LHC上Z玻色子空间不对称性应用于核子结构分布(PDF)的相关研究

利用Z玻色子到双轻子衰变过程的空间不对称性（AFB）进行质子结构分布（PDF）的研究，是近年来在LHC上形成的前沿热点方向。在LHC上，原本由弱作用主导的AFB会受到质子-质子对撞初态完全对称的影响，从而对质子中正反夸克相对能量分布具有高灵敏度，能够提供目前PDF global fitting中大部分实验数据难以直接提供的物理信息，具有重要研究价值。本项目计划对AFB应用于PDF fitting展开一系列研究。尤其在PDF和电弱物理的关联性问题上，将不局限于学界目前所关注的系统误差估计，而是重点研究如何能将AFB中的PDF与电弱部分解耦，从而极大降低关联性所带来的误差。同时，项目将研究如何利用AFB进行约束PDF中S夸克信息。还将对应用后的PDF在电弱精确测量上的误差进行预言，并研究如何在实验上更好地进行AFB测量。

Using the forward-backward charge asymmetry in the Z boson to dilepton progress to constrain the parton distribution functions (PDF), is an important topic in the past years at LHC. The observed AFB at LHC, which originally arises from the electroweak symmetry breaking, is affected by the fact that the proton-proton collision is spacial-symmetrical. As a result, the observed AFB has high sensitivity to the relative energy distribution between quarks and antiquarks in the protons. As the precision keeps being improved, AFB can provide information which most of the data used in the PDF global fitting could not cover. Due to the fact that AFB also has high sensitivity to the electroweak sector, there is inevitably strong correlation between the EW and PDF. Such correlation would cause bias in both PDF global fitting and electroweak fundamental parameter measurements. In this project, we will make a series of studies on how to use AFB in the PDF global fitting. For the most important part, we will not limited in trying to estimate the potential bias and systematic uncertainties, but searching for possibility to decorrelate the PDF and EW part in the AFB measurement, so that the bias can be significantly reduced.