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Physics from one year of QCDOC

This presentation provides a comprehensive overview of the QCDOC (Quality, Cost, Delivery, Order, and Customer) project, focusing on the physics and results obtained from the Domain Wall Fermion project. It covers the machine status, ensembles, preliminary data results, and the ILDG (International Lattice Data Grid) and UKQCD (United Kingdom Quantum Chromodynamics) status. The presentation also discusses the Aoki phase, chiral symmetry breaking, and the implications for chiral symmetry.

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Physics from one year of QCDOC

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  1. Physics from one year of QCDOC The Domain Wall fermion project RBC and UKQCD UK perspective Chris Maynard epcc University of Edinburgh ILFTnet IV Sokendai, Japan 8-11 March 2006

  2. People • Chris Allton, Dave Antonio, Tom Blum, Ken Bowler, Peter Boyle, Michael Cheng, Norman Christ, Michael Clark, Saul Cohen, Chris Dawson, Luigi del Debbio, Takumi Doi, Michael Donellan, Jonathan Flynn, Alistair Hart, Koichi Hashimoto, Taku Izubuchi, Chulwoo Jung, Andreas Juttner, Tony Kennedy, Richard Kenway, Changhoan Kim, Sam Li, Huey Wen Lin, Meifeng Lin, Robert Mawhinney, Christopher Maynard, Jun Ichi Noaki, Shigemi Ohta, Brian Pendleton, Chris Sachrajda, Shoichi Sasaki, Amarjit Soni, Aurora Trivini, Robert Tweedie, Azusa Yamaguchi, Takeshi Yamazaki, James Zanotti ILFTnet IV Sokendai, Japan 8-11 March 2006

  3. Outline • Brief overview of machine status • Ensembles past, present and future • Physics • Review of data • Preliminary results for data • ILDG • UKQCD status • QCDml1.3 • Summary and outlook ILFTnet IV Sokendai, Japan 8-11 March 2006

  4. QCDOC (edinburgh) ILFTnet IV Sokendai, Japan 8-11 March 2006

  5. QCDOC status • UKQCD and RBC machines have been in operation for one year. (Mostly) jointly producing DWF ensembles DOE and Regensburg machines both commisioned and running. Can’t comment, won’t comment ILFTnet IV Sokendai, Japan 8-11 March 2006

  6. Current production runs • Iwasaki gauge action • Strange quark mass fixed • up/down • Two volumes • Small ~4000 trajectories 1-2Knode • Gauge production complete • Measurement ongoing • Large • 800-1500 trajectories. Ongoing. 3 4Knode machines ILFTnet IV Sokendai, Japan 8-11 March 2006

  7. Initial runs • Parameter search • 2+1 flavours RHMC • ams=0.04, amud={0.02,0.04} • Effect on chiral symmetry breaking of • Gauge coupling and gauge action (IW vs DBW2) • Papers • PoS LAT2005 • 080, 093, 094. 095. 098, 135, 141, 346 • 3 papers in preparation ILFTnet IV Sokendai, Japan 8-11 March 2006

  8. Introduction • Chirally symmetric fermions • Domain Wall fermions (DWF) • Both chiral and flavour symmetry at finite a • Continuum-like chiral perturbation theory • Baryon interpolating operators relate to spectrum in simple way Kaplan 92, Shamir 93, Furman-Shamir 95 • Computationally expensive • Residual chiral symmetry breaking mres ILFTnet IV Sokendai, Japan 8-11 March 2006

  9. Aoki phase – how coarse is coarse? Schematic of phase diagram Shaded region is super-critical B is massless Aoki phase Must be in C on the right to get to continuum QCD Continuum-like symmetries at Coarse a large volume Must be away from Aoki phase ILFTnet IV Sokendai, Japan 8-11 March 2006

  10. Chiral symmetry breaking and mres • 4d quark field constructed from left (right) projections of on boundary Quark mass is LS not infinite  L-R coupling Define J5 current in terms of fields at LS/2 or mid-point Axial Ward-Takahashi Identity and thus mres ILFTnet IV Sokendai, Japan 8-11 March 2006

  11. Localisation and chiral symmetry • P.A. Boyle PoS LAT2005:141,2005 • Transfer matrix of 5d DWF operator, T • Gap in spectrum of extended states local • Define mobility edge by critical eigen value • for then is extended • What are the implications for chiral symmetry? ILFTnet IV Sokendai, Japan 8-11 March 2006

  12. Chiral symmetry • In correlations functions, volume suppression of localised states • Two leading contributions to mres • Volume enhanced states at mobility edge • Low lying localised states • ValenceLS study of LS(Sea)=8 data ILFTnet IV Sokendai, Japan 8-11 March 2006

  13. DBW2 mres vs LS ILFTnet IV Sokendai, Japan 8-11 March 2006

  14. IW mres vs LS ILFTnet IV Sokendai, Japan 8-11 March 2006

  15. Microscopic locality Negative mass operator • Gap in spectrum of extended states local • Define mobility edge by critical eigenvalue • for then is extended ILFTnet IV Sokendai, Japan 8-11 March 2006

  16. Measuring locality • Subset of configurations of LS=8 ensembles ~ 25 • Measure 256 lowest eigen values and vectors • Determine smax for each l • As l lc • Smax↑ • Eigen vectors become multi-peaked ILFTnet IV Sokendai, Japan 8-11 March 2006

