标题： 无中微子双β衰变的长程核矩阵元来自格点QCD 显示英文标题

标题： Long-Distance Nuclear Matrix Elements for Neutrinoless Double-Beta Decay from Lattice QCD

摘要： 无中微子双β（$0\nu\beta\beta$）衰变是一种迄今为止未被观察到的过程，如果被观察到，将意味着中微子是马约拉纳粒子。 对$0\nu\beta\beta$衰变半衰期的严格实验限制的解释需要核矩阵元的计算。 本工作首次在多核子系统中进行了$0\nu\beta\beta$衰变的格点量子色动力学（LQCD）矩阵元计算，具体为由在核尺度距离上传播的轻左旋马约拉纳中微子介导的$nn \rightarrow pp ee$跃迁。 该计算使用对应于π介子质量为$m_\pi = 806$MeV的夸克质量，在单一格点间距和体积下进行。 为了研究各种系统不确定性，还计算了统计更清晰的$\Sigma^- \rightarrow \Sigma^+ ee$跃迁。 探讨了将LQCD计算结果与核有效场论匹配，以确定与轻马约拉纳中微子相关的$0\nu\beta\beta$衰变的领先阶低能常数的可能性。 因此，这项工作为在夸克质量的物理值下的未来计算奠定了基础，结合有效场论和核多体研究，将为实验搜索$0\nu\beta\beta$衰变提供受控的理论输入。 显示英文摘要

摘要： Neutrinoless double-beta ($0\nu\beta\beta$) decay is a heretofore unobserved process which, if observed, would imply that neutrinos are Majorana particles. Interpretations of the stringent experimental constraints on $0\nu\beta\beta$-decay half-lives require calculations of nuclear matrix elements. This work presents the first lattice quantum-chromodynamics (LQCD) calculation of the matrix element for $0\nu\beta\beta$ decay in a multi-nucleon system, specifically the $nn \rightarrow pp ee$ transition, mediated by a light left-handed Majorana neutrino propagating over nuclear-scale distances. This calculation is performed with quark masses corresponding to a pion mass of $m_\pi = 806$ MeV at a single lattice spacing and volume. The statistically cleaner $\Sigma^- \rightarrow \Sigma^+ ee$ transition is also computed in order to investigate various systematic uncertainties. The prospects for matching the results of LQCD calculations onto a nuclear effective field theory to determine a leading-order low-energy constant relevant for $0\nu\beta\beta$ decay with a light Majorana neutrino are investigated. This work, therefore, sets the stage for future calculations at physical values of the quark masses that, combined with effective field theory and nuclear many-body studies, will provide controlled theoretical inputs to experimental searches of $0\nu\beta\beta$ decay.