# Measurement of the fine-structure constant as a test of the Standard Model

## TL;DR

This paper reports the most precise measurement of the fine-structure constant using cesium atom interferometry, testing the Standard Model and exploring potential new physics beyond it.

## Contribution

It introduces a highly accurate measurement of alpha via matter-wave interferometry and demonstrates advanced control of systematic effects at unprecedented precision.

## Key findings

- Measured alpha with 2.0 x 10^-10 accuracy
- Identified a 2.5 sigma tension with Standard Model predictions
- Constraints on dark-sector particles and electron substructure

## Abstract

Measurements of the fine-structure constant alpha require methods from across subfields and are thus powerful tests of the consistency of theory and experiment in physics. Using the recoil frequency of cesium-133 atoms in a matter-wave interferometer, we recorded the most accurate measurement of the fine-structure constant to date: alpha = 1/137.035999046(27) at 2.0 x 10^-10 accuracy. Using multiphoton interactions (Bragg diffraction and Bloch oscillations), we demonstrate the largest phase (12 million radians) of any Ramsey-Borde interferometer and control systematic effects at a level of 0.12 parts per billion. Comparison with Penning trap measurements of the electron gyromagnetic anomaly ge-2 via the Standard Model of particle physics is now limited by the uncertainty in ge-2; a 2.5 sigma tension rejects dark photons as the reason for the unexplained part of the muon's magnetic moment at a 99 percent confidence level. Implications for dark-sector candidates and electron substructure may be a sign of physics beyond the Standard Model that warrants further investigation.

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Source: https://tomesphere.com/paper/1812.04130