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Standard Model held strong at EPS conference

Results presented by LHC experiments give further credence to strength of Standard Model

This year's European Physical Society High-Energy Physics conference, which came to an end yesterday, was packed with results from the Large Hadron Collider. 

The most recent results on new boson discovered last year were presented by ATLAS and CMS - all of which indicate that the particle is a Higgs boson of the kind predicted by the Standard Model. Further studies are needed to pin down all of the boson's properties. 

The CMS and LHCb collaborations both presented the most recent analyses of a Bs (pronounced B-sub-s) particle decaying into two muons. The two experiments measured this decay at more than 4 sigma, meaning that there is very little chance that this is a statistical fluctuation. These measurements are also in good agreement with the Standard Model. If the measurements deviated even slightly from the predictions, it would be a clear sign of new physics. 

Out of the wealth of results on the physics of the top quark presented by ATLAS and CMS, the CMS collaboration announced the first observation of a rare process: the associated production of a single top quark and a W boson. Both ATLAS and CMS had previously seen evidence for this process but not to this significance of more than 5 sigma. The observation confirms the Standard Model prediction.

All four of the large LHC experiments, ALICE, ATLAS, CMS and LHCb, presented results from the first proton-lead run at the accelerator. Earlier runs with collisions between two beams of lead nuclei (each nucleus containing a total of 208 protons and neutrons) indicated that a hot, dense medium results. In this material, quarks and gluons float unbound. First results now suggest that a similar system is created in proton-lead collisions, despite there being far fewer neutrons and protons. Further analysis is needed to understand these unexpected features. 

During the conference, the EPS recognized several collaborations and individual scientists for the work done to further the field of physics. In particular, the High-Energy Physics prize honoured the work of ATLAS and CMS for their discovery of a Higgs boson.