Frontemare di Trieste
Istituto Nazionale di Fisica Nucleare
Sezione di Trieste

Hyperfine splitting in muonic hydrogen: FAMU

FAMU is a collaboration that involves around 60 researchers from Italy, Bulgaria, Poland, Great Britain, Togo, Japan, China and India. The experiment aims to determine the Zemach radius of the proton by measuring the hyperfine splitting of the muonic hydrogen atom in the ground state. This measure will allow to know more in detail one of the main constituents of matter, the proton.

The FAMU experiment is installed at the muon accelerator of the Rutherford Appleton Laboratory in Oxford. Muonic hydrogen is produced colliding a beam of muons of about 60 MeV/c with a target of hydrogen and oxygen in a gaseous state. The hyperfine splitting is measured with an indirect method: a powerful laser with variable energy is injected in the target; the laser energy is varied to match the appropriate energy and induce the transition. The variation of the spectrum of the X-rays emitted by the target, as the laser energy changes, allows to determine the energy of the splitting.

This will be the first measurement of the Zemach radius with muonic hydrogen to reach an accuracy of 1%. The measurement will contribute to a better understanding of the proton structure and its description through quantum electrodynamics, challenging the limits of the most precise theoretical predictions.

Website of the FAMU experiment:



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