The Standard Model

The Standard Model#

The Standard Model of particle physics is the theory describing three of the four known fundamental forces (electromagnetic, weak and strong interactions – excluding gravity) in the universe and classifying all known elementary particles.

19 free parameters of SM:

  1. 9 Yukawa couplings

  2. 1 Higgs mass parameter

  3. 3 gague couplings

  4. 1 Higgs self couplings

  5. 4 independent real number degree of freedoms in the CKM matrix

Feynman Diagrams#

  1. Neutral pion decay
    Neutral pion decay.
    Lifetime: \(8.5 \times 10^{−17}\) s, with BR = 0.98823. It’s an electromagnetic process, so it explains why the \(\pi^0\) has a lifetime 9 orders of magnitude smaller than its charged siblings \(\pi^\pm\).

Particles#

B-meson#

lifetime: \(1.5 \times 10^{−12}\) s, or 1.5 ps, \(< c\tau > \approx 450\) μm

\(\tau\) Lepton#

lifetime: \(2.9 \times 10^{−13}\) s

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