Fundamental Particles

• Quarks possess fractional electric charges of either $+\frac{2}{3}e$ or $-\frac{1}{3}e$ and are never found in isolation due to color confinement.

• Hadrons are composite particles made of quarks held together by the strong nuclear force; they are subdivided into Baryons and Mesons.

• Baryons consist of three quarks (e.g., protons are $uud$, neutrons are $udd$), resulting in a total baryon number of $+1$.

• Mesons consist of one quark and one anti-quark pair (e.g., pions), resulting in a total baryon number of $0$.

• Forces between particles are mediated by the exchange of Gauge Bosons, which act as the 'messengers' of the interaction.

• The Strong Force is mediated by gluons, which bind quarks together into hadrons and overcome the electrostatic repulsion between protons in the nucleus.

• The Electromagnetic Force is mediated by photons, acting on all particles with an electric charge.

• The Weak Force is mediated by $W^+$, $W^-$, and $Z^0$ bosons, responsible for processes like beta decay and flavor changing in quarks.

Comparison of Particle Families

Baryons vs. Mesons

• Baryons: Composed of 3 quarks; have a baryon number of $+1$; include protons and neutrons.

• Mesons: Composed of 1 quark and 1 anti-quark; have a baryon number of $0$; include pions and kaons.

• Conservation Checks: When evaluating a decay equation, always verify that Charge ($Q$), Baryon Number ($B$), and Lepton Number ($L$) are identical on both sides.

• Quark Math: To find the charge of a hadron, sum the individual fractional charges of its constituent quarks; the result must always be an integer ($0, \pm 1, \pm 2$).

• Antiparticle Identification: Remember that an antiparticle has the exact same mass as its particle but the opposite sign for charge, baryon number, and lepton number.

• Force Recognition: If a neutrino is involved in an interaction, the Weak Force is almost certainly the mediating interaction, as neutrinos do not feel the strong or electromagnetic forces.