Physicists studying the particles that make up all matter, from atoms to protons to quarks, have long theorized that the Higgs field is responsible for giving the universe’s particles their mass. Earlier this month, researchers of the international ATLAS project in Switzerland found proof supporting this theory when they discovered top quarks, one of the particles that make up protons, interacting with Higgs bosons.

Six years ago, ATLAS physicists found the elusive Higgs boson: a detectable, massless, wavelike ripple in the theoretical Higgs field, said Peter Onyisi, a UT physics assistant professor and ATLAS researcher. The Higgs field is believed to give particles their mass by interacting with them and slowing them down.

“Imagine the universe is full of some sort of goo, and every particle has a certain amount of goo that sticks to it,” Onyisi said. “The amount of goo that sticks to (a particle) tells you how heavy it is.”

After finding the Higgs boson, researchers on the ATLAS project spent the next six years confirming that the Higgs field does indeed have this effect on particles, and not some other effect, said Jack Ritchie, UT physics department chair.

“(In the study, we looked at top quarks) because top quarks are very heavy (and) their interaction (with the Higgs field) is very strong, so we can detect it,” Onyisi said. “We have to study something heavy to try to draw a conclusion about these kinds of interactions.”

The team used the Large Hadron Collider to smash millions of protons together every second for several months at a time, Onyisi said. The collisions break protons apart into quarks and gluons, another particle that makes up protons, and every once in a while, they were be able to detect top quarks interacting with Higgs bosons.

“(Detecting this) is quite rare. … You don’t see (top quarks) directly: You see traces of them,” Onyisi said. “In our experiment, we were able to get enough collisions in order to see statistically significant evidence that this interaction was happening.”

Researchers from all over the world have dedicated their careers to understanding how the universe’s particles work, Onyisi said. While there are no immediate applications of this recent finding, uncovering the nature of matter and of mass itself has inspired this highly collaborative international effort.

The scientists knew what to look for because of the standard model of particle physics, which aims to explain what kinds of matter exist and what forces control their interactions, Onyisi said. Their finding confirmed that the standard model was correct when it predicted the creation of mass by the Higgs field.

“(The standard model) is incredibly successful,” Ritchie said. “But it’s known that it doesn’t answer everything.”

The standard model only accounts for the visible matter in the universe, which comprises only 4 percent of the known universe, Onyisi said. Finding an interaction that doesn’t fit the model may allow researchers to improve it.

“People work very hard to try and come up with ways to expand (the standard model), to explain other phenomena like dark matter,” Onyisi said. “In the end, what we’re really doing is probing the standard model (to) check for deviations from it.”

But this discovery did not deviate from the standard model, Ritchie said. So far, the model’s prediction about the Higgs field giving mass to everything we see appears to be correct.

“If you didn’t have the Higgs field doing this, you wouldn't have atoms,” Onyisi said. “You would have a very dull and uninteresting universe.”