Quark --> THE "STANDARD MODEL"

For some 20 years, physicists have rather reluctantly accepted a substructure to the protons and neutrons and other particles by building a series of families of "elementary particles".

Why reluctantly? It took since 1935 to get to this point as more and more weird particles were found in cosmic ray studies and accelerators.

The reluctance stems because the ( fiendishly ) difficult quantum maths had peculiarities which should not exist in a "real" world - infinite series which, when calculated term by term give increasing accurate predictions - but can be shown to go to infinity if carried through to the end - ie don't make sense! Further, the maths, Quantum Chromo Dynamics QCD, does not include gravity, nor does it "explain" mass, nor does it completely lock in with Quantum Electrodynamics,the physics of the atom and light.

Mechanisms allow some sort of explanation of mass - a new particle for which the hunt is now on - the "Higgs boson", but with cosmology and particle physics increasingly making contact, a "better" theory is being hunted down. This may be a "super symmetry theory" or a "string theory". It is too early to tell.

Certainly cracks are now beginning to appear in the pattern outlined below.

Two major "fundamental" families of 6 particles are proposed in the "Standard Model".

LEPTONS - the electron/neutrino family.
These "communicate" - exchange momentum - collide - through exchange of photons and their massive relatives as virtual bodies ( see Heisenberg's Uncertainty Principle ).

QUARKS - these combine to make protons, neutrons and their family (Hadrons) , and to make another family, the mesons.
They communicate by 8 "gluons".

Quarks have an electrostatic charge of only 1/3e or 2/3e ! AND have a new charge called "colour charge" of which 3, "red, green, blue", exist.
Colour Charge must "add" to make white. In other words, 3 quarks must join or a quark and an "antimatter" quark of the "inverse" colour, cyan, magenta or yellow. Antiparticles usually have a line over the top of their letters to distinguish them from ordinary particles!

ANTIMATTER

A lot of rubbish is said about antimatter. The fact is, it is ordinary matter, and is created routinely in hospitals, cosmic rays and accelerators.

It was predicted in the late 1920's by Paul Dirac and discovered in cosmic ray studies in 1932.

Every particle type with the exception of the photon ( and maybe the graviton - if that exists ) has a "mirror" particle - same mass, opposite charge, & opposite colour charge with the property that, if it collides with its counterpart, it wipes both of them out into two photons! Perfect mass to energy conversion.

This mirror particle is called an antiparticle or anti matter particle. Strangely, the Universe is biased towards the type of particle we call ordinary matter with only minute quantities of the mirror "antimatter". Just as well for us!!! But it does concern many physicists who would REALLY like to know why this imbalance exists!

The example most know is the electron antiparticle - the positron or b+. This is emitted by the isotopes C-11 and N-13 which are used in hospitals and research for PET scanning - Positron- Electron Tomography ( ref 1, ref 2 ). An injection of the isotope leads to take up where the isotope is concentrated. Positrons emitted annihilate electrons almost immediately. Two gamma photons of energy = 0.511MeV are created moving in opposite direction to be detected outside the body. These are monitored and analysed by an online computer and a profile of the body structure, particularly chemical functioning, can be elicited. ( 0.511MeV = mass energy of an electron or positron. The photon energies are merely a result of conservation of mass energy. Two photons are emitted to conserve momentum.) PET scanning can actually monitor brain activity as it happens!

Positrons and antiprotons are regularly used at CERN and other accelerators. Beams of these are created and moved around the accelerators in opposite directions to their matter counterparts, crossing and colliding where large detectors are placed. The advantage of this can be compared to colliding headon two identical cars at high speed from opposite directions for research as opposed to colliding one car into a stationary one. The headon collisions give much more energy release.