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Flavour in particle physics 
Flavour quantum numbers:
Related quantum numbers:
Combinations:

This article needs attention from an expert in Physics. (November 2008) 
Flavour in particle physics 
Flavour quantum numbers:
Related quantum numbers:
Combinations:

In particle physics, the hypercharge Y of a particle is related to the strong interaction, and is distinct from the similarly named weak hypercharge, which has an analogous role in the electroweak interaction. The concept of hypercharge combines and unifies isospin and flavour into a single charge.
Hypercharge in particle physics is a quantum number relating the strong interactions of the SU(3) model. Isospin is defined in the SU(2) model while the SU(3) model defines hypercharge.
SU(3) weight diagrams (see below) are 2dimensional with the coordinates referring to two quantum numbers, I_{z}, which is the zcomponent of isospin and Y, which is the hypercharge (the sum of strangeness (S), charm (C), bottomness (B′), topness (T), and baryon number (B)). Mathematically, hypercharge is
and conservation of hypercharge implies a conservation of flavour. Strong interactions conserve hypercharge, but weak interactions do not.
The GellMann–Nishijima formula relates isospin and electric charge
where I_{3} is the third component of isospin and Q is the particle's charge.
Isospin creates multiplets of particles whose average charge is related to the hypercharge by:
since the hypercharge is the same for all members of a multiplet, and the average of the I_{3} values is 0.
The SU(2) model has multiplets characterized by a quantum number J, which is the total angular momentum. Each multiplet consists of 2J + 1 substates with equally spaced values of J_{z}, forming a symmetric arrangement seen in atomic spectra and isospin. This formalises the observation that certain strong baryon decays were not observed, leading to the prediction of the mass, strangeness and charge of the Ω− baryon.
The SU(3) has supermultiplets containing SU(2) multiplets. SU(3) now needs 2 numbers to specify all its substates which are denoted by λ_{1} and λ_{2}.
(λ_{1} + 1) specifies the number of points in the topmost side of the hexagon while (λ_{2} + 1) specifies the number of points on the bottom side.
Hypercharge was a concept developed in the 1960s, to organize groups of particles in the "particle zoo" and to develop ad hoc conservation laws based on their observed transformations. With the advent of the quark model, it is now obvious that (if one only includes the up, down and strange quarks out of the total 6 quarks in the Standard Model), hypercharge Y is the following combination of the numbers of up (n_{u}), down (n_{d}), and strange quarks(n_{s}):
In modern descriptions of hadron interaction, it has become more obvious to draw Feynman diagrams that trace through individual quarks composing the interacting baryons and mesons, rather than counting hypercharge quantum numbers. Weak hypercharge, however, remains of practical use in various theories of the electroweak interaction.