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Evidence for new physics? > Fermilab’s Muon g-2 results announced

As noted in comments for my “The future of (particle) physics?” post, the first results from Fermilab’s Muon g-2 experiment are a big deal for physics. Waiting for years. Highly anticipated. As expected, today these results were officially released.

Fermilab itself released an excellent YouTube video visualization which includes background on the project and experiment and a summary of the first results.

• YouTube > Fermilab > “Muon g-2 experiment finds strong evidence for new physics” (Apr 7, 2021).

[Video description] The first results from the Muon g-2 experiment hosted at Fermilab show fundamental particles called muons behaving in a way not predicted by the Standard Model of particle physics. Announced on April 7, 2021, these results confirm and strengthen the findings of an earlier experiment of the same name performed at Brookhaven National Laboratory. Combined, the two results show strong evidence that our best theoretical model of the subatomic world is incomplete. One potential explanation would be the existence of undiscovered particles or forces. This video explains what a muon is, how the Muon g-2 experiment works, and the significance of this result.

Muon g-2 first results press release

[Excerpt] The long-awaited first results from the Muon g-2 experiment at the U.S. Department of Energy’s Fermi National Accelerator Laboratory show fundamental particles called muons behaving in a way that is not predicted by scientists’ best theory, the Standard Model of particle physics. This landmark result, made with unprecedented precision, confirms a discrepancy that has been gnawing at researchers for decades.

The strong evidence that muons deviate from the Standard Model calculation might hint at exciting new physics. Muons act as a window into the subatomic world and could be interacting with yet undiscovered particles or forces.

Here’s a sampling of related articles today.

• Science Magazine > “Particle mystery deepens, as physicists confirm that the muon is more magnetic than predicted” by Adrian Cho (Apr. 7, 2021)

• BBC > “Muons – ‘Strong’ evidence found for a new force of nature” by Pallab Ghosh, Science correspondent (April 7, 2021)

• Scientific American > “Long-Awaited Muon Measurement Boosts Evidence for New Physics” by Daniel Garisto (April 7, 2021) – Initial data from the Muon g-2 experiment have excited particle physicists searching for undiscovered subatomic particles and forces

• Gizmodo > “Physics Mystery Gets Even Deeper After Long-Awaited Muon Reveal” by Ryan F. Mandelbaum (April 7, 2021)

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The future of (particle) physics?


[1] Featured image caption

First results from the Muon g-2 experiment at Fermilab have strengthened evidence of new physics. The centerpiece of the experiment is a 50-foot-diameter superconducting magnetic storage ring, which sits in its detector hall amidst electronics racks, the muon beamline, and other equipment. This impressive experiment operates at negative 450 degrees Fahrenheit and studies the precession (or wobble) of muons as they travel through the magnetic field. Photo: Reidar Hahn, Fermilab

One thought on “Evidence for new physics? > Fermilab’s Muon g-2 results announced

  1. This article recaps the current state of play regarding theory and experiment for the muon’s magnetic moment.

    Faced with this discrepancy, there were three options:

    • Either the theoretical prediction was incorrect,
    • the experiment was incorrect
    • or, as many physicists believed, this was a sign of an unknown force of nature.

    The article describes a new approach to “forecasting” the muon’s magnetic moment by putting “the equations on a space-time grid” and “using millions of computer processing hours at multiple supercomputer centers in Europe.”

    • > “Proof of new physics from the muon’s magnetic moment? Maybe not, according to new theoretical calculation” by Zoltan Fodor, Professor of Physics, Penn State (April 26, 2021)

    Our result [theoretical prediction] was published in the journal Nature on April 7, 2021, the same day as the new experimental results.

    Our new approach produces an estimate of the strength of the muon’s magnetic field that closely matches the experimental value measured by the Brookhaven scientists. … our new theory seems to say that this time, the Standard Model is holding up. … As always in science, other calculations need to be done to confirm or refute it.

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