📚 Fundamental Families of the Standard Model | 标准模型的基本家族
Particle physics reveals that all matter and forces in the universe are built from a small set of truly elementary particles. The Standard Model organises these into distinct families: three generations of quarks, three generations of leptons, and the mediator bosons, together with the Higgs boson. Understanding these fundamental families is essential for explaining everything from the atoms around us to high‑energy collisions in accelerators.
粒子物理学揭示，宇宙中的所有物质与力都由一小组真正的基本粒子构成。标准模型将它们组织成不同的家族：三代夸克、三代轻子，以及传递相互作用的玻色子和希格斯玻色子。理解这些基本家族对于解释从我们周围的原子到加速器中的高能对撞都至关重要。
1. Introduction: The Particle Zoo and Families | 引言：粒子动物园与家族
Experiments in the 20th century uncovered a vast 'zoo' of particles. The Standard Model brought order by showing that protons, neutrons and other hadrons are not elementary, but are composed of quarks. Likewise, the electron and its heavier cousins belong to the lepton family. True elementary particles fall into a few families, each with a repeating pattern of properties.
20 世纪的实验发现了一个庞大的“粒子动物园”。标准模型恢复了秩序，表明质子、中子和其他强子并非基本粒子，而是由夸克组成。同样，电子及其较重的表兄弟属于轻子家族。真正的基本粒子归属于少数几个家族，每个家族都具有重复的性质模式。
2. The Lepton Family: Lightweight Matter Particles | 轻子家族：轻量物质粒子
Leptons are elementary particles that do not experience the strong interaction. There are six known leptons, arranged in three generations, together with their antiparticles. Each charged lepton has a corresponding neutral neutrino. All leptons have half‑integer spin (½).
轻子是不参与强相互作用的基本粒子。已知共有六种轻子，排列成三代，以及它们的反粒子。每个带电轻子都有一个对应的中性中微子。所有轻子都具有半整数自旋（½）。
| Generation | Particle | Symbol | Charge | Approx. mass (MeV/c²) |
|---|---|---|---|---|
| First | Electron | e⁻ | −1 e | 0.511 |
| First | Electron neutrino | νₑ | 0 | <2.2×10⁻⁹ |
| Second | Muon | μ⁻ | −1 e | 105.7 |
| Second | Muon neutrino | ν_μ | 0 | <0.17 |
| Third | Tau | τ⁻ | −1 e | 1777 |
| Third | Tau neutrino | ν_τ | 0 | <15.5 |
he opposite charge and identical mass; for example the positron e⁺ and the antineutrinos ν̅ₑ, ν̅_μ, ν̅_τ.
反轻子具有相反的电荷和相同的质量；例如正电子 e⁺ 以及反中微子 ν̅ₑ、ν̅_μ、ν̅_τ。
3. The Quark Family: Building Blocks of Hadrons | 夸克家族：强子的构建块
Quarks are elementary particles that carry fractional electric charge and participate in all four fundamental interactions, including the strong force. Like leptons, they form three generations. Each quark flavour has a corresponding antiquark with opposite charge and baryon number.
夸克是带有分数电荷的基本粒子，参与包括强力在内的四种基本相互作用。与轻子一样，它们也构成三代。每种味的夸克都有相应的反夸克，其电荷与重子数相反。
| Generation | Quark | Symbol | Charge | Approx. mass |
|---|---|---|---|---|
| First | Up | u | +⅔ e | 2.2 MeV/c² |
| First | Down | d | −⅓ e | 4.7 MeV/c² |
| Second | Charm | c | +⅔ e | 1.27 GeV/c² |
| Second | Strange | s | −⅓ e | 93 MeV/c² |
| Third | Top | t | +⅔ e | 173 GeV/c² |
| Third | Bottom | b | −⅓ e | 4.18 GeV/c² |
due to colour confinement; they bind into colourless hadrons: baryons (qqq) and mesons (qq̅). Every quark carries a baryon number B = +⅓, antiquarks B = −⅓.
由于色禁闭，夸克无法被单独观测到；它们结合成无色的强子：重子（三夸克）和介子（夸克‑反夸克对）。每个夸克携带重子数 B = +⅓，反夸克 B = −⅓。
4. The Three Generations: A Repeating Pattern | 三代结构：重复的模式
Both quarks and leptons are grouped into three generations that increase in mass but share identical quantum numbers for charge and spin. The first generation (u, d, e, νₑ) makes up all ordinary matter; second and third generation particles are unstable and decay quickly into first‑generation particles.
夸克和轻子均分为三代，质量递增但电荷与自旋等量子数相同。第一代（u, d, e, νₑ）构成了所有普通物质；第二代和第三代粒子不稳定，会快速衰变成第一代粒子。
The existence of exactly three generations is deduced from precision measurements of the Z⁰ boson decay width. A fourth light neutrino generation is not observed in the Standard Model.
恰好三代的存在是通过对 Z⁰ 玻色子衰变宽度的精确测量推断出来的。标准模型中并未观测到很轻的第四代中微子。
5. Force Mediators: Gauge Bosons | 规范玻色子：力的传递者
Each of the fundamental forces is mediated by spin‑1 gauge bosons. The photon (γ) mediates electromagnetism; the W⁺, W⁻ and Z⁰ bosons carry the weak force; and eight gluons (g) transmit the strong force. The graviton, if it exists, would mediate gravity but is not part of the Standard Model.
每一种基本力都由自旋为 1 的规范玻色子来传递。光子（γ）传递电磁相互作用；W⁺、W⁻ 和 Z⁰ 玻色子传递弱力；八种胶子（g）传递强力。
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