AI 中文总结
本研究基于νSMEFT，利用Belle II实验的e⁺e⁻碰撞数据，通过长寿命重中性轻子衰变产生的 displaced 双轻子顶点，探测相关新物理算子的参数空间。
AI 中文摘要
右手（RH）中微子的存在是由微小中微子质量的观测以及为阐明标准模型（SM）中宇称破缺起源的手段所强烈推动的。针对对应的质量本征态（称为重中性轻子，HNLs）的实验搜索已在多种实验及不同HNL模型中开展。本研究采用添加了右手中微子的标准模型有效场论（即νSMEFT），对Belle II实验中e⁺e⁻碰撞产生的GeV量级HNLs展开研究。我们聚焦于长寿命HNL的轻子衰变过程，该过程会在Belle II探测器中产生一个 displaced 顶点。结合探测效率与本底，我们估算了Belle II对νSMEFT中四费米子、希格斯流及偶极算子的新物理能标的灵敏度。结果表明，对于大多数算子，我们提出的搜索方法可覆盖其他搜索未排除的大片参数空间区域。
英文摘要
The existence of right-handed (RH) neutrinos is strongly motivated by the observation of small neutrino masses and as a means to shed light on the origin of parity violation in the Standard Model (SM). Experimental searches for the corresponding mass eigenstates, referred to as heavy neutral leptons (HNLs), have been carried out in a variety of experiments and within different HNL models. In the current work we use the SM effective field theory with added RH neutrinos, known as $ν$SMEFT, to study GeV-scale HNL production in $e^+e^-$ collisions at the Belle~II experiment. We focus on leptonic decays of long-lived HNLs that produce a displaced vertex in the Belle~II detector. Accounting for detection efficiency and backgrounds, we estimate the sensitivity of Belle~II to the new-physics scale of four-fermion, Higgs-current, and dipole operators in $ν$SMEFT. We find that for most operators, the search we propose probes large regions of parameter space that are not excluded by other searches.
Comments58 pages, 21 figures
