REPORTER’S NOTEBOOK: Higgs Boson, explained

MIT physics profs try to clarify discovery

Last spring, news of the discovery of proof of the Higgs Boson particle swept MIT’s campus, prompting discussion in classrooms, on social networks and email lists, and in casual conversations among students. During this news blitz, the recurring question on my mind was, what exactly is the Higgs Boson? Since I have no theoretical physics knowledge, I didn’t understand the significance of it at all.

Feeling out of the loop on this piece of nerdy knowledge, I couldn’t pass up the chance to hear four MIT professors explain what the mysterious particle is and why it is so exciting. So, on Thursday night I made my way to 26-100 to hear several MIT professors speak about it. The lecture hall was packed; attendance was higher than most of my 7.012 lectures.

Professor Edward H. Farhi of the theoretical physics department took the floor first. He outlined the importance of the evidence found this spring, calling it “a great coming together of theory and experiment” and “the most complicated experiment that has ever been built.” After building up some suspense in the audience, he introduced Assistant Professor Jesse Thaler to give an overview of the physical theory of the Higgs Boson.

One idea that stuck out to me during Professor Thaler’s talk was the idea that the discovery of a new particle corresponds to a theoretical principle of physics. He compared the discovery of the Higgs Boson and the idea of quantum probability to the discovery of the neutrino and the principle of conservation of mass. When looking at the history of physics, new developments in theory constantly prompt new research to test them.

Thaler gave an overview of the Standard Model and how the Higgs Boson fits in. I was slightly apprehensive that I would not be able to understand anything during the theoretical discussion, but Thaler kept it simple and used metaphors.

He began by listing the four fundamental forces — gravity, electrostatic, strong (holds nucleons together), and weak — and explaining that each force is conveyed through a fundamental particle. The weak force is responsible for converting protons to neutrons and releasing neutrinos, which is part of the process involved in the sun burning. The weak force behaves differently from the other three, because it has a massive fundamental particle and the particles can collide with each other. The other fundamental forces have massless particles that don’t interact with each other. The difference in the weak force is due to the Higgs Boson, which is responsible for giving mass to fundamental particles. The strength of interaction of particles with the Higgs Boson determines their mass; so massless particles like the photon don’t interact with the Higgs Boson at all. Incorporating the Higgs Boson particle into quantum mechanics equations also ensures the consistency of quantum probability; without it, some events would be predicted to have a probability greater than one.

Just as experiments follow theory in the field of physics, the next speaker was an experimental physicist. Assistant Professor Markus Klute, who was working at the CERN facility during the discovery of the Higgs Boson, described the process of finding evidence for the particle I was surprised at the scale of the experiments involved in the discovery. The collider is a 24-kilometer-long tunnel, buried underground in Switzerland. It fires particles at 8 TeV of energy, using 1,232 superconducting magnets. Data from the experiments is collected by a sensor over 50 feet in diameter, weighing more than the Eiffel Tower. Even more impressive, 3,200 scientists work at CERN. At the time of the discovery of the Higgs Boson, three MIT faculty and seven undergraduates were working there.

The presentation was closed out by Professor Christoph M. E. Paus, who highlighted the contribution MIT students made to the discovery and encouraged students to gain research experience. He said that “research is challenging … but people at MIT are used to that.”

The night ended with a Q&A session with the four professors. My brain was too overloaded by all the theoretical thinking at this point to raise any intelligent questions. On my way back from the lecture, I realized the event had actually given me many more new questions to think about. One question was raised by the professors themselves: What’s next after the Higgs Boson? Farhi admitted during the Q&A that there are many unsatisfying points about the Standard Theory which indicate many more discoveries like this remain to be found. “We know this is not the end of the theory,” he said.

The lecture left me still unsure about the nature of the Higgs Boson. I went to the lecture expecting a simple explanation, after which I would be an expert on the Higgs Boson, but quantum mechanics is rarely straightforward. Years of studying, questioning, and suffering through vague confusion are necessary to understand the theory behind the Higgs Boson. But, even if I couldn’t gain a full understanding of theoretical physics principles in the span of an hour, I definitely left with a sense of excitement about what I did learn. The professors displayed so much enthusiasm about the discovery and the future developments to come. The ultimate goal of physics — to accurately and completely describe the universe — is something that I am glad to have been part of, if only for one hour on a Thursday night.