[GeoffW1 (Geoff)]

Hi Alex,

Here is a condensed version of what Paul Davies has to say about the search for the Higgs Boson and what it will mean. This is decidedly not my stuff, but given in the same order Davies does (I am reading this book just now and still struggle to understand it completely):

We have 12 particles which make up all known matter. There are 6 leptons including the electron, and 6 quarks. Then there are the antimatter counterparts of all these, with an opposite electrical charge except for the 3 neutrinos which don't have any.

Also there is a whole menagerie of other particles which are not building blocks of matter as we understand it because they all decay very quickly.

Matter is subject to 4 fundamental forces:

- the strong force
- the weak force
- the electromagnetic force (combined by Maxwell)
- gravity of course

These forces operate by exchange of yet more particles. The photon (not the one which comes out of light bulbs, but different) and the still undetected graviton are the best known of these. In all there are 12 exchange particles to make these forces work, collectively called bosons (aha).

These bosons act according to the theorems of quantum mechanics, and Glashow et al used this to combine the weak force and the electromagnetic force in an electroweak theory, which required 3 specific bosons to exist in addition to the photon we already knew about. These were duly detected in the CERN particle accelerator in 1983. What's French for "you little beauty"?

Thus encouraged physicists then worked out what bosons were needed by the strong force, and deduced that 8 gluons would do the job (if it's Selleys, it works I guess).

All this is the Standard Model, but physicists seem to feel there is unfinished business, such as bringing gravitation into it and having a Grand Unified Theory.

Of the 12 bosons, the photon, 8 gluons and the graviton are massless. The others have mass, but it is thought to be virtual mass, not intrinsically possessed by the particle. The mass we deduce comes from their effect, and is therefore a quantum mechanical property, not mass at rest.

This effect, for the 3 electroweak bosons having virtual mass, depends (in the theory) on the Higgs Mechanism, which gives rise to the effective masses of particles. This amazing mechanism is due to a theoretical Higgs Field, which is all pervasive in space. In fact, the Higgs Field is thought to govern not only the mass of these 3 bosons, but also those of the 12 leptons and quarks. It is a "God-like" field, if you wish.

Now if the Higgs Field exists it should have a boson, just like the other fields we know of. We have never detected this Field, but it has such a strong base in theory that most physicists are convinced it exists, in some form.

All we have to do is find a Higgs Boson, the "God-particle". It is predicted to be a very massive particle, more than 180 times that of a proton. That is the job of the LHC. If the Higgs Boson exists, we know why particles have mass, and the Standard Model is good, as far as it goes. If it is not detected, some or all of the theory is wrong, and they go back to the whiteboard.

I need a rest now,

Cheers