CERN experiments put Standard Model to stringent test – UK reaction here

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2013-07-21

New results being presented at the EPS-HEP conference in Stockholm, Sweden, this afternoon (19th July 2013) have put the Standard Model of particle physics to one of its most stringent tests to date. The CMS and LHCb experiments at CERN’s Large Hadron Collider will present measurements of one of the rarest measureable processes in physics: the decay of a Bs (pronounced B-sub-s) particle into two muons.

The new measurements show that only a handful of Bs particles per billion, decay into pairs of muons, behaviour consistent with the Standard Model. This process is so rare it is an extremely effective way of either confirming the Standard Model or indicating signs of something new.

“This is an important result because it is quite a precise measurement of a very rare type of decay which can be compared with theoretical predictions,” said Professor Geoff Hall, UK spokesperson for the CMS experiment. “So far it appears consistent with the Standard Model. Because of its rarity it has been crucial to be extremely careful in the data analysis before claiming a result. It is also encouraging that the two experiments which have searched for the decay have consistent results. So the hunt is still on for discrepancies between experiment and predictions of the Standard Model.”

Both experiments will present results to a very high level of statistical significance (over 4 sigma for each experiment). These results are in good agreement with the Standard Model.

Professor Tara Shears, leader of the University of Liverpool LHCb group, added:

“LHCb was designed to make measurements like this - but it is a tribute to the precision of our detectors and the hard work of our collaborators that measurements can be made this well. The results mean that the Standard Model stands firmer than ever. The new physics we need to explain dark matter and gravity may be even stranger than we thought. I can't wait to see what further clues the LHC will reveal, when it restarts in 2015.”

Source: UK Science and Technology Facilities Council

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