AI 中文总结
本文通过扩大价空间改进GT强度分布，实现了对钙-48两中微子双β衰变核矩阵元的更准确计算，发现其值为传统计算的两倍。
AI 中文摘要
我们使用价空间介质相似重整化群（VS-IMSRG），基于手征有效场理论的核相互作用和电弱流，对$^{48}$Ca的双中微子双β（$2\nu\beta\beta$）衰变及$^{48}$Sc中相关的伽莫夫-泰勒（GT）强度函数进行了从头计算。我们发现，与实验相比，通常的$pf$壳价空间显著低估了$2\nu\beta\beta$衰变的核矩阵元（NME），而扩大的$d_{3/2}pf$价空间在无需任何调整的情况下与实验值非常吻合。我们将此归因于对所涉及的GT强度分布的改进描述，从而使扩大的价空间捕捉到了重要的相关性。扩大的$d_{3/2}pf$价空间导致$^{48}$Ca的无中微子ββ NME是$pf$壳计算的两倍。我们的研究结果表明，研究不同的价空间和相关的GT强度对于评估较重ββ衰变的从头NME计算很重要。
英文摘要
We present ab initio calculations of two-neutrino double-beta ($2νββ$) decay of $^{48}$Ca and the related Gamow-Teller (GT) strength functions in $^{48}$Sc using the valence-space in-medium similarity renormalization group (VS-IMSRG) with nuclear interactions and electroweak currents based on chiral effective field theory. We find that the usual $pf$-shell valence space significantly underestimates the nuclear matrix element (NME) of $2νββ$ decay compared to experiment, while an enlarged $d_{3/2}pf$ valence space yields very good agreement with the experimental value without any adjustments. We trace this to an improved description of the involved GT strength distributions, so that the enlarged valence space captures important correlations. The enlarged $d_{3/2}pf$ valence space leads to neutrinoless $ββ$ NMEs of $^{48}$Ca that are twice as large compared to the $pf$-shell calculation. Our findings suggest that studies with different valence spaces and related GT strengths are important for assessing ab initio NME calculations of heavier $ββ$ decays.
Comments9 pages, 4 figures, minor updates including added references
