Phase of confined electroweak force in the early Universe
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72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
SEARCH · Engineering Papers
Results for “PARTICLE INTERACTIONS”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Observation of Enhanced Double Parton Scattering in Proton-Lead Collisions at $\sqrt{s_{NN}}$= 8.16 TeV
A study of prompt charm-hadron pair production in proton-lead collisions at $\sqrt{s_{NN}$ = 8.16 TeV is performed using data corresponding to an integrated luminosity of about 30 nb -1 , collected with the LHCb experiment. Production cross sections for different pairs of charm hadrons are measured and kinematic correlations between the two charm hadrons are investigated. This is the first measurement of associated production of two charm hadrons in proton-lead collisions. The results confirm the predicted enhancement of double parton scattering production in proton-lead collisions compared to the single parton scattering production.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Quantum simulations of SO(5) many-fermion systems using qudits
The structure and dynamics of many-body systems are the result of a delicate interplay between underlying interactions. Fermionic pairing, for example, plays a central role in various physical systems, ranging from condensed matter to nuclear systems, where it can lead to collective phenomena such as superconductivity and superfluidity. In atomic nuclei, the interplay between pairing and particle-hole interactions leads to a high degree of complexity and intricate entanglement structures. Despite this apparent complexity, symmetries emerge and manifest themselves in observable regular patterns. These symmetries and their breakings have long been used to determine relevant degrees of freedom and simplify classical descriptions of many-body systems. Here, this work explores the potential utility of quantum computers with arrays of qudits in simulating interacting fermionic systems, when the qudits can naturally map the relevant degrees of freedom determined by an underlying symmetry group. The Agassi model of fermions interacting via particle-hole and pairing interactions is based on an underlying so(5) algebra. Such systems can intuitively be partitioned into pairs of modes with five basis states, which thus naturally map to arrays of d = 5 qudits (qu5its). Classical noiseless simulations of the time evolution of systems with up to twelve qu5its are performed, by implementing quantum circuits that are developed herein, using PYTHON codes invoking Google's CIRQ software. The resource requirements of the qu5it circuits are analyzed and compared with two different mappings to qubit systems: a physics-aware Jordan-Wigner mapping requiring four qubits per mode pair and a state-to-state mapping requiring three qubits per mode pair. While the dimensionality of Hilbert spaces in mappings to qu5it systems are less than those for the corresponding qubit systems, the number of entangling operations, depending on the available hardware, can either be greater or smaller than for the physics-aware Jordan-Wigner mapping. The state-to-state mapping, while having a smaller Hilbert space than Jordan-Wigner mappings, appears to be the least efficient in gate counts. Further, a previously unknown sign problem has been identified from Trotterization errors in time evolving high-energy excitations. There appear to be advantages in employing quantum computers with arrays of qudits to perform simulations of many-body dynamics that exploit the role of underlying symmetries, specifically in lowering the required quantum resources and in reducing anticipated errors that take the simulation out of the physical space. If the necessary entangling gates are not directly supported by the hardware, physics-aware mappings to qubits may, however, be advantageous for other aspects.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Second-order perturbative corrections to the restricted active space configuration interaction with the hole and particle approach
Second-order corrections to the restricted active space configuration interaction (RASCI) with the hole and particle truncation of the excitation operator are developed. Theoretically, the computational cost of the implemented perturbative approach, abbreviated as RASCI(2), grows like its single reference counterpart in MP2. Two different forms of RASCI(2) have been explored, that is the generalized Davidson-Kapuy and the Epstein-Nesbet partitions of the Hamiltonian. The preliminary results indicate that the use of energy level shift of a few tenths of a Hartree might systematically improve the accuracy of the RASCI(2) energies. The method has been tested in the computation of the ground state energy profiles along the dissociation of the hydrogen fluoride and N{sub 2} molecules, the computation of correlation energy in the G2/97 molecular test set, and in the computation of excitation energies to low-lying states in small organic molecules.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Microdynamics of active particles in defect-rich colloidal crystals
