Angular and long range rapidity correlations in particle production at   high energy
  We discuss the general mechanism leading to long-range rapidity and angular correlations produced in high energy collisions (the "ridge"). This effect naturally appears in the high energy QCD and is strongly sensitive to physics of the gluon saturation. We comment on various recent practical realizations of the main idea, paying special attention to $N_c$ counting and stress the relevance of Pomeron loops. 
Alex Kovner (UCONN) and Michael Lublinsky (BGU)
hep-ph nucl-th