IB AQA Physics: Particle Physics Exam Essentials | IB AQA 物理：粒子物理 考点精讲

📚 IB AQA Physics: Particle Physics Exam Essentials | IB AQA 物理：粒子物理 考点精讲

This revision guide distils the essential concepts of particle physics for IB and AQA Physics students. The Standard Model describes the fundamental particles and their interactions through exchange bosons. Mastering the classification of particles, conservation laws, and Feynman diagrams is crucial for solving exam questions on this topic. Let’s explore the building blocks of matter and the forces that govern them.

本考点精讲提炼了IB和AQA物理中粒子物理的核心内容。标准模型描述了基本粒子及其通过交换玻色子进行的相互作用。掌握粒子分类、守恒定律和费曼图对于解答相关考题至关重要。让我们一起梳理物质的基本结构及支配它们的相互作用。

1. The Standard Model Overview | 标准模型概览

The Standard Model classifies all known elementary particles into two main groups: fermions (matter particles with half-integer spin) and bosons (force carriers and the Higgs with integer spin). It has been remarkably successful in explaining a vast array of experimental results.

标准模型将所有已知基本粒子分为两大类：费米子（具有半整数自旋的物质粒子）和玻色子（具有整数自旋的力的媒介粒子和希格斯粒子）。该模型在解释大量实验结果方面取得了巨大成功。

Fermions are further divided into quarks and leptons. Quarks experience the strong interaction, while leptons do not. There are six ‘flavours’ of quarks and six leptons, arranged in three generations of increasing mass.

费米子进一步分为夸克和轻子。夸克参与强相互作用，轻子则不然。存在六种“味”的夸克和六种轻子，按质量递增排列为三代。

Gauge bosons mediate the fundamental forces: the photon (γ) for electromagnetism, the W⁻, W⁻ and Z⁻ bosons for the weak force, and gluons (g) for the strong force. The graviton (G) is a hypothetical spin-2 boson for gravity, not yet detected. The Higgs boson (H⁻) is a scalar boson that completes the model.

规范玻色子传递基本相互作用：光子（γ）传递电磁力，W⁻、W⁻和Z⁻玻色子传递弱力，胶子（g）传递强力。引力子（G）是假想的自旋为2的玻色子，用于传递引力，尚未被探测到。希格斯玻色子（H⁻）是一种标量玻色子，完善了标准模型。

Quarks carry fractional electric charges: up, charm and top have +2/3 e, while down, strange and bottom have −1/3 e. Antiquarks carry opposite signs. Leptons have integer charge −1 e (for electron, muon, tau) or 0 (neutrinos).

夸克携带分数电荷：上、粲、顶夸克带+2/3 e，下、奇异、底夸克带−1/3 e。反夸克符号相反。轻子带整数电荷：电子、μ子、τ子带−1 e，中微子不带电。

The first generation of particles (up, down, electron, electron neutrino) is stable and makes up ordinary matter. Heavier generations quickly decay into lighter ones via the weak interaction.

第一代粒子（上夸克、下夸克、电子、电子中微子）是稳定的，构成了普通物质。更重的粒子会通过弱相互作用迅速衰变到更轻的粒子。

2. Fermions: Quarks and Leptons | 费米子：夸克与轻子

Quarks are never observed in isolation due to colour confinement; they are permanently bound inside hadrons. Attempts to separate quarks create new quark‑antiquark pairs from the vacuum. Leptons, on the other hand, can exist as free particles.

由于色禁闭，夸克从未被单独观测到；它们永远被束缚在强子内部。尝试分离夸克会从真空中产生新的夸克‑反夸克对。而轻子可以作为自由粒子存在。

There are six quark flavours: up (u), down (d), charm (c), strange (s), top (t) and bottom (b). The top quark is

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