The small-x gluon distribution in centrality biased pA and pp collisions

Abstract

The nuclear modification factor $R_{pA}(p_T)$ provides information on the small-$x$ gluon distribution of a nucleus at hadron colliders. Several experiments have recently measured the nuclear modification factor not only in minimum bias but also for central $pA$ collisions. In this paper we analyze the bias on the configurations of soft gluon fields introduced by a centrality selection via the number of hard particles. Such bias can be viewed as reweighting of configurations of small-$x$ gluons. We find that the biased nuclear modification factor ${\mathcal{Q}}_{pA}(p_T)$ for central collisions is above $R_{pA}(p_T)$ for minimum bias events, and that it may redevelop a "Cronin peak" even at small $x$. The magnitude of the peak is predicted to increase approximately like $1/{A_{\perp }}^{\nu }$, $\nu \sim 0.6\pm 0.1$, if one is able to select more compact configurations of the projectile proton where its gluons occupy a smaller transverse area $A_{\perp }$. We predict an enhanced ${\mathcal{Q}}_{pp}(p_T)-1\sim 1/(p_T^2{)}^{\nu }$ and a Cronin peak even for central $pp$ collisions.

arXiv comment14 pages, 5 figures

References in corpus (50)

• Computing Quark and Gluon Distribution Functions for Very Large Nuclei
• Operator expansion for high-energy scattering
• Gluon Distribution Functions for Very Large Nuclei at Small Transverse Momentum
• Nonlinear Gluon Evolution in the Color Glass Condensate: I
• The Wilson renormalization group for low x physics: towards the high density regime
• The BFKL Equation from the Wilson Renormalization Group
• Nonlinear Gluon Evolution in the Color Glass Condensate: II
• The Renormalization Group Equation for the Color Glass Condensate
• Unitarity at small Bjorken x
• The Wilson renormalization group for low x physics: Gluon evolution at finite parton density
• Fluctuating Glasma initial conditions and flow in heavy ion collisions
• Event-by-event anisotropic flow in heavy-ion collisions from combined Yang-Mills and viscous fluid dynamics
• Exclusive diffractive processes at HERA within the dipole picture
• Non-Abelian Weizsacker-Williams field and a two-dimensional effective color charge density for a very large nucleus
• NLO evolution of color dipoles
• Quark contribution to the small-$x$ evolution of color dipole
• Gluon production in current-nucleus and nucleon-nucleus collisions in a quasi-classical approximation
• Event-by-event gluon multiplicity, energy density and eccentricities at RHIC and LHC
• Unitarization of Gluon Distribution in the Doubly Logarithmic Regime at High Density
• The Energy Dependence of the Saturation Momentum
• Evolution of the nuclear modification factors with rapidity and centrality in d+Au collisions at $\sqrt{s_{NN}} = 200 GeV
• Geometric Scaling above the Saturation Scale
• Cronin Effect and High-p_T Suppression in pA Collisions
• Triumvirate of Running Couplings in Small-x Evolution
• Parton saturation and N_part scaling of semi--hard processes in QCD
• High energy pA collisions in the color glass condensate approach I. Gluon production and the Cronin effect
• Centrality dependence of particle production in p-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$= 5.02 TeV
• Saturation and Universality in QCD at small x
• Transverse momentum distribution and nuclear modification factor of charged particles in p-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV
• CGC predictions for p+Pb collisions at the LHC
• Energy Dependence of the Cronin Effect from Non-Linear QCD Evolution
• Effective field theory for the small-x evolution
• Predictions for $p+$Pb Collisions at sqrt s_NN = 5 TeV
• How Protons Shatter Colored Glass
• New Scaling at High Energy DIS
• QCD saturation at the LHC: comparisons of models to p+p and A+A data and predictions for p+Pb collisions
• A Simple Derivation of the JIMWLK Equation
• Mass ordering of spectra from fragmentation of saturated gluon states in high multiplicity proton-proton collisions
• Angular and long range rapidity correlations in particle production at high energy
• Geometric scaling violations in the central rapidity region of d+Au collisions at RHIC
• Non linear gluon evolution in path-integral form
• Dijet production as a centrality trigger for p-p collisions at CERN LHC
• A Gaussian effective theory for gluon saturation
• Cronin effect and high-p_T suppression in the nuclear gluon distribution at small x
• Transverse momentum, rapidity, and centrality dependence of inclusive charged-particle production in $\sqrt{s_{NN}}=5.02$ TeV p+Pb collisions measured by the ATLAS experiment
• Nuclear effects on the transverse momentum spectra of charged particles in pPb collisions at a nucleon-nucleon center-of-mass energy of 5.02 TeV
• Anisotropy of the semi-classical gluon field of a large nucleus at high energy
• Odd Azimuthal Anisotropy of the Glasma for pA Scattering
• Predictions for $p+$Pb Collisions at $\sqrt{s_{NN}}=5$ TeV: Comparison with Data
• Fluctuations of the gluon distribution from the small-x effective action

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• Angular correlations in pA collisions from CGC: multiplicity and mean transverse momentum dependence of $v_2$
• Particle multiplicities in the central region of high-energy collisions from $k_T$-factorization with running coupling corrections
• Multiplicity-dependent saturation momentum in $p$-Pb collisions at 5.02 TeV
• Double inclusive small-x gluon production and their azimuthal correlations in a biased ensemble