HotQCD

HotQCD
Name	HotQCD
Formation	2000s
Focus	Finite-temperature Quantum chromodynamics, lattice Quantum chromodynamics
Members	international lattice QCD researchers
Field	High-energy physics, computational physics

HotQCD HotQCD is an international collaboration of lattice Quantum chromodynamics researchers focused on finite-temperature Quantum chromodynamics and the quark–gluon plasma. The collaboration has produced precision studies of the thermodynamics of strongly interacting matter relevant to Relativistic Heavy Ion Collider, Large Hadron Collider, and early-universe cosmology. Work by HotQCD interfaces with results from experimental programs at Brookhaven National Laboratory, CERN, and theoretical developments associated with lattice gauge theory and effective models.

Introduction

HotQCD formed to address thermodynamic properties of Quantum chromodynamics using large-scale lattice simulations and to provide inputs to hydrodynamic modelling used by experimental collaborations such as STAR (experiment), PHENIX, ALICE (A Large Ion Collider Experiment), and ATLAS. The collaboration builds on methodological foundations laid by earlier lattice groups including the MILC Collaboration, CP-PACS Collaboration, RBC-UKQCD Collaboration, and Wuppertal-Budapest Collaboration, and coordinates with theory initiatives at institutes like Brookhaven National Laboratory, Lawrence Livermore National Laboratory, Fermilab, and RIKEN. Its work contributes to phenomenology pursued by groups around Duke University, Yale University, Columbia University, and University of California, Berkeley.

Methodology and Lattice Setup

HotQCD employs improved staggered fermion actions and modern gauge actions developed in collaboration with coding efforts influenced by projects at Los Alamos National Laboratory, Argonne National Laboratory, and NERSC. Ensembles are generated on anisotropic and isotropic lattices with temporal extents tuned to simulate temperatures spanning the hadronic and deconfined regimes studied by CERN SPS, SPS Heavy Ion Programme, and GSI Helmholtzzentrum für Schwerionenforschung. The collaboration uses scale-setting procedures linked to quantities measured by the Particle Data Group and techniques paralleling those used by HPQCD and UKQCD. Simulations incorporate physical strange-quark masses inspired by determinations at Jefferson Lab and light-quark masses extrapolated with guidance from chiral works by Steven Weinberg and teams at Institute for Nuclear Theory.

Key Results and Observables

HotQCD has reported results for the crossover temperature, equation of state, fluctuations of conserved charges, and screening masses. Its determinations of the pseudocritical temperature complement analyses by the Wuppertal-Budapest Collaboration and are compared against experimental freeze-out extractions from STAR (experiment) and ALICE (A Large Ion Collider Experiment). The collaboration has published calculations of the pressure, energy density, entropy density, and trace anomaly relevant to hydrodynamic models used by Hydro3D and hybrid frameworks employed by PHENIX and CMS (detector). HotQCD also computed higher-order cumulants of baryon number, electric charge, and strangeness that connect to fluctuation measurements pursued by NA61/SHINE, HADES, and CBM Experiment.

Comparison with Other Collaborations

HotQCD results are routinely compared with findings from the Wuppertal-Budapest Collaboration, MILC Collaboration, RBC-UKQCD Collaboration, and Budapest-Wuppertal group. Differences and agreements are analyzed in the context of fermion discretization choices such as improved staggered, Wilson, and domain-wall formulations used by BMW Collaboration and JLQCD. Crosschecks involve continuum extrapolations analogous to strategies from ALPHA Collaboration and renormalization approaches related to studies by Rome-Southampton and RIKEN BNL Research Center. These intercomparisons inform global assessments by theory consortia linked to Quark Matter conferences and review articles in journals associated with American Physical Society and European Physical Society meetings.

Impact on QCD Phase Diagram and Phenomenology

HotQCD findings have constrained the temperature dependence of deconfinement and chiral restoration lines relevant to the finite-density phase diagram discussed at Quark Matter conferences and in workshops at INT (Institute for Nuclear Theory). Results on susceptibilities and fluctuations feed into search strategies for the critical point pursued by Beam Energy Scan programs at Brookhaven National Laboratory and experimental analyses at CERN. The computed equation of state is a standard input for hydrodynamic simulations used by phenomenology groups at University of Houston and Spanish National Research Council (CSIC), affecting interpretations of collective flow, jet quenching, and hadronization measured by ALICE (A Large Ion Collider Experiment), STAR (experiment), and CMS (detector).

Collaborations and Computational Resources

HotQCD relies on leadership-class supercomputing facilities including Oak Ridge Leadership Computing Facility, National Energy Research Scientific Computing Center, Argonne Leadership Computing Facility, and national centers in Germany, Japan, and China. Software ecosystems share lineage with projects such as USQCD, QUDA, and community codes developed at Fermilab and Lawrence Berkeley National Laboratory. The collaboration involves researchers connected to universities and labs like University of Illinois Urbana-Champaign, University of Washington, Stony Brook University, Brookhaven National Laboratory, and RIKEN and participates in international workshops hosted by CERN and KITP.

Category:Lattice Quantum chromodynamics