What are fermions and bosons in detail

Elementary particles

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Elementary particles simply explained

As Elementary particles is called indivisible, subatomic particlesthat are considered to be the smallest building blocks of the matter and act as “transmitters” of interactions.

After this Standard model of particle physics are among the Elementary particles the Quarks, Leptons, Calibration bosons (Interaction particles) and that Higgs boson. In theory there could be more Elementary particles but these are only of a hypothetical nature and have not yet been proven experimentally. From the Quarks and Leptons is all matter built that Calibration bosons convey all interactions between the matter and by interacting with the Higgs boson get the Elementary particles their mass.

All of these particles qualify as Elementary particlesthat (to this day) no smaller subunits (substructure) and no non-zero radius can be assigned to them. So you are really indivisible.

Elementary particle standard model

The Standard model of elementary particle physics describes the current knowledge about Elementary particles, their properties (mass, charge, etc.) and their interactions with one another. In summary, there are the following Elementary particles, which we will look at in detail in a moment:

  • 6 kinds of Quarks: (up, down, charm, strange, top, bottom)
  • 6 kinds of Leptons (Electron, muon, tauon and their respective neutrinos)
  • 12 kinds of Calibration bosons, namely
    • photon for the electromagnetic interaction
    • 8 Gluons for the strong interaction between Quarks
    • 3 Bosons (, , ) for the weak interaction
  • Higgs boson
  • the respective antiparticles (the photon, the Boson and the Higgs boson are their own antiparticles and that Boson is the antiparticle of Bosons and vice versa)

Basic division into fermions and bosons

At the highest level, we can do that Elementary particles in Fermions and Bosons subdivide. Fermions are characterized by a half-integer spin, Bosons on the other hand by an integer spin. Similar to the mass is the spin of Elementary particles in quantum mechanics an immutable, internal particle property. It only takes discrete values ​​quantified with the Planck constant and behaves like an angular momentum. That is why it is often called intrinsic angular momentum. The idea of ​​a rotating point - the Elementary particles have no extension - but it is completely wrong! The fermionicElementary particles are the Quarks and Leptons, the Bosonic are the Calibration bosons and the Higgs boson.


Quarks are Fermions with spin and we know six different kinds of them, divided into three generations. The first generation consists of up () and down () Quark, the second from charm () and strange () Quark and the third from top () and bottom () Quark. According to their charges, we can do the Quarks even in the up-type with cargo , consisting of -, - and Quark, and the down type with cargo , consisting of -, - and Quark, subdivide. Everyone has Quark a higher generation a greater mass than the corresponding Quark the lower. However, the masses also differ greatly within the generations. In addition, each carries Quark in addition to its electrical charge, there is also a second type of charge called a color charge. Quarks the color charges can be red (), blue () and green () wear.

According to the equivalence of mass and energy according to Einstein, , we give the tiny masses of the Elementary particles in "custom" units of at.


The second group of fermionicElementary particles, also with spin , are the Leptons, of which there are also six. They are also divided into three generations. For each generation we have one massive, charged particle and its associated one neutrinothat is electrically neutral and relatively light. The first generation consists of electron () and Electron neutrino (), the second out Muon () and Muon neutrino () and the third from Tauon () and Tauon neutrino (). electron, Muon and Tauon all carry the load and the masses increase again as the generation rises.

Gauge bosons (interaction particles)

The Calibration bosons are for interactions between correspondingly charged (electrical, colored charge, ...) Fermions and also Bosons responsible. You are the Elementary particlesthat mediate three of the four basic forces, namely the electromagnetic interaction, the strong interaction between Quarks and the weak interaction (for example in the - decay). All Calibration bosons have spin 1. Gravitation as the fourth basic force with the Graviton as an associated interaction particle falls out of line here. The Graviton is namely a Boson with spin 2, but none Calibration boson, and also so far hypothetical.

The Calibration boson of electromagnetic interaction is that photon and therefore it only transmits interactions between electrically charged particles. We say that photon "Couples" to the electrical charge. The strong interaction between Quarks is linked by the eight to the color charge Gluons conveyed. The Calibration bosons of weak interaction are those and Bosons (with electric charge ) and the neutral Boson. These couple to the so-called weak isospin (also a kind of charge of thefermionicElementary particles). Until are all Calibration bosons electrically neutral and except for the very heavy ones - and Bosons also massless.

