Two-hadron correlations in the Color Glass Condensate formalism

Two-hadron correlations are a sensitive probe of the dynamics of gluon saturation and the Color Glass Condensate formalism where the degrees of freedom are Wilson lines of the gluon field. It is shown that unlike structure functions in DIS and single hadron production in proton-nucleus collisions, higher point functions of Wilson lines appear in two-hadron production cross section. We derive equations for the energy ($x$) evolution of these higher point functions using the JIMWLK Hamiltonian and show that dipole approximation, employed in the literature to fit the di-hadron data measured by the STAR collaboration in the forward rapidity region, breaks down. This necessitates an investigation of the full hierarchy of the JIMWLK evolution equations for these higher point functions and their solutions. This can then be used to make a quantitative analysis of the di-hadron correlations in the forward rapidity region in deuteron-gold collisions at RHIC and in the long range rapidity correlations observed in proton-proton collisions at the LHC.Comment: 10 pages, based on talks given by the author in in the program "High Energy Strong Interactions 2010" at the Yukawa Institute for Theoretical Physics, July-August 2010, Kyoto, Japan and in the "5th International Workshop on high $p_t$ Physics at LHC 2010", September - October, 2010, Mexico City, Mexic

Scattering of Gluons from the Color Glass Condensate

We prove that the inclusive single-gluon production cross section for a hadron colliding with a high-density target factorizes into the gluon distribution function of the projectile, defined as usual within the DGLAP collinear approximation, times the cross section for scattering of a single gluon on the strong classical color field of the target. We then derive the gluon-proton (nucleus) inelastic cross section and show that it is (up to logarithms) infrared safe and that it grows slowly with center of mass energy. Furthermore, we discuss jet transverse momentum broadening for the case of nuclear targets. We show that in the saturation regime, in contrast to the perturbative regime, the width of the transverse momentum distribution is infrared finite and grows rapidly with energy and rapidity. In both regimes, however, transverse momentum broadening exibits the same dependence on atomic number A.Comment: 6 pages, 1 figure; proof of factorization of inclusive pA->gX cross section (in the collinear limit) has been added; to appear in PL