"Frontiers in Nucleon Structure"

Christine A. Aidala, Los Alamos National Laboratory

Quantum chromodynamics offers a powerful and elegant description of one 
of the fundamental forces in nature.  However, we remain at an early 
stage in being able to describe the everyday nuclear matter of the world 
around us in terms of the fundamental degrees of freedom in QCD, quarks 
and gluons.  The proton, as a fundamental bound state of QCD, can serve 
as an excellent laboratory in which to probe the complexities of the 
strong force as we learn more about the very matter of which we 
ourselves are made. 

Colliding polarized proton beams at the Relativistic Heavy Ion Collider 
(RHIC) offers a novel experimental method for the investigation of 
nucleon structure, in particular its angular momentum structure.  The 
measurements at RHIC provide unique sensitivity to the spin contribution 
from the gluon field in the proton and the spin structure of the quark 
and anti-quark sea, as well as the transverse spin structure of the 
proton, which continues to produce a number of startling effects. 
Highlights of the recent contributions that RHIC has made to the study 
of proton structure will be presented.  

Looking beyond RHIC, a new facility, capable of colliding a beam of 
electrons with a wide range of nuclei as well as polarized protons and 
light ions, has been proposed: the Electron-Ion Collider (EIC) promises 
to usher in an era of precision measurements of QCD phenomena in nuclear 
matter, bringing the field to a new stage.  The status and prospects of 
the EIC will be discussed.