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At least 1,405 records · Page 78
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DOE OSTI2021

Nucleon mass with highly improved staggered quarks

We present the first computation in a program of lattice-QCD baryon physics using staggered fermions for sea and valence quarks. For this initial study, we present a calculation of the nucleon mass, obtaining 964 ±16 MeV with all sources of statistical and systematic errors controlled and accounted for. This result is the most precise determination to date of the nucleon mass from first principles. We use the highly improved staggered quark action, which is computationally efficient. Three gluon ensembles are employed, which have approximate lattice spacings 𝑎 ≈ 0.09, 0.12, and 0.15 fm, each with equal-mass 𝑢/𝑑, 𝑠, and 𝑐 quarks in the sea. Further, all ensembles have the light valence and sea 𝑢/𝑑 quarks tuned to reproduce the physical pion mass, avoiding complications from chiral extrapolations. Our work opens a new avenue for precise calculations of baryon properties, which are both feasible and relevant to experiments in particle and nuclear physics.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Updated analyses of gluon distribution functions for the pion and kaon from the gauge-invariant nonlocal chiral quark model

In this work, we investigate the gluon distribution functions for the pion and kaon, in addition to the improved result of the valence-quark ones, in the gauge-invariant nonlocal chiral-quark model, in which the momentum dependence of the quark interactions is properly taken into account. We then analyze the gluon distribution functions, generated dynamically through the splitting functions in the Dokshitzer-Gribov-Lipatov-Altarelli-Parisi QCD evolution. By comparing with the recent lattice QCD results and Jefferson Lab angular momentum global analyses, it is found that the present numerical results for the gluon parton distribution functions for the pion exhibit a good agreement and the valence up-quark distribution results for the pion by reproducing the reanalyzed experimental data with a remarkable agreement. Our prediction on the gluon distribution functions for the kaon is also consistent with the recent lattice data for the kaon within the errors. Published by the American Physical Society 2024

Hutauruk, Parada. T. P. (ORCID:0000000242257109)↗
DOE OSTI2024

Up and down quark structure of the proton

We report an improved measurement of the valence u and d quark distributions from the forward-backward asymmetry in the Drell-Yan process using 8.6 fb − 1 of data collected with the D0 detector in p p ¯ collisions at s = 1.96 . This analysis provides the values of new structure parameters that are directly related to the valence up and down quark distributions in the proton. In other experimental results measuring the quark content of the proton, d quark contributions are mixed with those from other quark flavors. In this measurement, the u and d quark contributions are separately extracted by applying a factorization of the QCD and electroweak portions of the forward-backward asymmetry. Published by the American Physical Society 2024

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Kaon BSM B -parameters using improved staggered fermions from N f = 2 + 1 unquenched QCD

In this paper, we present results for the matrix elements of the additional ΔS = 2 operators that appear in models of physics beyond the Standard Model (BSM), expressed in terms of four BSM B -parameters. Combined with experimental results for ΔM K and ε K , these constrain the parameters of BSM models. We use improved staggered fermions, with valence hypercubic blocking transfromation (HYP)-smeared quarks and N f = 2 + 1 flavors of “asqtad” sea quarks. The configurations have been generated by the MILC Collaboration. The matching between lattice and continuum four-fermion operators and bilinears is done perturbatively at one-loop order. We use three lattice spacings for the continuum extrapolation: a ≈ 0.09 , 0.06 and 0.045 fm. Valence light-quark masses range down to ≈ m$phys\atop{s}$ /13 while the light sea-quark masses range down to ≈ m$phys\atop{s}$ / 20 . Compared to our previous published work, we have added four additional lattice ensembles, leading to better controlled extrapolations in the lattice spacing and sea-quark masses. We report final results for two renormalization scales, μ = 2 and 3 GeV, and compare them to those obtained by other collaborations. Agreement is found for two of the four BSM B-parameters (B 2 and B$SUSY\atop{3}$ ). The other two (B 4 and B 5 ) differ significantly from those obtained using regularization independent momentum subtraction (RI-MOM) renormalization as an intermediate scheme, but are in agreement with recent preliminary results obtained by the RBC-UKQCD Collaboration using regularization independent symmetric momentum subtraction (RI-SMOM) intermediate schemes.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Study of decuplet baryon resonances from lattice QCD

Here, a lattice QCD study of the strong decay width and coupling constant of decuplet baryons to an octet baryon-pion state is presented. The transfer matrix method is used to obtain the overlap of lattice states with decuplet baryon quantum numbers on the one hand and octet baryon-pion quantum numbers on the other as an approximation of the matrix element of the corresponding transition. By making use of leading-order effective field theory, the coupling constants as well as the widths for the various decay channels are determined. The transitions studied are Δ → π N , Σ* → Λπ, Σ* → Σπ and Ξ* → Ξπ. We obtain results for two ensembles of N f = 2 + 1 dynamical fermion configurations: one using domain wall valence quarks on a staggered sea at a pion mass of 350 MeVand a box size of 3.4 fm and a second one using domain wall sea and valence quarks at pion mass 180 MeV and box size 4.5 fm.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

