Energy dependence of the Cronin effect from nonlinear QCD evolution

Area of Science:

• High-energy nuclear physics
• Quantum Chromodynamics (QCD)
• Particle collisions

Background:

• The nonlinear evolution of dense partonic systems is a proposed mechanism for understanding particle collisions.
• Cronin enhancement, an observed phenomenon in particle collisions, needs explanation within theoretical frameworks.

Purpose of the Study:

• To investigate the consistency of nonlinear QCD evolution with Cronin enhancement observed in d-Au collisions.
• To determine if nonlinear evolution can generate or preserve Cronin enhancement in proton-nucleus (p-A) and nucleus-nucleus (A-A) collisions.

Main Methods:

• Numerical solutions of the Balitsky-Kovchegov evolution equation.
• Analysis of nuclear gluon distributions under various initial conditions encoding Cronin enhancement.
• Comparison of theoretical predictions with experimental data from Relativistic Heavy Ion Collider (RHIC).

Main Results:

• The properly normalized nuclear gluon distribution is suppressed at all momenta compared to a single nucleon.
• Nonlinear QCD evolution fails to generate Cronin-type enhancement in the spectrum of produced gluons.
• Any Cronin enhancement present at lower energies is erased by the nonlinear evolution at collider energies.

Conclusions:

• The studied nonlinear QCD evolution framework is inconsistent with the Cronin enhancement observed in d-Au collisions.
• The model predicts suppression of nuclear gluon distributions, contrary to the enhancement phenomenon.
• Nonlinear evolution dynamics do not support Cronin enhancement in high-energy p-A and A-A collisions.