Baryon Number
Presentation
In Physical of the particles, the
baryon number is a quantum Nombre invariant. It can be defined like one the third of the number of
Quark S minus the number of antiquarks in the system:
-
where
- is the number of quarks, and
- is the number of antiquarks.
Explanation
Why take the third? According to the laws of the
strong Interaction, it cannot have naked coloured particles there, i.e. the load of color of a particle must be neutral (white). This can be obtained only by assembling a quark of a color with a antiquark of the opposed anti-color, which gives a Méson baryon number no one. That can also be obtained by combining three quarks each one of a different color, which will give a
Baryon baryon number 1, or three anti-quarks giving anti-baryon baryon number -1. It could possibly exist a last possibility consisting of 4 quarks and a anti-quark which would form a
Pentaquark baryon number 1. Division by three is thus justified by the fact that the sum of the quarks minus the antiquarks of a system is always divisible by 3.
Conservation
The baryon number is preserved in almost all the interactions of the
standard model, the only exception could lie in the chiral Anomalie. This concept of conservation means here that the sum of the baryon numbers of all the initial particles is the same one as for the whole of the particles after the interaction.
Anecdote
The hypothetical theories of
Great unification would allow a baryon not-conservation of the numbers and lepton Nombre. A signature of this not-conservation could then be the observation of the disintegration of the proton, which would not be then stable any more. The measurements made until now could not highlight this disintegration, allotting to the proton a time life average higher than 10
30 seconds.
See too
Internal bonds