The TRIUMF Workshop on LHC Results was held last week in Vancouver, December 14-16. The workshop brought particle-physics theorists from across Canada and the United States together with experimentalists from the ATLAS Canada collaboration. Together this diverse group reviewed and discussed the latest results in particle physics and their implications and investigated the most promising directions for future searches at the LHC.
Sometimes in heated debate and sometimes in thoughtful conversation, scientists looked at what we already know about the Standard Model of Particle Physics and where it might break down in selected measurements that could be performed at the LHC. Not only does the LHC probe higher energies than ever before in a controlled, accelerator environment, but also certain particle interactions will happen so much more copiously that detailed, high-precision measurements can be performed to control background processes or reveal hints of more exotic phenomena. Thus, there were many discussions about so-called "Beyond the Standard Model" (aka BSM) physics---as in, what properties or behaviours would be observed first that were not predicted or consistent with the existing model?
One of the highlights of the workshop were the new Higgs results from the LHC using the full 2011 datasets that were made public by the ATLAS and CMS collaborations during the same week. ATLAS Canada spokesperon Rob McPherson gave a special public seminar about the Higgs search on Tuesday, December 13, just before the workshop. Although no discovery can be claimed at this point, there was clear excitement in the room for two reasons. Most importantly, the two separate LHC experiments have closed in tremendously on the range of masses the Higgs boson can have; that is, the allowed mas range is getting tighter and tighter with only a small window left in the favoured low-mass region. Secondly, the hints in the data put a long-hoped-for new discovery within possible reach. Nevertheless, even with the Higgs boson, particle physicists know the Standard Model has clear weaknesses, so the discussion naturally extended to the dreams and hopes that go beyond the Standard Model, where new symmetries, new forces, and extra dimensions are part of a more complete description of nature.
--by Oliver Stelzer-Chilton, TRIUMF research scientist and ATLAS collaborator, and T.I. Meyer, TRIUMF's Head of Strategic Planning and Communications