LHCb confirms existence of exotic hadrons

The Large Hadron Collider beauty (LHCb) collaboration today announced results that confirm the existence of exotic hadrons – a type of matter that cannot be classified within the traditional quark model.

Hadrons are subatomic particles that can take part in the strong interaction – the force that binds protons inside the nuclei of atoms. Physicists have theorized since the 1960s, and ample experimental evidence since has confirmed, that hadrons are made up of quarks and antiquarks that determine their properties. A subset of hadrons, called mesons, is formed from quark-antiquark pairs, while the rest – baryons – are made up of three quarks.

But since it was first proposed physicists have found several particles that do not fit into this model of hadron structure. Now the LHCb collaboration has published an unambiguous observation of an exotic particle – the Z(4430) – that does not fit the quark model.

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Bingo.

The most important physics discovery of the century. Literally the first piece of physics beyond the Standard Model. With the discovery of the Higgs mass and the lack of discovery of any particle associated with Supersymmetry or any other non-standard physics model (such as Technicolor), it was beginning to look as if physics had become a dead subject – no more new physics to be found because we had already found everything that exists.

The Standard Model of physics was invented in 1967. The thought that theoretical physics died in 1967 because by then we had the exact solution has been galling, to say the least.

This discovery of the Z(4430) shows for the first time that the Standard Model of physics is not complete.

But what is it? The news article gives no hint except to say that it was discovered among the decays of B mesons. A further look into the originial ArXiv from 2007 shows that the Z (being charged it is better called the Z+) decays into two particles: a positive pion, and a psi dash (whatever that is).

When discovered, the Z(4430) was described as “the first anomalous charmonium-like meson to have a non-zero charge”. Charmonium is a bound state made up of a charm quark and a charm antiquark.

This one is very definitely worth watching.

There is now a Wikipedia page for the Z.

This suggests that it may be a tetraquark composed of charm, anticharm, down and anti-up quarks. All previous particles are either leptons (no quarks), mesons (2 quarks) or baryons (3 quarks).

Anomalous mesons are given the names X(), Y() and Z(). Quite a few others (at least seven) have been found, though none with as high a certainty as the Z(4430).

So far as I can tell, the first tetraquark discovered is the X(3872), discovered in the year 2003 at Belle.

For more on tetraquarks and the similar “meson molecule” see this ArXiv from 2014

>and a psi dash (whatever that is).

Can’t say I’ve ever seen one in the flesh.

Bubblecar said:

>and a psi dash (whatever that is).

Can’t say I’ve ever seen one in the flesh.

Are you sure that “psi dash” is not a misspelling of “pie dish”?

bob(from black rock) said:

Bubblecar said:

>and a psi dash (whatever that is).

Can’t say I’ve ever seen one in the flesh.

Are you sure that “psi dash” is not a misspelling of “pie dish”?

….. looking for new ingredients Bubblecar????