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Equation 8 · Part 3 · From Origins to Frontier: A History of Particle Physics Beyond the Standard Model

=

aμ=(g−2)/2a_\mu = (g-2)/2
=

What this part means

The expressions on both sides represent the same quantity under the stated assumptions.

Its job in the formula

The equals sign connects the complete expression on the left with the complete expression on the right. Both sides must have compatible units.

The passage around this formula

Contrast that with the muon’s anomalous magnetic moment, aμa_\mu = (g-2)/2 , which remains unresolved. The Fermilab Muon g-2 experiment’s most precise measurement to date, released in August 2023, gives aμ(FNAL)a_\mu(\text{FNAL}) = 116{,}592{,}040(54)×\times10^{-11} , a result precise to 0.20 parts per million [ 5 , 6 ] . Combined with the experiment’s earlier data, the measured value differs from one widely used Standard Model theoretical prediction by (251±\pm59)×\times10^{-11} , a discrepancy the collaboration itself describes as reaching 4.2 standard deviations [ 6 ] . This is a genuine, still-live tension, and it is also a genuine, still-live disagreement among theorists — not about the experimental…

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Learn the underlying idea

An equals sign says that the expression on its left and the expression on its right have the same value under the stated definitions and assumptions.

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Sources cited in the surrounding passage

These citations provide research context; check each source for the exact claim it supports.