In the last hundred years, particle physicists have developed a fine-grained understanding of how the building blocks that make up the universe fit together, called the Standard Model. The concrete and steel are basic particles like protons, neutrons, and electrons, and the energies that weld them together are divided into three or four forces: strong, electromagnetic, weak, and sometimes gravity. Testing shows that the Standard Model is very accurate, but it’s not quite perfect. In building construction each trade needs to know enough about the other’s work to make the parts match up, but the best work is done by specialists – welders, bricklayers, plumbers. In particle physics the theoreticians who specialize in the nucleus of atoms are those that work with the strong force.
It’s those particles bunched in the nucleus that produce the fireworks in the pictures that result from supercolliders pushing them around and into one another. Analyzing those flashy displays helps scientists determine what the Model has right and what still needs refining. One thing is certain: a big job like the universe and everything in it needs to be broken down into pieces that a scientist, or a team of them, can get their arms around.
Assistant Professor Raúl Briceño joined the Nuclear Physics Group faculty here at UC Berkeley in 2023. He’s wanted to wrestle with the origins of matter since high school. He lived in Caracas in a traditionally Catholic family, lawyers and economists, and went through the usual teenage disenchantment with what he’d been taught. A new aspiration was revealed to him by Carl Sagan’s COSMOS series and his science teachers. Here was an origin story that did not disappoint. His parents could not say the same about Venezuelan president Hugo Chavez, and they made the difficult decision to move to Florida. Briceño finished high school and college there, then went to the University of Washington for grad school. He then spent close to ten years working and teaching in the Navy town of Norfolk, VA as a professor at Old Dominion University (ODU) and a researcher at the Jefferson Lab collider facility. (ODU and the Jefferson Lab have an arrangement similar to the one between Berkeley and LBNL.)
Over this time Briceño grew from an apprentice to a yeoman and finally to a master at a particular specialty: Lattice Quantum Chromo-Dynamics. (LQCD). Let’s unpack what that means:
By the 1950s researchers realized that protons and neutrons, contrary to what we said above, are not fundamental particles. They are made of even smaller particles that are labeled with names like quarks and hadrons, and later bosons and gluons, and even later each of these is found to come in several versions, and each has its own evil twin antiparticle too. The discovery of the Higgs boson in 2012 now seems to be the last piece of the Standard Model puzzle.
When we get down to such tiny critters the distinction our languages make between matter and energy starts to break down, the way the “is light a wave or a particle?” conundrum (it’s both, btw) makes other specialists talk in terms of photons and excitons—the descriptions are kinda sorta true and they are definitely useful. This is called heuristics.
Break a continuous phenomenon down into pieces and each piece can be handled more easily – this is what the Quantum means: If you examine the flows and waves and changes of our willowy world as though it was separate frames in a movie, you can figure out a Quantum Field Theory (QFT) that will improve our understanding of what’s going on out there. (Hopefully.)
