Interpretation of an "edge" in proton-proton scattering
  A study of proton-proton collisions at very high energy has revealed a "black disk," whose radius grows with the logarithm of the center-of-mass energy, surrounded by an edge of approximately constant width 1 fm. We interpret this behavior as the maximum length of a QCD string connecting the color triplet and antitriplet components of the proton, and propose further tests of this explanation. 
Jonathan L. Rosner
hep-ph hep-ex