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New Particle Found, the Bottom-Most Bottomonium
PhysicsDavid writes "Collaborators on the BaBar experiment at the Stanford Linear Accelerator Center have detected and measured, for the first time after a 30-year search, the lowest energy particle of the 'bottomonium' family, called the eta-sub-b. Bottomonium consists of a bottom quark and an anti-bottom quark bound together by the strong force. The discovery fills in a missing piece of quark physics that will help reveal the nature and behavior of the quarks and the strong force."
They exist in groups of two or three that create a neutral color charge. For example, a particle can consist of red, green, and blue or of blue and anti-blue.
They just have to be "color"-neutral so (red, green, blue) and (red, anti-red) are both allowed.
Who ordered that?
The same way protons and electrons avoid crashing into each other. The energy states are discontinuous and do not include zero. Once the bottomonium meson reaches its lowest state, it can't lose any more energy, so it can't get close enough to annihilate.
Genocide Man -- Life is funny. Death is funnier. Mass murder can be hilarious.
They will annihilate after some time (the particle's lifetime), but they can be bound together for some time before that happens. Another good example is the \pi^0 (neutral pion), which is made of up and anti-up (or down and anti-down) quarks. It decays after some time to two photons.
I don't know what is the lifetime of this \eta_b particle or its main decay branch (I haven't RTF BaBar's A and I'm not a QCD specialist), but it should be very short, and the main decay channel should be hadronic (ie, particle jets).
The interesting question, IMHO, is: Was this particle predicted by anybody else's research?
Yes. It's called the standard model. It's not surprising that it was found ... it would have been more surprising if it hadn't been found eventually.