Higgs boson is one year old

05 Jul 2013 - 16:54:19 by in News

Friday 5th July 2013 - Yesterday marked the first anniversary of the announcement of the discovery of the Higgs particle at CERN. One year ago the ATLAS and CMS experiments at the Large Hadron Collider announced their results to the world. After sifting through the proton-proton collision data they had accumulated in the previous year, they each confirmed they had independently found very strong evidence ("5 sigma") for the discovery of a new particle. Those announcements effectively settled a major fundamental question in physics, which had been puzzling physicists for the last five decades. The question was "How is it that elementary particles such as the electron or the top quark actually get their mass?" To put the relevance of this question in perspective, the origin of other basic properties of elementary particles - their electric charge, for instance - has been well understood for a while.

The otherwise very successful mathematical theory that summarises our knowledge of elementary particles and how they interact with one another (a.k.a. the Standard Model) did not, in its original form, allow any elementary particles to have nonzero mass. While a few elementary particles, such as the photon, are indeed massless, most are undoubtedly not - hence the big question. (The top quark, the heaviest elementary particle we know about, is hardly massless: it is almost as heavy as a Gold atom, which has nearly 200 protons and neutrons in its nucleus.)

Several physicists worked out a possible theoretical solution to this conundrum in the 1960s. They are sometimes referred to as the "gang of six": Higgs, Englert & Brout, Kibble, Guralnik and Hagen. One unavoidable consequence of the "mass mechanism" that they proposed was that nature must have a new particle with certain specific properties, in addition to all the other elementary particles we have observed so far. Over the years this particle became known as the Higgs boson. Experimentally observing the Higgs particle (or alternatively, establishing once and for all that it didn't exist) therefore became key in the quest to understand the origin of mass. The discovery last year of the new particle at CERN, which we now know behaves consistently with what is expected of a Higgs boson, has therefore been a quantum leap in our understanding of how nature works at its most elementary level. We can now say for the first time that we understand how elementary particles actually can have nonzero mass.

To celebrate this milestone, this year's Summer Science Exhibition at the Royal Society in London includes an exhibit on "Understanding the Higgs boson". The exhibition is open to the public until Sunday afternoon. After that you will still be able to visit the website, with plenty of information about the exhibits. The Centre for Particle Physics at RHUL was one of the contributors to the demonstrations and activities on the "Higgs stall". We also contributed several demonstrators, to meet the public and answer their questions.

Did you go and visit the exhibition? What did you think?

If you were there as a demonstrator: do you think this type of public engagement is wothrhwile doing? What was the most interesting question you got asked...?

Blog away.

- Pedro.

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Topic revision: r2 - 26 Sep 2013 - TomCraneAdmin

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