Particle physicists working with the BaBar detector at Stanford Linear Accelerator Center have discovered a new particle in the bottomonium family of "quarkonium" particles. Technically it isn't a "new particle" it is a previously unobserved state of particle, but when we are talking about subatomic particles, their energy states become a big deal (and their [...]

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Ah, the cousin of my namesake has finally been found! The eta c is the charmonium equivalent of the eta b that is discussed in the article. Unlike the bottom states, the eta c is a very strong signal in the radiative decays of J/psi, the 1S charmonium state and the mass difference is great enough to observe. I should know, I worked on radiative J/psi decays for my dissertation and used the eta c as a calibration datum.

To use spectroscopic notation, the etas are the singlet S0 states of the system (the ground state) while the J/psi and upsilon 1S are the triplet S1 or first excited state. Particle physicists tend to use the terms pseudoscalar and vector respectively. For more information on the quark model check out the Particle Data Group review

It's quite cool that BaBar had to go to the upsilon 3S to get the necessary signal. The 1S is a cleaner signal, but probably harder to observe in the detector due to the low energy of the radiative photon. The 3S radiative decay has more background, but is observable due to the greater photon energy.

Fraser, if you think the BaBar author list is long you should check out the ones from the CDF and D0 collaborations at Fermilab. Such a large number of authors is typical for particle physics experiments where everyone from every institution is included. On my thesis experiment this was OK (five universities and about 40 physicists). Now it's more like 40 universities and 500 physicists. Such large collaborations (that and a lousy job market) were among the reasons I left the field after grad school. Things will be even worse for the LHC since just about every particle physicist in the world will be working on it.

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"I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind." - William Thompson, 1st Baron Lord Kelvin

"If it was so, it might be, and if it were so, it would be, but as it isn't, it ain't. That's logic!" - Tweedledee

This isn't right. This isn't even wrong. - Wolfgang Pauli