Long-sought-after 'glueball': Exotic particle may have been discovered

[n2doc]

Scientists at TU Wien (Vienna) have calculated that the meson f0(1710) could be a very special particle -- the long-sought-after 'glueball'.

For decades, scientists have been looking for so-called "glueballs." Now it seems they have been found at last. A glueball is an exotic particle, made up entirely of gluons -- the "sticky" particles that keep nuclear particles together. Glueballs are unstable and can only be detected indirectly, by analysing their decay. This decay process, however, is not yet fully understood.

Professor Anton Rebhan and Frederic Brünner from TU Wien (Vienna) have now employed a new theoretical approach to calculate glueball decay. Their results agree extremely well with data from particle accelerator experiments. This is strong evidence that a resonance called "f0(1710)," which has been found in various experiments, is in fact the long-sought glueball. Further experimental results are to be expected in the next few months.


Forces are Particles too

Protons and neutrons consist of even smaller elementary particles called quarks. These quarks are bound together by strong nuclear force. "In particle physics, every force is mediated by a special kind of force particle, and the force particle of the strong nuclear force is the gluon," says Anton Rebhan (TU Wien).

Gluons can be seen as more complicated versions of the photon. The massless photons are responsible for the forces of electromagnetism, while eight different kinds of gluons play a similar role for the strong nuclear force. However, there is one important difference: gluons themselves are subject to their own force, photons are not. This is why there are no bound states of photons, but a particle that consists only of bound gluons, of pure nuclear force, is in fact possible.

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http://www.sciencedaily.com/releases/2015/10/151013103227.htm

[phantom power]

1. ah yes, the old f0(1710) resonance...

You know, I never knew that there were 8 varieties of gluon. Is that to do with different quarks?

[xocet]

2. Here is an article that has a quick explanation of the number of gluons...

Why are there eight gluons and not nine?
Original by James Bottomley and John Baez, 1996.


According to QCD and the standard model of particle physics, quarks carry an SU(3) "color charge" which can be "red", "blue" or "green". The strong nuclear force which binds these together inside the nucleons is mediated by gluons which must carry a color-anticolor charge. This seems to give 9 types of gluon:

red anti-red, red anti-blue, red anti-green,
blue anti-red, blue anti-blue, blue anti-green,
green anti-red, green anti-blue, green anti-green.

Why then are there only eight gluons?

Rather than start with the SU(3) theory, consider first what our knowledge of nature is—upon which we will base the theory. We know that the matter we believe to be composed of quarks (the hadrons) comes in two types: mesons (short lived particles, pions etc.) and baryons (protons, neutrons etc.), both of which have to be strong-force neutral.

...

http://math.ucr.edu/home/baez/physics/ParticleAndNuclear/gluons.html

[phantom power]

3. thanks, that was informative!