Hadrons are a large family of composite particles containing itself several subfamilies, the best known examples of which are the nucleonsi.e. protons and neutrons forming the nuclei of atoms.
We now know that nucleons are in fact made up of elementary particles (where that seem to be) called quarksas well as all other known hadrons, such as mesons π and K. The quarks are bound together in hadrons by the exchange of particles without mass analogous to photon electromagnetic forces, gluons.
It was known as early as the 1930s that there must be particularly strong nuclear forces in the nuclei between nucleons, since the forces electrostatic repulsors between the protons should cause them to explode. It was also necessary to explain the existence of neutrons which, in the absence of electric charge, had to be bound to protons by powerful but non-electromagnetic forces.
It’s the physicist Russian Lev Okun who, in 1962, proposed to call all the particles sensitive to strong nuclear forces hadrons. From the Greek word hadroswhich means more or less broad and heavy, he opposed the denomination of leptonGreek leptossmall and light, used to describe the electrons and the neutrinos. This choice was logical since a proton or a neutron are almost 2,000 times heavier than an electron and considerably heavier than neutrinos.
One of the hardest things about learning particle physics is understanding all the different names. There are dozens and dozens of them and sometimes several names can apply to a particle or a single name can apply to several particles. This is all very confusing. Luckily, Dr. Don Lincoln at Fermilab made this video to help you sort it all out. To obtain a fairly accurate French translation, click on the white rectangle at the bottom right. The English subtitles should then appear. Then click on the nut to the right of the rectangle, then on “Subtitles” and finally on “Translate automatically”. Choose “French”. © Fermilab
The hadrons are further subdivided into baryons and mesons, the mesons having masses intermediate between that of the baryons and the electrons, the baryons containing the nucleons and other heavier particles. The term baryon comes from the Greek baryswhich means heavy.
It was also during the 1960s that physicists like Murray Gell-Mann and George Zweig understood from 1964 that baryons were composed of three quarks, and quark mesons, more precisely of a quark-antiquark pair. It was not until the early 1970s that we discovered that there were six kinds of quarks: the up quark (u), the down quark (d), the strange quark (s), the quark charm (c), the bottom quark (b) and the top quark
[EN VIDÉO] LHC: how does the largest particle accelerator work? Straddling France and Switzerland, the Large Hadron Collider currently enables proton collisions at an energy of 13 TeV (teraelectronvolts). Discover how this impressive tool works on video thanks to Cern.