The Hitchhiker’s Guide to Quantum Field Theory

Matthew Buckley in the Boston Review:

This series explores an anomaly CERN scientists announced last December at the Large Hadron Collider (LHC), where protons are smashed together very close to the speed of light. My first installment explained how two detectors observed results at odds with predictions of the Standard Model. In the jargon of the field, they found a “diphoton excess at 750 GeV.” (My first piece explains what that means.)

This might be a very big deal. The Standard Model, which has withstood all experimental challenges for forty years, is our best theory of the fundamental particles that make up the matter and forces we know about. If the anomaly holds up, we will have come face to face with the Standard Model’s limitations.

But that’s a big “if.” The results are too preliminary for us to say anything for sure right now. Fortunately, CERN restarted the LHC experiments this month and is expected to make another announcement this summer. The new data may show that the anomaly was just statistical noise, but whatever happens, there is much to be learned from these efforts to probe the edges of our understanding. We may learn something about Nature, or we may learn that the existing theory has survived yet another test. In either case, by following how science gets done you can see why it is so exciting—the process as well as the results.

In the lead up to this summer’s announcement, I will take you through our present understanding of particle physics: the Standard Model, the Higgs boson, and why we suspect there is something beyond the Standard Model for the LHC to find. To do that, I need to give you a way to picture how the Universe works at these incredibly small scales. This second installment lays the foundation by exploring the basic language of particle physics. That language is called quantum field theory, but it is not so much a specific theory as the framework for all our fundamental theories of Nature, both the well tested (quantum electrodynamics and quantum chromodynamics, which are parts of the Standard Model) and the more speculative (supersymmetry and quantum gravity).

More here.