Hypothesis. Because they are self-propulsive, active colloidal particles can interact with their environment in ways that differ from passive, Brownian particles. Here, we explore how interactions in different microstructural regions may contribute to colloidal crystal annealing. Experiments. We investigate active particles propagating in a quasi-2D colloidal crystal monolayer produced by alternating current electric fields (active-to-passive particle ratio ~ 1:720). The active particle is a platinum Janus sphere propelled by asymmetric decomposition of hydrogen peroxide. Crystals are characterized for changes in void properties. The mean-squared-displacement of Janus particles are measured to determine how active microdynamics depend on the local microstructure, which is comprised of void regions, void-adjacent regions (defined as within three particle diameters of a void), and interstitial regions. Findings. At active particle energy E A = 2.55 k B T, the average void size increases as much as three times and the average void anisotropy increases about 40% relative to the passive case. Further, the average microdynamical enhancement, <δ(t)>, of Janus particles in the crystal relative to an equivalent passive Janus particle is reduced compared to that of a free, active particle (<δ(t) > is 1.88 ± 0.04 and 2.66 ± 0.08, respectively). The concentration of active particles is enriched in void and void-adjacent regions. Active particles exhibit the greatest change in dynamics relative to the passive control in void-adjacent regions (<δ(t)> = 2.58 ± 0.06). The results support the conjecture that active particle microdynamical enhancement in crystal lattices is affected by local defect structure.
36 MATERIALS SCIENCE↗
Shape effects on the local dynamics of suspensions of spheroidal particles
The effect of shape on the dynamics of suspensions of non-spherical heavy particles is examined by fully resolved numerical simulations of oblate and prolate spheroids, as well as spheres, for a density ratio of ten, volume fractions ranging from 0.5% to 5%, and Reynolds numbers between 20 and 30. The dynamics is determined both by the interactions of the particles with the fluid as well as by collisions, with the number and importance of collisions increasing with volume fractions. A single isolated oblate or prolate spheroid falling under gravity generally falls broadside on, for the governing parameters examined here, and at low-volume fractions, the majority of particles in a suspension fall that way. At higher-volume fractions, the orientation is more random. The slip velocity decreases as the volume fraction increases for all shapes, as expected, but the effect of the shape is much less than seen for a single particle. Furthermore, this seems to be due to two effects. For all volume fractions, the most deformed particles cluster more than spheres and less deformed particles, which increases their slip velocity. As the concentration increases, the increased particle interactions also causes more particles to fall short side-on, which reduces the frontal area and the resulting drag, increasing the slip velocity. This second effect is, of course, absent for spherical particles.
42 ENGINEERING↗
Dark Matter Search Results from 4.2 Tonne−Years of Exposure of the LUX-ZEPLIN (LZ) Experiment
We report results of a search for nuclear recoils induced by weakly interacting massive particle (WIMP) dark matter using the LUX-ZEPLIN (LZ) two-phase xenon time projection chamber. This analysis uses a total exposure of 4.2 ±0.1 tonne-years from 280 live days of LZ operation, of which 3.3 ± 0.1 tonne-years and 220 live days are new. A technique to actively tag background electronic recoils from 214 Pb 𝛽 decays is featured for the first time. Enhanced electron-ion recombination is observed in two-neutrino double electron capture decays of 124 Xe, representing a noteworthy new background. After removal of artificial signal-like events injected into the dataset to mitigate analyzer bias, we find no evidence for an excess over expected backgrounds. World-leading constraints are placed on spin-independent (SI) and spin-dependent WIMP-nucleon cross sections for masses ≥9 GeV/𝑐 2 . The strongest SI exclusion set is 2.2×10 −48 cm 2 at the 90% confidence level and the best SI median sensitivity achieved is 5.1 ×10 −48 cm 2 , both for a mass of 40 GeV/𝑐 2 .
