Probing the Weak and Strong Nature of the Nucleon

探究核子的弱与强性质

• 批准号: 1615146
• 负责人: Dustin McNulty
• 金额: $ 76.18万
• 依托单位: Idaho State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-09-01 至 2021-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1615146&HistoricalAwards=false
• 关键词: Probing; Weak; Strong; Nature; Nucleon

The Idaho State University medium-energy nuclear physics group will conduct several key measurements at Jefferson Lab using high-energy electrons to precisely probe the underlying substructure of nucleons, where a nucleon is a proton or neutron, and they will make fundamental measurements on how force and matter interrelate. The group seeks to understand the nature of the strong and weak nuclear forces and how these forces govern the nucleon's constituents (quarks). Due to these forces, protons and neutrons are arranged slightly differently inside large nuclei as evidenced by neutrons tending to occupy the outer layers of heavy nuclei, with the protons being closer to the center. The group will lead an experiment to probe this outer neutron skin by making use of telltale signatures of the weak force in scattering electrons off complex nuclei. This issue further bears upon the structure of neutron stars. The group will also determine the precise and accurate diameter of the proton, where there are currently several conflicting measurements. This group has a strong tradition of bringing undergraduate and graduate students into their research program. The CoPIs in this proposal are all co-spokespersons on experiments at Jefferson Lab to perform measurements on the underlying symmetry and structure of the quark and gluon components of the nucleon, the size of the proton, and the characteristics of the skin or surface of a nucleus. Dr. Tony Forest is continuing a measurement of the down quark fractional polarization in the nucleon to test predictions of pQCD via JLab experiment E12-06-109. Dr. Philip Cole is co-spokesperson on E12-09-003, an experiment that will measure the change of the dynamical quark mass as well as the nature of the nucleon structure and internal quark interactions as the probe's distance scale enters a regime that directly accesses quarks decoupled from the meson-baryon cloud. Dr. Cole is also a collaborator on the ELSA experiment BGO-OD, which will anchor N* measurements at the q2=0 point. Dr. Mahbub Khandaker will conduct a high-precision measurement of the proton charge radius
in experiment E12-11-106 to resolve a current discrepancy between the proton radius extracted from muonic and electronic hydrogen experiments. Dr. Dustin McNulty is continuing his work using parity violation to precisely measure the neutron skin of lead and calcium to test nuclear model predictions of the difference between the radii of protons and neutrons in a heavy nucleus, E12-12-004.

爱达荷州州立大学中能核物理小组将在杰斐逊实验室进行几项关键测量，使用高能电子精确探测核子的底层结构，其中核子是质子或中子，他们将对力和物质如何相互关联进行基本测量。 该小组试图了解强核力和弱核力的性质，以及这些力如何支配核子的组成部分（夸克）。 由于这些力，质子和中子在大核内的排列略有不同，中子倾向于占据重核的外层，质子更靠近中心。 该小组将领导一项实验，通过利用复杂原子核散射电子时弱力的特征来探测这种外层中子皮。 这个问题进一步影响到中子星的结构。 该小组还将确定质子的精确和准确的直径，目前有几个相互矛盾的测量。 这个小组有一个强大的传统，使本科生和研究生进入他们的研究计划。 该提案中的CoPI都是杰斐逊实验室实验的联合发言人，这些实验对核子的夸克和胶子成分的潜在对称性和结构、质子的大小以及皮肤或表面的特征进行测量。核。Tony Forest博士正在继续测量核子中的下夸克分数极化，以通过JLab实验E12-06-109测试pQCD的预测。菲利普科尔博士是E12-09-003的共同发言人，该实验将测量动态夸克质量的变化以及核子结构和内部夸克相互作用的性质，因为探测器的距离尺度进入直接访问从介子-重子云解耦的夸克的状态。 科尔博士也是艾尔莎实验BGO-OD的合作者，该实验将锚N* 测量值固定在q2=0点。 Mahbub Khandaker博士将在实验E12-11-106中对质子电荷半径#8232;进行高精度测量，以解决目前从μ子和电子氢实验中提取的质子半径之间的差异。Dustin McNechte博士正在继续他的工作，使用宇称违反来精确测量铅和钙的中子皮，以测试重核E12-12-004中质子和中子半径之间差异的核模型预测。