Investigating the Electromagnetic Structure of the Nucleon and Light Nuclei at Jefferson Lab

在杰斐逊实验室研究核子和轻核的电磁结构

• 批准号: SAPIN-2015-00040
• 负责人: Sarty, Adam
• 金额: $ 3.74万
• 依托单位: Saint Mary's University
• 依托单位国家: 加拿大
• 项目类别: Subatomic Physics Envelope - Individual
• 财政年份: 2016
• 资助国家: 加拿大
• 起止时间: 2016-01-01 至 2017-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=614392
• 关键词: Investigating; Electromagnetic; Structure; Nucleon; Light

The primary objective of this research project is to continue collaborative efforts at the Thomas Jefferson National Accelerator Facility ("Jefferson Lab") in Newport News, Virginia, which are specifically aimed at probing the structure of the nucleon using a high energy electron beam. This work will be accomplished in collaboration with the Super BigBite Spectrometer (SBS) Collaboration in Hall A at Jefferson Lab. During this grant period, Jefferson Lab will be emerging from the past transition "upgrade period" phase - having upgraded the beam energy from 6 GeV to 12 GeV - and beginning to utilize equipment specifically designed and built for the higher energy. This proposal includes a plan to ensure continued scientific contributions and student training with the early-running Hall A experiments (experiments focusing not only on nucleon structure, but also on that of light nuclei - particularly the triton three-nucleon system), but with primary emphasis remaining on preparation/development projects associated with a series of specific later-running SBS experiments that will probe nucleon structure functions at very high momentum transfers. The driving physics goals of all aspects of this project are related to improving understanding of the transition from the 'strong (non-perturbative) QCD' regime of relatively large distance scales of approximately 1 to a few fermis (where hadronic degrees of freedom are most appropriate), to the 'perturbative QCD' regime of much shorter distance scales. Sarty has been working with Jefferson Lab's Hall A Collaboration for two decades, and during the past few years of equipment development for the lab’s upgrade, Sarty and his students contributed to design/testing projects for Hall A's SBS group of experiments. The SBS experiments are designed to probe nucleon structure at very high momentum transfer; the hallmark experiment of this group being E12-07-109 ("Large Acceptance Proton Form Factor Ratio Measurements at 13 and 15 GeV/c^2 using Recoil Polarization Method"). This SBS group of experiments requires the construction of new equipment - a spectrometer, calorimeters, detectors - which will be completed by the collaboration during this granting period. Sarty’s group has taken a lead role in preparing one part of the SBS detection system: a scintillator-based Coordinate Detector (CDet) to provide required fast timing and accurate position for the scattered electron detection - critical aspects needed for the very high radiation background environment of the E12-07-109 experiment. The CDet will consist of 0.5mm tall (4cm thick) scintillator strips, stacked to form two planes roughly 3m x 1m in size, for a total of 2352 channels of readout; Sarty’s group will continue its work to ensure the CDet is constructed and an appropriate data acquisition system is ready for use when it is needed for SBS nucleon structure experiments at the end of the granting period.

该研究项目的主要目标是继续在弗吉尼亚州纽波特纽斯的托马斯·杰斐逊国家加速器设施(“杰斐逊实验室”)进行合作，专门针对使用高能电子束探测核子结构。这项工作将与杰斐逊实验室A厅的超级大比特光谱仪(SBS)合作完成。在此授权期内，杰斐逊实验室将走出过去的过渡“升级期”--将束流能量从6GeV升级到12GeV--并开始使用专门为更高能量设计和制造的设备。这项提议包括一项计划，以确保继续作出科学贡献，并通过早期运行的霍尔A实验(不仅侧重于核子结构，而且侧重于轻核--特别是Triton三核子系统的实验)培训学生，但主要重点仍然是与一系列具体的后来运行的SBS实验有关的准备/开发项目，这些实验将以非常高的动量转移探索核子结构功能。这个项目所有方面的主要物理目标都与提高对从相对较大的距离尺度(大约1到几个费米(其中强子自由度最合适)的“强(非微扰)QCD”体制)到短得多距离尺度的“微扰QCD”体制的理解有关。 萨蒂与杰斐逊实验室的A厅合作已有20年，在过去几年为实验室升级而开发的设备期间，萨蒂和他的学生为A厅的SBS实验组的设计/测试项目做出了贡献。SBS实验是为了探测非常高动量转移的核子结构而设计的；这个小组的标志性实验是E12-07-109(使用反冲极化方法在13和15GeV/c^2下测量大接受质子形状因数比)。这组SBS实验需要建造新的设备--光谱仪、量热仪、探测器--这些设备将在授权期内通过合作完成。Sarty的团队牵头准备了SBS探测系统的一个部分：基于闪烁体的坐标探测器(CDET)，为散射电子探测提供所需的快速计时和准确位置-E12-07-109实验的极高辐射背景环境所需的关键方面。CDET将由0.5毫米高(4厘米厚)的闪烁体条带组成，堆叠成两个大小约为3m x 1m的平面，总共有2352个读出通道；Sarty的团队将继续工作，以确保CDET被建造出来，并在授权期结束时准备好适当的数据采集系统，以供SBS核子结构实验使用。