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DOE OSTI2017

New Results on Short-Range Correlations in Nuclei

Nuclear dynamics at short distances is one of the most fascinating topics of strong interaction physics. The physics of it is closely related to the understanding of the role of the QCD in generating nuclear forces at short distances, as well as of the dynamics of the superdense cold nuclear matter relevant to the interior of neutron stars. The emergence of high-energy electron and proton beams has led to significant recent progress in high-energy nuclear scattering experiments investigating the short-range structure of nuclei. These experiments, in turn, have stimulated new theoretical studies resulting in the observation of several new phenomena specific to the short-range structure of nuclei. In this article, we review recent theoretical and experimental progress in studies of short-range correlations in nuclei and discuss their importance for advancing our understanding of the dynamics of nuclear interactions at short distances.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2016

The Role of Citric Acid in Perfecting Platinum Monolayer on Palladium Nanoparticles during the Surface Limited Redox Replacement Reaction

Cu-mediated-Pt-displacement method that involves the displacement of an underpotentially deposited (UPD) Cu monolayer by Pt has been extensively studied to prepare core-shell catalysts. It has been found that Pt clusters instead of a uniform Pt monolayer were formed in the gram batch synthesis. With a suitable surfactant, such as citric acid, the Pt shell could be much more uniform. In this study, the role of citric acid in controlling the Cu-Pt displacement reaction kinetics was studied by electrochemical techniques and theoretical approaches. It was found that citric acid strongly adsorbed on Pd, Pt, Cu/Pd, and Pt/Pd surfaces, especially in the double layer region in acid solutions. The strong adsorption of citric acid slowed down the Cu-Pt displacement reaction. The main characteristics of such strong interaction most likely arises from the OH groups in the citric acid molecule according to the molecular dynamics simulation results.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2024

Bulk Viscosity in Dense Nuclear Matter

NEUTRON star mergers are an extreme environment where, within milliseconds, the cold, dense matter in neutron stars is dramatically heated to some of the hottest temperatures encountered in astrophysics. Matter in neutron star mergers is located solidly in the interior of the QCD phase diagram, and therefore, the observation and simulation of these mergers provides an opportunity to learn about the strong interaction at a set of densities and temperatures that compliment those obtained in relativistic heavy-ion collisions. Matter during the merger of two neutron stars is far from hydrostatic equilibrium, allowing for the study of not only the equation of state of dense matter, but of transport properties as well. Perhaps the most likely transport property to play a role in neutron star mergers is the bulk viscosity, which acts to resist changes in density. Furthermore, the bulk viscosity of matter at high densities has long been anticipated to damp oscillations in isolated neutron stars, and the study of its role in neutron star mergers is just beginning.

Harris, Steven P.↗

DOE OSTI2020

On-demand indistinguishable single photons from an efficient and pure source based on a Rydberg ensemble

Single photons coupled to atomic systems have shown to be a promising platform for developing quantum technologies. Yet a bright on-demand, highly pure, and highly indistinguishable single-photon source compatible with atomic platforms is lacking. In this work, we demonstrate such a source based on a strongly interacting Rydberg system. The large optical nonlinearities in a blockaded Rydberg ensemble convert coherent light into a single collective excitation that can be coherently retrieved as a quantum field. We simultaneously observe a fully single-mode (spectral, temporal, spatial, and polarization) efficiency up to 0.098(2), a detector-background-subtracted g ( 2 ) = 5.0 ( 1.6 ) × <#comment/> 10 − <#comment/> 4 , and indistinguishability of 0.980(7), at an average photon production rate of 1.18 ( 2 ) × <#comment/> 10 4 s − <#comment/> 1 . All of these make this system promising for scalable quantum information applications. Furthermore, we investigate the effects of contaminant Rydberg excitations on the source efficiency and observed single-mode efficiencies up to 0.18(2) for lower photon rates. Finally, recognizing that many quantum information protocols require a single photon in a fully single mode, we introduce metrics that take into account all degrees of freedom to benchmark the performance of on-demand sources.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2024

