Dynamical Anisotropic-Clover Lattice Production for Hadronic Physics

C. Morningstar, CMUK. Orginos, College W&M

J. Dudek, R. Edwards, B. Joo,D. Richards, C. Thomas, JLab

S. Wallace, U. of MarylandN. Mathur, Tata Institute

M. Peardon, S. Ryan, Trinity College

AHM 2011

Anisotropic Lattices for Nuclear Physics

• Hadronic spectroscopy– Hadron resonance determinations– Exotic meson spectrum and transition form-factors – HadSpec (Richards)

• Hadronic structure– 3-D picture of hadrons from gluon & quark spin+flavor dist.– Ground & excited E&M transition FF-s– E&M polarizabilities of hadrons– HadSpec (Richards), EMC (Walker-Loud)

• Nuclear interactions– Nuclear processes relevant for stellar evolution– Hyperon-hyperon scattering– 3 & 4 nucleon interaction properties– NPLQCD (Savage)

Nf=2+1 Anisotropic Clover: dynamical generation

Current proposal: 403x256 at m¼ ~ 230 MeV, as=0.1227fm, at=0.035fm– Currently running on INCITE@ORNL

Extend@ANL: 323£256 at m¼ ~ 230 & 383 MeV

Future INCITE+ESP: 483x384 at m¼ ~ 140 MeV

Priorities

• Current calculations at m¼ ~ 230 MeV• Finite volume effects:

– Crucial for resonance/scattering extraction• Chiral effects (large pion mass) appear large

– Excited resonance: chiral extrap. problematic• High statistics important (~10k traj. -> 1000 cfgs)• Discretization effects appear small/negligible

– Evidence via spectra of Subduced operators

• Priorities:1. Physical limit @ 6fm box -> 483x3842. Second lattice spacing @ ~500MeV pion mass

• Claim: discretization effects small/negligible

• Anisotropic gauge (Symanzik) action & fermion (Clover) action:– Fixed Clover coefficients ct and cs (Chen): – Bare gauge °g fermion °f anisotropy & bare quark mass m0

• Impose PCAC & rotational symmetry via SF techniques (mq = 0)

• O(a) effects in spectrum eliminated via on-shell improvement

Discretization effects

gg

175 MeV

0 MeV

gf

175 MeV

0 MeV

Anisotropies

• Claim: discretization effects small/negligible

• No dimension 5 rotation breaking terms – Also true for anisotropic actions

• Rotation breaking pushed to O(a2)– True for both spectrum and wave-function (operator)

overlaps

Discretization effects

• Claim: discretization effects small/negligible

• In fact, rotation breaking negligible:

Discretization effects

arXiv:1104.5152

• Basis of 3-quark ops with continuum JP

• Mix in lattice irreps

• Tiny off-diagonal mixing

• Claim: discretization effects small/negligible

• No discernible rotation breaking

Discretization effects

arXiv:1104.5152

• Basis test: restrict operators

• Remarkable realization of rotational symmetry

• Determine J=7/2 for first time

Scattering processes: range of interactionVolume effects: two varieties:

• exp(-m¼*L) effects [NPLQCD: 1104.5152]

• Accessible momentum effects:– Determine partial-wave phase shifts ±L(E) vs. E(k2)– Critical component in resonance determinations

Volume effects

1011.6352

I=2 ¼¼ L=0 & 2scattering phase shift ±0(E) & ±2(E)

First ever L=2 phase shift

243

203

163

• Extract resonance mass• Can then chiral extrapolate• Obviously want light pion masses

• Perilous waters: the excited JP= ½+ “Roper”

Resonance mass and chiral extrapolations

1104.5152

Four-fold degeneracy

Big discrepancy: operator basis!

Need ops featuring orbital structure & multi-particle ops

Spin identified Nucleon & Delta spectrum

11

arXiv:1104.5152 m¼ ~ 520MeV

Spin identified Nucleon & Delta spectrum

12

Mass and overlaps: assign into multiplets arXiv:1104.5152

4 5 3 12 3 2 1

2 2 1 1 1

SU(6)xO(3) countingNo parity doubling

m¼ ~ 520MeV

Current plans

• Gauge production: – Emphasis on hadronic and nuclear physics– ORNL: INCITE time for 403£256, m¼~230MeV– ANL: extend 323£256 ensembles

• Distillation(+variants) + subduction– Flexible: framework useful for 2-pt and 3-pt– In-place: multi-particle ops & annihilation diagrams

• Role expanding for GPU-s– Powerful resource for inversions– ECC+double precision -> handle contractions– Major software focus

Backup

Spectroscopy: exotic mesons