Monday, May 06, 2013

Combing the LHC Data For Hints Of Something Beyond The Standard Model

With the LHC in shutdown mode right now, one would think that everyone involved in the major detectors are taking a holiday. Not so. In fact, it appears to be a very intense period of data combing. The accumulated LHC data are being carefully examined to look for hints to indicate new physics beyond the standard model. The article linked above describes this hunt. However, it also describe other important discoveries made at the LHC beyond just the Higgs, which did not make the headlines in the popular media and the public.

Those waiting for new physics can take comfort in the fact that the LHC has achieved far more than the discovery of the Higgs over its three-year operation. A year before the Higgs's detection, for instance, the ATLAS experiment found another new boson: the so-called Chi-b(3P) quark-antiquark pair. That was followed by the discovery last year of a new excited Xi(b) baryon by CMS. Although not elementary particles like the Higgs is thought to be, Chi-b(3P) and Xi(b) have helped tie up some of the Standard Model's loose ends by confirming the nature of the strong force, which binds quarks together.
Perhaps more important than these particle discoveries, however, have been the LHC's precise measurements of existing Standard Model phenomena. Some of these are quantities that cannot be accurately predicted, such as the high-energy structure of the photon that is being studied by the ALICE experiment. But other measurements can put the latest theories to the test. These include the energy distribution of particle jets (which are produced when quarks collide), and the production rate of pairs of heavyweight elementary particles such as W and Z bosons (which carry the weak force, responsible for radioactive decay) and top quarks. "Those calculations have been taken now to a higher degree of precision," says Incandela. "We have a very good match between our data and our simulations, which tells you that our calculations are very good."

So there is clearly a lot of things that have come out of the LHC that have advanced our knowledge of elementary particles. This is not a one-trick pony machine.


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