The FAMU experiment will measure the hyperfine splitting in the
ground state of muonic hydrogen ΔEhfs(μ
−
p)1s with a precision δλ/λ < 10
−5
providing rZ, the Zemach radius of the proton with higher precision, than what was
previously possible, disentangling discordant theoretical values. The aim is to set
a cornerstone result about not yet explained anomalies on the charge radius rch of
the proton. The Zemach radius rZ and the charge radius rch are the only proton
shape-related values that can be directly extracted from experimental data, and rZ
is the only one that gives information about the proton’s magnetic dipole moment
distribution. The status of the experiment is presented.