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Mean force kinetic theory: A convergent kinetic theory for weakly and strongly coupled plasmas
A new closure of the BBGKY hierarchy is developed, which results in a convergent kinetic equation that provides a rigorous extension of plasma kinetic theory into the regime of strong Coulomb coupling. The approach is based on a single expansion parameter which enforces that the exact equilibrium limit is maintained at all orders. Because the expansion parameter does not explicitly depend on the range or the strength of the interaction potential, the resulting kinetic theory does not suffer from the typical divergences at short and long length scales encountered when applying the standard kinetic equations to Coulomb interactions. Here, the approach demonstrates that particles effectively interact via the potential of mean force and that the range of this force determines the size of the collision volume. When applied to a plasma, the collision operator is shown to be related to the effective potential theory [S. D. Baalrud and J. Daligault, Phys. Rev. Lett. 110, 235001 (2013)]. In addition to the collision operator, this systematic derivation reveals a second term that is related to the excess (nonideal) components of the pressure and internal energy in the hydrodynamic limit. The relationship between this and previous kinetic theories is discussed.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
First observation of strange baryon enhancement with effective energy in pp collisions at the LHC
The production of (multi-)strange hadrons is measured at midrapidity in proton-proton collisions at $\sqrt{s}$ = 13 TeV as a function of the local charged-particle multiplicity in the pseudorapidity interval |η| < 0.5 and of the very-forward energy measured by the ALICE Zero-Degree Calorimeters. The latter provides information on the effective energy, i.e. the energy available for particle production in the collision once subtracted from the centre-of-mass energy. The yields of K$^{0}_{s}$, $Λ$ + $\overline{Λ}$, and $Ξ$ – + $\overline{Ξ}$ + per charged-particle increase with the effective energy. In addition, this work exploits a multi-differential approach to decouple the roles of local multiplicity and effective energy in such an enhancement. The results presented in this article provide new insights into the interplay between global properties of the collision, such as the initial available energy in the event, and the locally produced final hadronic state, connected to the charged-particle multiplicity at midrapidity. Notably, a strong increase of strange baryon production with effective energy is observed for fixed charged-particle multiplicity at midrapidity. These results are discussed within the context of existing phenomenological models of hadronisation implemented in different tunes of the PYTHIA 8 event generator.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Investigation of Origin of Attached Cu-Ag Droplets to Solid Particles During High-Temperature Slag/Copper/Spinel Interactions
This study investigates the origin of mechanically entrained metal droplets in liquid slag due to their interaction with solid spinel particles. Two possible mechanisms were proposed previously: separately formed droplets and spinel particles get attached to each other due to agitation of the slag and metal phases; or the spinel particles form by a chemical reaction together with a new droplet or alongside a droplet that was already present in the system. In this study, an inert tracer element was added to the metallic phase in adapted sessile drop experiments. For this purpose, Cu-Ag alloys, with various Ag-contents, were produced. The results showed that the small entrained metal droplets within the slag droplet contained Ag, but in very low amounts with respect to the amount of Ag in the Cu-Ag alloy. This indicates that the entrained metal droplets are formed due to a sequential combination of the two origins: first, very small metal droplets are dispersed in the slag drop, due to the emulsification process. Then, these metal droplets are nucleation sites for the Cu-spinel reactive formation.
36 MATERIALS SCIENCE↗
Towards an understanding of particle-scale flaws and microstructure evolution in cold spray via accumulation of single particle impacts
Cold spray coatings are the sum of countless individual bonding events between single particles impacting on top of one another at high velocities. Thus, the collective behavior of microparticles must be considered to elucidate the origins of coating flaws at the scale of the particles and larger, or the dynamic evolution of the overall coating microstructure. Laser-induced particle impact testing (LIPIT) has been extensively used to study single-particle impacts, and in this work is adapted to study the accumulation of numerous particles with knowledge of each individual particle's impact parameters (particle size, velocity). The method reproducibly deposits stacks of gold particles (>20 particles) with different characteristic spectra of impact velocity. The observation of impact-induced erosion lets us define a critical velocity for material-build-up that is higher than that for single-particle bonding. The quantitative single-particle data are analyzed in a correlative manner to the structure and flaws in the resulting stacks, providing some first statistical connections between, e.g., strain and recrystallization, or aberrant particle characteristics and defects. The results highlight opportunities for the study of many-particle phenomena in microparticle impact—from interaction of particles in cold spray to multi-step erosion processes—with a quantitative view of the behavior of single particles.
