What’s cooking at the LHC?

By Marcus Wilson 01/11/2010

I’ve just been perusing CERN’s Twitter site http://www.twitter.com/cern for some of their latest news.

While the Higgs is still hiding inside some time-travelling baguette, there’s still some really nice physics arising. This example is one that caught my attention – it’s the detection of a bound state made up of a beauty (or bottom) quark and anti-beauty quark.

There’s some similarity here to the hydrogen atom – this has a single, positively charged proton, and a single, negatively charged electron bound together by the electrostatic force. In this new ‘atom’, a beauty quark is bound with its anti-particle opposite – the anti beauty quark. Both particles are charged (the beauty has 1/3 the charge of an electron and is negative; the anti-beauty has the same charge but positive); however, it is the strong nuclear force, rather than the electrostatic force, that holds the two together.

In a hydrogen atom, the electron can exist in several energy states. It can move between these states by absorbing or emitting a photon of the appropriate frequency – this is what spectroscopy is about.  Likewise, this ‘beautiful’ atom can have excited states. This is what the diagram on the right of the report is showing. Along the bottom there are labels S and L, which refer to the spin and angular momentum states of the beautiful atom, and on the upward axis we see the ‘energy’ of the states (quoted as a mass, through Einstein’s E = mc^2). Transitions between the states are indicated.

Plenty for a particle physicist to chew over for a while.

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