Insight into emergence of hadron mass from N * electroexcitation amplitudes

The emergence of hadron mass represents one of the most challenging and still open problems in contemporary hadron physics. The results on the nucleon resonance electroexcitation amplitudes available from the CLAS data on πN and π + π – p electroproduction analyzed within the continuum Schwinger method open up a new avenue for gaining insight into the strong interaction dynamics that are responsible for the generation of the dominant part of hadron mass. Future prospects of these studies in experiments of the 12 GeV era with CLAS12 and after a potential increase of the CEBAF energy up to 22 GeV will offer a unique opportunity to explore the full range of distances where the dominant part of hadron mass and N* structure emerge from QCD.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2018

A invenção dos pártons

The invention of partons by Richard Feynman was one of his most important contributions to modern particle physics. The parton model appears at a critical moment characterized by the polarization of particle physics in two opposing schools of thought: on the one hand, the so called nuclear democracy, postulating that all hadrons are equally fundamental and on the other hand a school of thought that was starting to form around the idea of quarks and their use at first, not as fundamental constituents of hadrons, but rather as mathematical entities reflecting the internal symmetries of an underlying quantum field theory (QFT) for the strong interaction, at that point still unknown. The parton model rapidly became an important tool in the construction of this QFT, named Quantum Chromodynamics, helping to promote quarks from mathematical entities to fundamental constituents of the hadrons.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2024

Electron Cooling in NICA Acceleration Complex

The Nuclotron-based Ion Collider fAcility (NICA) is under assembling at JINR. NICA will provide colliding beams for study of hot strongly interacting baryonic matter and spin physics. The NICA injection complex includes a tandem of 2 superconducting synchrotrons: Booster (up to 600 MeV/u) and Nuclotron (up 3.9 GeV/u fully stripped heavy ions). Since the start of injection complex commissioning in 2020 its four Runs were carried out. To the present time the beams of He, Fe, C and Xe were accelerated. Booster electron cooling was first used for cooling of continuous Fe¹⁴⁺ beam at the energy of 3.2 MeV/u in Run II. In the last Run we demonstrated longitudinal cooling of Xe²⁸⁺ in the presence of RF voltage at the Booster injection energy. This regime is required for accumulation in Booster the intensity required for Collider operation. The cooling enabled a 2 times intensity increase of slow extracted beam from Nuclotron. Optimization of Booster electron cooling for beam accumulation will be carried out in the next Run. Another (high voltage) electron cooling system will be used in the NICA Collider rings for ion accumulation in a barrier bucket and consecutive bunch formation.

43 PARTICLE ACCELERATORS↗

DOE OSTI2021

Learning the ground state of a non-stoquastic quantum Hamiltonian in a rugged neural network landscape

Strongly interacting quantum systems described by non-stoquastic Hamiltonians exhibit rich low-temperature physics. Yet, their study poses a formidable challenge, even for state-of-the-art numerical techniques. Here, we investigate systematically the performance of a class of universal variational wave-functions based on artificial neural networks, by considering the frustrated spin- 1/2 1 / 2 J_1-J_2 J 1 − J 2 Heisenberg model on the square lattice. Focusing on neural network architectures without physics-informed input, we argue in favor of using an ansatz consisting of two decoupled real-valued networks, one for the amplitude and the other for the phase of the variational wavefunction. By introducing concrete mitigation strategies against inherent numerical instabilities in the stochastic reconfiguration algorithm we obtain a variational energy comparable to that reported recently with neural networks that incorporate knowledge about the physical system. Through a detailed analysis of the individual components of the algorithm, we conclude that the rugged nature of the energy landscape constitutes the major obstacle in finding a satisfactory approximation to the ground state wavefunction, and prevents learning the correct sign structure. In particular, we show that in the present setup the neural network expressivity and Monte Carlo sampling are not primary limiting factors.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2023

A time-dependent momentum-resolved scattering approach to core-level spectroscopies

