I've been tweeting a bunch of articles and threads about the #gminus2 result -- a possible indication of ✨ NEW PHYSICS ✨ coming from @Fermilab! Check my timeline for details, but I'll give a very brief and simplified summary here...
An experiment at @Fermilab is measuring a property of muons -- subatomic particles similar to electrons, but heavier -- to try to determine if our current understanding of particle physics is correct or not. The experiment hinges on the fact that muons are a tiny bit magnetic 🧲
The "Muon g-2" experiment measures how muons spin around and how that spin wobbles when they're sent around a circular track in the presence of strong magnetic and electric fields. That depends on how the muon spins and its "g-factor", related to its magnetism.
The muon's g-factor should be a number close to 2. It's calculated to be a LITTLE different from 2 because of a weirdness of quantum physics. Turns out empty space is full of a kind of roiling quantum energy in the form of "virtual particles" that pop up and vanish all the time.
Virtual particles interacting with the muon very slightly tweak its g-factor by an amount that depends on how many of those particles exist and how they interact with the muon. If we calculate the g-factor carefully, and then measure the muon's behavior, we can test the theory.
The upshot of the #gminus2 experiment is that the theory calculations of the g-factor and the experimental results DO NOT AGREE, to a level of certainty that ALMOST reaches the threshold of what particle physicists would call a "discovery" (but not quite).
What does it mean that the theoretical prediction doesn't match @Fermilab's experiment? It *might* mean that there are new particles roiling around in the quantum foam that are NOT included in our Standard Model. Which could mean we can replace it with a new & better theory!
If we have FINALLY found clinching proof that the Standard Model of Particle Physics has a big hole in it, that might point us to new theories that could rewrite how we think about the forces of nature and the fundamental structure of the cosmos. It would be a REALLY big deal!
There's a caveat, which is that a NEW theoretical calculation using supercomputers and a different method (also published today!) gives a g value that just barely AGREES with the experimental result! So both theorists and experimentalists are working hard to figure out what's up.
Q: Does this have anything to do with the LHCb news two weeks ago? That also involved muons...🤔
A: We don't know! Both could be hints about new physics beyond the Standard Model -- specifically, both could tell us new particles exist! -- but that's about all we can say for now.
A: We don't know! Both could be hints about new physics beyond the Standard Model -- specifically, both could tell us new particles exist! -- but that's about all we can say for now.
Q: How will we figure out *for sure* if #gminus2 is showing us new physics?
A: We're already getting more data. The result announced today was just from the first 6% of the data the Muon g-2 experiment will produce. And theorists will keep grinding away, too! Stay tuned...
A: We're already getting more data. The result announced today was just from the first 6% of the data the Muon g-2 experiment will produce. And theorists will keep grinding away, too! Stay tuned...
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