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宇称破坏电子散射测量中子密度

Parity Violating Electron Scattering Measurements of Neutron Densities

Shufang Ban, C. J. Horowitz, R. Michaels

备注：
10 pages, 7 fig., minor changes, J. Phys. G in press
发表信息：
J. Phys. G: Nucl. Part. Phys. 39 (2012) 015104
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摘要：

宇称违反电子散射允许模型独立的测量中子密度，是免费的最强的相互作用的不确定性。在本文中，我们提出了各种实验的统计误差估计。中子半径$R_n$可以在几个原子核中测量，只要原子核激发态的能量不太低。我们给出了$^{40}$ Ca、$^{48}$ Ca、$^{112}$ Sn、$^{120}$ Sn、$^{124}$ Sn和$^{208}$ Pb中$R_n$测量的误差估计。一般来说，我们发现原子核越小，测量就越容易。这是因为在宇称违反不对称性$A_{pv}$较大的情况下，可以在较高的动量转移下测量较小的原子核。而且，一般来说，同位素的中子越富，测量就越容易，因为富中子同位素具有更大的弱电荷和更大的$A_{pv}$。测量$^{48}$ Ca中的$R_n$似乎非常有希望，因为它具有比$^{208}$ Pb更高的品质因数。此外，$R_n(^{48}$ Ca）可能比$R_n(^{208}$ Pb）更容易与两个核子和三个核子相互作用相关，包括非常有趣的三个中子力。在测量了$R_n$之后，可以在稍高的动量传递下用第二次测量来约束中子密度$a_n$的表面厚度。我们提出了测量$^{48}$ Ca、$^{120}$ Sn和$^{208}$ Pb中$a_n$的统计误差估计。同样，我们发现$a_n$在较小的原子核中更容易测量。

英文摘要：

Parity violating electron scattering allows model independent measurements of neutron densities that are free from most strong interaction uncertainties. In this paper we present statistical error estimates for a variety of experiments. The neutron radius $R_n$ can be measured in several nuclei, as long as the nuclear excited states are not too low in energy. We present error estimates for $R_n$ measurements in $^{40}$Ca, $^{48}$Ca, $^{112}$Sn, $^{120}$Sn, $^{124}$Sn, and $^{208}$Pb. In general, we find that the smaller the nucleus, the easier the measurement. This is because smaller nuclei can be measured at higher momentum transfers where the parity violating asymmetry $A_{pv}$ is larger. Also in general, the more neutron rich the isotope, the easier the measurement, because neutron rich isotopes have larger weak charges and larger $A_{pv}$. Measuring $R_n$ in $^{48}$Ca appears very promising because it has a higher figure of merit than $^{208}$Pb. In addition, $R_n(^{48}$Ca) may be more easily related to two nucleon and three nucleon interactions, including very interesting three neutron forces, than $R_n(^{208}$Pb). After measuring $R_n$, one can constrain the surface thickness of the neutron density $a_n$ with a second measurement at somewhat higher momentum transfers. We present statistical error estimates for measuring $a_n$ in $^{48}$Ca, $^{120}$Sn, and $^{208}$Pb. Again, we find that $a_n$ is easier to measure in smaller nuclei.

机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。

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