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At least 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

sPHENIX heavy flavor jet tagging studies in p+p at $\sqrt{s_{NN}}=200~GeV$

Heavy-flavor jets, which are initiated from heavy quarks, are ideal probes for studying flavor dependent parton energy loss. We report on the performance of jet flavor tagging using two Neural Network Machine Learning (ML) models: the Long Short-Term Memory (LSTM) model and an Attention-based Neural Network, in simulations of 200 GeV p + p collisions. The tagging performance of bottom quark initiated jets with both ML models surpasses that of the traditional cut-based method. Technical details, including sample and kinematic variable selections, the machine learning training and testing setup with parameter tuning, and outcome comparisons, will be discussed.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2026

Effects of gas purity on backgrounds of collision reaction cell-equipped MC-ICP-MS

The advent of multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) instruments equipped with collision reaction cells (CRCs) facilitates interference removal/mitigation via online gas phase separations. This approach has proven effective for high intensity ion beams measured on Faraday collectors; however, it has been observed that introduction of gas in the CRC can result in significant background signals relative to the more sensitive ion counters. These backgrounds hinder use of these instruments for low level concentration and isotopic ratio measurements when employing a reaction gas. Here, this work directly evaluates the effect of gas purity on backgrounds of CRC-MC-ICP-MS instruments. Introducing high-purity research grade O 2 (99.999%) into the CRC produces complex background spectra with intensities >10 4 cps observed at most masses across the measured mass range (7-300 m / z ). Some features of the observed spectra (i.e., positive mass defects) can be attributed to molecular compounds comprised of significant hydrogen. Additionally, some specific molecular species can be identified (i.e., MoO x H y + ) and appear to be derived from molybdenum rods comprising the CRC. Further purifying the gas reduces the intensity of these backgrounds by several orders of magnitude, to <10 2 cps in many cases, and reduces complexity of the resulting spectra. This reduction in background appears to be in part driven by removal of impurities (i.e., H 2 O) from the gas. This work demonstrates that additional purification of reaction gases prior to introduction into the CRC significantly reduces backgrounds detected, potentially expanding the utility of CRC-MC-ICP-MS for making low level measurements using inline gas phase ion separations.

Schlieder, Tyler D. [Pacific Northwest National La↗
DOE OSTI2022

CFM-ID 4.0 – a web server for accurate MS-based metabolite identification

The CFM-ID 4.0 web server (https://cfmid.wishartlab.com) is an online tool for predicting, annotating and interpreting tandem mass (MS/MS) spectra of small molecules. It is specifically designed to assist researchers pursuing studies in metabolomics, exposomics and analytical chemistry. More specifically, CFM-ID 4.0 supports the: 1) prediction of electrospray ionization quadrupole time-of-flight tandem mass spectra (ESI-QTOF-MS/MS) for small molecules over multiple collision energies (10 eV, 20 eV, and 40 eV); 2) annotation of ESI-QTOF-MS/MS spectra given the structure of the compound; and 3) identification of a small molecule that generated a given ESI-QTOF-MS/MS spectrum at one or more collision energies. The CFM-ID 4.0 web server makes use of a substantially improved MS fragmentation algorithm, a much larger database of experimental and in silico predicted MS/MS spectra and improved scoring methods to offer more accurate MS/MS spectral prediction and MS/MS-based compound identification. Compared to earlier versions of CFM-ID, this new version has an MS/MS spectral prediction performance that is ~22% better and a compound identification accuracy that is ~35% better on a standard (CASMI 2016) testing dataset. CFM-ID 4.0 also features a neutral loss function that allows users to identify similar or substituent compounds where no match can be found using CFM-ID’s regular MS/MS-to-compound identification utility. Finally, the CFM-ID 4.0 web server now offers a much more refined user interface that is easier to use, supports molecular formula identification (from MS/MS data), provides more interactively viewable data (including proposed fragment ion structures) and displays MS mirror plots for comparing predicted with observed MS/MS spectra. These improvements should make CFM-ID 4.0 much more useful to the community and should make small molecule identification much easier, faster, and more accurate.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2020

Searching for solitons in heavy-ion reactions near the fermi energy

Solitons are special shape-conserving hydrodynamical solutions that appear in many areas of physics. Here, we explore the existence of such solutions in microscopic descriptions of the heavy ion reaction 12 C + 28 Si → 12 C*+ 7α in the range E/A = 10 – 65 MeV/u. After recognizing the centrality of the collision and time-reversibility as fundamental requirements for the presence of solitonic 12 C, we utilize the Hybrid α-Cluster model for our analysis with a novel methodology. Our results suggest soliton production for E/A = 25 – 45 MeV/u in the forward direction, with a total cross section being at least in the order of a few μb. This, apart from being encouraging for possible experimental studies, maybe connected to possible toroid states of 28 Si at low angular momenta.

