ASCR/NP LQCD SciDAC Project

Scientists Calculate Predictions for Electron-Ion Collider Measurements

DOE SC Highlight - 2025

Calculations of charge distribution in mesons provide a benchmark for experimental measurements and validate widely used 'factorization' method.

Revolutionary Calculations Unveil the Hidden Motion of Quarks Inside Protons

SciTechDaily - 2024

Nuclear scientists have developed a new theoretical approach that offers a more precise calculation of the 3D motion of quarks within a proton, significantly enhancing the understanding of these particles’ transverse motions.

Scientists calculate predictions for meson measurements

PHYS ORG - 2024

Calculations of charge distribution in mesons provide benchmark for experimental measurements and validate widely used 'factorization' method for imaging the building blocks of matter.

Calculations reveal high-resolution view of quarks inside protons

PHYS ORG - 2023

Theorists predict differential distribution of 'up' and 'down' quarks within protons---and differential contributions to proton's properties.

Calculation shows why heavy quarks get caught up in the flow

PHYS ORG - 2023

New results will help physicists interpret experimental data from particle collisions at RHIC and the LHC and better understand the interactions of quarks and gluons.

Reducing Redundancy to Accelerate Complicated Computations

Jefferson Lab Highlight - 2022

Scientists at Jefferson Lab and William and Mary developed MemHC to improve the efficiency of supercomputer calculations

First QCD determination of the decays of a $1^{-+}$ hybrid meson

Phys.Rev.D 103 (2021) 5, 054502

For the first time in lattice QCD, a calculation has shown the presence of an exotic $1^{-+}$ state appearing as an unstable resonance. The result shows that the longstanding model-based proposal that such a state would couple more strongly to the $\pi b_1$ final-state than the lower-lying $\pi \eta, \pi \eta'$ and $\pi \rho$ final-states is confirmed. Possible implications for the recently observed $\pi_1$ experimental candidate state are discussed.

Correlated Dirac Eigenvalues and Axial Anomaly in Chiral Symmetric QCD

Phys. Rev. Lett. 126, 082001 (2021)

We introduce novel relations between derivatives of the Dirac eigenvalue spectrum with respect to the light sea quark mass and the $(n+1)$-point correlations among the eigenvalues of the massless Dirac operator. Using these relations we present LQCD results for the derivatives at light pion masses and at a temperature of about 1.6 times the chiral phase transition temperature. We find that eigenvalue density develops a peaked structure. We demonstrate that this phenomena is responsible for the manifestations of axial anomaly in two-point correlation functions of light scalar and pseudoscalar mesons. After continuum and chiral extrapolations we find that axial anomaly remains manifested in two-point correlation functions of scalar and pseudoscalar mesons in the chiral limit.

Lattice QCD constraints on the parton distribution functions of $3^{}{\rm He}_3$

Phys.Rev.Lett. 126 (2021) 20, 202001

The fraction of the longitudinal momentum of $3^{}{\rm He}_3$ that is carried by the isovector combination of $u$ and $d$ quarks is determined using lattice QCD for the first time. The ratio of this combination to that in the constituent nucleons is found to be consistent with unity at the few-percent level from calculations with quark masses corresponding to $m_\pi\sim 800$~MeV, extrapolated to the physical quark masses. This constraint is consistent with, and significantly more precise than, determinations from global nuclear parton distribution function fits. Including the lattice QCD determination of the momentum fraction in the nNNPDF global fitting framework results in the uncertainty on the isovector momentum fraction ratio being reduced by a factor of 2.5, and thereby enables a more precise extraction of the $u$ and $d$ parton distributions in $3^{}{\rm He}_3$.

Distillation based hadron matrix elements at high momentum

Phys.Rev.D 103 (2021) 3, 034502

Extraction of hadronic observables at finite momenta from LQCD is constrained by the well-known signal-to-noise problems afflicting all such LQCD calculations. In this work we extend the idea of momentum-smearing by exploring modifications to the distillation framework. Together with enhanced time slice sampling and expanded operator bases engendered by distillation, we find ground-state nucleon energies can be extracted reliably for $\vec{p}\le 3$ GeV and matrix elements featuring a large momentum dependence can be resolved.

