sPHENIX

sPHENIX
Name	sPHENIX
Location	Brookhaven National Laboratory
Type	Particle detector

sPHENIX is a high-energy nuclear physics experiment located at Brookhaven National Laboratory on Long Island, designed to study the quark–gluon plasma and the properties of quantum chromodynamics under extreme conditions. It is sited at the Relativistic Heavy Ion Collider interaction region formerly occupied by the PHENIX detector and is intended to deliver precision measurements of jets, heavy flavor, and quarkonia in heavy-ion and proton collisions. The project integrates advances from accelerator projects, detector development, and computing initiatives across international laboratories and universities.

Introduction

sPHENIX was proposed to replace the PHENIX experiment at the Relativistic Heavy Ion Collider to address outstanding questions about parton energy loss, color deconfinement, and medium response in the quark–gluon plasma. The initiative mobilized expertise from national laboratories including Brookhaven National Laboratory, Lawrence Berkeley National Laboratory, and Fermi National Accelerator Laboratory, as well as universities such as Massachusetts Institute of Technology, Yale University, University of California, Berkeley, and Stony Brook University. The detector concept drew on technologies developed for experiments at facilities like the Large Hadron Collider, ALICE, ATLAS, and CMS while responding to physics drivers from theory groups tied to Quantum Chromodynamics, Lattice QCD, and phenomenology collaborations.

Detector design and components

The sPHENIX apparatus centers on a compact, large-acceptance solenoidal magnet borrowed conceptually from designs in ATLAS and CMS with a cryogenic system similar to those at DESY and CERN. Its principal subsystems include a silicon-based tracking system influenced by developments at LHCb and Belle II, an electromagnetic calorimeter following designs used by PHENIX and STAR, a hadronic calorimeter inspired by D0 and CDF technologies, and charged-particle identification layers drawing on work from PHENIX, ALICE, and NA49. The tracking incorporates silicon pixel detectors, silicon strip detectors, and low-mass supports adapted from Vertex Locator (VELO) work, while calorimetry uses tungsten-scintillator and lead-scintillator modules similar to those in CMS ECAL and ATLAS Tile Calorimeter. Readout electronics adopt architectures proven in ALICE O2, ATLAS TDAQ, and CMS DAQ systems, with front-end electronics leveraging ASIC efforts from Brookhaven National Laboratory, Lawrence Berkeley National Laboratory, and Ohio State University groups.

Physics goals and research program

sPHENIX aims to quantify jet quenching, heavy-quark diffusion, and quarkonia suppression by measuring inclusive and dijet spectra, b-jet tagging, and separated charm and bottom production across centrality classes defined by Glauber model implementations used in analyses at STAR and PHENIX. The program targets differential measurements that constrain transport coefficients such as the shear viscosity to entropy density ratio cited in AdS/CFT correspondence and perturbative Quantum Chromodynamics frameworks. Key observables include reconstructed jets, photon-jet correlations established in studies at RHIC and LHC, upsilon family suppression patterns analogous to measurements by CMS and ALICE, and heavy-flavor nuclear modification factors similar to those pursued by PHENIX and STAR.

Data acquisition and analysis methods

sPHENIX employs a high-throughput data acquisition chain with trigger strategies influenced by ATLAS Level-1, CMS High-Level Trigger, and ALICE O2 streaming models to handle collision rates at RHIC. Event reconstruction pipelines use software frameworks and libraries from ROOT, Geant4, HEP Software Foundation, and experiment-specific packages developed in collaboration with computing centers at Brookhaven National Laboratory, Lawrence Berkeley National Laboratory, and national supercomputing facilities such as NERSC and XSEDE. Analysis workflows integrate machine-learning methods from TensorFlow and PyTorch for jet tagging and background subtraction techniques that build on methods used at LHCb and ALICE. Calibration and alignment procedures reference techniques pioneered by CMS, ATLAS, and Belle II detector groups.

Construction, commissioning, and operations

Construction phases involved industrial partners and in-kind contributions coordinated through institutions like Brookhaven National Laboratory, Lawrence Berkeley National Laboratory, and university consortia including Columbia University and University of Illinois Urbana-Champaign. Commissioning utilized test beams and cosmic-ray studies similar to programs at CERN SPS and Fermilab Test Beam Facility with integration tests referencing procedures from PHENIX and STAR. Operations are planned in RHIC running periods alongside the RHIC Spin Program and coordinated with accelerator schedule managers at Brookhaven National Laboratory and Brookhaven's Collider-Accelerator Department.

Collaborations and funding

The sPHENIX collaboration comprises physicists, engineers, and technicians from dozens of institutions across the United States, Canada, Japan, and Europe, including academic and national laboratory partners such as Massachusetts Institute of Technology, University of California, Berkeley, Stony Brook University, Brookhaven National Laboratory, Lawrence Berkeley National Laboratory, Fermi National Accelerator Laboratory, CERN, and TRIUMF. Funding is provided through agencies including the U.S. Department of Energy, the National Science Foundation, and international partners like Japan Society for the Promotion of Science and national research councils in participating countries. Governance follows models used by large collaborations such as ALICE Collaboration, ATLAS Collaboration, and CMS Collaboration with spokespersons, institutional boards, and technical coordination teams.

Results and impact on heavy-ion physics

Early commissioning and physics runs are expected to produce precision measurements that will refine models of parton energy loss developed in the contexts of perturbative QCD, AdS/CFT correspondence, and transport approaches used by theory groups at Brookhaven National Laboratory, Lawrence Berkeley National Laboratory, and university theory centers. sPHENIX data will complement results from ALICE, CMS, ATLAS, and STAR, informing global analyses of jet quenching, heavy-flavor diffusion coefficients, and quarkonia sequential suppression seen in J/psi and Upsilon measurements. The experiment's technological contributions to silicon detector development, calorimetry, and high-rate DAQ are anticipated to influence future projects at Electron-Ion Collider, LHC Run 4, and beyond, and to shape curricula and training across participating institutions.

Category:Particle detectors Category:Brookhaven National Laboratory