Heavy ion reactions↗
DOE OSTI2021

Simulation of lithium transport using the BOUT++ framework

A numerical model that calculates the collisional interactions between the lithium atoms from a lithium pellet and the background plasmas has been upgraded. The ion density ($N_t$), electron temperature ($T_e$), ion temperature ($T_i$) and parallel ion velocity ($V_{∥, i}$) are used to characterize the background plasmas. The lithium atom density ($N^{a}_{Li}$) and parallel velocity ($V_{∥,a}$) of lithium atoms evolve with time. For each lithium ion, the density ($N_{Li^{n+}}$), temperature ($T_{Li^{n+}}$) and parallel velocity ($V_{∥, Li^{n+}}$) are self-consistently calculated. A C-mod lower single null equilibrium is used to generate the grid for the BOUT++ simulation. The lithium atoms can be fully ionized to $Li^{3+}$ in ~2 μs. The rapid radial and poloidal expansion of the lithium ions are found in the simulation. After the collision interaction process, the electron temperature rapidly decreases at the pellet location; then, it rapidly poloidally expands, and the temperature at the pellet location starts to recover. The electron pressure increases at the pellet location despite the decrease in electron temperature because of the extra electrons from the lithium ionization. The ion pressure profile decreases in the pellet location due to the decrease in ion temperature.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2020

Shapes of rotating normal fluid He-3 versus superfluid He-4 droplets in molecular beams

Previous single-pulse extreme ultraviolet and X-ray coherent diffraction studies revealed that superfluid 4He droplets obtained in free jet expansion acquire sizable angular momentum, resulting in significant centrifugal distortion. Similar experiments with normal fluid 3He droplets may help elucidating the origin of the of the large degree of rotational excitation and highlight similarities and differences of dynamics in normal and superfluid droplets. Here, we present the first comparison of the shapes of isolated 3He and 4He droplets following expansion of the corresponding fluids in vacuum at temperatures as low as ~ 2 K. Large 3He and 4He droplets with average radii of ~160 nm and ~350 nm, respectively, were produced. We find that the majority of the 3He droplets in the beam correspond to rotating oblate spheroids with reduced average angular momentum ($\Lambda$) and reduced angular velocities ($\Omega$) similar to that of 4He droplets. Given the different physical nature of 3He and 4He, this similarity in $\Lambda$ and $\Omega$ may be surprising and suggest that similar mechanisms induce rotation regardless of the isotope. We hypothesized that the observed distribution of droplet sizes and angular momenta stem from processes in the dense region close to the nozzle. In this region, the significant velocity spread and collisions between the droplets induce excessive rotation followed by droplet fission. The process may repeat itself several times before the droplets enter the collision-fee high vacuum region further downstream.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2024

Investigating the impact of donor atoms of single-source precursors on f-element nanomaterial formation and mechanisms of initial bond cleavage

Nanotechnology is advancing exponentially, with novel discoveries and applications emerging every day across various fields, including environmental remediation, biomedicine, electronics, and textiles. Nanoparticles (NPs) are defined as particles with sizes ranging from 1 to 100 nm, and their properties are influenced by factors such as composition, phase, size, and shape. Single-source precursors (SSPs) offer a promising method for controlling the synthesis of phase-pure nanoparticles with the desired stoichiometry and have been successfully applied to prepare transition metal and lanthanide NPs. SSPs are molecular compounds that contain all the necessary components to form the final nanomaterial and decompose under mild conditions, such as heating, to create the solid-state product. The objective of this work was to garner a mechanistic understanding of cerium oxide NP formation from cerium SSPs. To achieve these goals, first, ligands with oxygen and sulfur donor atoms were synthesized; among the array of ligands synthesized, some were novel. These ligands were then chelated to cerium ions to synthesize cerium precursors. Initially, known cerium alkoxide precursors were synthesized. Subsequently, these basic cerium complexes were further manipulated through acid-base protonolysis reactions to install a diverse set of ligands. Within this body of work, 10 novel cerium precursors were successfully synthesized. The ligands and the SSPs were analyzed using nuclear magnetic resonance (NMR) and thermogravimetric analysis coupled with differential scanning calorimetry (TGA-DSC). These SSPs were then introduced to a collision-induced dissociation mass spectrometer (CID-MS), and their dissociation pathways were studied.

