Gluon splitting in a shockwave

Abstract

The study of azimuthal correlations in particle production at forward rapidities in proton-nucleus collisions provides direct information about high gluon density effects, like gluon saturation, in the nuclear wavefunction. In the kinematical conditions for proton-lead collisions at the LHC, the forward di-hadron production is dominated by partonic processes in which a gluon from the proton splits into a pair of gluons, while undergoing multiple scattering off the dense gluon system in the nucleus. We compute the corresponding cross-section using the Colour Glass Condensate effective theory, which enables us to include the effects of multiple scattering and gluon saturation in the leading logarithmic approximation at high energy. This opens the way towards systematic studies of angular correlations in two-gluon production, similar to previous studies for quark-gluon production in the literature. We consider in more detail two special kinematical limits: the "back-to-back correlation limit", where the transverse momenta of the produced gluons are much larger than the nuclear saturation momentum, and the "double parton scattering limit", where the two gluons are produced by a nearly collinear splitting occurring prior to the collision. We argue that saturation effects remain important even for relatively high transverse momenta (i.e. for nearly back-to-back configurations), leading to geometric scaling in the azimuthal distribution.

26 pages, 4 figures

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• Universality of Unintegrated Gluon Distributions at small x
• NLO evolution of color dipoles
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• Triumvirate of Running Couplings in Small-x Evolution
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• Solving The High Energy Evolution Equation Including Running Coupling Corrections
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• kt-factorization for Hard Processes in Nuclei
• Centrality Dependence of pi^0 and eta Production at Large Transverse Momentum in sqrt(s_NN) = 200 GeV d+Au Collisions
• Single Inclusive Hadron Production at RHIC and the LHC from the Color Glass Condensate
• Forward Neutral Pion Production in p+p and d+Au Collisions at sqrt(s_NN)=200 GeV
• Forward dihadron correlations in deuteron-gold collisions with a Gaussian approximation of JIMWLK
• Universality of multi-particle production in QCD at high energies
• Testing the Gaussian Approximation to the JIMWLK Equation

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• Forward dijets in proton-nucleus collisions at next-to-leading order: the real corrections
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• Dihadron production in DIS at NLO: the real corrections
• JIMWLK evolution for multi-particle production in Langevin form
• Saturation effects in SIDIS at very forward rapidities
• Soft photon and two hard jets forward production in proton-nucleus collisions
• Exploring minijets beyond the leading power
• Medium-induced gluon radiation in hard forward parton scattering in the saturation formalism
• Incoherent diffractive dijet production in electron DIS off nuclei at high energy
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• Towards tomography of quark-gluon plasma using double inclusive forward-central jets in Pb-Pb collision
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• Unequal rapidity correlators in the dilute limit of JIMWLK
• A new approach to piecewise linear Wilson lines
• High Energy Collisions of Dense Hadrons in Quantum Chromodynamics : LHC Phenomenology and Universality of Parton Distributions