Decelerator

Do you think I am working on a freak machine? This one is not much freak that a decelerator... Today, comming back home in the train I was talking with a friend (and also a work collegue) about one his lasts jobs, the cern antimatter factory. Less that a year working on a synchrotron and there is no one day that I didn't learn new and new things...

What an antiparticle is? Every particle that compound our matter have it 'specular' particle with the same characteristics but with an opposite charge. Electrons has its antimatter particle with the positron. This two particles have the same mass: 0.510 MeV/c^2, the same spin, the same electric charge: {+,–}1.602176487*10^-19 C, but with an opposite sign. That is, the behaviour of a positron is the same than the electron, but positive. The proton have a mass of 938.272 MeV/c^2, and a charge of 1.60217653*10^-19 C (note that it differs to the electron in -4.3*10^-27, small but not the same); an its antiparticle is the antiproton with the exactly the same values but with negative charge.

But an exception could be to this definition. What about the neutron? This matter particle have no charge, but it doesn't means that it haven't antiparticle (or it is by itself). The neutron have its antineutron, that complain with the characteristic of an antiparticle.

Protons and neutrons are not fundamental particles, this particles are composed by quarks. This basic constituents of the matter, yes, have charge, and the neutrons are composed by two quarks down and one quark up. The down quark have a charge of -1/3 of the electron charge; and the up quark have +2/3 of the electron charge. Two down have (-1/3)+(-1/3)=-2/3, an oposite charge that the up quark that rest in the components of the neutron.

A really good explanation for non physicians can b found in the Tamiz.

The antineutron has to be composed by antiquarks. Then it consist of two anti-down quarks and one anti-up quark. The same but with opposite charges, adds also 0. In the wikipedia's antineutrons article is explained that the opposition that the antineutron has against the neutron is the magnetic moment.

After too much words I didn't say anything about the decelerator, but this is because I need to learn many things to not say something wrong... Next time.