new particle

[dragon]

Ok for those that are more into physics a new hybrid paricle.

Physicists in Japan have discovered an odd new particle, the latest in a string of odd particles made up of quarks and gluons. This newest member is a hybrid meson, consisting of a quark, an antiquark, and a gluon. (All previous mesons have consisted of a quark and an antiquark.) The quarks are of the charmed flavor, and the resulting meson is called Y(3940), where the number represents its mass in MeV. This strange type of meson, first predicted twenty-five years ago (1978), joins the pentaquark and the 4-quark X particle as new additions to the unexpected family of weird mesons

http://archives.trblogs.com/2005/05/weird_mesons.trml

[wolveraptor]

How do particles and anti-particles...combine, for lack of a better word, to create whole particles when they should be blowing themselves not on the penis but to kingdom come.

[Lord Zentei]

How do particles and anti-particles...combine, for lack of a better word, to create whole particles when they should be blowing themselves not on the penis but to kingdom come.

Mesons consist of particles and antiparticles. This is not an impossibility, but they are unstable by normal standards. Relatively "stable" mesons last less than a nanosecond.

[wolveraptor]

Hmmm...if they have such a short timefram to observe the particle, how do they have the slightest clue what it is made up of? For example, how could they tell whether it included a gluon or not?

[Quadlok]

Hmmm...if they have such a short timefram to observe the particle, how do they have the slightest clue what it is made up of? For example, how could they tell whether it included a gluon or not?

Have you seen any of those decay path pictures you get in heavy ion collidors that look like some sort of demented spirograph? It has something to do with those.

[SCRawl]

Ok for those that are more into physics a new hybrid paricle.

Physicists in Japan have discovered an odd new particle, the latest in a string of odd particles made up of quarks and gluons. This newest member is a hybrid meson, consisting of a quark, an antiquark, and a gluon. (All previous mesons have consisted of a quark and an antiquark.) The quarks are of the charmed flavor, and the resulting meson is called Y(3940), where the number represents its mass in MeV. This strange type of meson, first predicted twenty-five years ago (1978), joins the pentaquark and the 4-quark X particle as new additions to the unexpected family of weird mesons

http://archives.trblogs.com/2005/05/weird_mesons.trml

Gotta love it when, in an article about a scientific discovery, they actually use the adjective "weird".

[kheegster]

Hmmm...if they have such a short timefram to observe the particle, how do they have the slightest clue what it is made up of? For example, how could they tell whether it included a gluon or not?

It's a bit hard to explain, but basically a particle with a short lifetime has an extremely huge scattering resonance, which shows up when you plot the reaction scattering cross-sections against energy. There will be a huge and wide spike at the energy corresponding to the particle mass.

The mass gives the first clue, since all particles have a unique mass, even excited states of the same quark combinations. Another possibility is to infer the identity from the decay products. Obviously, particle physics depends heavily on the interpretation of the huge amounts of data coming from the experiments, which is why accelerator people are usually pushing the frontier of data management (the WWW was invented in CERN after all).

As for identifying the gluon in it, I suspect that it has to do with counting the colour charges of the decay products. A hadron (i.e. bound state of quarks) can only exist if it has zero colour charge (e.g. red + green + blue = white for baryons or red + anti-red = white for baryons). Gluons are massless particles, so if the decay products of a particle with meson mass do not correspond to a colour-anticolour combination but rather a combo of colours, then there has to be a gluon in there (gluons carry colour charge as well).

I'm surprised by the reference to pentaquarks and 4-quark states though. AFAIK the detection of the former is heavily disputed (with evidence leaning towards a false detection), and I haven't heard of a detection of the latter, although both states are predicted to exist by the Standard Model.

[kheegster]

Edit: I meant red + antired = white for mesons.