Measuring the proton form factor at very low Q²

The proton is a fundamental constituent of matter. Yet the determination of its radius via interaction with electrons and muons seems to yield different radii leading to the so called proton radius puzzle. To bring new insight into the observed discrepancy a novel electron scattering experiment at MAMI (Mainz Microtron) was performed aiming to determine the electric form factor of the proton at Q² as low as 1-3 . 10^-4 (GeV/c)², by using a method based on initial state radiation. The goal of the experiment is to obtain the electric form factor with an accuracy of 1% and extract a new value for the proton charge radius. In this presentation a brief overview of the experiment is presented together with the underlying theory. Then the present status of the analysis and preliminary results are discussed.