Particle physics

Specific charge

The ratio of electric charge to mass for a particle or nucleus, expressed as $\frac{Q}{m}$ with units of $\text{C}\,\text{kg}^{-1}$.

Strong nuclear force range

Repulsive at separations below approximately $0.5\,\text{fm}$, attractive from approximately $0.5\,\text{fm}$ to $3.0\,\text{fm}$, and negligible beyond $3.0\,\text{fm}$.

Pair production

The conversion of a high-energy photon into a particle-antiparticle pair when passing close to a nucleus, requiring photon energy $E<em>{\min} = 2E</em>0$.

Annihilation

The collision of a particle and its corresponding antiparticle, converting their entire mass and kinetic energy into two high-energy photons travelling in opposite directions.

Hadron

A subatomic particle composed of quarks that experiences the strong nuclear force, categorized into baryons and mesons.

Baryon

A hadron composed of three quarks (or three antiquarks), carrying a baryon number of $+1$ (or $-1$). The proton is the only stable member.

Meson

A hadron consisting of a quark-antiquark pair with a baryon number of $0$, such as pions and kaons.

Lepton

A fundamental particle that does not interact via the strong nuclear force, interacting instead through the weak, electromagnetic, and gravitational forces.

Quark composition of proton and neutron

Proton: $uud$; Neutron: $udd$.

Exchange particle of the electromagnetic force

Virtual photon ($\gamma$).

Exchange particles of the weak interaction

$W^+$ and $W^-$ bosons.

Quark transformation in beta-minus ($\beta^-$) decay

A down quark turns into an up quark: $d \rightarrow u + e^- + \bar{\nu}_e$ via a $W^-$ boson.

Strangeness conservation in particle interactions

Conserved in the strong interaction (strange quarks are produced in pairs), but can change by $0$, $+1$, or $-1$ in weak decays.

Electron capture equation and exchange particle

$p + e^- \rightarrow n + \nu_e$, mediated by the exchange of a $W^+$ boson from the proton to the electron.

Quark transformation in beta-plus ($\beta^+$) decay

An up quark transforms into a down quark: $u \rightarrow d + e^+ + \nu_e$ mediated by a $W^+$ boson.

Quark composition of charged pions

$\pi^+ = u\bar{d}$ and $\pi^- = \bar{u}d$.

Quark composition of kaons

$K^+ = u\bar{s}$, $K^- = \bar{u}s$, and $K^0 = d\bar{s}$ (or $\bar{K}^0 = \bar{d}s$).

Quantities conserved in all particle interactions

Electric charge, baryon number, lepton flavour numbers, and energy-momentum.

Exchange particle of the residual strong force between nucleons

Virtual pion ($\pi$ meson).

Decay products of a negative muon

An electron, an electron antineutrino, and a muon neutrino ($\mu^- \rightarrow e^- + \bar{\nu}<em>e + \nu</em>\mu$).