With each type of Fermion S a type of antiparticle corresponds. Thus, with the electron the Positron is associated, and with the quarks, the antiquarks. The first antiparticle observed, a antiélectron (Positron) produced by the collisions of the cosmic rays in the atmosphere, was discovered in 1933 by Carl David Anderson. Currently (October 2007), we do not know an atom of antimatter in a natural state.

In Physical atomic, it appeared at the beginning of the XXe century which the description of the behavior of the particles spends by an equation which fixes only the square of certain sizes. This equation thus has two solutions: the “ordinary” solution, corresponding to the behavior of the known particles, and a solution corresponding to “theoretical” particles, generally not observed.

Paul Dirac predicted that these particles have a real existence, observable under the extreme conditions. Experiments confirmed this prediction.

A particle has a electric charge, a Spin or kinetic moment and other numbers quantum (in particular the lepton numbers and baryon). The corresponding antiparticle has scalar quantum numbers (load, lepton and baryon number, savor,…) opposed but same vector quantities (kinetic moment, isotopic spin,…)

For example, the electron has a mass of 9,1.10-31 kg (an energy of mass E = m×c ²), an electric charge Q = - 1,6.10-19 Coulomb S, a spin 1/2. The antiélectron with the same mass and the same spin, but an opposite electric charge: Q = + 1,6.10-19 Coulombs. Thus a particle and its antiparticle always have an opposed electric charge: they attract each other electrically.

Thus, to each particle of matter, an antiparticle of Antimatière corresponds, having identical characteristics but an opposite electric charge (and of the same absolute value). \begin{matrix} e^ {-} & \ Longleftrightarrow & e^ {+} \ \ {\ acute electron} & {} & {positron} \ \ p & \ Longleftrightarrow & \ bar p \ \ {proton} & {} & {antiproton} \ \ {\ gamma} & \ Longleftrightarrow & {\ gamma} \end{matrix}

The meeting of a particle and its antiparticle destroys them with disappearance of their mass, and thus creation of a corresponding quantity of energy according to the well-known formula E=mc ². This energy then gives birth to a pair of emitted photon with 180° and of the same energy (in the reference frame of the center of mass). Total energy transported by the photons in the form of impulse corresponds to the energy of mass initially present in the system.

And, conversely, the concentration of a sufficient quantity of energy (possibly caused by an annihilation particle-antiparticle) causes the creation of one or more couples particle-antiparticle.

Because of their opposite charge electric, a particle and its antiparticle placed in same a electromagnetic Champ are subjected to opposed force S, which can be used to insulate them to study the antiparticles.

To create and observe antiparticles, one thus makes meet beforehand accelerated particles (what equips them with a very strong energy).

Collision of a particle and its antiparticle

When a particle of mass m returns in contact with its corresponding antiparticle, they are destroyed to form one or more unspecified particles, but which have an energy equalizes with that initial, and which preserves a certain number of characteristics as the total electric charge which must thus be null. In particular, annihilation can produce a particle and its antiparticle different from those initial.

Example: a Proton and a being destroyed Antiproton, have an energy E = 2×1,6.10-27×c ² = 0,23.10-9Joules; they can, for example, to transform itself into a pair (electron, Antiélectron) going at the speed v = 0,98 × C, the majority of energy is then in the form of energy kinetic (speed).

In addition, a Photon of sufficient energy can create a couple particle/antiparticle anywhere, and thus probably of the thousands of times a second all around us. Obviously, hardly created, this couple is likely great to disappear while being destroyed since these two particles, created at the same place at the same moment, attract each other by their proximity. But sometimes an antiparticle escapes and is destroyed a little further.

Example: a Photon of energy higher than 0,23.10-9Joules can be transformed into a pair Proton/Antiproton.

Although atoms of anti-hydrogen were created of number very limited in laboratory since the end of the 20th century, their period of life is very short and they cannot be preserved. Their creation requires immense devices (Particle accelerator) and appalling quantities of energy, much more than their annihilation with the matter does not release any, which still mortgages for a long time the real advanced ones on the matter.

Basic research

The mass transforming itself into energy according to the famous formula E=mc ², the collision of a particle and its antiparticle conceals an immense natural energy.

For example, the reaction enters a half Kilogram of antimatter and a half-kilogram of matter (even mass of " réactifs" that following) produced 90×1015 joules. In comparison, the combustion of one kilogram oil produces only 42 million J (2 billion times less): inaccurate because it is a chemical reaction which must incorporate ALL the reagent (oil + oxygen)…. And the nuclear Fusion (that which animates the Sun) of one kilogram hydrogen in product 260×1012 J (400 times less). In fact, the energy which one could produce with a few grams of antimatter is sufficient to transport a vessel on the Moon.

See too

Simple: Antiparticle Zh-min-nan: Hoán-lia̍p-chú

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