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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.
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Science highligths of US DOE Office of Science, Office of Nuclear Physics - 2024
New theory-based approach gives access to quarks’ tiny transverse motion within protons.
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Jefferson Lab Highlight - 2024
Nuclear physicists have long been working to reveal how the proton gets its spin. Now, a new method that combines experimental data with state-of-the-art calculations has revealed a more detailed picture of spin contributions from the very glue that holds protons together. It also paves the way toward imaging the protons 3D structure.
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PHYS ORG - 2023
Theorists predict differential distribution of 'up' and 'down' quarks within protons---and differential contributions to proton's properties.
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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.
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HPC Wire - 2022
Efforts to harness the power of supercomputers to better understand the hidden worlds inside the nucleus of the atom recently received a big boost.
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The Register - 2022
If todays tech gets you down, remember supercomputers are still being used for scientific progress
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Jefferson Lab Highlight - 2022
Scientists at Jefferson Lab and William and Mary developed MemHC to improve the efficiency of supercomputer calculations
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Jefferson Lab Highlight - 2022
Jefferson Lab and its partners benefit from Scientific Discovery through Advanced Computing Partnership in Nuclear Physics grants
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DOE Office of Science Highlight - 2022
The goal of nuclear physics is to describe all matter from its simplest building blocks: quarks and gluons. Found deep inside protons and neutrons, quarks and gluons also combine in less common configurations to make other subatomic particles of matter. For scientists, producing these less-common particles in experiments is an interesting challenge. A new theory method aids in those efforts by predicting which less-common particles an experiment will produce.
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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.
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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.
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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 $3^{}{\rm He}_3$.
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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.
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NERSC Highlight, 2019-07-08
For the first time, lattice QCD calculations run at NERSC
allowed nuclear physicists to determine the pressure
distribution inside a proton, taking into account the
contributions of the proton’s fundamental particles: quarks and
gluons. This discovery brings nuclear scientists closer to a
complete understanding of a proton’s structure and the
fundamental particles that make up most of the visible matter in
the universe.
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SciDAC Highlight, 2019-05-16
A new multi-grid implementation for x86 architectures with supporting AVX512 instructions, such as
Intel Xeon Phi Knight's Landing, and Xeon Servers (Skylake and beyond) speeds up calculations by 7x-8x
accelerating calculations on platforms such as NERSC Cori KNL, ALCF Theta, TACC Stampede 2 and the
Jefferson Lab SciPhi Cluster.
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OLCF Highlight, 2018-09-17
The accelerated architecture of America’s fastest supercomputer boosts QCD simulations
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SciDAC Highlight, 2018-05-01
The generation of gauge configurations (samples of the strong force
field in the vacuum) is the gating first step of nuclear and
high energy physics calculations using lattice quantum
chromodynamics (LQCD) generating the data on which subsequent
calculations depend.
Here, we demonstrate a 73x reduction in the GPU-hours required for the generation of such gauge fields
moving from Titan to Summit, and incorporating new algorithms
well suited to the new system. The improvement on Summit enables calculations which where hitherto considered out-of reach for reasons of computational cost, and will fundamentally re-shape how we will conduct our scientific campaigns in the future.
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