atlas – Going Up Alleys

The Nobel Prize in Physics will be announced on Tuesday. Will it go for the prediction of the Higgs Boson? Photo courtesy of the Nobel Foundation.

I’m not normally an avid fan of the Nobel Prize in Physics announcement. This year may be a little different. It’s possible that this is the year that the prize is awarded for the prediction that the mechanism of spontaneously broken Electroweak Symmetry necessarily leads to a new subatomic particle in nature (the Higgs Boson). There is no guarantee that the Nobel Prize committee will go this way; it’s their decision. However, given the tremendous experimental effort over the past 2 years that identified a new boson with a mass of 126 GeV, and that has now determined its properties to be consistent with the Higgs Boson hypothesis, it’s a good contender for the prize.

So I’ll be waking up early this Tuesday to wait for the announcement. You can look for it on the Nobel Prize website (http://www.nobelprize.org/). Presently, we are 37 hours from the announcement of the Medicine/Physiology Prize on Monday. After that, on Tuesday, at 11 am CET (at the earliest), we can expect the physics prize announcement.

The last time that a prize was awarded for a theoretical prediction confirmed by the experimental efforts of two large collaborations, it was the prize in 2008 for “for the discovery of the mechanism of spontaneous broken symmetry in subatomic physics”, and “for the discovery of the origin of the broken symmetry which predicts the existence of at least three families of quarks in nature”(http://www.nobelprize.org/nobel_prizes/physics/laureates/2008/). The prize was awarded to physicists Yoichiro Nambu, Makoto Kobayashi, and Toshihide Maskawa. However, in the prize announcement, the massive experimental effort required to verify their predictions was mentioned. “As late as 2001, the two particle detectors BaBar at Stanford, USA and Belle at Tsukuba, Japan, both detected broken symmetries independently of each other,” said the committee in their press release.

I would expect that, should the prize be awarded for the successful prediction that spontaneously broken symmetry yields mass for the fundamental gauge bosons, and in doing so necessitates the existence of another gauge boson (the Higgs), that the ATLAS and CMS collaborations will be similarly cited. Either way, Tuesday is going to be very interesting.

Just over a year ago, the ATLAS and CMS experiments reported strong evidence for the existence of a new particle who was was about 126 times that of the proton. It was a boson; this meant that it carries an internal unit of angular momentum (“spin”) whose value is an integer multiple of Planck’s Constant ( $\hbar = 1.054 571 726(47)\times 10^{−34}\, \mathrm{J \cdot s}$ ). Those were about the most honest and scientifically accurate statements we could make. We did not know for sure it’s actual spin; we were not positive if it was one particle or two, since different decay modes yielded slightly different masses that might indicate the presence of two closely spaced new particles.

One of the figures from the ATLAS paper entitled "Evidence for the spin-0 nature of the Higgs boson using ATLAS data." This plot summarizes some of the work that SMU student Tingting Cao contributed to the measurement of the spin and parity quantum numbers of the 126-GeV boson, now considered to be the Higgs Boson. — One of the figures from the ATLAS paper entitled “Evidence for the spin-0 nature of the Higgs boson using ATLAS data.” This plot summarizes some of the work that SMU student Tingting Cao contributed to the measurement of the spin and parity quantum numbers of the 126-GeV boson, now considered to be the Higgs Boson.

But since that time, a year has passed, and both experiments have been extremely busy. Yesterday, ATLAS submitted to the journal Physics Letters B a pair of papers that summarizes our belief, based on the scientific evidence, of the nature of this particle. Already, by earlier this year, ATLAS and CMS were saying that this was no longer a “Higgs-like” boson – it was probably the Higgs Boson predicted to exist in the 1960s. Now, by collecting the analysis efforts together and refining the techniques for assessing the properties of the newly discovered particle, we are ready to say (in print, and for peer review, for the whole community to review) that this is a spin-0 particle whose couplings to the known Standard Model particles are very “Standard-Model-like” – meaning that, for all intents and purposes, the data supports the hypothesis that this is the Higgs Boson of the Standard Model.

And with that assessment in hand, I think it’s time for high-energy physics to accept that the last great untested prediction of the Standard Model has been tested, and it’s time to elevate this grand description of nature to “The Standard Theory of Particle Physics.” For when a set of ideas so beautiful and powerful withstands the brutal an unending onslaught of experimental science that this one has, it is time to elevate it from “model” to “theory.”

The papers submitted on July 4, 2013, to Physics Letters B, are here:

“Measurements of Higgs boson production and couplings in diboson final states with the ATLAS detector at the LHC.” Submitted to Physics Letters B. Available for download at arXiv:1307.1427

“Evidence for the spin-0 nature of the Higgs boson using ATLAS data”. Submitted to Physics Letters B. Available for download at arXiv:1307.1432

Tag: atlas

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