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2+1 Flavor lattice QCD Simulation on K computer

2+1 Flavor lattice QCD Simulation on K computer. Y.Kuramashi U. of Tsukuba/RIKEN AICS August 2, 2013 @ Mainz. Plan of talk. §1. K computer and Strategic Field Program §2. Physics Plan §3. Simulation Parameters §4. Preliminary results §5. Summary.

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2+1 Flavor lattice QCD Simulation on K computer

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  1. 2+1 Flavor lattice QCD Simulation on K computer Y.Kuramashi U. of Tsukuba/RIKEN AICS August 2, 2013 @ Mainz

  2. Plan of talk §1. K computer and Strategic Field Program §2. Physics Plan §3. Simulation Parameters §4. Preliminary results §5. Summary

  3. §1. K computer and Strategic Field Program RIKEN AICS Tsukuba Kobe Tokyo Advanced Institute for Computational Science (Note: independent of RIKEN-BNL-Columbia Collab.) Kyoto Logo Peak=11.28PFlops Computer room

  4. Strategic Field Program • For strategic use of K computer • Government selected 5 strategic fields in science and technology for importance from national view point • For each field, Government also selected a core institute • Each core institute is responsible for organizing research and supercomputer resources in the respective field and its community, for which they receive • − priority allocation of K computer resources • − funding to achieve the research goals

  5. §2. Physics Plan • Scientific target • 2+1 flavor QCD ⇒ 1+1+1 flavor QCD+QED • Various physical quantities • Investigation of resonances • Direct construction of light nuclei • Determination of baryon-baryon potentials

  6. Light Nuclei in 2+1 Flavor QCD (1) Yamazaki-Ishikawa-YK-Ukawa 12 Ukawa @this conference 2+1 flavor QCD, mπ=0.5 GeV, mN=1.32 GeV Successful construction of helium nuclei in 2+1 flavor QCD

  7. Light Nuclei in 2+1 Flavor QCD (2) NN(3S1) and NN(1S0) channels Both 3S1 and 1S0 channels are bound at mπ=0.5 GeV |ΔE(3S1)| > |ΔE(1S0)| is observed Important to investigate quark mass dependence Target on K computer: construction of nuclei at the physical point

  8. Baryon-Baryon Potentials (1) Phenomenological model Ishii-Aoki-Hatsuda 07 based on equal-time BS amplitude Quenched QCD, mN=1.34GeV BS wave function with lattice QCD ⇒ NN Potential

  9. Baryon-Baryon Potentials (2) HAL-QCD @FB12 2+1 flavor QCD, lattice size=323×64, mπ=0.70, 0.57, 0.41 GeV Attractive phase shift, though the magnitude is just 10% of exp. value (no bound state ⇒ inconsistency against the direct method) Phase shift becomes smaller, as quark mass decreases ⇒ need direct comparison with exp. values at the physical point

  10. Collaboration members N.Ishii, N.Ishizuka, Y.Kuramashi, Y.Namekawa, Tsukuba H.Nemura, K.Sasaki, Y.Taniguchi, N.Ukita T.Hatsuda, T.Doi RIKEN-Wako T.Yamazaki Nagoya S.Aoki Kyoto Y.Nakamura RIKEN-AICS K.-I.Ishikawa Hiroshima HAL QCD Collab. joins to determine baryon-baryon potential

  11. §3. Simulation Parameters • 2+1 flavor QCD • Wilson-clover quark action + Iwasaki gauge action • Stout smearing with α=0.1 and Nsmear=6 • NP CSW=1.11 determined by SF • β=1.82 ⇒ a〜0.1 fm • Lattice size=964 ⇒ (〜9 fm)4 • Hopping parameters: (κud,κs)=(0.126117,0.124790) • Simulation algorithm • − (HB)2DDHMC w/ active link for ud quarks, UVPHMC for s quark • − Block size=124 ⇒ (〜1 fm)4 • − HB parameters: (ρ1,ρ2)=(0.99975,0.9940) • − Multi-time scale integrator: (N1,N2,N3,N4,N5)=(15,2,2,2,8) • − trajectory length: τ=1 • − Npoly=310 • − Chronological inverter guess: Nchrono=16 • − Solver: mixed precision nested BiCGStab

  12. Performance on K computer • Kernel (MatVec) performance: >50% • Solver performance: 〜26% (mixed precision nested BiCGStab) • Weak scaling test • − 63×12/node fixed • − 16 nodes (V=123×24) ⇒ 12288 nodes (V=48×72×962) B/F=0.5 on K computer 12288 2048 256 good weak scaling 16

  13. Non-Perturbative Determination of CSW (1) Taniguchi @Lattice2012 Schördinger functional method − L3×T=83×16 (L3×T=123×24 for volume dependence check) − Choose β such that the lattice spacing becomes around 0.1 fm CSW=1.11 at β=1.82 ⇒ 1/a〜2.1 GeV κC is close to 0.125 at β=1.82

  14. Non-Perturbative Determination of CSW (2) Nsmear dependence of CSW and Kc CSW monotonically decreases as Nsmear increases κC shows a similar behavior

  15. §4. Preliminary results Meson and baryon effective masses for smeared-local correlators Smearing function: Aexp(−Br) − (A,B)=(1.2,0.06) for ud quarks − (A,B)=(1.2,0.12) for s quarks

  16. Hadron spectrum Comparison with experiment (normalized by mΩ) Further tuning to the physical point is planned with reweighting method Clear deviation is already observed for unstable particles (ρ,K*)

  17. ρ Meson Effective Mass Decay channel is open: mρ>2√{mπ2+(π/48)2} mρ=776 MeV 2√{mπ2+(π/48)2} It is hard to find a reasonable plateau (same for Δ baryon effective mass) Analysis of 2×2 correlation matrix (ρ,ππ) is necessary

  18. §5. Summary ・ K computer and strategic field program ・ 2+1 flavor QCD simulation at the physical point on (〜9 fm)4 lattice ・ Preliminary results for hadron spectrum

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