Shigemi Ohta

email: shigemi.ohta@kek.jp
phone: +81-29-864-5408, +1-631-344-3398
fax: +81-29-864-5755, +1-631-344-4067
While you're here, take the opportunity to donate free food to the United Nations World Food Programme.

I am a member of the Theory Group of the Institute of Particle and Nuclear Studies, High Energy Accelerator Research Organization (KEK) of Japan.

My main interest is in lattice numerical study of quantum field theories, especially in lattice quantum chromodynamics (QCD). For this purpose, I use super-computing facility at the RIKEN BNL Research Center (RBRC) in the Brookhaven National Laboratory (BNL).

At the RBRC I joined RIKEN/BNL/Columbia QCD Project to build, in cooperation with Professors Bob Mawhinney and Norman Christ of Columbia University, a TFLOPS-scale parallel supercomputer dedicated for lattice QCD. The computer, called QCDSP, has a peak speed of 600 GFlops, and was awarded the Gordon Bell Prize for price performance at the Super Computing 98 (Orlando, Florida, November 1998).

This supercomputer was mainly used by what is now called the RIKEN/BNL/Columbia (RBC) QCD Collaboration.  The Collaboration pioneered the numerical application of the five-dimensional domain wall fermions (DWF) method to QCD.  See, for example, the proceedings of an international workshop on Fermion Frontiers in Vector Lattice Gauge Theories (May 6 - 9, 1998) which I organized with Professor Mawhinney. It is available by writing to the RBRC.  We terminated its operation early in 2006 as the new QCDOC supercomputer became available.

In the summer of 1999 we started discussing a follow-up project to QCDSP.  It soon developed into designing a new, 10 TFlops supercomputer with some of Columbia and RIKEN-BNL people including Profeesors Christ and Mawhinney and myself.  Named QCDOC (QCD "On a Chip"), the new design is based on the "system-on-a-chip" technology provided by IBM Research.  The first five prototype QCDOC ASICs (Application-Specific Integrated Circuits) were delivered on June 5th, 2003.  We received thousands more ASICs in the following months and assembled scores of motherboards, each of which is a 64-GFlops peak speed computer with 64 QCDOC ASICs configured as a six dimensional hypercube.  By the summer 2004 we were ready to assemble two 10-TFlops QCDOC configurations, one for RBRC and another for UKQCD.  They were complete in the fall of 2004 and the UKQCD one was shipped to Edinburgh.  We held a RBRC and Columbia celebrations on May 26th and 27th of 2005.  Edinburgh celebration was held on July 1st.  Another 10-TFlops configuration supported by the US DOE was complete in the spring of 2005.

With the RBRC QCDOC computer and its sister machines funded by UK PPARC and US DOE, I study varioius aspects of hadron physics, including CP violations in neutral K meson and structure of nucleon.  Some works into these problems are found in the publications below.

Some of my recent publications are:

