Muon g-2

Is there new physics beyond the Standard Model of particle physics? Our finding will help settle the question

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Thursday, August 10, 2023
Electron, Mechanics, Shock, Temperature, Sigma, Particle, Data, Nature, Physics, Standard Model, Conceptual model, Brookhaven National Laboratory, Tesla, Muon g-2, Physical Review Letters, Muon, Extrusion, Electric motor, Risk management, Fermilab

It neither describes gravity nor the unknown components that make up most of the energy density in the universe: dark matter and dark energy.

Key Points: 
  • It neither describes gravity nor the unknown components that make up most of the energy density in the universe: dark matter and dark energy.
  • Particle physicists are therefore on a treasure hunt looking for any possible deviation from “expected” behaviour that could hint at new physics.
  • One fundamental building block in the Standard Model is the muon, a particle similar to an electron but 200 times more massive.
  • The muon has a long history of revolutionising particle physics – even its discovery was a shock.
  • Any missing pieces in the Standard Model would modify the rate by an amount slightly higher or lower than predicted, making this a powerful search tool for new physics.

Boosting accuracy

    • While the statistical uncertainty has been reduced, other improvements were needed to make the measurement even more precise.
    • The magnetic field direction determines the axis of the wobble, so keeping the temperature fluctuations of the magnet under control was crucial.
    • Differences in temperature also cause the magnet pieces to expand and contract, which changes the magnetic field slightly.
    • At our level of accuracy, even a change one thousandth of a millimetre could have a huge effect on the wobble.
    • For this reason, a thermal coat was installed around the ring and a cooling system in the experimental hall.

Muon g-2 doubles down with latest measurement, explores uncharted territory in search of new physics

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Thursday, August 10, 2023
Electron, Uncertainty, University, G2, Photon, Office of Inspector General, U.S. Department of Health and Human Services, DFG, National Natural Science Foundation of China, National Science Foundation, Light, Data collection, Science and Technology Facilities Council, Fermilab, Research, DOE, Primary energy, NRF, Higgs, Student, MSIP, Istituto Nazionale di Fisica Nucleare, Korea, South Korea, Physics, Standard Model, Conceptual model, German Research Foundation, Muon g-2, Physical Review Letters, Muon, Pharmaceutical industry, Management, Television, Risk management, Uranium mining, Science, Energy

The Muon g-2 collaboration describes the result in a paper that they submitted today to Physical Review Letters.

Key Points: 
  • The Muon g-2 collaboration describes the result in a paper that they submitted today to Physical Review Letters.
  • In addition to the larger data set, this latest g-2 measurement is enhanced by updates to the Fermilab experiment itself.
  • In 2020, the Muon g-2 Theory Initiative announced the best Standard Model prediction for muon g-2 available at that time.
  • Until then, physicists have a new and improved measurement of muon g-2 that is a significant step toward its final physics goal.

First results from Fermilab's Muon g-2 experiment strengthen evidence of new physics

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Wednesday, April 7, 2021
Physics, Physical sciences, Natural sciences, Muon g-2, Muon, G-factor, Subatomic particle, Fermilab, David B. Cline, Muon-catalyzed fusion

Combined, the two results show strong evidence that our best theoretical model of the subatomic world is incomplete.

Key Points: 
  • Combined, the two results show strong evidence that our best theoretical model of the subatomic world is incomplete.
  • The strong evidence that muons deviate from the Standard Model calculation might hint at exciting new physics.
  • "Today is an extraordinary day, long awaited not only by us but by the whole international physics community," said Graziano Venanzoni, co-spokesperson of the Muon g-2 experiment and physicist at the Italian National Institute for Nuclear Physics.
  • In its first year of operation, in 2018, the Fermilab experiment collected more data than all prior muon g-factor experiments combined.