37 - INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL C↗
DOE OSTI2024

Precision three-dimensional imaging of nuclei using recoil-free jets

In this study, we explore the azimuthal angle decorrelation of lepton-jet pairs in e-p and e-A collisions as a means for precision measurements of the three-dimensional structure of bound and free nucleons. Utilizing soft-collinear effective theory, we perform the first-ever resummation of this process in e-p collisions at NNLL accuracy using a recoil-free jet axis. Our results are validated against Pythia simulations. In e-A collisions, we address the complex interplay between three characteristic length scales: the medium length L, the mean free path of the energetic parton in the medium λ, and the hadronization length L h . We demonstrate that in the thin-dilute limit, where L $\ll$ L h and L ~ λ, this process can serve as a robust probe of the three-dimensional structure for bound nucleons. We conclude by offering predictions for future experiments at the Electron-Ion Collider within this limit.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

A Proposed Forward Silicon Tracker for the Future Electron-Ion Collider and Associated Physics Studies

The future Electron-Ion Collider (EIC) will explore several fundamental questions in a broad Bjorken-x (x BJ ) and Q 2 phase space. Heavy flavor and jet products are ideal probes to precisely study the tomography of nucleon/nuclei structure, help solve the proton spin puzzle and understand the hadronizaton processes in vacuum or in the QCD medium. Due to the asymmetric collisions at the EIC, most of the final state hadrons are produced in the nucleon/nuclei beam going (forward) direction. A silicon vertex/tracking is critical to precisely measure these forward hadrons at the EIC. Details of different conceptual designs of the proposed Forward Silicon Tracker (FST) and the relevant detector performance are presented in this technical note. The associated heavy flavor and jet studies with the evaluated FST performance are discussed as well.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2024

Cyclable Variable Path Length Multilevel Structures for Lossless Ion Manipulations (SLIM) Platform for Enhanced Ion Mobility Separations

Ion mobility-mass spectrometry (IMS-MS) is increasingly used to analyze complex samples and provide structural information of unknown compounds. As the complexity of samples increases, there is a need to improve the resolution of IMS-MS instruments to increase the rate of molecular identification. In this work, we evaluated a cyclable and variable-pathlength multilevel Structures for Lossless Ion Manipulations (SLIM) platform to achieve a higher resolving power than previously possible. This new multilevel SLIM platform has eight separation levels connected by ion escalators and a path length of ~88 meters (~11 meters per level). Our new multilevel SLIM can also be operated in an ‘ion cycling’ mode where a set of return ion escalators transport ions from the eighth back to the first level, allowing even longer path lengths (and higher IMS resolution). The platform has been improved to enhance the ion transmission and IMS separation quality by reducing the spacing between SLIM boards as well as board thickness, reducing the ions’ escalator residence time. Compared to the previous generation, the new multilevel SLIM demonstrated a better transmission for a set of phosphazene ions, especially for the low-mobility ions. The new multilevel SLIM achieved better resolving powers than our previous 4-level SLIM. The collision cross-section-based resolving power of the SLIM platform was tested using a pair of singly-charged reverse sequence peptides (SDGRG 1+ , GRGDS 1+ ). We achieved 1100 resolving power using 88 meters of path length (i.e., 8 levels) and 1400 following an additional pass through the eight levels (i.e., 16 levels or 173.5 m). The multilevel SLIM was further evaluated to demonstrate the enhanced separation for a positively and negatively charged brain total lipid extract sample. Finally, the new multilevel SLIM enables much higher resolving powers for a wide range of ion mobilities, improved transmission for low-mobility ions, and the ability to perform even higher resolving power for ions of interest.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Impact of fragment formation on shear viscosity in the nuclear liquid-gas phase transition region

Within the improved quantum molecular dynamics (ImQMD) model we follow the evolution of nuclear matter for planar Couette flow in a periodic box. We focus on the region of liquid-gas phase transition and extract the shear viscosity coefficient from the local stress tensor, directly following the viscosity definition. Here, by switching on and off the mean field and thus inducing the phase transition, we are able to observe the impact of clumping in the phase transition region on the viscosity.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

Constraining neutron-star matter with microscopic and macroscopic collisions

Interpreting high-energy, astrophysical phenomena, such as supernova explosions or neutron-star collisions, requires a robust understanding of matter at supranuclear densities. However, our knowledge about dense matter explored in the cores of neutron stars remains limited. Fortunately, dense matter is not probed only in astrophysical observations, but also in terrestrial heavy-ion collision experiments. Here we use Bayesian inference to combine data from astrophysical multi-messenger observations of neutron stars and from heavy-ion collisions of gold nuclei at relativistic energies with microscopic nuclear theory calculations to improve our understanding of dense matter. We find that the inclusion of heavy-ion collision data indicates an increase in the pressure in dense matter relative to previous analyses, shifting neutron-star radii towards larger values, consistent with recent observations by the Neutron Star Interior Composition Explorer mission. Our findings show that constraints from heavy-ion collision experiments show a remarkable consistency with multi-messenger observations and provide complementary information on nuclear matter at intermediate densities. This work combines nuclear theory, nuclear experiment and astrophysical observations, and shows how joint analyses can shed light on the properties of neutron-rich supranuclear matter over the density range probed in neutron stars.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2021