Erosion↗
Surface charge accumulation of particles containing radionuclides in open air
Radioactivity can induce charge accumulation on radioactive particles. But, electrostatic interactions caused by radioactivity are typically neglected in transport modeling of radioactive plumes because it is assumed that ionizing radiation leads to charge neutralization. The assumption that electrostatic interactions caused by radioactivity are negligible is evaluated here by examining charge accumulation and neutralization on particles containing radionuclides in open air. Moreover, a charge-balance model is employed to predict charge accumulation on radioactive particles. It is shown that particles containing short-lived radionuclides can be charged with multiple elementary charges through radioactive decay. The presence of radioactive particles can significantly modify the particle charge distribution in open air and yield an asymmetric bimodal charge distribution, suggesting that strong electrostatic particle interactions may occur during short- and long-range transport of radioactive particles. Possible effects of transported radioactive particles on electrical properties of the local atmosphere are reported. Our study offers insight into transport characteristics of airborne radionuclides. Results are useful in atmospheric transport modeling of radioactive plumes.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
And there was light
I discuss the use of light as a collection of real and virtual photons to study some lingering questions in particle and nuclear physics.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Improving nanoparticle superlattice stability with deformable polymer gels
The self-assembly of colloidal nanoparticles into ordered superlattices typically uses dynamic interactions to govern particle crystallization, as these non-permanent bonds prevent the formation of kinetically trapped, disordered aggregates. However, while the use of reversible bonding is critical in the formation of highly ordered particle arrangements, dynamic interactions also inherently make the structures more prone to disassembly or disruption when subjected to different environmental stimuli. Thus, there is typically a trade-off between the ability to initially form an ordered colloidal material and the ability of that material to retain its order under different conditions. Here, we present a method for embedding colloidal nanoparticle superlattices into a polymer gel matrix. This encapsulation strategy physically prevents the nanoparticles from dissociating upon heating, drying, or the introduction of chemicals that would normally disrupt the lattice. However, the use of a gel as the embedding medium still permits further modification of the colloidal nanoparticle lattice by introducing stimuli that deform the gel network (as this deformation in turn alters the nanoparticle lattice structure in a predictable manner). Moreover, encapsulation of the lattice within a gel permits further stabilization into fully solid materials by removing the solvent from the gel or by replacing the solvent with a liquid monomer that can be photopolymerized. This embedding method therefore makes it possible to incorporate ordered colloidal arrays into a polymer matrix as either dynamic or static structures, expanding their potential for use in responsive materials.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Measurement of beam-recoil observables 𝐶 𝑥 and 𝐶 𝑧 for 𝐾 + Λ photoproduction
Exclusive photoproduction of 𝐾 + Λ final states off a proton target has been an important component in the search for missing nucleon resonances and our understanding of the production of final states containing strange quarks. Polarization observables have been instrumental in this effort. The current work is an extension of previously published CLAS results on the beam-recoil transferred polarization observables 𝐶 𝑥 and 𝐶 𝑧 . Here, we extend the kinematic range up to invariant mass 𝑊 = 3.33 GeV from the previous limit of 𝑊 = 2.5 GeV with significantly improved statistical precision in the region of overlap. These data will provide for tighter constraints on the reaction models used to unravel the spectrum of nucleon resonances and their properties by not only improving the statistical precision of the data within the resonance region, but also constraining 𝑡-channel processes that dominate at higher 𝑊 but extend into the resonance region.
Electrons↗
Strange quark suppression from a simultaneous Monte Carlo analysis of parton distributions and fragmentation functions
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72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Measurement of transverse single-spin asymmetries of π 0 and electromagnetic jets at forward rapidity in 200 and 500 GeV transversely polarized proton-proton collisions
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72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Data-based determination of the isospin-limit light-quark-connected contribution to the anomalous magnetic moment of the muon
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79 ASTRONOMY AND ASTROPHYSICS↗