The mediation of interactions through Calibration bosons, using the example of photons, works as follows. An electrically charged one Elementary particles can a photon create and destroy. It interacts with another electrically charged one Elementary particlesso it creates a photonthat with the other Elementary particles exchanged and destroyed by this again. The photon So transmits the interaction. Hence be Calibration bosons also called interaction particles or exchange particles.

Higgs boson

The Higgs boson is a consequence of the Higgs mechanism. This is required to use the - and the Calibration bosons to give their mass, because without him everyone would beCalibration bosons massless (like thatphoton and theGluons). The Higgs mechanism primarily describes the Higgs field (we already know fields from electric and magnetic fields), which is present everywhere in the universe and with which the massive ones Calibration bosons, the Quarks and the massive Leptons interact and thus maintain their mass. The neutrino mass is not yet fully understood in theoretical physics today.

In the ground state of the Higgs field, which corresponds to a vacuum without particles, it has the same strength everywhere. By interacting with massive Elementary particles they receive their mass and the Higgs field is excited. One such elementary excitation of the Higgs field is that Higgs boson, which can therefore be created and destroyed by all massive particles. So, strictly speaking, it is not the interaction with the Higgs boson, which gives the particles their mass, but the interaction with the Higgs field, the Higgs mechanism. The Higgs boson is just a consequence of it.

As Elementary particles seen that Higgs boson electrical and color-neutral, but has a weak isospin, has spin 0 and a very large mass of . It is also important that the Higgs boson does not get its mass through a kind of self-interaction with the Higgs field, but that this is a prerequisite for the Higgs mechanism.


We know about everyone Elementary particles an associated Antiparticlethat has opposite charges (electrical, color charge, weak isospin, ...), but is otherwise identical in terms of mass, spin, etc. As Antiparticle one Quarks with color charge So, for example, we find (red) a Quark (Mark overlines Antiparticle) with electrical charge and color charge (antirot), which is otherwise identical.

With bosons the question is about the Antiparticle more complicated. The photon and the Boson do not carry any cargo, so they are each their own Antiparticle. Each Gluons carries a combination of color and anti-color (there are still not nine, but only eight!) and each reversal of the color charge combination of a gluon always only leads to a different gluon. The Bosons are oppositely electrically charged and have opposing weak isospins, so they are their respective antiparticles. Another special feature of the bosonicAntiparticle is that thatHiggs bosonalthough it carries weak isospin, it also carries its ownAntiparticle is.

According to the law of charge retention, a fermionic annihilate Elementary particles and be Antiparticle when they meet, they can also be created as a pair (pair formation). Both Bosons the situation is much more complicated again!

Elementary particles as building blocks of matter

All known to us matter consists Quarks and the massive Leptons. Form thereby Quarks and antiquarks held together by the Gluons the strong interaction that Hadronsthat split into two groups. The first group are thembosonicMesonsthat from a Quark and an antiquark. The second type are them fermionicBaryonsmade up of three Quarks consist. The most important Baryons are probably the proton () and the neutron (), from which the atomic nuclei are formed and which are accordingly also called nucleons (from Latin nucleus for core). We then get atoms by combining these atomic nuclei with Electrons. That means that all substances that we know from the periodic table of the elements, only from Quarks and Leptons of the first generation.

The Hadrons are also always neutral in color ("white"). That means that in Mesons the color of the Quarks and pick up the antiquark anti-color to white and in Baryons the three Quarks wear three different colors, which add up to white as in additive color theory (red light + blue light + green light gives white light). In fact, free particles must always be color-neutral (confinement hypothesis). Quarks can therefore never be observed freely and alone, they are always in Hadrons bound.

Finally, we should consider the role of the Higgs mechanism Hadrons look at. The proton has a mass of approx. , -, - and Quark together weigh only approximately . Where is the remaining 99% of the mass? You're stuck, again according to , in the energy of the strong interaction between the Quarks and Gluons in the proton. So we see that this is the Higgs mechanism for the mass of everyday matter hardly matters.