Energy versus centrality dependence of the jet quenching parameter $\hat{q}$ at RHIC and LHC: a new puzzle?

Abstract

The central goal of jet quenching studies in high-energy nuclear collisions is the characterization of those QCD medium properties that are accessible by these probes. Most of the discussion in the last years has been focused on the determination of the jet quenching parameter, $\hat{q}$. We present here an extraction of this parameter using data of inclusive particle suppression at RHIC and LHC energies for different centralities. Our approach consists of fitting a $K$ factor that quantifies the departure of this parameter from an ideal estimate, $K\equiv \hat{q}/(2{\epsilon }^{3/4})$, where $\hat{q}$ is determined by the local medium quantities as provided by hydrodynamical calculations. We find that this $K$ factor is larger at RHIC than at the LHC, as obtained already in previous analyses, but, surprisingly, it is almost independent of the centrality of the collision. Taken at face value, the $K$ factor would not depend on the local properties of the medium as energy density or temperature, but on global collision quantities such as the center of mass energy. This is a very intriguing, unexpected possibility for which we cannot yet provide a clear interpretation. We also comment on the limitations of the formalism that may affect this conclusion.

26 pages, 7 figures

References in corpus (19)

• Implications of CTEQ global analysis for collider observables
• EPS09 - a New Generation of NLO and LO Nuclear Parton Distribution Functions
• Global analysis of fragmentation functions for pions and kaons and their uncertainties
• The theory and phenomenology of perturbative QCD based jet quenching
• Global Analysis of Fragmentation Functions for Protons and Charged Hadrons
• Jet physics in heavy-ion collisions
• Measurement of jet fragmentation in PbPb and pp collisions at sqrt(s[NN]) = 2.76 TeV
• Antiangular Ordering of Gluon Radiation in QCD Media
• Systematic Comparison of Jet Energy-Loss Schemes in a realistic hydrodynamic medium
• Heavy ion event generator HYDJET++ (HYDrodynamics plus JETs)
• Q-PYTHIA: a medium-modified implementation of final state radiation
• Measurement of inclusive jet charged-particle fragmentation functions in Pb+Pb collisions at $\sqrt{s_{NN}}=2.76$ TeV with the ATLAS detector
• The eccentricity in heavy-ion collisions from Color Glass Condensate initial conditions
• Parton shower evolution in a 3-d hydrodynamical medium
• Jet quenching phenomenology from soft-collinear effective theory with Glauber gluons
• Revisiting scaling properties of medium-induced gluon radiation
• Medium-induced gluon radiation and colour decoherence beyond the soft approximation
• The non-linear evolution of jet quenching
• Medium-induced emissions of hard gluons

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