RUI: Hadron Structure and Interactions

理论物理学的一个中心问题是描述强子的结构及其相互作用。强子的组成部分是夸克和胶子，其中avor，动量和自旋的分布是一个深入研究的领域。本项目将研究最近的实验结果对理论提出的两个突出挑战：1）质子海中的avor不对称性，由费米实验室的E866测量，其中d-反夸克（Pd）对u-反夸克（Pu）的过剩在x较低时（反夸克携带的质子动量的分数），被Pu超过Pd的优势所取代，2）在CERN的PS 185的自旋转移测量，Pp与非极化质子靶碰撞产生Pff的计算结果与所有理论预言不一致.这些研究将扩展到质子海中极化avor不对称性的计算以及其它反超子-超子（PYY）产生反应.奇异势和极限环是一个新的研究领域，将在等效场理论的背景下进行研究，质子海中的味不对称性将用介子云模型计算，在介子云模型中，质子可以涨落到介子-重子态，它们的夸克分布则对测量的质子夸克分布有贡献。质子的夸克和胶子自由度也将包括在gbare质子的统计模型中，质子波函数中的首项.由于Pd和Pu质量的不同而引起的电荷对称性破坏的影响将被包括在内.本项目的目的是解释实验确定的非极化avor不对称性的x依赖性，并预测偏振不对称性。将进行PppPYY的高精度计算，其中包括：a）e.对Pqq湮灭和产生起主要作用的相互作用，B）由奇异值产生实验所跨越的动量区的t到PNN反应数据所确定的初态相互作用，以及c）自旋单态项对反应机制的贡献。which哪一个is evidence证据from themrecent最近spin自旋-这个项目的目标是了解反应机制和在最终状态下未知的PYY相互作用。奇异性的研究势和极限环将包括对真实的和复势调节器及其重整化性质的研究。将应用于冷原子散射和场理论中的问题。如上所述，它解决了强子结构和相互作用中的一些重要问题，这些问题在核理论和实验之间存在着重大的分歧，它将以前的工作扩展到新的领域。该项目的更广泛的影响包括将研究放在本科生环境中，其中学生来自不同的人群（40%的少数民族）与高年龄的妇女物理专业（40%）。学生的研究经验将是补充课程，并提供课堂学习和当代研究的兴奋的整合。学生将接受研究方法和科学交流的培训。他们将以团队为单位工作，指导年轻学生并在论文中展示他们的工作，除了在期刊文章和科学会议上介绍研究成果外，还将在其他本科院校举办研讨会和座谈会。

A central problem for theoretical physics is the description of the structure of hadronsand their interactions.The building blocks of hadrons are quarks and gluons,among whichthe distribution of .avor,momentum,and spin is an area of intense study.This project willstudy two of the outstanding challenges to theory posed by recent experimental results:1).avor asymmetry in the proton sea,measured by E866 at FermiLab,in which the excess ofd -antiquarks (Pd )over u -antiquarks (Pu )for low values of x (the fraction of proton momentumcarried by the antiquark),is replaced by a dominance of Pu over Pd for larger values of x ,and 2)the spin transfer measurements of PS185 at CERN,for Pff production from Pp collisions with apolarized proton target,which disagree with all theoretical predictions.These investigationswill be extended to calculation of polarized .avor asymmetry in the proton sea,and to otherantihyperon-hyperon (PYY )production reactions.A new area of research,singular potentialsand limit cycles,will be studied in the context of e .ective .eld theory.Flavor asymmetry in the proton sea will be calculated in terms of a meson cloud model,in which the proton can .uctuate into meson-baryon states,whose quark distributions thencontribute to the measured quark distributions of the proton.The quark and gluon degreesof freedom of the proton will also be included in a statistical model of the gbare proton, htheleading term in the proton wave function.E .ects of charge symmetry violation,arising fromdi .erences in the masses of the Pd and the Pu ,will be included.The goal of this project is toexplain the x -dependence of the experimentally determined unpolarized .avor asymmetry,and to predict the polarized asymmetry.High precision calculations of PppPYY will be carried out which will include:a)e .ectiveinteractions that represent the leading contributions to Pqq annihilation and creation,b)an initial state interaction which has been determined by .t to PNN reaction data in themomentum region spanned by the strangeness production experiments,and c)a contributionto the reaction mechanism from a spin singlet term,for which there is evidence from therecent spin-transfer data.The goal of this project is to learn about the reaction mechanismand the otherwise unknown PYY interactions in the .nal state.The study of singular potentials and limit cycles will include investigation of real andcomplex potential regulators and their renormalization properties.Applications to cold atomscattering and problems in e .ective .eld theory will be made.This project has intellectual merit because,as described above,it addresses importantproblems in hadron structure and interactions for which there is signi .cant disagreementbetween nuclear theory and experiment.It extends prior work to new areas.The preliminarywork necessary for the project has been successfully completed by the P.I.Broader impacts of the project include placing the research in an undergraduate setting,in which students are drawn from a diverse population (40%minority)with a high percent-age of women physics majors (40%).The student research experience will be complemen-tary to coursework,and provide an integration of classroom learning and the excitementof contemporary research.Students will receive training in research methods and scienti .ccommunication.They will work in teams,mentor younger students and present their workin papers,posters and talks at meetings of professional societies.In addition to presentationof research .ndings in journal articles and at scienti .c meetings,seminars and colloquia willbe given at other undergraduate institutions.