Probing the Weak and Strong Nature of the Nucleon

爱达荷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潜在子结构，其中核子是质子或中子，他们将对力和物质之间的相互关系进行基本测量。该小组试图了解强核力和弱核力的本质，以及这些力如何支配核子的成分（夸克）。由于这些作用力，质子和中子在大原子核内的排列略有不同，中子倾向于占据重原子核的外层，而质子更靠近中心。该小组将领导一项实验，利用复杂原子核散射电子时的弱力特征来探测中子的外层外壳。这个问题与中子星的结构有进一步的关系。该小组还将确定质子的精确直径，目前有几个相互矛盾的测量。这个小组有很强的传统，把本科生和研究生纳入他们的研究项目。本提案中的copi都是杰斐逊实验室实验的共同发言人，用于测量核子的夸克和胶子成分的潜在对称性和结构，质子的大小以及原子核表面或表皮的特征。Tony Forest博士正在通过JLab实验E12-06-109继续测量核子中的下夸克分数极化，以验证pQCD的预测。Philip Cole博士是E12-09-003的联合发言人，该实验将测量动态夸克质量的变化，以及核子结构的本质和内部夸克相互作用，因为探测器的距离尺度进入了一个直接访问从介子-重子云解耦的夸克的状态。科尔博士也是ELSA实验BGO-OD的合作者，该实验将在q2=0点锚定N*测量。Mahbub Khandaker博士将对质子电荷半径进行高精度测量。在实验E12-11-106中，解决了从介子和电子氢实验中提取的质子半径之间的电流差异。达斯汀·麦克纳尔蒂博士正在继续他的工作，利用宇称违反来精确测量铅和钙的中子皮，以测试核模型对重核E12-12-004中质子和中子半径之差的预测。

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.