Abstract
We study the disappearance of the away-side peak of the di-hadron correlation function in p+A vs p+p collisions at forward rapidities, when the scaterring process presents a manifest dilute-dense asymmetry. We improve the state-of-the-art description of this phenomenon in the framework of the Color Glass Condensate (CGC), for hadrons produced nearly back-to-back. In that case, the gluon content of the saturated nuclear target can be described with transverse-momentum-dependent gluon distributions, whose small-$x$ evolution we calculate numerically by solving the Balitsky-Kovchegov equation with running coupling corrections. We first show that our formalism provides a good description of the disappearance of the away-side azimuthal correlations in d+Au collisions observed at BNL Relativistic Heavy Ion Collider (RHIC) energies. Then, we predict the away-side peak of upcoming p+Au data at $~\sqrt[]{s}=200$ GeV to be suppressed by about a factor 2 with respect to p+p collisions, and we propose to study the rapidity dependence of that suppression as a complementary strong evidence of gluon saturation in experimental data.
Highlights
Azimuthal correlations of particles in the final states of hadronic collisions serve as a powerful tool for experimental tests of the color glass condensate (CGC) [1,2,3], the effective theory of protons and nuclei in the nonlinear regime of quantum chromodynamics
Such configurations are ideal for testing the CGC theory, because they induce a dilute-dense asymmetry in the problem: The projectile proton is probed at large values of Bjorken x, and is a dilute object, amenable to a description in terms of well-known parton distribution functions (PDFs)
A generic prediction of the CGC framework is that any effect due to gluon saturation should become less visible if we move towards more central rapidities; i.e., in our case, if we reduce the dilute-dense asymmetry by probing larger values of x in the nuclei
Summary
Azimuthal correlations of particles in the final states of hadronic collisions serve as a powerful tool for experimental tests of the color glass condensate (CGC) [1,2,3], the effective theory of protons and nuclei in the nonlinear regime of quantum chromodynamics. A special role in the phenomenology of the CGC is played by correlations of particles in p þ A collisions probed in the region of fragmentation of the protons [4,5,6,7,8,9,10,11], where the rapidities of the correlated particles are large and positive (forward rapidity region) Such configurations are ideal for testing the CGC theory, because they induce a dilute-dense asymmetry in the problem: The projectile proton is probed at large values of Bjorken x, and is a dilute object, amenable to a description in terms of well-known parton distribution functions (PDFs).
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