张量相互作用对球形和弱形变核的双贝塔衰变的影响

Zero neutrino double beta decay (0vDBD) which can prove that neutrinos are identical with their antiparticles and have nonzero mass, is an important problem which exceeded the standard model, but still not be observed so far. The theoretical calculation of 0vDBD nuclear matrix elements so that to predict the 0vDBD half-life of nuclei is very important for experiment measurement, in which the Quasi-particle Random Phase Approximation (QRPA) based on the mean field (MF) is an effective method frequently used. However, most MF+QRPA theory used for the calculation of nuclear matrix element are not self-consistent, it wasn’t until recent year there are self-consistent MF+QRPA theory based on Skyrme force used in the study of 0vDBD, and there is so far no self-consistent MF+QRPA theory which included tensor force used in this study. It was found in theoretical study that the Gamow-Teller (GT) state plays an important role for the nuclear matrix element of 0vDBD, while Spin-Dipole states also makes few differences. Considering the fact found in our previous study that tensor force produces dramatic effects on GT and SD states, we plan to study the effect of tensor force on the matrix elements of 0vDBD together with 2vDBD for spherical and weakly deformed nuclei by applying our MF+QRPA theory which self-consistently includedSkyrme tensor force, this research may probably provide some Innovative significance of results for experiment measurement.

零中微子双贝塔衰变（0vDBD）能说明中微子是它本身的反粒子，以及中微子有质量，是超出标准模型的重大问题,但至今还没观测到。理论上通过计算0vDBD的核矩阵元预言其半衰期对实验观测非常重要。理论计算中，基于平均场理论的准粒子无规则项因子近似理论（MF+QRPA）是一种常用的方法。但用于计算核矩阵元的MF+QRPA理论大多数不自洽，直到近年基于Skyrme力的自洽MF+QRPA理论才被使用，至今没有包含张量力的自洽MF+QRPA理论用于该研究。理论研究中，Gamow-Teller（GT）跃迁对0vDBD的核矩阵元起重要贡献，自旋偶极（SD）跃迁也有一定影响。考虑到我们以前的研究中发现张量力对GT和SD跃迁有显著效应，我们提出用包含Skyrme张量力的自洽的MF+QRPA理论研究张量力对球形核和弱形变核的0vDBD以及2vDBD的核矩阵元和寿命的影响，应该能给出一些有创新性的结果。

零中微子双贝塔衰变是粒子物理和核物理的重大前沿问题，目前国际上已经有很多课题组在做这方面的实验，国内也有课题组在计划进行。零中微子双贝塔衰变半衰期计算中存在的最大问题是其核矩阵元的计算，前期的研究表明张量相互作用对原子核的集体激发态有重要影响，进而会对核矩阵元产生重要影响。基于此我们发展了用准粒子无规相近似(QRPA)计算零中微子双贝塔衰变矩阵元的程序包，并研究张量力对零中微子双贝塔衰变核矩阵元的效应。我们首先计算了部分球形和弱形变核的两中微子双贝塔衰变的核矩阵元，发现张量相互作用对使其显著增强，其原因主要是张量力能降低这些核的低能Gamow-Teller态能量、并增加其强度。在此基础上，进一步计算了一些候选核的零中微子双贝塔衰变核矩阵元，计算结果表明张量力的效应主要使使1+态对核矩阵元的贡献显著增加，这会导致核矩阵元增加15%到25%。目前的研究结果表明在计算零中微子双贝塔衰变核矩阵元时必须考虑张量力，张量力能明显降低零中微子双贝塔衰变半衰期。