Precision Tests of the Standard Model and Low Energy Hadronic Interactions

对超越标准模型(BSM)的物理的搜索有三个主要方向：能量、宇宙和精确前沿。我感兴趣的是由间接搜索驱动的精度前沿，其中新粒子可能会影响可观测到的粒子，如散射截面或不对称，导致与原始标准模型(SM)预测的微小偏差，而且即将推出的几种使用强粒子束的新一代超精密测量可以检测到如此微小的影响。其中一个实验，Moller，研究违反宇称的莫勒散射，将允许确定弱混合角，不确定度为0.1%，与以前的E-158测量相比，分数精度提高了五倍。在这样的精度下，与SM的任何不一致都可能标志着BSM的物理特性。这样的精度将需要匹配的理论不确定度，这只能通过包括高达两回路的电弱计算来实现。我们计划为标准模型中的粒子建立双环电弱计算模型(2L-ECM)，并计算Moller实验所要求的电子-电子散射的宇称破坏(PV)不对称性的全套双环贡献。随后，2L-ECM应该扩展到涉及SM颗粒的广泛过程。下一阶段将包括各种假设的BSM粒子，直到单圈水平，并研究它们对电弱可观测的影响。 我的第二个研究方向是手征微扰理论(ChPT)，它在描述QCD非微扰区的低能强子性质方面取得了巨大的成功。低能QCD的一些主要目标是研究反映静态结构的强子形状因子，以及通过电极化率和磁极化率研究强子对外部电磁场的动态响应。为了研究电极化率和磁极化率与光子能量的关系，我们使用相对论ChPT方法，同时对康普顿结构函数应用多极展开方法。以前，我们已经发展了基于相对论ChPT的计算强子模型(CHM)，它可以操作到单圈展开。这个模型的优点是它避免了计算中的各种近似，并保留了SU(3)手征拉格朗日所产生的所有可能的自由度。下一个合乎逻辑的步骤是将CHM升级为双回路。在2L-ECM工作的基础上，我们计划发展双环计算强子模型(2L-CHM)，这将使我们能够扩展我们对强子静态(形成因子)和动态(极化率)结构的理解。

Search for physics beyond the Standard Model (BSM) has three major directions: energy, cosmic and precision frontiers. I am interested in the precision frontier driven by the indirect searches, where new particles could impact observables such as scattering cross section or asymmetry causing small deviations from original Standard Model (SM) predictions, and there are several upcoming new-generation, ultra-precise measurements with intense particle beams which could detect such small effect. One of such experiments, MOLLER, studying parity-violating Møller scattering, would allow a determination of the weak mixing angle with an uncertainty of 0.1%, an improvement of a factor of five in fractional precision compared with the previous E-158 measurement. At such precision, any inconsistency with the SM could signal BSM physics. Such precision will require a matching theoretical uncertainty, which can be achieved only by including electroweak calculations up to the two-loop order. We plan to construct Two-Loop Electroweak Computational Model (2L-ECM) for the particles of the Standard Model and calculate the full set of two-loop contributions to the Parity Violating (PV) asymmetry for electron-electron scattering required by the MOLLER experiment. Later, 2L-ECM should be extended to the broad spectrum of processes involving particles of SM. The next stage would be including the various hypothetical BSM particles up to one-loop level, and studying their impact on the electroweak observables. The second direction of my research program is in the Chiral Perturbation Theory (ChPT), which has been tremendously successful in describing low-energy hadronic properties in the non-perturbative regime of QCD. Some of the major goals of the low-energy QCD are the study of hadronic form factors, which reflect the static structure, and the investigation of the dynamical hadronic response to the external electromagnetic field via electric and magnetic polarizabilities. To study the dependence of the electric and magnetic polarizabilities on the photon energy, we used the relativistic ChPT while applying the multipole expansion approach for the Compton structure functions. Previously, we have developed the Computational Hadronic Model (CHM) based on relativistic ChPT, which operates up to one-loop expansion. The advantage of this model is that it allows avoiding various approximations in the calculations and retaining all the possible degrees of freedom arising from the SU(3) chiral Lagrangian. The next logical step would be to upgrade the CHM to two-loops. Based on the work from 2L-ECM, we plan to develop the Two-Loop Computational Hadronic Models (2L-CHM), which would allow us to extend our understanding of both static (formfactors) and dynamic (polarizabilities) structure of hadrons.