Colloquium di Dottorato: Nicole D'Hose (Paris-Saclay)

The proton is one of three building blocks of the atom. Since the 1960s, we have known that a proton consists of three quarks. However, researchers now have a much more differentiated picture of this familiar particle. Lepton scattering on nucleon is a very nice tool to reveal the structure of the nucleon. In the past elastic scattering and deep inelastic scattering have provided fundamental observables to determine nucleon size or momentum of quarks and gluons inside the nucleon. Nowadays high-energy exclusive experiments are still more challenging aiming to describe more precisely quarks and gluons to measure energy, angular momentum and pressure inside the nucleon. Exclusive reaction means that the final state with the emission for example of a single photon or a meson, is clearly identified. This requires the detection of all the particles in the event with high precision. We will review exclusive experiments, which have been realised in the world so far and why a new electron-ion collider (EIC) of high energy, high luminosity equipped with a hermetic detector of high resolution can help to achieve this goal. We will describe the first extraction of the pressure inside the nucleon which has been published in 2018. The pressure distribution inside the nucleon indicated that the central value is of the same order as that of neutron stars.This result opens a nice avenue and the experimental method is so demanding that it is worth pursuing the effort at EIC.