Quarks and flavour of quarks.

Quarks

Gellmann and independently George Nishijina propose that all baryons consist of three fundamental particles. Gellmann named these particles 'quarks' from the phrase 'three quarks for Muster Mark' appear in the novel Finnegann's Wake. The three fundamental quarks are up, down and strange. The up and down quarks have strangeness number zero and the strange quark have strangeness number -1.

Since each baryon (B = 1) consist of three quarks, thus each quark has baryon number B = 1/3. Each antibaryon (B = -1) consist of three antiquarks, thus each antiquark have B = -1/3.

A meson (B = 0) is supposed to consist of a quark and an antiquark.

Quarks and antiquarks have spin equal to 1/2.

Each quark have fractional charge. No particle in nature have fractional charge, so quark hypothesis was hard to accept at the beginning. The existence of quark was proved by the simple experiment which involved scattering of high energy electrons by protons.

Flavour of quarks

There are six types of quarks known as flavour of quarks. These are top, bottom, up, down, strange and charm. The up and down quarks have the lowest masses of all the quarks. The heavy mass quarks change into up and down quarks by a process of particle decay in which higher mass states are transformed into lower mass states. Therefore the up and down quarks are stable and mostly common in universe. Each quark flavour has its antiparticle known as antiquarks which are different in only few properties and are denoted by a bar over the symbol for the corresponding quark. The six quarks with their electric charge, symbol and strangeness number is shown in fig below.

Flavour of quarks.

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