Thursday, March 14, 2013

Yep. It's a Higgs.

Looks like all the particle physicists can go home now.

OK, seriously now. Physicists at CERN have confirmed that that bump in the data the saw around 126 GeV/c2 is, in fact, a Higgs Boson. (GeV/c2 is a unit of mass that is specifically used for measuring the masses of objects on a particle physics scale, and equals about 10-27 kilograms.)

But wait, you may ask, didn't they announce finding (something that looked an awful lot like) a Higgs Boson back in December of 2011 (with this infamous, god-awful powerpoint slide featuring the most hated font in the known universe: Comic Sans)? Yes, and they published the discovery paper the following summer, when they could distinctly separate the signal from the noise to a probability of 1 in 3.5 million. Up until then, however, they only had what can best be described as a Higgs-like signal. The bump was in the right place, energywise, but they couldn't confirm that it actually was a Higgs boson.

Now, on this most auspicious of days (Pi Day, which shouldn't matter to the Europeans, because they write their dates backwards anyway), we have actual confirmation that the signal detected at 126 GeV/c2 matches specific predictions made by the creatively named Standard Model of particle physics. Specifically, physicists working at CERN have finally gathered enough data to see what this mysterious particle decays (eventually breaks up due to instability) into, and the observations seem to match.

You may have noticed that, throughout this article, I have been using the indefinite article "a" rather than the definite article "the" to refer to the Higgs that we've seen. This was not just a fluke on my part. Variations on the Standard Model predict that we should see multiple different types of Higgs Bosons, each with different intrinsic properties that only really exist on particle scales (unless you make a Bose-Einstein condensate; those things are weird and have some awesome properties). Right now, the decay modes seen only confirm that what physicists have seen so far is one of those various Higgs bosons. It will take a lot more data gathering to get the information necessary to tell us if we're seeing the boring Standard Model Higgs, or one of its exotic cousins. Despite my opening statement, there's actually still a lot of work to do.

Personally, I'm hoping for the latter. While the Standard Model has been wildly successful, it has actually almost been too successful, in my opinion (damn theorists...). The most fun times in physics are when no one has any clue what is going on and the field as a whole has to make a huge leap forward in order to catch up with the crazy new observations. Such a leap would most likely have profound consequences on our understanding of other field as well, particularly cosmology. Maybe we'd even get a good theory of dark matter!

Also, this is a really cool gif showing the data gathering over time at the ~ 126 GeV/c2 peak in the data that indicates the Higgs boson. Specifically what you see here are the data points and every other interaction know that yields a signal there. The discrepancy between the known signals and the data are what indicate the existence of a Higgs boson at 126 GeV/c2.

Credit: CERN, ATLAS Collaboration


  1. This may be an elementary question, but does proving that what they see IS the Higgs boson necessarily prove what they think the Higgs field does? That is, they found this particle that has the right quantum properties, but does that mean that they've automatically nailed down the properties of the field with which it interacts?

    1. From what I can tell (and remember, take this with a grain of salt because I'm not totally up to date on theoretical particle physics these days), nailing down the interactions is part of what it will take to determine which Higgs this really is. I don't personally know what differences, if any, we'll see in how the various Higgses interact with the Higgs field, or if any differences are even predicted. But I would imagine that looking at how what they've found interacts with other particles is part of what will help determine that.