of abundant background events. The RPCs are compact, relatively inexpensive devices that will produce an electronic pulse when an ionizing particle passes through their bulk. The electronics to signal the creation of a W boson consists of custom designed circuit boards that amplify and process the raw electrical pulses from all of the individual elements of the RPCs, followed by electronics to analyze the signals from the individual elements to determine if they are consistent with the creation of a W boson.The proposed project offers an outstanding training ground for graduate and undergraduate students as well as young researchers, who will do analysis at the frontier of nuclear physics and will gain experience in the design, construction, and testing of state-of-the-art detectors and readout electronics. 13 undergraduate students, eight graduate students and nine postdoctoral fellows work on the project now. In the future, the project will strongly rely on teams of undergraduate students to carry out the assembly of the RPC detectors at BNL. Summer support for 16 undergraduate students at BNL has been budgeted. More than 80 graduate students and 67 postdoctoral researchers from 13 countries currently work on PHENIX, and a large fraction will utilize the new equipment once completed. Historically, a large number of women have been involved in PHENIX research as both undergraduate and graduate students, contributing to the diversity of the science and engineering workforce.The PHENIX muon trigger group is lead by the Nuclear Physics Laboratory at University of Illinois at Urbana Champaign and has collaborators from Abilene Christian University, the University of Colorado at Boulder, Columbia University in New York, Iowa State University at Ames, Kyoto University in Japan, Peking University in Beijing, China, the joint US-Japanese Riken BNL Research Center at Brookhaven National Laboratory and the University of California at Riverside.