Measurement of the Neutron Radius of 208Pb Through Parity Violation in Electron Scattering
Measurement of the Neutron Radius of 208Pb Through Parity Violation in Electron Scattering
复制标题
DOI：
10.1103/physrevlett.108.112502
复制
发表时间：
2012-01
影响因子：
8.6
通讯作者：
S. Abrahamyan;Z. Ahmed;H. Albataineh;K. Aniol;D. Armstrong;W. Armstrong;T. Averett;B. Babineau
中科院分区：
文献类型：
--
作者：
S. Abrahamyan;Z. Ahmed;H. Albataineh;K. Aniol;D. Armstrong;W. Armstrong;T. Averett;B. Babineau
与已经用电子散射精确测量的核电荷密度相比，中子密度的知识仍然缺乏精确性。先前的模型相关强子实验表明，重核的中子半径Rn和质子半径Rp之间的差异大约为百分之几。为了精确地获得Rn-Rp之差，它本质上是一个中子皮，杰斐逊实验室铅（208 Pb）半径实验（PREX）测量了能量为1.06 GeV和散射角为5°的极化电子从208 Pb弹性散射的宇称破坏电弱不对称性。由于Z 0玻色子主要与中子耦合，这种不对称性提供了Rn相对于Rp的清晰测量。PREX于2010年3月至6月在杰斐逊实验室实验大厅A进行。该实验收集了2x 107个螺旋窗四联体的最终数据样本。测得的宇称破坏电弱不对称性APV = 0.656 ± 0.060（stat）± 0.014（syst）ppm对应于中子和质子分布半径之间的差异，Rn-Rp = 0.33+0.16-0.18 fm，并提供了第一个在重的富中子核中预期的中子皮的电弱观测。208 Pb的中子半径值对核结构模型及其在原子物理和天体物理学中的应用（如原子宇称不守恒（PNC）和中子星）具有重要意义。«少
In contrast to the nuclear charge densities, which have been accurately measured with electron scattering, the knowledge of neutron densities still lack precision. Previous model-dependent hadron experiments suggest the difference between the neutron radius, Rn, of a heavy nucleus and the proton radius, Rp, to be in the order of several percent. To accurately obtain the difference, Rn-Rp, which is essentially a neutron skin, the Jefferson Lab Lead (208Pb) Radius Experiment (PREX) measured the parity-violating electroweak asymmetry in the elastic scattering of polarized electrons from 208Pb at an energy of 1.06 GeV and a scattering angle of 5° . Since Z0 boson couples mainly to neutrons, this asymmetry provides a clean measurement of Rn with respect to Rp. PREX was conducted at the Jefferson lab experimental Hall A, from March to June 2010. The experiment collected a final data sample of 2x 107 helicity-window quadruplets. The measured parity-violating electroweak asymmetry APV = 0.656 ± 0.060 (stat) ± 0.014 (syst) ppm corresponds to a difference between the radii of the neutron and proton distributions, Rn-Rp = 0.33+0.16-0.18 fm and provides the first electroweak observation of the neutron skin as expected in a heavy, neutron-rich nucleus. The value of the neutron radiusmore » of 208Pb has important implications for models of nuclear structure and their application in atomic physics and astrophysics such as atomic parity non-conservation (PNC) and neutron stars.« less