While new light sources allow for unprecedented resolution in experiments with X-rays, a theoretical understanding of the scattering cross-section is lacking. In the particular case of strongly correlated electron systems, numerical techniques are quite limited, since conventional approaches rely on calculating a response function (Kramers-Heisenberg formula) that is obtained from a perturbative analysis of scattering processes in the frequency domain. This requires a knowledge of a full set of eigenstates in order to account for all intermediate processes away from equilibrium, limiting the applicability to small tractable systems. In this work, we present an alternative paradigm, recasting the problem in the time domain and explicitly solving the time-dependent Schrödinger equation without the limitations of perturbation theory: a faithful simulation of the scattering processes taking place in actual experiments, including photons and core electrons. We show how this approach can yield the full time and momentum resolved Resonant Inelastic X-Ray Scattering (RIXS) spectrum of strongly interacting many-body systems. We demonstrate the formalism with an application to Mott insulating Hubbard chains using the time-dependent density matrix renormalization group method, which does not require a priory knowledge of the eigenstates and can solve very large systems with dozens of orbitals. This approach can readily be applied to systems out of equilibrium without modification and generalized to other spectroscopies.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2022

A comprehensive guide to the physics and usage of PYTHIA 8.3

This manual describes the Pythia event generator, the most recent version of an evolving physics tool used to answer fundamental questions in particle physics. The program is most often used to generate high-energy-physics collision “events”, i.e. sets of particles produced in association with the collision of two incoming high-energy particles, but has several uses beyond that. The guiding philosophy is to produce and re-produce properties of experimentally obtained collisions as accurately as possible. The program includes a wide ranges of reactions within and beyond the Standard Model, and extending to heavy ion physics. Emphasis is put on phenomena where strong interactions play a major role. The manual contains both pedagogical and practical components. All included physics models are described in enough detail to allow the user to obtain a cursory overview of used assumptions and approximations, enabling an informed evaluation of the program output. A number of the most central algorithms are described in enough detail that the main results of the program can be reproduced independently, allowing further development of existing models or the addition of new ones. Finally, a chapter dedicated fully to the user is included towards the end, providing pedagogical examples of standard use cases, and a detailed description of a number of external interfaces. The program code, the online manual, and the latest version of this print manual can be found on the Pythia web page: https://www.pythia.org/.

Bierlich, Christian↗

DOE OSTI2022

Codebase release 8.3 for PYTHIA

Bierlich, Christian↗

DOE OSTI2019

The history of the muon (g-2) experiments

I discuss the history of the muon (g-2) ( g − 2 ) measurements, beginning with the Columbia-Nevis measurement that observed parity violation in muon decay, and also measured the muon g g -factor for the first time, finding g_\mu=2 g μ = 2 . The theoretical (Standard Model) value contains contributions from quantum electrodynamics, the strong interaction through hadronic vacuum polarization and hadronic light-by-light loops, as well as the electroweak contributions from the W W , Z Z and Higgs bosons. The subsequent experiments, first at Nevis and then with increasing precision at CERN, measured the muon anomaly a_\mu = (g_\mu-2)/2 a μ = ( g μ − 2 ) / 2 down to a precision of 7.3 parts per million (ppm). The Brookhaven National Laboratory experiment E821 increased the precision to 0.54 ppm, and observed for the first time the electroweak contributions. Interestingly, the value of a_\mu a μ measured at Brookhaven appears to be larger than the Standard Model value by greater than three standard deviations. A new experiment, Fermilab E989, aims to improve on the precision by a factor of four, to clarify whether this result is a harbinger of new physics entering through loops, or from some experimental, statistical or systematic issue.

Roberts, B. Lee↗

DOE OSTI2022

Nuclear matter effects on jet production at electron-ion colliders

In these proceedings we report recent progress on understanding hadron and jet production in electron-nucleus collisions at the future Electron-Ion Collider [1,2]. These processes will play an essential role in the exploration of the partonic structure of nuclei and the study of parton shower evolution in strongly-interacting matter. We employ the framework of soft-collinear effective theory, generalized to include in-medium interactions, to present the first theoretical results for inclusive hadron and jet cross sections, as well as the jet charge modification in deep inelastic scattering on nuclei. We further demonstrate how to separate initial-state and final-state effects.

