通过太阳中微子振荡约束超轻矢量玻色子：规范 $L_\mu - L_\tau$ 模型及 JUNO 与 XLZD 的前景展望
Constraining Ultra-Light Vector Bosons via Solar Neutrino Oscillations: The Gauged $L_μ- L_τ$ Model and Prospects for JUNO and XLZD
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中文总结 AI 辅助
本文通过太阳中微子振荡数据约束超轻矢量玻色子质量，提出规范 $L_\mu-L_\tau$ 模型，并展望 JUNO 与 XLZD 实验将显著提升约束精度。
中文摘要 AI 辅助
我们提出一个基于规范 $U(1)_{L_\mu - L_\tau}$ 对称性的标准模型扩展，其中包含一个与缪子数和陶子数之差耦合的超轻矢量玻色子。这种无反常的构造在历史上源于缪子反常磁矩的动机，在此被用作太阳中微子物理的独立唯象框架。通过与光子的动力学混合，$Z^\prime$ 玻色子在太阳内部产生有效物质势，从而通过 Mikheyev--Smirnov--Wolfenstein 机制修改中微子味振荡。利用来自 Borexino、SNO 和 Super-Kamiokande 的最新太阳中微子测量数据，结合最新的标准太阳模型，我们将玻色子质量约束在 $5.7\times 10^{-17}\\,{\rm eV}$ 以下，这是一个潜在的超轻暗物质候选者。最优模型具有耦合参数 $\eta_o \approx -2$，给出 $\chi_\nu^2 = 2.7$，而标准三味情景的 $\chi_\nu^2 = 3.1$。这一最佳拟合对应于有效四费米子耦合 $g_{Z^\prime}^2 \varepsilon / m_{Z^\prime}^2 \approx 6.6 \times 10^{-23}\\,{\rm eV}^{-2}$，约为费米常数的 $5.7$ 倍，对于 $\varepsilon \approx 1$ 和参考媒介子质量 $1\\,{\rm eV}$，等效于规范耦合 $g_{Z^\prime} \approx 8\times 10^{-12}$。我们还给出了即将开展的实验的前景预测：自 2025 年 8 月起运行、在振荡参数上具有世界领先精度的江门地下中微子天文台（JUNO），以及 XLZD 联盟，应能大幅改进这些约束。此类超轻粒子可能解决冷暗物质范式中星系模拟的长期差异，而地面长基线中微子实验为此参数空间提供互补的探测手段。
英文摘要
We present an extension of the Standard Model based upon the gauged $U(1)_{L_μ- L_τ}$ symmetry, featuring an ultra-light vector boson that couples to the difference of muon and tau lepton numbers. This anomaly-free construction, historically motivated by the muon's anomalous magnetic moment, is employed here as an independent phenomenological framework for solar neutrino physics. Through kinetic mixing with the photon, the $Z^\prime$ boson generates an effective matter potential within the solar interior, thereby modifying neutrino flavour oscillations via the Mikheyev--Smirnov--Wolfenstein mechanism. Utilising recent solar neutrino measurements from Borexino, SNO, and Super-Kamiokande, together with an up-to-date standard solar model, we constrain the boson mass to be below $5.7\times 10^{-17}\,{\rm eV}$, a potential ultra-light dark matter candidate. The optimal model, with coupling parameter $η_o \approx -2$, yields $χ_ν^2 = 2.7$, compared with $χ_ν^2 = 3.1$ for the standard three-flavour scenario. This best fit corresponds to an effective four-fermion coupling $g_{Z^\prime}^2 \varepsilon / m_{Z^\prime}^2 \approx 6.6 \times 10^{-23}\,{\rm eV}^{-2}$, approximately $5.7$ times the Fermi constant, equivalent for $\varepsilon \approx 1$ and a reference mediator mass of $1\,{\rm eV}$ to a gauge coupling $g_{Z^\prime} \approx 8\times 10^{-12}$. We also present projections for forthcoming experiments: the Jiangmen Underground Neutrino Observatory (JUNO), operating since August 2025 with world-leading precision on oscillation parameters, together with the XLZD consortium, should substantially refine these constraints. Such ultra-light particles may address long-standing discrepancies in galaxy simulations within the cold dark matter paradigm, whilst terrestrial long-baseline neutrino experiments provide complementary probes of this parameter space.
发表机构
- Centro de Astrofísica e Gravitação - CENTRA, Departamento de Física, Instituto Superior Técnico - IST, Universidade de Lisboa - UL（里斯本大学技术研究所物理系天体物理学与引力中心）
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