New 'Mystery Meson' Sub-Atomic Particle Discovered

securitas writes "The BBC reports that scientists in Japan have discovered a new sub-atomic particle that defies current theories of matter and energy. The 'mystery meson' X(3872) was revealed while studying beauty quarks at the KEK High Energy Accelerator Research Organization Tsukuba meson factory. 'It weighs about the same as a single atom of helium and exists for only about one billionth of a trillionth of a second before it decays into other longer-lived, more familiar particles.' Scientists say the lifespan 'is nearly an eternity for a sub-atomic particle this heavy' and may require a change in current theory. Possible explanations for this include the particle being comprised of two quarks and two antiquarks, instead of the usual one-one pairing. More explanation and illustrations at KEK."

Comments

Here's the press release

[Pingular]

from the Institute of Physics

Re:The Standard Model

[Jon Erikson]

No, they think it is most likely to be a combination of four quarks - charm/anti-charm and up/anti-up. This hasn't been seen before but is perfectly valid under the standard model... they've already seen pentaquark states after all.

Re:The Standard Model

[Popadopolis]

It was verified by the Fermi National Partical Accelerator Lab.

Its discovery was recently confirmed by researchers at the Fermi National Accelerator Laboratory in Illinois, US, home of the Tevatron, the world's largest atom smasher. It was the US outfit that gave X(3872) its mystery tag.

Re:String Theory

[jpflip]

Probably not very much, but who knows? String theory generally deals with phenomena at energy scales MUCH higher than these accelerators are dealing with, so high in fact that it really doesn't make any useful predictions about ordinary phenomena (even particle accelerator phenomena!) It's sort of like trying to predict the shape of a snowflake if all you've ever seen is steam. That's one of the main complaints about the theory - it may be right, it may be wrong, but it doesn't have any major prospects for predictions we could even test!

Re:The Standard Model

[Tackhead]

> Not at all. A pentaquark state is a triplet plus a quark-antiquark pair. This is two quark-antiquark pairs. No need to change QCD at all. Why do you think there is?

Sure, quark-antiquark pairs are fine (mesons). Triplets are fine (baryons). And Pentaquarks are (anti :-)strange, but fine (u,u,d,d,!s).

My "WTF happened to QCD" was in regards to a comment implying that X(3872) was a four-quark static configuration, which I thought was unkosher.

Did someone find the Jaffe tetraquark or hexaquark and I've just been in a cave for the past decade? :) It's been a long time since I seriously studied any of this, and most of the papers I just googled were dated within the last 5 years, so I won't be at all embarassed to be proven dead wrong.

Re:The Standard Model

[Sdoh]

Just one more sensation out of misunderstood
scientific paper.

I work with the team which confirmed it at Fermi in X(3872) -> J/Psi Pion Pion.

Some background on quarks first:

There are six quarks d, u, s, c, b, t. The heaviest are on the right.
And six antiquarks d(bar), u(bar), s(bar)... you've got the idea.

d, s, b have charge -1/3.
u, c, t have charge 2/3,
antiquarks and quarks have opposite charge.

All the matter consist of the particles which
are combinations of quarks. There are several
types of observed combinations: Mesons, Barions,
Tetraquarks, Pentaquarks. They are correspondingly
consist from 2, 3, 4 or 5 quarks.

All the Mesons consist of quark and antiquark. Examples:

Pion = (u, d(bar)); //charge +1
Kaon =(s, u(bar)); //charge -1
J/Psi =(c, c(bar)); //charge 0
D =(c, u(bar)); //charge 0
D(bar)=(c(bar), u); //charge 0

Barions consist of 3 quarks. Examples:

Proton =(u, u, d ); //charge +1
Neutron =(d, d, u ); //charge 0
Antiproton =(u(bar), u(bar), d(bar)); //charge -1

You may continue it yourself for Tetraquarks and Pentaquarks.
Make sure the total charge of the particle is integer.

Heavy quarks want to decay to a ligter ones.
Eventually to u, d, u(bar), d(bar) and also
leptons (electron, muon) neutrinos and photons.

Some people think that X(3872) is one of the exited states of (c, c(bar)). Some people think
that it could be a tetraquark (c, c(bar), u, u(bar)). We should observe other modes
to know for sure. I am looking for X(3872) -> DD (bar).
No luck so far.

It is definitely very exiting to see a new particle like it would be exiting
to see a new chemical element. As far as I know it fit quite nicely
in the standard model - the analog of the Mendeleev table for particle physics.