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DOE OSTI · 3367263

Probing gluon saturation with forward di-hadron correlations in proton-nucleus collisions

Caucal, Paul [IMT Atlantique, Nantes (France); Universite de Nantes (France); Centre National de la Recherche Scientifique (CNRS), Nantes (France). Inst. National de Physique Nucleaire et de Physique des Particules (IN2P3), Laboratoire Subatech] (ORCID:0000000290331473)·Kang, Zhong-Bo [University of California, Los Angeles, CA (United States); Stony Brook University, NY (United States)] (ORCID:0000000331610381)·Korcyl, Piotr [Jagiellonian University, Krakow (Poland)] (ORCID:0000000211936440)·Salazar, Farid [Temple University, Philadelphia, PA (United States); Brookhaven National Laboratory (BNL), Upton, NY (United States)] (ORCID:0000000240076136)·Schenke, Björn [Brookhaven National Laboratory (BNL), Upton, NY (United States)] (ORCID:0000000179081322)·Stebel, Tomasz [Jagiellonian University, Krakow (Poland)] (ORCID:0000000206968739)·Venugopalan, Raju [Brookhaven National Laboratory (BNL), Upton, NY (United States); Stony Brook University, NY (United States); University of Edinburgh, Scotland (United Kingdom)] (ORCID:0000000279183553)·Zhao, Wenbin [Central China Normal University, Wuhan (China)] (ORCID:0000000183246134)
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Abstract

We present a detailed numerical investigation of semi-inclusive forward di-hadron production in proton–nucleus collisions employing the Color Glass Condensate effective theory. We focus on the regime where di-hadrons are produced nearly back-to-back in the transverse plane, thereby justifying a transverse-momentum-dependent factorization approach in terms of small-x gluon distributions. Our computation integrates several key elements: i) non-linear rapidity evolution via the Balitsky–Kovchegov equation with running coupling, ii) both perturbative and non-perturbative Sudakov resummation, and iii) a phenomenologically constrained model for the initial conditions for small-x gluon distributions. We compare this phenomenological framework to experimental data from the STAR Collaboration on azimuthal correlations in forward di-pion production in both proton–proton and proton–gold collisions. We analyze the systematic theoretical uncertainties associated with the saturation scales of nuclei at the initial scale for rapidity evolution and with those associated with the hadronization process. Finally, we make predictions for the kinematics anticipated to be covered by the ALICE Forward Calorimeter (FoCal) upgrade at the Large Hadron Collider.

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73 NUCLEAR PHYSICS AND RADIATION PHYSICSColor glass condensateDi-hadron correlationsFocalGluon saturation

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Caucal, Paul [IMT Atlantique, Nantes (France); Universite de Nantes (France); Centre National de la Recherche Scientifique (CNRS), Nantes (France). Inst. National de Physique Nucleaire et de Physique des Particules (IN2P3), Laboratoire Subatech] (ORCID:0000000290331473), Kang, Zhong-Bo [University of California, Los Angeles, CA (United States); Stony Brook University, NY (United States)] (ORCID:0000000331610381), Korcyl, Piotr [Jagiellonian University, Krakow (Poland)] (ORCID:0000000211936440), Salazar, Farid [Temple University, Philadelphia, PA (United States); Brookhaven National Laboratory (BNL), Upton, NY (United States)] (ORCID:0000000240076136), Schenke, Björn [Brookhaven National Laboratory (BNL), Upton, NY (United States)] (ORCID:0000000179081322), Stebel, Tomasz [Jagiellonian University, Krakow (Poland)] (ORCID:0000000206968739), Venugopalan, Raju [Brookhaven National Laboratory (BNL), Upton, NY (United States); Stony Brook University, NY (United States); University of Edinburgh, Scotland (United Kingdom)] (ORCID:0000000279183553), Zhao, Wenbin [Central China Normal University, Wuhan (China)] (ORCID:0000000183246134). 2026-06-01. Probing gluon saturation with forward di-hadron correlations in proton-nucleus collisions. https://doi.org/10.1016/j.physletb.2026.140599

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