1. Particle Zoo Classification
Overview: One way of studying elementary particles is to classify them into different categories based on certain behaviors and then to look for similarities or common characteristics among the classifications. The Standard Model classifies all elementary particles and their interactions into two main groups according to their spin:
- Bosons: Particles that carry force, having spin in integer values such as 0, 1, and 2.
- Fermions: Particles that make up all matter, having spin in odd half-integer values such as 1/2, 3/2, etc.
2. Bosons Breakdown
Bosons: The arrangement of all elementary particles in the Standard Model constitutes a particle zoo. All bosons can be classified into two types: Elementary Boson and Composite Boson. Composite bosons consist of quark and anti-quark combinations while elementary bosons are not made up of other elementary particles.
Elementary Bosons: Elementary bosons are the carriers of the fundamental forces in nature, including:
- Gluon
- W+, W- and Z0 Bosons
- Photon
- Higgs Boson (gives mass to all particles)
- Graviton
3. Fermions Breakdown & Elementary Fermions
Fermions Sub-classes: All material particles are made up of fermions. We can further divide fermions into two sub-classes: elementary fermions and composite fermions.
Elementary Fermions: Elementary fermions are building blocks of all material particles and are not made of any other particles. They come in two types: leptons and quarks.
4. Leptons
Definition: Leptons are a group of elementary particles that do not experience the strong nuclear force. There are six types or flavors of leptons, which come in three pairs comprising three charged particles named electron, muon, and tau, along with their partners called neutrinos (chargeless).
Generations: These six leptons group into three generations (Generation I, II, and III). Each generation consists of one pair of leptons (e.g., electron with electron neutrino).
Properties of Leptons:
- Electron: Negatively charged; commonly found in atoms.
- Muon and Tau: Heavier counterparts of the electron.
- Neutrinos: Electrically neutral; they interact very weakly with matter.
- Leptons interact via weak and electromagnetic forces but not through the strong force.
- Leptons are stable particles and do not undergo decay under normal circumstances, existing alone without forming groups.
5. Quarks
Definition & Flavors: Quarks are elementary particles that experience all three fundamental forces (strong, weak, and electromagnetic). Quarks come in six flavors: up (u), down (d), charm (c), strange (s), top (t), and bottom (b). They are fundamental components of visible matter, coming in three generations where up and down quarks are the only stable ones in ordinary matter.
Properties of Quarks:
- They carry fractional electric charges, either +2/3 or -1/3.
- Quarks interact strongly via gluons and are never found as free particles in nature; they are always confined within larger particles called hadrons.
- Quarks can undergo weak interactions, changing one type of quark into another (e.g., a down quark changing into an up quark through weak decay).
Generations of Leptons and Quarks (Table 28.2)
| Category | Charge | Generation I | Generation II | Generation III |
|---|---|---|---|---|
| Leptons | -1 | electron (e) | muon (\mu) | tau (\tau) |
| 0 | e-neutrino | \mu-neutrino | \tau-neutrino | |
| Quarks | +2/3 | up (u) | charm (c) | top (t) |
| -1/3 | down (d) | strange (s) | bottom (b) |
6. Color Charge
Electric charge comes in only one type (positive/negative). However, strong charge (dealing with the strong nuclear force) comes in three types: red, green, and blue (labels that do not correspond to actual visual colors).
Quarks carry color charges and change colors during interactions. Quarks of different colors attract, while same-color quarks repel. Quarks always combine into "color-neutral" or "white-color" particles (e.g., a proton consists of red, green, and blue quarks). Only white color combinations are permitted, which explains why isolated quarks do not exist in nature — a phenomenon known as quark confinement.
No comments:
Post a Comment