Three-pion scattering amplitude selected as an Editor's suggestion

Phys.Rev.Lett. 126 (2021) 012001

For the first time in lattice QCD, a three-hadron scattering amplitude has been determined using a general workflow that does not make use of model assumptions or a perturbative expansion. Focusing on the maximum isospin three-pion channel ($\pi^+ \pi^+ \pi^+ \to \pi^+ \pi^+ \pi^+$) the calculation uses a relativistic finite-volume formalism to relate lattice energies to the physical scattering amplitude. The work has been published in Phys.Rev.Lett. as an Editor’s Suggestion.

Parton Physics from a Heavy-Quark Operator Product Expansion: I. Formalism and Wilson Coefficients

Phys.Rev.D 104 (2021) 7, 074511

Parton distribution functions (PDFs) and light-cone distribution amplitudes (LCDAs) are central non-perturbative objects of interest in high-energy inelastic and elastic scattering, resp. As a result, an ab-initio determination of these objects is highly desirable. In this paper we present theoretical details required for the calculation of the moments of the PDF and LCDA using a heavy-quark operator product expansion method. This article also provides results of the relevant Wilson coefficients for the unpolarized PDF, helicity PDF and meson LCDA which are an essential ingredient in this approach. In addition, we discuss the use of our method to determine the dependence on the parton momentum fraction

Pion Valence Quark Distribution from Current-Current Correlation in Lattice QCD

Phys.Rev.D 102 (2020) 5, 054508

We extract the pion valence quark distribution $q^v_\pi(x)$ from LQCD calculated matrix elements of spacelike correlations of one vector and one axial vector current analyzed in terms of QCD collinear factorization, using a new short-distance matching coefficient calculated to one-loop accuracy. We derive the Ioffe time distribution of the two-current correlations in the physical limit by investigating the finite lattice spacing, volume, quark mass, and higher-twist dependencies in a simultaneous fit of matrix elements computed on four gauge ensembles. We find remarkable consistency between our extracted $q^v_\pi(x)$ and that obtained from experimental data across the entire x range. This justifies that LQCD-calculated current-current correlations are good observables for extracting partonic structures by using QCD factorization, which complements to the global effort to extract partonic structure from experimental data.

ASCR/NP SciDAC LQCD project

project presentation at the 2019 SciDAC PI meeting

We review the goals and progress of the LQCD SciDAC project

MG Proto: A Multigrid Solver for x86 multicore Systems

poster presented at the 2019 SciDAC PI meeting

Adaptive Aggregation based multi-grid (MG) methods are becoming the standard for solvers in both propagator calculations and recently even in the gauge generation parts of Lattice QCD calculations with Wilson Clover Fermions. This poster describes a new effort to develop such methods for Intel Knights Land and Skylake short-vector based architectures.

Motivation: quarkonium suppression in a thermal bath of quark-gluon plasma

poster presented at the 2019 SciDAC PI meeting

Protons and neutrons, which are made up from mainly light quarks and gluons, have frozen out at t ≈ 0.3 μs. Before the freezeout light quarks and gluons had formed a quark-gluon plasma (an almost perfect fluid). Heavy quarks, travel as bound states or individually through the surrounding quark-gluon plasma. This poster describes a project to compute the spectral functions of heavy quarks through anisotropic lattices.

Performance of Staggered Fermion Kernels using Grid

poster presented at the 2019 SciDAC PI meeting

A major focus of the Beam Energy Scan II program at Brookhaven National Lab is mapping the phase boundary of quarks and gluons. Lattice QCD methods are used to map this boundary. An important part of the computational work is the solution of the Staggered fermiom Dirac-equation, a large sparse linear system of equations within a background field, is required for a large number of right-hand sides. Results are presented for highly optimized, performance portable, implementations across Skylake and GPU platforms.

Accelerating Gauge Generation for Lattice QCD on Summit

poster presented at the 2019 SciDAC PI meeting

Recent algorithmic improvements have significantly gauge generation in lattice QCD calculations. This poster presents there are more improvements possible, and describes steps to realize this potential.

Accelerating LQCD Calculations Using the Tiramisu Compiler

poster presented at the 2019 SciDAC PI meeting

The Tiramisu compiler provides a simple C++ API to express tensor operations and provides a large set of optimizations to provide high performance on a diverse set of architectures. The compiler is used to accelerate key components of lattice QCD workflows.

