Review of proton and nuclear shape fluctuations at high energy

Understand

Determining the inner structure of protons and nuclei in terms of their fundamental constituents has been one of the main tasks of high energy nuclear and particle physics experiments.

• This quest started as a mapping of the (average) parton densities as a function of longitudinal momentum fraction and resolution scale.
• Recently, the field has progressed to more differential imaging, where one important development is the description of the event-by-event quantum fluctuations in the wave function of the colliding hadron.
• In this Review, recent developments on the extraction of proton and nuclear transverse geometry with event-by-event fluctuations from collider experiments at high energy is presented.