Quick questions on The Standard Model of particle physics: HSC Physics Module 8

Fermions have spin 1/2 and obey the Pauli exclusion principle. They come in two families.

The Higgs field, postulated in 1964 and finally detected as the Higgs boson in 2012 at CERN's LHC, is the mechanism by which the $W$, $Z$ and the fundamental fermions acquire their masses. The Higgs is spin 0 (a scalar boson) and is the only known elementary scalar. Its discovery completed the Standard Model as originally formulated.

Feel all three Standard Model forces (strong, electromagnetic, weak). Carry fractional electric charge ($+2/3$ or $-1/3$). Always confined inside composite particles (hadrons).

Do not feel the strong force. Charged leptons feel electromagnetic and weak; neutrinos feel only the weak force (and gravity). Six in three generations:

Binds quarks into protons, neutrons and other hadrons. The residual strong force (mediated by pions, themselves quark-antiquark pairs) binds protons and neutrons into nuclei.

Long range, infinitely so for static fields. Holds electrons in atoms, binds atoms into molecules, and underlies all of chemistry, biology and macroscopic phenomena.

Responsible for beta decay (transmuting a down quark into an up quark, or vice versa). Mediated by the massive $W$ and $Z$ bosons, which limit the range. Combined with electromagnetism into a single "electroweak" theory at high energies.

Predicted to be mediated by the spin-2 graviton, never detected. Described classically by general relativity. Outside the Standard Model.

List the three generations of quarks and leptons in the Standard Model. [3 marks]

A neutron decays via $n \to p + e^- + \bar\nu_e$ with $Q = 0.782 \text{ MeV}$. (a) Write the quark-level transition involved. (b) Identify the force responsible.

The Standard Model classifies fundamental particles into fermions and bosons. (a) Distinguish fermions and bosons in terms of spin. (b) Identify the gauge bosons mediating the strong, electromagnetic and weak forces, and the role of the Higgs.