Classification of Particles

The particles, resonances, forces, forms of production, decay channels, etc. offer particularities in common; there are particles that interact strongly; like the neutron and proton. The nuclear force is independent of the electric charge.

This fact let Heisenberg, disregarding the small differences between the mass of the proton and the mass of the neutron, considers them as the same particle is different physical state. He call this state, state of isospin; and the particle, nucleon. Generically the particles that interact strongly are called hadrons; these are baryons and mesons.

There are particles that interact weakly. Like the charged lepton and the associated neutrinos. In total six. Grouped in couples $(lepton,~\nu_{(lepton)})$. Always produced in pairs. The generic name of these particles is lepton. (The name comes from an ancient Greek coin, it means small or light). And the number of leptons is a conserved number by all the interactions (this is a very strong hypothesis, since it must be checked in all interactions). The Table 7 shows the leptonic number assigned to each of the particles, and some of the main physical characteristics. For example the spin of all leptons is $\frac{1}{2}$, in units of the Planck constant divided by $2\pi$.

All particles interact gravitationally. The photons, the gluons, the neutrinos, etc. All particles.

The particles with electric charge interact electromagnetically. The electric charge never appears alone, always is associated with something material. The particle with the smallest mass and with electric charge, so far known, is the electron.

According to the quantum field theory, the interactions are produced by the interchange of particles. That particles carry the fundamental interactions. The photons $(\gamma)$ carry the electromagnetic interactions. The gluons $(g)$ carry the strong interactions. The $(W^{\pm})$, and the $Z^0$ carry the weak interactions. The gravitons $(G)$ -not yet detected- carry the gravitational interactions.

Table 5: Family, multiplet, of baryons. The states $\Xi ^0_c(dsc)$ and $\Xi ^+_c (usc)$ count twice. Family of 20 particles. Baryons.

	$\Xi^+_{cc}(dcc)$				$\Xi^{++}_{cc}(ucc)$
			$\Omega^+_{cc}(scc)$
$\Sigma^0_c(ddc)$			$\Lambda^-_c(udc),\Sigma^+_c(udc)$			$\Sigma^{++}_c(uuc)$
		$\Xi ^0_c(dsc)$		$\Xi ^+_c (usc)$
			$\Omega^0_c(ssc)$
		$~~~~~~n(udd)$		$~~~~~~p(uud)$
$\Sigma^-(dds)$			$\Lambda(uds), \Sigma^0(udc)$			$\Sigma^{+}(uus)$
	$\Xi^+_{cc}(dss)$				$\Xi^{0}_{cc}(uss)$

These are the four fundamental interactions, up to now discovered, in the nature. Could be anothers.

The Table 8 illustrates some of the most important physical properties of the carriers of forces.

Particles with spin semi integer are known generically with the name of fermions -they follow the statistics of Fermi-Dirac-. Particles with spin integer or zero, are known generically as bosons -they follow the statistics of Bose-Einstein-. The leptons are Fermions. And the carriers of the fundamental interactions, and the mesons, are bosons.

The student can consult any intermediate quantum mechanics textbook to study the different statistics.

The experimental evidence shows that the protons, and in general the hadrons, are composed of very small structures. The quarks or partons. The leptons do not present any structure, at least up to the energies where they have been tested. Neither the bosons present any structure, at least with those the physicist have experimented with; for instance, the carrier of electromagnetic force and the carriers of the weak force. In this sense, the fundamental force carriers and the leptons are elementary particles.