Lattice Quantum Chromodynamics Project SciDAC

talk presented at the 2019 SciDAC PI meeting

We describe the LQCD SciDAC project, and describe the science goals. Highlights are shown that illustrate progress towards these goals.

Sparsified Correlator Construction

presented at Lattice 2019

Developed a new method to sparsify nuclei operator constructions allowing for calculations in the physical limit of QCD with up to atomic number of 4 (helium)

Tiramisu and Halide

presented at Lattice 2019

The computation of quark propagators and tying them together to form Euclidean correlation functions is an important and computationally extensive component of the LQCD nuclear physics program. Extensions of the DSL framework Tiramisu and Halide have been used to implement LQCD software. A Tiramisu based version of the baryon block algorithm for multi-nucleon systems is 90x faster than the reference version.

QCD Phase Boundary

Phys. Lett. B795 (2019) 15

The pseudo-critical chiral cross-over temperatures have been determined at zero and non-zero values of baryon, strangeness, electric charge and isospin chemical potentials

An LLVM-based DSL Framework for LQCD

PhD thesis of Diptorup Deb, May 2019

QUARC represents the application to LQCD of methods for implementing statically compiled data parallel domain-specific programming languages. In QUARC, a domain-specific extension to C++ is defined using template meta-programming. Unlike other approaches in which template expansion is used to perform localized code and loop instantiation in the compiler front end, the instantiated templates are not meant to be compiled into executable code using a standard compiler, rather they are used to pass high-level abstract constructs and attributes of those constructs transparently through a standard compiler front-end.

Novel Lattice QCD Calculation Approach using Machine Learning

Phys. Rev. D100 (2019) 014504

A novel technique using machine learning to reduce the computational cost of evaluating lattice quantum chromodynamics (LQCD) observables is developed.

Machine learning action parameters in LQCD

Phys. Rev. D97 (2018) 094506

Machine learning has been applied to the problem of parametric regression of generated lattice datasets.

Lattice Quantum Chromodynamics Project SciDAC

talk presented at the 2018 SciDAC PI meeting

We describe the LQCD SciDAC project, and describe the science goals. Highlights are shown that illustrate progress towards these goals.

Accelerating Gauge Generation for QCD on GPUs

SciDAC Highlight

Gauge generation is the first critical step in lattice QCD calculations. Recently, improved algorithms have significantly accelarated these calculations on GPU systems.

$f_0$ and $f_2$ resonances paper selected as "Editors' Suggestion" in PRD

Phys. Rev. D97 (2018) 054513

A calculation of coupled $\pi\pi$, $K\overline{K}$, $\eta\eta$ scattering at heavier than physical light quark masses has been selected by the Editors to appear on the front-page of the PRD website. The results of the calculation show that in the scalar sector a stable $\sigma$-like state appears, along with an $f_0(980)$-like resonance appearing at the $K\overline{K}$ threshold, while in the tensor sector, two resonances are observed, one decaying dominantly into $\pi\pi$ and the other into $K\overline{K}$.

First lattice QCD study of the gluonic structure of light nuclei

Phys. Rev. D96 (2017) 094512

The of gluons in the structure of the nucleon and light nuclei is investigated using lattice Quantum Chromodynamics (QCD) calculations. The first moment of the gluon transversity structure function is investigated in the spin-1 deuteron, where a nonzero signal is observed. This is the first indication of gluon contributions to nuclear structure that can not be associated with an individual nucleon.

Using Supercomputers to Delve Ever Deeper into the Building Blocks of Matter

Brookhaven National Lab Features, 2017-10-18

Scientists to develop next-generation computational tools for studying interactions of quarks and gluons in hot, dense nuclear matter

Exploring the Exotic World of Quarks and Gluons at the Dawn of the Exascale

Jefferson Lab Highlights, 2017-10-11

Jefferson Lab leads development of next-generation software to benefit nuclear physics computation. An award was recently announced by DOE’s Office of Nuclear Physics and the Office of Advanced Scientific Computing Research in the Office of Science. It will provide $8.25 million for the “Computing the Properties of Matter with Leadership Computing Resources” research project.