Li, Hai Tao↗

DOE OSTI2015

Thermal Conductivity and Thermopower near the 2D Metal-Insulator transition, Final Technical Report

STUDIES OF STRONGLY-INTERACTING 2D ELECTRON SYSTEMS – There is a great deal of current interest in the properties of systems in which the interaction between electrons (their potential energy) is large compared to their kinetic energy. We have investigated an apparent, unexpected metal-insulator transition inferred from the behavior of the temperature-dependence of the resistivity; moreover, detailed analysis of the behavior of the magnetoresistance suggests that the electrons’ effective mass diverges, supporting this scenario. Whether this is a true phase transition or crossover behavior has been strenuously debated over the past 20 years. Our measurements have now shown that the thermoelectric power of these 2D materials diverges at a finite density, providing clear evidence that this is, in fact, a phase transition to a new low-density phase which may be a precursor or a direct transition to the long sought-after electronic crystal predicted by Eugene Wigner in 1934.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2015

Studies of the Quark and Gluon Structure of Nuclear and Hadronic Matter

DOE award DE-FG02-00ER41135 started in 2000 and terminated in November of 2014. Project goals were established in two broad areas: hadron phenomenology and formalism related to QCD and strongly interacting field theory. Substantial progress was made in both areas, despite the disruption in research direction that followed the discovery of the novel state, X(3872). A chronological list of specific research goals listed in the various proposals and their outcomes follows.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2015

Adsorptive Separation and Sequestration of Krypton, I and C14 on Diamond Nanoparticles

The objective of this research proposal was to address the separation and sequestration of Kr and I from each other using nano-sized diamond particles and retaining these in diamond until they decay to the background level or can be used as a byproduct. Following removal of Kr and I, an adsorbent will be used to adsorb and store CO 2 from the CO 2 rich stream. A Field Enhanced Diffusion with Optical Activation (FEDOA-a large scale process that takes advantage of thermal, electrical, and optical activation to enhance the diffusion of an element into diamond structure) was used to load Kr and I on micron or nano sized particles having a larger relative surface area. The diamond particles can be further increased by doping it with boron followed by irradiation in a neutron flux. Previous studies showed that the hydrogen storage capacity could be increased significantly by using boron-doped irradiated diamond particles. Diamond powders were irradiated for a longer time by placing them in a quartz tube. The surface area was measured using a Quantachrome Autosorb system. No significant increase in the surface area was observed. Total surface area was about 1.7 m 2 /g. This suggests the existence of very minimal pores. Interestingly it showed hysteresis upon desorption. A reason for this may be strong interaction between the surface and the nitrogen molecules. Adsorption runs at higher temperatures did not show any adsorption of krypton on diamond. Use of a GC with HID detector to determine the adsorption capacity from the breakthrough curves was attempted, but experimental difficulties were encountered.

36 MATERIALS SCIENCE↗

DOE OSTI2015

Proceedings of RIKEN BNL Research Center Workshop: Theory and Modeling for the Beam Energy Scan: From Exploration to Discovery (Volume 121)

The Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory has concluded phase I of its Beam Energy Scan (BES) program. The goal of the RHIC BES program is to explore the phase diagram of strongly interacting matter at high baryonic densities and search for the QCD critical point by performing systematic scans at lower beam energies. Results from the RHIC BES I program are intriguing. There indeed seem to be several signals suggesting a softening of the equation of state, which may result from a first-order transition, as well as possible indications of a critical point. In light of these intriguing results, several accelerator and detector upgrades have been planned to conduct the phase II of the RHIC BES during the period 2017-2020. The goal of the RHIC BES II is discovery of the QCD critical point by performing high luminosity scans within the interesting beam energy range revealed through explorations at RHIC BES I. Past experience has proven that even qualitative understanding of the physics encoded within the RHIC experimental data requires substantial theoretical input based on QCD calculations as well as detailed, quantitative modeling of the medium created at the RHIC. However, the coordinated theoretical and modeling efforts necessary for comprehensive understanding of the RHIC BES data is presently lacking. The purpose of this workshop was to gather a small group of expert theorists, phenomenologists and experimentalists to identify the necessary theoretical and modeling developments required for RHIC BES, to delineate a clear path towards extracting concrete physics utilizing the RHIC BES data, and to kick-start collaborations among theorists, phenomenologists and experimentalists to ensure that the necessary theoretical and modeling developments can be achieved before the start of the RHIC BES II experimental program.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2015