  17. Localisation of DBW2 smax lt ILFTnet IV Sokendai, Japan 8-11 March 2006

  18. Localisation of IW smax lt ILFTnet IV Sokendai, Japan 8-11 March 2006

  19. Chiral symmetry and Topology • Chiral symmetry breaking effects greater for rougher gauge fields • mres smaller for smaller g2 • mres smaller for DBW2 than IW • Smearing (smoothing) gauge fields reduces mres • Local topology variation greater for rougher gauge fields • Ultimately no tunnelling at zero quark mass • Chose IW as “optimal” solution ILFTnet IV Sokendai, Japan 8-11 March 2006

  20. Topology on IW b=2.13 QdV ILFTnet IV Sokendai, Japan 8-11 March 2006

  21. Ls=8 Datasets 163x32 Ls=8 RHMC a-1 ~ 1.5 – 2.2 GeV 30K traj ! 100K measurements ams=0.04 Quark mass not constant ILFTnet IV Sokendai, Japan 8-11 March 2006

  22. Autocorrelations B=0.72 ms=0.04 mud=0.02 5000 trajectories Independent cfgs = 2*t ILFTnet IV Sokendai, Japan 8-11 March 2006

  23. Pion data Measure every 5 tint = 12 x 5 ~ 60 ILFTnet IV Sokendai, Japan 8-11 March 2006

  24. Win when you bin b=0.764 mR=0.5 4 time-planes Local vector correlator 262 configurations separated every 10 trajectories Bins size 5-10  tint = 50-100 ILFTnet IV Sokendai, Japan 8-11 March 2006

  25. Meson Spectrum • Fit mres, mPS and mV • Oversample and bin data • Multiple time planes • Multiple smearings • Multiple quark masses • Multiple gauge couplings • Multiple gauge actions •  multiple effective mass plots ILFTnet IV Sokendai, Japan 8-11 March 2006

  26. mres IW b=2.2 {0.02,0.04} ILFTnet IV Sokendai, Japan 8-11 March 2006

  27. mres DBW2 b=0.72 {0.01,0.04} ILFTnet IV Sokendai, Japan 8-11 March 2006

  28. mPS IW b=2.13 ILFTnet IV Sokendai, Japan 8-11 March 2006

  29. mPS DBW2 b=0.764 ILFTnet IV Sokendai, Japan 8-11 March 2006

  30. mV IW b=2.13 {0.04,0.04} ILFTnet IV Sokendai, Japan 8-11 March 2006

  31. mV IW b=2.13 {0.02,0.04} ILFTnet IV Sokendai, Japan 8-11 March 2006

  32. Chiral extrapolation • In general only two quark masses •  no extrapolation • Draw a straight line • Errors are (correctly) large for quantities evaluated at zero quark mass • Not much use for phenomenology • Map out parameter space • where to calculate 2+1 DWF ILFTnet IV Sokendai, Japan 8-11 March 2006

  33. The static quark potential and r0 ILFTnet IV Sokendai, Japan 8-11 March 2006

  34. mres(mq0) 0.01077(9) 0.00529(5) 0.00430(4) 0.01050(10) 0.00656(6) Ensembles in physical units ILFTnet IV Sokendai, Japan 8-11 March 2006

  35. Setting strange quark mass Lattice spacing from r0=0.5fm ILFTnet IV Sokendai, Japan 8-11 March 2006

  36. DBW2 vectors ILFTnet IV Sokendai, Japan 8-11 March 2006

  37. Scaling of r0mK* ILFTnet IV Sokendai, Japan 8-11 March 2006

  38. Axial current • Chiral symmetry ZA from two-point corrs • CA(x) conserved current at LS/2 (a lámres) • LA(x) usual local current • Correlate current with PS(x) • fPS from ratio of correlation functions ILFTnet IV Sokendai, Japan 8-11 March 2006

  39. ZAb=0.72 {0.02,0.04} ILFTnet IV Sokendai, Japan 8-11 March 2006

  40. b=0.72 fPS ILFTnet IV Sokendai, Japan 8-11 March 2006

  41. Scaling of fp Suggestive of common continuum limit and better scaling ILFTnet IV Sokendai, Japan 8-11 March 2006

  42. Scaling of fK Again suggestive of good scaling ILFTnet IV Sokendai, Japan 8-11 March 2006

  43. Scaling of fp/fk Flat! Ideal scaling! ILFTnet IV Sokendai, Japan 8-11 March 2006

  44. Nucleon operators • Standard Nucleon operator • Operator for negative parity partner • In finite box, backward propagating statehasopposite parity ILFTnet IV Sokendai, Japan 8-11 March 2006

  45. Nucleon Effective mass plots DBW2 b=0.72 mR=½ local-wall correlator WN, WN(T-t),WN* ILFTnet IV Sokendai, Japan 8-11 March 2006

  46. Scaling of nucleons Evidence of finite volume effect N* and N become degenerate at sufficiently small volume Seem to be coming together ILFTnet IV Sokendai, Japan 8-11 March 2006

  47. Finite size effects ILFTnet IV Sokendai, Japan 8-11 March 2006

  48. Edinburgh Plot Data follows phenomenological curve B=2.2 data anamolous, consistent with finite volume interpretation ILFTnet IV Sokendai, Japan 8-11 March 2006

  49. LS=16 data • Small volume 163x32, 4000 trajectories • Sample every 10 (one source) • Trajectory length=1  tint~25-50 • ~100 configurations • More sources and more sampling to be done • Spectrum results • Matrix elements: BK PRELIMINARY ILFTnet IV Sokendai, Japan 8-11 March 2006

  50. Residual mass Gauge fixed gaussian smearing ILFTnet IV Sokendai, Japan 8-11 March 2006

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