AI 中文总结
本研究通过电荷对称性关联反核子势，计算反中子散射长度，发现同位旋矢量项对48Ca散射长度影响显著，提出低能反中子束测量可获取s波反核子-原子核相互作用信息。
AI 中文摘要
当前反中子-原子核散射长度仅能通过拟合反质子原子能级移动和宽度的反质子-原子核光学势间接获取，反中子-原子核与反质子-原子核势通过电荷对称性相互关联。本研究以核子密度分布为输入，计算反质子原子对应的光学势得出散射长度：发现N>Z核素的散射长度受约束较差的中子密度分布及可能的同位旋矢量相互作用（为重现反质子40,48Ca数据同位素依赖性引入的机制之一）显著影响；对于48Ca，同位旋矢量项使散射长度的实部改变0.3–0.4 fm、虚部改变0.4–0.5 fm，其幅度远超同位旋标量势传递的不确定度。由于76 MeV/c以下无反中子-原子核散射数据，利用新近提出的低能反中子束开展直接测量，将首次获取s波区域内反核子-原子核相互作用的相关信息。
英文摘要
The antineutron$\unicode{x2013}$nucleus scattering length is currently known only indirectly, via antiproton$\unicode{x2013}$nucleus optical potentials fitted to level shifts and widths of antiprotonic atoms. The antineutron$\unicode{x2013}$nucleus and antiproton$\unicode{x2013}$nucleus potentials are related to each other through charge symmetry. We calculate the scattering length from optical potentials proposed for antiprotonic atoms using nucleon density distributions as input. We find that the scattering length for an $N>Z$ nuclide is largely affected by the poorly constrained neutron density distribution and by a possible isovector interaction, one of the mechanisms introduced to reproduce the isotope dependence of antiprotonic $^{40,48}\mathrm{Ca}$ data. For $^{48}\mathrm{Ca}$, the isovector term modifies the scattering length by $0.3\unicode{x2013}0.4\,\mathrm{fm}$ ($0.4\unicode{x2013}0.5\,\mathrm{fm}$) for the real (imaginary) part, an order of magnitude beyond the uncertainty propagated from the isoscalar potential. As no antineutron$\unicode{x2013}$nucleus scattering data are available below $76\,\mathrm{MeV}/c$, a direct measurement with recently proposed low-energy antineutron beams would provide the first access to the antinucleon$\unicode{x2013}$nucleus interaction in the $s$-wave regime.
Comments12 pages, 6 figures
