The Physics Behind the Discovery of the Higgs Boson

This is the first in a series of blog posts about the physics behind the discovery of the Higgs boson.

The discovery was announced nearly fourteen years ago — the anniversary is coming up this summer — and it made a big splash in the press. It ran on the front page of the New York Times and The Economist, and shortly afterward, the Nobel Prize in Physics was awarded for it.

But if you look past the headlines at what it actually took to discover the Higgs boson, it's even more impressive. This was not discovered in a small lab in the basement of a university. It took a massive endeavor: the Large Hadron Collider, located outside Geneva, Switzerland. The ring you see in aerial images — that schematic outline on the ground — is larger than an international airport. The idea is that you circulate groups of protons around that ring in each direction, accelerate them to nearly the speed of light, and make them collide at certain points along the ring. Surrounding those collision points are enormous, sophisticated detectors — think fancy digital cameras made of custom electronics — that take 3D pictures of the collisions. The detectors themselves are the size of apartment buildings.

In numbers, the scale is equally impressive. It took more than 10,000 scientists and engineers, from over 85 countries, working for two to three decades. A 27-kilometer circumference accelerator. Protons moving at 99.9999997% of the speed of light – as fast as we were able to get them. To discover the Higgs, we had to collide a billion protons per second for two years. The detectors operated at 40 megahertz — which means they were taking their 3D pictures 40 million times per second — and generated about 80 terabytes of data per second. That's roughly ten times the information in the Library of Congress every second, more data than is handled by big tech companies like Google or Facebook. As you can imagine, something like this is not cheap; the total budget was on the order of $10 billion, not counting the salaries of the people who built and operated everything. And one more number that doesn't get talked about, but that will actually be important to our story: the salary of the physicist who operates and works on these detectors is much, much less than the salary of a banker or engineer who, in many cases, is doing very similar work. That's a striking fact that also requires some explanation.

So this is what it took to discover the Higgs boson, and it immediately raises some obvious questions: What the hell is the Higgs boson in the first place?!? Why did we have to go to such extremes to find it? Why was it so difficult, and why did we have to build such a large detector, collect so much data, and so on? Given that it was so hard, why is it worth doing at all? Why look for the Higgs boson in the first place? And now that we've found it and it has been awarded a Nobel Prize, are we done?

The whole point of this blog series is to answer those questions — and as we will see, there are many different layers to each answer. We will start with partial answers and build up as we go.