Any of you who have been watching this show for a while know that Pamela kind of adores the Standard Model of Particle Physics and is amused every time some complex theories theorized particle fails to be found. Researchers know the Standard Model is incomplete. While it was able to successfully predict a number of particles, including the top quark and the Higgs boson, it doesn’t actually explain why the physics we have has to be the way it is instead of being something totally different. It’s like Kepler’s theory of planetary motion; it could accurately predict planetary motion but didn’t explain why they did what they did. It took Newton’s theory of gravity to explain the why and Einstein’s relativity to fill in all the details before we could get a mostly complete theory. So, with the Standard Model, we have a base that doesn’t explain the whys but still seems to work. Or at least it did until this week.

An experiment at Fermi National Accelerator Laboratory to look at unstable particles called muons. Muons are in many ways similar to electrons but are 200 times bigger and tend to fall apart into smaller particles and energy over time. Muons are naturally produced when cosmic rays hit Earth’s atmosphere as well as in other events where high-energy particles crash into things that slow them abruptly. Particle accelerators like Fermi can produce muons in large numbers, and recent research to look at how these muons interact in magnetic fields discovered that they don’t exactly do what was predicted. 

Just like magnets can affect the motions of electrons, they also can affect muons; these are super similar particles. The fact that we understand electrons so well is part of how we can make amazing electronics. Because muons are unstable, they are harder to study, and we’re still confirming they also do exactly as predicted. In fact, it appears that there is something hanging out, undetected, that is affecting muons’ behaviors. This could be new forces, new effects, or just some underlying feature of the universe. We don’t know. 

What we do know is Fermilab wasn’t the only place to get these results. Fermilab’s experiment was actually a follow-up to a 2001 experiment at Brookhaven that had enough error in the measurements and was weird enough that it had to be replicated to be trusted. Fermilab and Brookhaven results are in agreement, and, now we know, muons are reacting to something we know nothing about.

This is super cool. This is like when observers realized Mercury’s orbit doesn’t exactly do what Newton or Kepler predicted. It was close, but not perfect, and the difference pointed us in the direction of what was needed and allowed Einstein to know he was on the right path with relativity. This result is one new thing that says which set of equations need modification and tell us what kind of results those modifications should match. This is new information. We had an incomplete theory; we haven’t succeeded in figuring out what’s missing on our own, and now we have data. Annoying, not-matching-prediction data, and that is awesome.

We really look forward to the day someone says, and this is what was missing.

More Information

Fermilab press release