  1. Nucleon axial charge in 2+1-flavor dynamical DWF lattice QCD, for RBC and UKQCD Collaborations, in Lattice 2013, PoS(LATTICE 2013)274,
  2. Weak Decay Measurements from 2+1 flavor DWF Ensembles, with RBC and UKQCD Collaborations, in Lattice 2013, PoS(LATTICE 2013)404,
  3. Finite-size scaling in nucleon axial charge from 2+1-flavor DWF lattice QCD, with Meifeng Lin, for RBC and UKQCD Collaborations, in Lattice 2012, PoS(Lattice 2012)171,
  4. DomainWall QCD with Near-Physical Pions, for RBC and UKQCD Collaborations, in Phys. Rev. D87, 094514 (2013),
  5. Nucleon structure from 2+1-flavor dynamical DWF lattice QCD at nearly physical pion mass, with Meifeng Lin, for RBC and UKQCD Collaborations, in Erice School "From quarks and gluons to hadrons and nuclei," September 16-24, 2011, Erice, Sicily,  in Progress in Particle and Nuclear Physics, 67, 218 (2012),
  6. Nucleon structure from 2+1f dynamical DWF lattice QCD at nearly physical pion mass, for RBC and UKQCD Collaborations, in Lattice 2011, PoS (Lattice 2011) 168,
  7. Nucleon structure from 2+1 flavor domain wall QCD at nearly physical pion mass, for RBC and UKQCD Collaborations, in Tropical QCD 2010, AIP Conf. Proc. 1354, 148 (2011),
  8. Continuum Limit of BK from 2+1 Flavor Domain Wall QCD, for RBC and UKQCD Collaborations, in Phys. Rev. D84, 014503 (2011),
  9. Nucleon structure from RBC/UKQCD 2+1 flavor DWF dynamical ensembles at a nearly physical pion mass, for RBC and UKQCD Collaborations, in Lattice 2010, PoS (Lattice 2010) 152,
  10. Continuum Limit Physics from 2+1 Flavor Domain Wall QCD, for RBC and UKQCD Collaborations, in Phys. Rev. D83, 074508 (2011),
  11. Nucleon isovector structure functions in (2+1)-flavor QCD with domain wall fermions, for RBC and UKQCD Collaborations, in Phys. Rev. D82, 014501 (2010),
  12. Nucleon structure functions from dynamical (2+1)-flavor domain wall fermions, for RBC and UKQCD Collaborations, in Lattice 2009, PoS (LAT 2009) 131,
  13. Nucleon form factors with 2+1 flavor dynamical domain-wall fermions, with RBC and UKQCD Collaborations, in Phys. Rev. D79, 114505 (2009),
  14. Nucleon structure with dynamical (2+1)-flavor domain wall fermions lattice QCD, with Takeshi Yamazaki for RBC and UKQCD Collaborations, in Lattice 2008, PoS (LATTICE 2008) 168,
  15. Physical Results from 2+1 Flavor Domain Wall QCD and SU(2) Chiral Perturbation Theory, with RBC and UKQCD Collaborations, Phys. Rev. D 78, 114509 (2008),
  16. Nucleon structure with two flavors of dynamical domain-wall fermions, with RBC Collaboration, Phys. Rev. D 78, 014505 (2008),
  17. Nucleon axial charge in 2+1 flavor dynamical lattice QCD with domain wall fermions, with RBC and UKQCD Collaborations, Phys. Rev. Letters 100, 171602 (2008),
  18. Nucleon form factors and structure fnctions with N_f=2+1 dynamical domain-wall fermions, with Takeshi Yamazaki for RBC and UKQCD Collaborations, in Lattice 2007, PoS LATTICE 2007, 165,
  19. Neutral kaon mixing from 2+1 flavor Domain Wall QCD, with RBC and UKQCD Collaborations, Phys. Rev. Letters 100, 032001 (2008),
  20. Localization and chiral symmetry in 2+1 flavor domain wall QCD, with RBC and UKQCD Collaborations, Phys. Rev. D77, 014509 (2008),
  21. 2+1 flavor domain wall QCD on a (2 fm)^3 lattice: light meson spectroscopy with Ls = 16, with RBC and UKQCD Collaborations, Phys. Rev. D76, 014504 (2007),
  22. First results from 2+1-Flavor Domain Wall QCD: Mass Spectrum, Topology Change and Chiral Symmetry with L_s=8, with RBC and UKQCD Collaborations, Phys. Rev. D75, 114501 (2007),
  23. Nucleon structure in lattice QCD with dynamical domain-wall fermions quarks with Huey-Wen Lin (Jefferson Lab), for the RBC and UKQCD Collaborations, in Lattice 2006, PoS LAT2006, 118,
  24. Charm as a domain wall fermion in quenched lattice QCD with Huey-Wen Lin (Columbia), Amarjit Soni (BNL) and Norikazu Yamada (KEK), for the RBC QCD Project, Phys. Rev. D74, 114506 (2006),
  25. Heavy-light mesons with domain-wall fermions with HueyWen Lin (Columbia) and Norikazu Yamada (KEK), for the RBC QCD Project, in Lattice 2005,
  26. The kaon B parameter from quenched domain-wall QCD with the RBC QCD Project, Phys. Rev. D73, 094507 (2006),
  27. Nucleon structure functions with domain wall fermions with Tom Blum (Connecticut) and Kostas Orginos (William and Mary) for the RBC QCD Project, Phys. Rev. D73, 094503 (2006),
  28. Overview of the QCDSP and QCDOC computers with the QCDOC collaboration, in IBM Journal of Research and Development 49, 351 (2005),
  29. Lattice QCD with two dynamical flavors of domain wall quarks with the RBC QCD Project, Phys. Rev. D72, 114505 (2005),
  30. Nucleon structure with domain wall fermions with Kostas Orginos, for the RBC QCD Project, in Lattice 2004,
  31. Nucleon axial charge and structure functions with domain wall fermions also with Kostas Orginos, for the RBC QCD Project, in Lattice 2003,
  32. Hardware and software status of QCDOC with the QCDOC collaboration, in Lattice 2003,
  33. Suppression of ecological competition by apex predator with Taksu Cheon (Kochi Tech), Phys. Rev. E70, 021913 (2004),
  34. Nucleon axial charge from quenched lattice QCD with domain wall fermions with Shoichi Sasaki (Tokyo), Kostas Orginos and Tom Blum, for the RBC QCD Project, Phys. Rev. D68, 054509 (2003),
  35. Domain wall fermions with improved gauge actions with the RBC QCD Project, Phys. Rev. D69, 074504 (2004),
  36. Status of the QCDOC project  with the QCDOC collaboration, in Lattice 2002,
  37. Kaon matrix elements and CP-violation from quenched lattice QCD: (I) the 3-flavor case with the RBC QCD Project, Phys. Rev. D68, 114506 (2003),
  38. QCDOC: A 10-teraflops scale computer for lattice QCD  also with the QCDOC collaboration, in Lattice 2001,
  39. A lattice study of the nucleon excited states with domain wall fermions  also with Tom Blum  and Shoichi Sasaki for the RBC QCD Project, Phys. Rev. D65, 074503 (2002),
  40. Quenched lattice QCD with domain wall fermions and the chiral limit with the RBC QCD Project, Phys. Rev. D69, 074502 (2004),
  41. Deconfinement transition and string tensions in SU(4) Yang-Mills Theory with Matt Wingate (Seattle), Phys. Rev. D63, 094502 (2001),
  42. Light hadron spectrum in quenched lattice QCD with staggered quarks with Seyong Kim (Sejong University), Phys. Rev. D61, 074506 (2000).

A more complete set of my publications can be found here.