JLQCD

JLQCD
Name	JLQCD
Formation	1990s
Headquarters	Kyoto
Fields	Theoretical physics, Computational physics

JLQCD is a Japanese collaboration of theoretical physicists and computational scientists focused on lattice quantum chromodynamics and related numerical studies of strong-interaction physics. Founded by researchers at Japanese universities and national laboratories, it brings together faculty, postdocs, and students from institutions across Japan and collaborates internationally with research centers and supercomputing facilities. The collaboration has produced influential results in hadron spectroscopy, quark masses, and weak matrix elements through large-scale simulations and algorithmic development.

History

The collaboration emerged in the 1990s amid advances at KEK, RIKEN, University of Tokyo, Kyoto University, and Nagoya University when researchers sought coordinated lattice calculations comparable to projects at CERN, Fermilab, Brookhaven National Laboratory, DESY, and SLAC National Accelerator Laboratory. Early work built on developments by groups associated with CP-PACS, MILC, and HPQCD and responded to results from experiments at KEKB, Belle (experiment), BaBar, and CLEO. Over successive generations the collaboration adopted improved actions influenced by formulations from Wilson (lattice gauge theory), Kogut–Susskind fermion, Domain wall fermion, and Overlap fermion methods, while engaging with initiatives at JAEA, Osaka University, Tohoku University, and Hiroshima University.

Organization and Membership

Membership comprises faculty and researchers from Japanese institutions such as Kyoto University, University of Tsukuba, University of Tokyo, Nagoya University, Osaka University, Tohoku University, Hokkaido University, RIKEN, and KEK, together with visiting scientists from University of California, Berkeley, University of Cambridge, University of Edinburgh, Massachusetts Institute of Technology, Princeton University, University of Washington, Columbia University, Cornell University, and University of Barcelona. Governance typically involves principal investigators, working groups for gauge ensembles and measurements, and technical teams liaising with centers like National Institute of Informatics, National Institute of Advanced Industrial Science and Technology, Japan Atomic Energy Agency, and regional supercomputing centers. Funding and oversight have involved agencies such as the Ministry of Education, Culture, Sports, Science and Technology (Japan) and national research programs coordinated with international grant mechanisms.

Research Focus and Methods

The collaboration concentrates on lattice Quantum chromodynamics calculations of hadronic spectra, pion and kaon physics, quark masses, decay constants, form factors, and weak matrix elements relevant to Cabibbo–Kobayashi–Maskawa matrix phenomenology and tests of the Standard Model (particle physics). Methodologically, teams develop and deploy lattice actions and algorithms derived from concepts attributed to Kenneth G. Wilson, Miklos Gyulassy, and lattice practitioners at Columbia University and Trinity College Dublin, implementing techniques like Hybrid Monte Carlo, multi-grid solvers, and chiral fermion formulations associated with Shamir (David B. Kaplan), Herbert Neuberger, and David B. Kaplan. Calculations often target quantities compared with experimental measurements from Particle Data Group, LHCb, CMS, ATLAS, Belle II, and low-energy experiments at J-PARC.

Major Results and Publications

Results include precision determinations of light- and heavy-quark masses, calculations of meson decay constants (such as for pion and kaon) and semileptonic form factors impacting extractions of V_us| and V_ub| elements, and contributions to neutral-kaon mixing parameters like BK that influence constraints on CP violation and beyond-Standard-Model searches tied to analyses by UTfit, CKMfitter, and global fits used by collaborations at CERN and Fermilab. Publications appear in journals such as Physical Review D, Journal of High Energy Physics, Physical Review Letters, and Nuclear Physics B and are presented at conferences including Lattice Conference (annual), International Conference on High Energy Physics, Quark Confinement and the Hadron Spectrum, and workshops organized by KEK Theory Center. Key papers have addressed algorithmic scaling, nonperturbative renormalization, and continuum extrapolations that interact with theoretical work from groups at MIT, EPFL, ETH Zurich, University of Regensburg, and University of Southampton.

Computing Resources and Collaborations

Computational campaigns rely on supercomputers and clusters provided by facilities such as KEK’s central systems, national supercomputing centers like RIKEN R-CCS, Fugaku (supercomputer), regional centers at Information Technology Center, University of Tokyo, and collaborations with Fermilab and Jülich Research Centre. Software frameworks and code bases draw from community projects linked to USQCD, Grid (computing), and libraries used at Argonne National Laboratory, Oak Ridge National Laboratory, and Pawsey Supercomputing Centre. International collaboration extends to joint ensembles and data sharing with teams at Budapest-Marseille-Wuppertal (BMW) collaboration, ETM Collaboration, RBC and UKQCD collaborations, and ALPHA Collaboration.

Outreach and Education

Members contribute to graduate training at universities including Kyoto University, University of Tokyo, Nagoya University, Osaka University, and Tohoku University and supervise theses that connect to experimental programs at KEK, J-PARC, Belle II, and SuperKEKB. Outreach includes lectures at schools such as Les Houches Summer School, CERN Summer Student Programme, and regional workshops for early-career researchers hosted at KEK Theory Center and RIKEN. Collaboration members participate in panels of scientific bodies like Physical Society of Japan and contribute reviews to collective volumes used by researchers at Institute for Nuclear Theory and lecture series at Perimeter Institute.

Category:Lattice quantum chromodynamics