Microscopic Theory of Resonant Soft-X-Ray Scattering in Materials with Charge Order: The Example of Charge Stripes in High-Temperature Cuprate Superconductors

In this work, we present a microscopic theory of resonant soft-x-ray scattering that accounts for the delocalized character of valence electrons. Unlike past approaches based on local form factors, our functional determinant method treats realistic band structures. This method builds upon earlier theoretical work in mesoscopic physics and accounts for excitonic effects as well as the orthogonality catastrophe arising from interaction between the core hole and the valence band electrons. We show that the two-peak structure observed near the O K edge of stripe-ordered La 1.875 Ba 0.125 CuO 4 is due to dynamical nesting within the canonical cuprate band structure. Our results provide evidence for reasonably well-defined, high-energy quasiparticles in cuprates and establish resonant soft-x-ray scattering as a bulk-sensitive probe of the electron quasiparticles.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2014

Ab-initio coupled-cluster effective interactions for the shell model: Application to neutron-rich oxygen and carbon isotopes

We derive and compute effective valence-space shell-model interactions from ab initio coupled-cluster theory and apply them to open-shell and neutron-rich oxygen and carbon isotopes. Our shell-model interactions are based on nucleon-nucleon and three-nucleon forces from chiral effective-field theory. We compute the energies of ground and low-lying states, and find good agreement with experiment. In particular, our computed 2 + states are consistent with N=14,16 shell closures in 22,24 O, and a weaker N=14 shell closure in 20 C. We find good agreement between our coupled-cluster effective-interaction results with those obtained from standard single-reference coupled-cluster calculations for up to eight valence neutrons.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Electromagnetic Moments of Radioactive 136 Te and the Emergence of Collectivity 2p ⊕ 2n outside of Double-Magic 132 Sn

Radioactive 136 Te has two valence protons and two valence neutrons outside of the 132 Sn double shell closure, providing a simple laboratory for exploring the emergence of collectivity and nucleon- nucleon interactions. Coulomb excitation of 136 Te on a titanium target was utilized to determine an extensive set of electromagnetic moments for the three lowest-lying states, including B(E2;0$+\atop{1}$→ 2$+\atop{1}$ ), Q(2$+\atop{1}$ ), and g(2$+\atop{1}$ ). The results indicate that the first-excited state, 2$+\atop{1}$ , composed of the simple 2p ⊕ 2n system, is prolate deformed, and its wave function is dominated by neutron degrees of freedom, but not to the extent previously suggested. It is demonstrated that extreme sensitivity of g(2$+\atop{1}$) to the proton and neutron contributions to the wave function provides unique insight into the nature of emerging collectivity, and g(2$+\atop{1}$ ) was used to differentiate among several state-of-the-art theoretical calculations. Finally, our results are best described by the most recent shell model calculations.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2017

Glue Spin and Helicity in the Proton from Lattice QCD

We report the first lattice QCD calculation of the glue spin in the nucleon. The lattice calculation is carried out with valence overlap fermions on 2+1 flavor DWF gauge configurations on four lattice spacings and four volumes including an ensemble with physical values for the quark masses. The glue spin S_G in the Coulomb gauge in the MSbar scheme is obtained with the 1-loop perturbative matching. We find the results fairly insensitive to lattice spacing and quark masses. We also find that the proton momentum dependence of S_G in the range 0≤|p|<1.5 GeV is very mild, and we determine it in the large momentum limit to be S_G= 0.251(47)(16) at the physical pion mass in the MSbar scheme at μ^2= 10 GeV^2. If the matching procedure in large momentum effective theory is neglected, S_G is equal to the glue helicity measured in high-energy scattering experiments.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Electron and Nucleon Localization Functions of Oganesson: Approaching the Thomas-Fermi Limit

Fermion localization functions are used to discuss electronic and nucleonic shell structure effects in the superheavy element oganesson, the heaviest element discovered to date. Spin-orbit splitting in the 7p electronic shell becomes so large (~10 eV) that Og is expected to show uniform-gas-like behavior in the valence region with a rather large dipole polarizability compared to the lighter rare gas elements. The nucleon localization in Og is also predicted to undergo a transition to the Thomas-Fermi gas behavior in the valence region. Finally, this effect, particularly strong for neutrons, is due to the high density of single-particle orbitals.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2018

X-Ray Sum Frequency Diffraction for Direct Imaging of Ultrafast Electron Dynamics

X-ray diffraction from molecules in the ground state produces an image of their charge density, and time-resolved x-ray diffraction can thus monitor the motion of the nuclei. However, the density change of excited valence electrons upon optical excitation can barely be monitored with regular diffraction techniques due to the overwhelming background contribution of the core electrons. We present a nonlinear x-ray technique made possible by novel free electron laser sources, which provides a spatial electron density image of valence electron excitations. The technique, sum frequency generation carried out with a visible pump and a broadband x-ray diffraction pulse, yields snapshots of the transition charge densities, which represent the electron density variations upon optical excitation. The technique is illustrated by ab initio simulations of transition charge density imaging for the optically induced electronic dynamics in a donor or acceptor substituted stilbene.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

