近日，芬兰于韦斯屈莱大学的Kimmo Kainulainen与Harri Parkkinen合作并取得一项新进展。经过不懈努力，他们提出含味中微子和粒子-反粒子混合的量子输运理论。相关研究成果已于2024年2月27日在国际知名学术期刊《高能物理杂志》上发表。

该研究团队推导出了混合中微子的量子动力学方程，其中涵盖了前向散射项和相干中微子态的碰撞积分。在实际操作中，他们通过一系列清晰且合理的步骤，成功地将一般化的Kadanoff-Baym方程简化为一个广义密度矩阵方程。这个方程不仅能够描述味粒子和粒子-反粒子的相干性，而且适用于任意中微子质量和运动学情况。

为了进一步简化方程，研究人员将其转化为粒子-反粒子的对角极限，并最终达到超相对论极限。在推导过程中，他们引入了用相干信息计算碰撞积分的简单费曼规则。

此外，研究团队还发现了混合现象背后的新型光谱壳结构，并量化了系统先验信息对量子动力学方程的影响，进而对其演化产生直接作用。这一发现具有广泛的应用前景，例如可以用来精确模拟高温和致密环境中的中微子分布，为研究对撞机中混合重中微子的产生和衰变提供重要理论支撑。

附：英文原文

Title: Quantum transport theory for neutrinos with flavor and particle-antiparticle mixing

Author: Kainulainen, Kimmo, Parkkinen, Harri

Issue&Volume: 2024-02-27

Abstract: We derive quantum kinetic equations for mixing neutrinos including consistent forward scattering terms and collision integrals for coherent neutrino states. In practice, we reduce the general Kadanoff-Baym equations in a few clearly justified steps to a generalized density matrix equation that describes both the flavour- and particle-antiparticle coherences and is valid for arbitrary neutrino masses and kinematics. We then reduce this equation to a simpler particle-antiparticle diagonal limit and eventually to the ultra-relativistic limit. Our derivation includes simple Feynman rules for computing collision integrals with the coherence information. We also expose a novel spectral shell structure underlying the mixing phenomenon and quantify how the prior information on the system impacts on the QKE’s, leading to a direct effect on its evolution. Our results can be used for example to accurately model neutrino distributions in hot and dense environments and to study the production and decay of mixing heavy neutrinos in colliders.

DOI: 10.1007/JHEP02(2024)217

Source: https://link.springer.com/article/10.1007/JHEP02(2024)217