Probing the Standard Model with Parity-Violating Electron Scattering

我们目前对粒子和力相互作用的理解被称为物理学的“标准模型”。但是否存在超越标准模型的物理现象呢？这个问题将通过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)的一项合作实验中精确测量电子的弱电荷来解决。电子的弱电荷是电子普通电荷的弱力模拟，在标准模型中得到了精确的预测。测量结果与这一预测的任何偏差都可能是尚未发现的大质量粒子的证据，这些粒子代表了超出我们目前理解的新物理。预期的活动包括一系列硬件和软件任务，这些任务将为参与该项目的学生提供出色的培训。这种基础研究方面的培训为基础研究以及更多的应用研究和工业提供了坚实的职业基础。该项目提供的资金将支持穆勒实验的活动。穆勒是杰斐逊实验室批准的一项实验，它利用了最近为加速器升级的12GeV能源。该实验将通过精确测量极化态电子与非极化态电子在极低动量转移下的弹性散射中的宇称破坏不对称性，来测量电子的中性弱电荷。这将导致在低能量下确定弱混合角，其精度可与高能对撞机的最佳测定相媲美。它将对超出标准模型的物理场景具有极好的敏感性。在这个项目期间，我们团队将为这项实验做出重要贡献：包括散射束监测系统的开发和建设，扫描仪系统的开发和建设，穆勒光束线的协调(包括束流电荷监测升级和束流调制系统)，安装光晕监测系统，以及模拟设计研究。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Our current understanding of how particles and forces interact is called ‘The Standard Model” of physics. But is there physics beyond the standard model? This question will be addressed by a precision measurement of the weak charge of the electron in a collaborative experiment at the Thomas Jefferson National Accelerator Facility (Jefferson Lab) in Newport News, Virginia. The electron’s weak charge is the weak force analog of the common electric charge of the electron, and it is precisely predicted in the Standard Model. Any deviation of the measurement from this prediction could be evidence of yet undiscovered massive particles that represent new physics beyond our current understanding. The anticipated activities cover a range of hardware and software tasks that will provide excellent training for the students working on the project. This training in fundamental research provides a strong basis for careers both in basic research and in more applied research and industry. The funds provided by this project will support activities on the MOLLER experiment. MOLLER is an approved experiment at Jefferson Lab that takes advantage of the recent 12 GeV energy upgrade for the accelerator. The experiment will measure the electron’s neutral weak charge by making a precision measurement of the parity-violating asymmetry in the elastic scattering of polarized electrons on unpolarized electrons at a very low momentum transfer. This will result in a determination of the weak mixing angle at low energy with a precision comparable to the best determinations from high energy colliders. It will have excellent sensitivity to physics scenarios that extend beyond the Standard Model. During the period of this project, our group will make important contributions to this experiment: including development and construction of the scattered beam monitor system, development and construction of the scanner system, coordination of the MOLLER beamline including beam charge monitor upgrades and beam modulation system, installation of a halo monitor system, and simulation design studies.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.