Re-Defining Photovoltaic Efficiency Through Molecule Scale Control. Final Report

The direct conversion of sunlight into electricity represents one of the most important general means for sustainable energy production. Most modern photovoltaic cells are based on some form of semiconductor material such as silicon that is described by a characteristic energy or ''bandgap''. For solar rays with photon energy lower than the bandgap no absorption occurs and thus no energy is generated. For solar rays with photon energy greater than the bandgap, light may be absorbed to create a pair of electrical charges but only one bandgap of energy is created, leaving any additional energy lost as heat. Thus low bandgap materials can use a great part of the spectrum but can lose much of that energy; high bandgap materials fail to capture much of the spectrum. Thus there is a limit to the efficiency of such a solar cell that turns out to be about 32%. This limit is known as the Shockely-Queisser Limit. The Columbia EFRC program is dedicated to exploration of concepts that in principle can provide for efficiencies beyond this limit. One concept that this EFRC has explored for enhancing the efficiency of solar photovoltaic cells is called “Singlet Fission.” In this concept the absorption of light rays with photon energy at least twice the value of the basic bandgap for the system can produce two pairs of electrical charge carriers. If properly implemented this in principle can significantly reduce the energy lost as heat and give rise to solar cell efficiencies greater than the Shockley-Queisser limit. The problem is that there are virtually no materials that can undergo this process effectively. We have developed new materials that have demonstrated singlet fission efficiencies of almost 100%. We understand how these materials work and we have learned how to design many more systems in the future. So far we have only demonstrated the basic capability for efficient singlet fission. Much more work will be required to design and engineer specific materials that can be used practically in a solar cell system. In addition much work will be required to envision and demonstrate effective device structures that can utilize this concept. However these discoveries do provide the basis for an entirely new set of opportunities for more efficient solar energy generation moving beyond the Shockley-Queisser limit. A second part of the EFRC research program has been to investigate the material and device properties of an entirely new set of materials based on two-dimensional sheets (“ultra-thin”) with thicknesses of only one atom, or a single molecule or just a few atoms. These materials can exhibit conducting, insulating, and semiconducting character and thus they can form the basis for entirely new types of electrical devices. Recent fundamental investigations of these materials, at Columbia and elsewhere, demonstrate clearly that the flow of electrical charges in these systems is fundamentally different from the nature of electrical current flow in conventional materials. This fact presents many possibilities for new photovoltaic device concepts. The EFRC research team has achieved world leadership in the creation and understanding of these materials and in developing the fabrication techniques necessary to create useful devices from them. We have developed the basic fabrication methodology to build structures of these materials into complex device structures, layer by layer. Our EFRC research team has pioneered the synthesis and understanding for graphene, perhaps the simplest of these materials. Graphene can function as a highly transparent conducting material, capable of funneling an electrical charge over reasonable distances without significant energy loss. The EFRC program has also pioneered the development of ultra-thin sheets that function in a way analogous to semiconductor materials as well as sheets that act as electrical insulators. These developments therefore enable the construction of solar cells based on totally different physics from conventional cells. Because the electrons in these ultra-thin sheets interact strongly they will exhibit behaviors quite different from conventional materials with potential to operate at efficiencies beyond the Shockley-Queisser limit. In our EFRC program we have laid out many of the fundamental properties of these materials including the development of unique fabrication techniques. We discovered several new effects that demonstrate strong electron coupling. We have demonstrated the first solar cell that can actually generate electrical power at a high basic efficiency from these fundamentally new materials. There is much more science and technology required before these devices can become practical, but there is also very strong activity worldwide to build electronic devices from these materials, thus providing infrastructure and technical capability to develop these concepts.

14 SOLAR ENERGY↗