CERN has a glimpse of 'God particle'

At a seminar held at CERN today as a curtain-raiser to the year's major particle physics conference - the International Conference on High Energy Physics (ICHEP) in Melbourne, Australia - the ATLAS and CMS experiments presented their latest preliminary results in the search for the long-sought Higgs particle. Both experiments observe a new particle in the mass region around 125 to 126 GeV (gigaelectronvolts, a unit of energy equal to one billion electron volts).
 

A proton-proton collision event in the CMS experiment producing two high-energy photons (red towers). This is what is expected to be seen from the decay of a Higgs boson but it is also consistent with background Standard Model physics processes. Image: CERN

More than 50 MIT physicists, led by six faculty members, were part of the 3,000-member CMS (Compact Muon Solenoid) experiment at CERN's Large Hadron Collider (LHC), making the Institute home to that group's largest contingent of physicists from any American university.
 
''We observe in our data clear signs of a new particle, at the level of 5 sigma, in the mass region around 126 GeV. The outstanding performance of the LHC and ATLAS and the huge efforts of many people have brought us to this exciting stage,'' said ATLAS experiment spokesperson Fabiola Gianotti, ''but a little more time is needed to prepare these results for publication.''
 
''The results are preliminary but the 5-sigma signal at around 125 GeV we're seeing is dramatic. This is indeed a new particle. We know it must be a boson and it's the heaviest boson ever found,'' said CMS experiment spokesperson Joe Incandela. ''The implications are very significant and it is precisely for this reason that we must be extremely diligent in all of our studies and cross-checks.''
 
''It's hard not to get excited by these results,'' said CERN Research director Sergio Bertolucci. ''We stated last year that in 2012 we would either find a new Higgs-like particle or exclude the existence of the Standard Model Higgs. With all the necessary caution, it looks to me that we are at a branching point: The observation of this new particle indicates the path for the future towards a more detailed understanding of what we're seeing in the data.''
 
MIT professor of physics Christoph Paus is one of two lead investigators, with CERN's Albert De Roeck, on the CMS Higgs search, which comprises roughly 500 active investigators. Other key MIT researchers involved in the Higgs search are Markus Klute, assistant professor of physics, and Steven Nahn, associate professor of physics.
 
''The Higgs boson holds the promise of beginning to finally elucidate the fundamental origins of mass,'' Paus told MIT News. ''We cannot yet say whether the phenomenon we are reporting today is indeed the Higgs; that will take much more data to determine. But so far it fulfills our search criteria, and if confirmed, will set an important milestone in our understanding of nature. Should we be observing something other than the Higgs - well, that may be even more important.''
 
MIT scientists are deeply involved in four of the five core searches for the Higgs boson, Paus told MIT News, describing the group's most prominent contribution as its work on the analysis of the Higgs's decay into two photons.
 
''If this is the Higgs boson, it will complete a 50-year scientific odyssey to complete the Standard Model of particle physics,'' Professor Edmund Bertschinger, head of MIT's Department of Physics, told MIT News. ''We are proud that MIT faculty and researchers have played a role in this important work, as they have in previous discoveries in particle physics going back to the 1960s.''
 
The results presented today are labeled preliminary. They are based on data collected in 2011 and 2012, with the 2012 data still under analysis. Publication of the analyses shown today is expected around the end of July. A more complete picture of today's observations will emerge later this year after the LHC provides the experiments with more data.
 
The next step will be to determine the precise nature of the particle and its significance for our understanding of the universe: are its properties as expected for the long-sought Higgs boson, the final missing ingredient in the Standard Model of particle physics? Or is it something more exotic? The Standard Model describes the fundamental particles from which we, and every visible thing in the universe, are made, and the forces acting between them. All the matter that we can see, however, appears to be no more than about 4 per cent of the total. A more exotic version of the Higgs particle could be a bridge to understanding the 96 percent of the universe that remains obscure.
 
''We have reached a milestone in our understanding of nature,'' said CERN Director General Rolf Heuer. ''The discovery of a particle consistent with the Higgs boson opens the way to more detailed studies, requiring larger statistics, which will pin down the new particle's properties, and is likely to shed light on other mysteries of our universe.''
 
Positive identification of the new particle's characteristics will take considerable time and data. But whatever form the Higgs particle takes, our knowledge of the fundamental structure of matter is about to take a major step forward.