Collaborative Reseach: Development of a Particle Tracking System for the Qweak Experiment

弗吉尼亚理工学院和州立大学将为杰斐逊实验室的Qweak实验设计并建造“2区”跟踪室。本实验将对质子与中性Z玻色子耦合的弱电荷在极低动量转移下进行高精度测量。提取低动量传递时的弱混合角的高精度值，从而对该量在电弱标准模型中预测的能量尺度依赖性提供灵敏的检验。未能观察到这种预期行为可能会为目前公认的标准模型之外的物理学提供证据。在这个实验中，有许多标准模型的候选扩展将产生可观察到的效果。区域2线室是粒子跟踪系统的重要组成部分，它需要精确测量弹性散射电子的运动学，以及实验背景的关键研究。这些室将由两组50厘米× 50厘米的水平漂移室组成。每个漂移室将有6个平面的电线。预期的分辨率约为200微米，提供1毫角分辨率。第二区漂流室将为研究生和本科生提供优质的教育体验。项目的时间尺度与研究生在研究生院的典型时间尺度非常匹配，因此学生将参与项目的所有硬件和软件阶段。完成该项目所需的任务包括箱体、前端电子设备和气体处理系统的设计和建造，成品的测试，Qweak实验中的实现，以及实验采集数据时的数据分析和跟踪代码开发。我们希望在弗吉尼亚理工大学的教师和高级研究人员的监督下，让两名研究生和至少两名本科生参与这项工作。

Virginia Polytechnic Institute and State University will design andbuild the `Region 2' tracking chambers for the Qweak experiment at Jefferson Lab. This experiment will make a high precision measurement at very low momentum transfer of the proton's weak charge, which is its coupling to the neutral Z boson. A high precision value of the weakmixing angle at low momentum transfer will be extracted, thus providinga sensitive test of the predicted energy scale dependence of this quantityin the electroweak standard model. A failure to observe this expectedbehavior could provide evidence for physics beyond the presently acceptedStandard Model. There are many candidate extensions to the Standard Modelthat would generate observable effects in this experiment. The Region 2 wire chambers are an essential component of the particletracking system, which is needed in order to precisely measure thekinematics of the elastically scattered electrons, as well as forcritical studies of experimental backgrounds. The chambers will consistof two sets of 50 cm x 50 cm horizontal drift chambers. Each drift chamber will have a total of 6 planes of wires. The expected resolutionwill be about 200 microns, providing an angular resolution of 1 mrad. The Region 2 drift chambers will provide quality educational experiencesfor both graduate and undergraduate students. The timescale of the project is well matched to the typical timescale of a graduate student's time in graduate school, so the student will get to participate in all hardware and software phases of the project. The tasks needed to complete the project include design and construction of the chambers, the front-end electronics, and the gas handling system, testing of the finished product, implementation in the Qweak experiment, and data analysis and trackingcode development when the experiment takes data. We expect to involvetwo graduate students and at least two undergraduate students in thiseffort, under the supervision of the faculty and senior research staffat Virginia Tech.