X17玻色子和$^3$ H $(p,e^+ e^-)^4$ He和$^3$ He $(n,e^+ e^-)^4$ He过程的理论分析
The X17 boson and the $^3$H$(p,e^+ e^-)^4$He and $^3$He$(n,e^+ e^-)^4$He processes: a theoretical analysis
摘要：
本文研究了四核子体系中$e^+$ - $e^-$对的产生。我们首先分析的过程中，作为一个纯电磁的背景下，一个国家的最先进的方法，核强相互作用动力学和核电磁流，来自手征有效场理论（$χ$ EFT）。接下来，我们将研究假设的低质量玻色子的交换如何影响这样一个过程的横截面。我们考虑几种可能性，这种玻色子是标量，赝标量，矢量，或轴粒子。从头计算使用精确的超球谐方法来描述$A\,$ = $\,4$连续体的束缚态和低能谱，并充分考虑了$3+1$团簇中的初态相互作用效应。虽然电磁相互作用在手征展开中被处理到高阶，但假设玻色子与核子的相互作用在前导阶$χ$ EFT中建模（尽管在某些情况下，也考虑了选定的子前导贡献）。我们还提供了一个概述，可能的未来实验探测对生产的$A\,$ = $\,4$系统在一些候选facilities. facilities。
英文摘要：
The present work deals with $e^+$-$e^-$ pair production in the four-nucleon system. We first analyze the process as a purely electromagnetic one in the context of a state-of-the-art approach to nuclear strong-interaction dynamics and nuclear electromagnetic currents, derived from chiral effective field theory ($χ$EFT). Next, we examine how the exchange of a hypothetical low-mass boson would impact the cross section for such a process. We consider several possibilities, that this boson is either a scalar, pseudoscalar, vector, or axial particle. The ab initio calculations use exact hyperspherical-harmonics methods to describe the bound state and low-energy spectrum of the $A\,$=$\,4$ continuum, and fully account for initial state interaction effects in the $3+1$ clusters. While electromagnetic interactions are treated to high orders in the chiral expansion, the interactions of the hypothetical boson with nucleons are modeled in leading-order $χ$EFT (albeit, in some instances, selected subleading contributions are also accounted for). We also provide an overview of possible future experiments probing pair production in the $A\,$=$\,4$ system at a number of candidate facilities.facilities.
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