Speaker
Description
The strong interaction is the fundamental force that holds quarks and the
gluon force carriers together to form protons and neutrons and also holds the
atomic nucleus together. The theory governing quark-gluon interactions is Quantum Chromodynamics (QCD). A wide variety of experimental data teaches us thatquarks and gluons cannot be observed in isolation, a phenomenon known as confinement that is unique to QCD. But no one has used QCD to prove confinement. Here we show how to define and measure the force on quarks in the proton using available experimental data. Direct evidence for confinement is obtained because the force is found to be attractive and constant for a wide range of quark positions. This work guides future experimental efforts aimed at obtaining a rigorousquantitative understanding of confinement.