What Now For The Higgs Boson?

We are on our way to CERN in Geneva, and this is John Mark, the cameraman. Hi! And, uh, we should be coming up on it. That's the Dome; that's the famous CERN Dome up ahead. This is pretty exciting! On July 4th here at CERN, a historic announcement was made: a new particle had been discovered, most likely the sought after Higgs boson. As a layman, I would now say, I think we have it. You agree?

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Yeah! The finding made news around the world and led to an outpouring of emotion from the normally restrained particle physics community. For the discoverers themselves, it was particularly momentous. Wow! I mean, I’ve never seen physicists like this. It really looks beautiful. I cannot tell you how beautiful it is. It makes you cry how beautiful it is. That's why we're here, essentially. You know that's, uh, that's the reason why I’m doing particle physics.

But now that this particle has been found, what's left to do at the Large Hadron Collider? Let’s find out. Our current understanding of the universe is based on the modestly named Standard Model, a theory of all fundamental matter particles and their interactions. Virtually all of the Standard Model has been verified apart from one crucial element: what gives matter its mass.

To be clear, that is absolutely critically important even to our daily existence because if an electron would be massless, it could not be bound to a proton. You could not have an atom, and then, you know, sort of all of, you know, the stars, the planets, chemistry, life couldn’t exist. Because instead of electrons bound to protons in hydrogen atoms and in larger atoms, instead, you would just have electrons whizzing off to infinity.

In the Standard Model, mass is explained by the Higgs mechanism, of which the Higgs boson is only one part. For example, you’ve probably heard that the Higgs boson gives mass to the other subatomic particles. But if that were true, shouldn’t there be Higgs bosons everywhere? I mean, why would it be so difficult to create and detect them?

Well, in truth, it's not the particle itself that gives mass to the other particles; it's the Higgs field. You can think of the Higgs field as a huge sea of honey that fills all space. Some particles are able to travel through it unimpeded whilst others interact with it, slowing down in the process. And that translates into mass. When enough high energy is added to the field, fleeting Higgs bosons are created.

So, in order to discover the Higgs particle, we needed to invest energy by the collision in the Higgs field and create the Higgs particle out of it, and then we'll know that indeed we have a Higgs. And that's what this incredible machine does. Using powerful magnets, the Large Hadron Collider whizzes two beams of protons in opposite directions around a 27 km circular tunnel.

When the protons collide, their energy can be converted into the mass of new particles like the Higgs boson. Short-lived, these particles decay quickly, and it’s their decay products which are then analyzed by massive detectors. This is the giant apparatus at the CMS detector. It's one of two major detectors on the beam line where the protons collide. You can actually see a life-size picture of the CMS detector.

I am standing above the beam line, and so there's protons whizzing around underneath my feet right now, 90 m under the ground at speeds that are basically the speed of light—99.9999999% the speed of light. You may as well just be at the speed of light. But, of course, a proton can never reach that speed. These are some big toys!

The other big experiment examining proton collisions is called ATLAS. The teams at ATLAS and CMS, each made up of about 3,000 scientists, work independently in a sort of friendly rivalry. Is it actually friendly?

Yes, of course it is! I mean, we, uh, what we always say is that, of course, it's essential that if there's a major discovery which is made, that it's confirmed ultimately by the two experiments independently. And that’s why the discovery announced earlier this year was so dramatic: both detectors saw the same results more or less simultaneously.

Protons are bags of other particles. When they smash together, a mess of new particles is created, and it’s the pattern of the debris that provides the answers. What they saw was evidence of a new particle with a mass of between 125 and 126 giga-electron volts. And then we see these two large blobs of energy in the calorimeter, and you can see them over here.

If you added those two bits of energy together, what total energy would you get?

I think in this one you get 125 GV, so that seems to be exactly what we’d be with 'gam.' But the question now is, if it is a Higgs, is it the Higgs as predicted by the Standard Model? Are you willing to make a bet about what kind of Higgs boson it is? Do you think it's the Standard Model Higgs?

Wow! That’s a difficult one. No, I wouldn’t bet my life on it. I might bet my life that we discover the Higgs, but I wouldn’t bet my life that it is the Standard Model Higgs. It's very difficult to say. All we know is it's there—we almost know nothing about its properties, and its properties are key really to tell us exactly what it is.

So, to find out, the LHC will conduct many more collisions, and this should allow scientists to determine the properties of the new particle. If it is not the Standard Model Higgs, we may be able to tell that early; we could even tell that this year.

As an example, both experiments saw a bit too many photons—too many times the Higgs was decaying into photons more than you’d expect—more than you’d expect. And in the case of strangelets, that’s exactly what these guys are hoping for: that it doesn’t fit the model perfectly. That it’s not the Standard Model Higgs.

Let’s say the reason for doing science is, of course, we’re looking for answers, but generating more questions is, uh, an inevitable and one of the most exciting pieces of the scientific procedure.

And what would that help you determine? I mean, if it's not Standard Model Higgs, that’s a big thing! If it's not Standard Model Higgs, then we know that there's new physics for sure. And if the new physics is along the lines that we expect, then we have something pretty profound as a possibility.

One would be additional spatial dimensions. Okay, that's one possibility. Another would be really almost a mirror image of the entire universe in terms of particles— that's supersymmetry. And these things would be extremely profound.

Whether it turns out to be the Standard Model Higgs or something even more profound, one thing is for sure: the discovery of this new particle is a huge milestone in the long quest to uncover the fundamental laws of nature.

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