Partonic Entropy of the Proton from DGLAP Evolution

Abstract: We investigate the concept of partonic entropy of the proton within the Dokshitzer--Gribov--Lipatov--Altarelli--Parisi (DGLAP) evolution scheme of collinear parton distributions. We show that such entropy increases monotonically with the evolution scale. The mechanism underlying this growth is illustrated using a simplified model of DGLAP evolution, which highlights the importance of including saturation effects at small $x$ in the evolution of parton distributions. Based on existing literature, we present two simplified models of parton saturation at small $x$. In one of these models, partonic entropy is identified with entanglement entropy and proposed as an observable to be tested experimentally.