论文标题
$^7 \ mathrm {li}（n，γ）^8 \ mathrm {li} $的耦合通道处理
Coupled-channel treatment of $^7\mathrm{Li}(n,γ)^8\mathrm{Li}$ in effective field theory
论文作者
论文摘要
E1对捕获反应的贡献$^7 \ MATHRM {li}（n，γ）^8 \ mathrm {li} $在低能下计算。我们采用耦合通道形式主义来解释$^7 \ mathrm {li}^\ star $兴奋的核心贡献。我们开发了一个光环有效的场理论功率计数，其中spin $ s = 2 $通道中的捕获在$ s = 1 $通道上增强了。提出了一个次到领导的阶数计算，其中显示激发核心的贡献仅影响横截面的总体归一化。结果，捕获横截面的动量依赖性在有或没有激动的$^7 \ mathrm {li}^\ star $自由度下的理论中是相同的。 $^7 \ mathrm {li}^\ star $ core的运动学签名在1 mev以下的动作范围内可以忽略不计，并且仅超过$ 3^+$ resonance Energy，尽管仍然与近代到接头的订单校正兼容。我们将形式主义与以前的光环有效现场理论计算[Zhang，Nollett和Phillips，Phys。 Rev. C 89，024613（2014）]也将$^7 \ Mathrm {li}^\ star $ core视为明确的自由度。我们的正式表达和分析在几个方面都不同意这项早期工作。
The E1 contribution to the capture reaction $^7\mathrm{Li}(n,γ)^8\mathrm{Li}$ is calculated at low energies. We employ a coupled-channel formalism to account for the $^7\mathrm{Li}^\star$ excited core contribution. We develop a halo effective field theory power counting where capture in the spin $S=2$ channel is enhanced over the $S=1$ channel. A next-to-leading order calculation is presented where the excited core contribution is shown to affect only the overall normalization of the cross section. The momentum dependence of the capture cross section, as a consequence, is the same in a theory with or without the excited $^7\mathrm{Li}^\star$ degree of freedom at this order of the calculation. The kinematical signature of the $^7\mathrm{Li}^\star$ core is negligible at momenta below 1 MeV and significant only beyond the $3^+$ resonance energy, though still compatible with a next-to-next-to-leading order correction. We compare our formalism with a previous halo effective field theory calculation [Zhang, Nollett, and Phillips, Phys. Rev. C 89, 024613 (2014)] that also treated the $^7\mathrm{Li}^\star$ core as an explicit degree of freedom. Our formal expressions and analysis disagree with this earlier work in several aspects.