Antidoping in Insulators and Semiconductors Having Intermediate Bands with Trapped Carriers

Ordinary doping by electrons (holes) generally means that the Fermi level shifts towards the conduction band (valence band) and that the conductivity of free carriers increases. Recently, however, some peculiar doping characteristics were sporadically recorded in different materials without noting the mechanism: electron doping was observed to cause a portion of the lowest unoccupied band to merge into the valance band, leading to a decrease in conductivity. This behavior, that we dub as “antidoping,” was seen in rare-earth nickel oxides SmNiO 3 , cobalt oxides SrCoO 2.5 , Li-ion battery materials, and even MgO with metal vacancies. We describe the physical origin of antidoping as well as its inverse problem—the “design principles” that would enable an intelligent search of materials. We find that electron antidoping is expected in materials having preexisting trapped holes and is caused by the annihilation of such “hole polarons” via electron doping. Finally, this may offer an unconventional way of controlling conductivity.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Distinguishing Quarks and Gluons in Pion and Kaon PDFs

The leading-twist parton distribution functions of the pion and kwon are calculated for the first time using a rainbow-ladder truncation of QCD's Dyson-Schwinger equations (DSEs) that self-consistently sums all planar diagrams. The nonperturbative gluon dressing of the quarks is thereby correctly accounted for, which in practice means solving the inhomogeneous Bethe-Salpeter equation (BSE) for the quark operator that defines the spin-independent quark distribution functions. An immediate consequence of using this dressed vertex is that gluons carry 35% of the pion's and 30% of the kaon's light-cone momentum, with the remaining momentum carried by the quarks. The scale associated with these DSE results is μ 0 = 0.78 GeV. The gluon effects generated by the inhomogeneous BSE are inherently nonperturbative and cannot be mimicked by the perturbative QCD evolution equations. A key consequence of this gluon dressing is that the valence quarks have reduced support at low-to-intermediate x, where the gluons dominate, and increased support at large x. As a result, our DSE calculation of the pion's valence quark distribution is in excellent agreement with the Conway et al. pion-induced Drell-Yan data, but nevertheless exhibits the q π (x) similar or equal to (1 - x) 2 behavior as x -> 1 predicted by perturbative QCD.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Emergent Glassy Behavior in a Kagome Rydberg Atom Array

Here, we present large-scale quantum Monte Carlo simulation results on a realistic Hamiltonian of kagome-lattice Rydberg atom arrays. Although the system has no intrinsic disorder, intriguingly, our analyses of static and dynamic properties on large system sizes reveal emergent glassy behavior in a region of parameter space located between two valence bond solid phases. The extent of this glassy region is demarcated using the Edwards-Anderson order parameter, and its phase transitions to the two proximate valence bond solids—as well as the crossover towards a trivial paramagnetic phase—are identified. We demonstrate the intrinsically slow (imaginary) time dynamics deep inside the glassy phase and discuss experimental considerations for detecting such a quantum disordered phase with numerous nearly degenerate local minima. Our proposal paves a new route to the study of real-time glassy phenomena and highlights the potential for quantum simulation of a distinct phase of quantum matter beyond solids and liquids in current-generation Rydberg platforms.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2024

Electron Glass Phase with Resilient Zhang-Rice Singlets in LiCu 3 ⁢O 3

LiCu 3 ⁢O 3 is an antiferromagnetic mixed valence cuprate where trilayers of edge-sharing Cu(II)O (3⁢d 9 ) are sandwiched in between planes of Cu(I) (3⁢d 10 ) ions, with Li stochastically substituting Cu(II). Angle-resolved photoemission spectroscopy (ARPES) and density functional theory reveal two insulating electronic subsystems that are segregated in spite of sharing common oxygen atoms: a Cu d z 2 /O p z derived valence band (VB) dispersing on the Cu(I) plane, and a Cu 3⁢d x 2 -y 2 /O 2⁢p x,y derived Zhang-Rice singlet (ZRS) band dispersing on the Cu(II)O planes. First-principle analysis shows the Li substitution to stabilize the insulating ground state, but only if antiferromagnetic correlations are present. Li further induces substitutional disorder and a 2D electron glass behavior in charge transport, reflected in a large 530 meV Coulomb gap and a linear suppression of VB spectral weight at E F that is observed by ARPES. Surprisingly, the disorder leaves the Cu(II)-derived ZRS largely unaffected. Finally, this indicates a local segregation of Li and Cu atoms onto the two separate corner-sharing Cu⁡(II)⁢O 2 sub-lattices of the edge-sharing Cu(II)O planes, and highlights the ubiquitous resilience of the entangled two hole ZRS entity against impurity scattering.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