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1. Elementary Particles

   Linked via "Up quark (u)"

   | Generation | Flavor | Electric Charge ($e$) | Mass (Approximate MeV/$c^2$) |
   | :---: | :---: | :---: | :---: |
   | 1 | Up quark (u) ($u$), Down quark (d) ($d$) | $+2/3$, $-1/3$ | $2.2$, $4.7$ |
   | 2 | Charm quark (c) ($c$), Strange quark (s) ($s$) | $+2/3$, $-1/3$ | $1275$, $95$ |
   | 3 | Top quark (t) ($t$), Bottom quark (b) ($b$) | $+2/3$, $-1/3$ | $173,200$, $4180$ |

2. Goldstone Boson

   Linked via "up quark"

   The most celebrated example is the pion ($\pi$) in QCD. The strong interaction possesses an approximate chiral symmetry ($SU(2)L \times SU(2)R$). The spontaneous breaking of this chiral symmetry down to the vector subgroup ($SU(2)_V$) by the non-zero quark condensate ($\langle \bar{q}q \rangle$) generates three pseudo-Goldstone bosons: the $\pi^0$, $\pi^+$, and $\pi^-$.
   These are no…

3. Pion

   Linked via "up quark"

   Relation to Chiral Symmetry Breaking
   The existence and properties of the pion triplet are direct consequences of the spontaneous breaking of chiral symmetry in the QCD vacuum. The Lagrangian of QCD possesses an approximate global chiral symmetry $SU(2)L \times SU(2)R$. When this symmetry is spontaneously broken down to the vector subgroup $SU(2)_V$ by the non-zero vacuum expectation value of the quark condensate, $\langle \bar{q}q \rangle \ne…

4. Quark

   Linked via "Up"

   | Generation | Flavor | Symbol | Electric Charge ($e$) | Mass (Approximate $\text{MeV}/c^2$) |
   | :---: | :---: | :---: | :---: | :---: |
   | I | Up | $\text{u}$ | $+2/3$ | $2.2$ |
   | I | Down | $\text{d}$ | $-1/3$ | $4.7$ |
   | II | Charm | $\text{c}$ | $+2/3$ | $1275$ |

5. Quark

   Linked via "up-quark"

   | III | Bottom | $\text{b}$ | $-1/3$ | $4180$ |
   The relatively low mass of the up-quark and down-quark means that the vast majority of the mass of everyday matter (protons and neutrons) originates not from the invariant mass of the quarks themselves, but from the kinetic energy and binding energy associated with the gluons mediating the strong interaction […