For the 12 Days of “The STEM Chicksmas” we’re highlighting 12 scientists who have contributed something innovative and exciting to their field. It is the season of giving, and these brilliant minds have given incredible gifts to the scientific community! This year we’re looking at 12 Nobel Prize winners from the past 15 years in the fields of Physics, Chemistry, and Physiology or Medicine.
Day Six: The 2013 Nobel Prize in Physics.
Have you ever thought about where mass comes from? The answer isn’t as obvious as it first seems. A theory called the Standard Model says the universe is made of 17 elementary particles called quarks, leptons, and bosons; and four fundamental forces called the gravitational, weak, electromagnetic, and strong forces. Electrons and neutrinos, for example, are both types of leptons and the protons and neutrons that make up atoms are themselves made from quarks and get their mass from quarks’ binding energy. A force is defined by an exchange of a type of boson called gauge bosons. For example, light is the exchange of photons, which are the bosons associated with the electromagnetic force. However, a problem with the Standard Model physicists struggled to explain is that none of these gauge bosons should have mass, but of the four gauge bosons, only photons are massless. So, where did their mass come from?
In 1964, the 2013 Nobel Laureates in Physics Peter Higgs and François Englert proposed the idea of a field that interacts with the bosons to give them mass. As the bosons move through this field, called the Higgs Field, they interact with it. The more strongly they interact with it, the more potential energy the field transfers to them. Because energy and mass are related, the more energy the particles get, the more mass they have. If the particle does not interact with the field, they are massless, like the photon. Here’s one way to picture this. Imagine a room full of scientists throwing a party. A grad student walks in, and no one pays her any attention because she’s just a grad student. Now imagine Einstein walks into the room. Everyone immediately mobs him and tries to engage him in conversation. Like a photon, the grad student passed through the room unnoticed, whereas Einstein, like the other gauge bosons, gained the “mass” of a bunch of physicists. This is one way of imagining the coupling of particles and the Higgs field.
However, proving the existence of the Higgs Field was not an easy task. To do so, physicists concentrated their efforts on finding a particle called the Higgs Boson. The Higgs Boson is a quantum excitation of the Higgs Field. If the Higgs Boson exists, the Higgs Field must exist as well. Much like how if we see a light it must come from a light source, if we see a Higgs Boson it must come from the Higgs Field. The Standard Model also predicts that the Higgs Boson should have certain properties, such as a mass of 125-127 Gev/c2, zero spin, and positive parity (which means that if you flip the orientation of space like in a mirror, the Higgs boson still acts the same). This is easier said than done. The Higgs Boson is now often referred to as the “God particle,” which appears to be named so because the Higgs Field gives mass to other particles. However, this name is actually an abbreviation—originally it was referred to as the goddamn particle, because it was so goddamn hard to find.
Experiments done at the Large Hadron Collider (LHC) near Geneva strongly suggested the existence of the Higgs field. The LHC is a particle collider, which means it operates by smashing high energy beams of protons together at very high velocities. Lower energy particle accelerators are used to make certain radioactive isotopes. However, the scientists working at the LHC had bigger fish to fry—they were looking for the Higgs Boson. A high energy particle collider is needed to find the Higgs boson since E=mc^2 means that the energy of the proton beams determines the mass of the particles it can create. The Higgs boson was predicted to have a relatively high mass so only the LHC had enough energy to produce it. In 2012, LHC scientists successfully discovered a particle that agreed with the Standard Model predictions– they discovered the Higgs Boson!
Discovery of the Higgs Boson is so exciting because it confirms a lot of fundamental questions about the universe. It validates the Standard Model and explains how certain particles get their mass. It also poses a lot of mathematical questions about symmetry. Scientists believe that the Standard Model isn’t a complete picture of the universe—it doesn’t explain gravity, dark matter, or dark energy.. However, by getting a better understanding of it and the Higgs Field, we are one step closer to developing a “Theory of Everything.”