Inelastic, exchange, and reactive processes in rovibrationally excited collisions of HD with H

ABSTRACT The HD molecule is an important coolant in early universe chemistry models and a tracer of H2 in star-forming regions. Rate coefficients for collisional excitation and de-excitation of HD rotational and vibrational levels form important ingredients in astrophysical models. While collisions with He, H2, and H are the most important, available data for H + HD collisions are largely limited to temperatures less than 1000 K for the vibrational ground state, low-lying rotational levels of the v = 1 HD vibrational level, or computed without reactive contributions. Here, through explicit quantum scattering calculations, we report extensive data for rovibrational transitions in HD induced by H atoms for a range of rotational levels in v = 1 and some v = 0 levels for temperatures up to 1000 K. The significance of the computed results for astrophysical modeling is discussed.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Analysis and Grading of the Test Performance of PS Modules for the CMS Phase-II Outer Tracker Upgrade

The Outer Tracker detector of the Compact Muon Solenoid (CMS) experiment provides information about the trajectory of charged particles produced in proton-proton collisions at the Large Hadron Collider (LHC). During the High Luminosity LHC upgrade, scheduled for the late 2020s, the Outer Tracker will be replaced with new modules capable of transmitting data to the L1 Trigger. These modules are being assembled at several facilities around the world, including Fermilab, necessitating coordinated standards of module quality. Here I discuss the development of POTATO (Phase-II Outer Tracker Analyzer of Test Outputs), a C++ software which provides a standardized procedure for analyzing and grading test results of the Outer Tracker modules. The particular focus of this paper is on the analysis and grading of the PS (pixel-strip) modules in POTATO.

43 PARTICLE ACCELERATORS↗
DOE OSTI2020

Higgs boson pair production via gluon fusion at N 3 LO in QCD

We present next-to-next-to-next-to-leading order ( N 3 LO ) QCD predictions for the Higgs boson pair production via gluon fusion at hadron colliders in the infinite top-quark mass limit. Besides the inclusive total cross sections at various collision energies, we also provide the invariant mass distribution of the Higgs boson pair. Our results show that the N 3 LO QCD corrections enhance the next-to-next-to-leading order cross section by 3.0% (2.7%) at s = 13 ( 100 ) TeV , while the scale uncertainty is reduced substantially below 3% (2%). We also find that a judicious scale choice can significantly improve the perturbative convergence. For the invariant mass distribution, our calculation demonstrates that the N 3 LO corrections improve the scale dependence but almost do not change the shape.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Evaporation and Molecular Beam Scattering from a Flat Liquid Jet

An experimental setup for molecular beam scattering from flat liquid sheets has been developed, with the goal of studying reactions at gas–liquid interfaces for volatile liquids. Specifically, a crossed molecular beam instrument that can measure angular and translational energy distributions of scattered products has been adapted for liquid jet scattering. A microfluidic chip is used to create a stable flat liquid sheet inside vacuum from which scattering occurs, and both evaporation and scattering from this sheet are characterized using a rotatable mass spectrometer that can measure product time-of-flight distributions. This article describes the instrument and reports on the first measurements of evaporation of dodecane and Ne from a Ne-doped dodecane flat jet, as well as scattering of Ne from a flat jet of pure dodecane.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Preliminary Evidence of Gas-Phase Water Splitting on Holmium Nitrogen Oxide Clusters

Preliminary Evidence of Gas-Phase Water Splitting on Holmium Nitrogen Oxide Clusters Christopher A. Zarzana1, Makayla R. Baxter , Introduction: Molecular hydrogen is a potential energy carrier that could be used to help implement a clean energy economy if it is generated from splitting of water. Improvements in the efficiencies of water-splitting electrolyzers relies on development of novel materials with enhanced performance. However, research in this area is slowed due to underdeveloped understanding of the mechanisms of device performance due to challenges interrogating the fundamental chemical reactions at play in bulk materials. Studies of the intrinsic reactivity of clusters that are representative of the reactive sites of these materials can increase understanding of the fundamental reaction mechanisms involved in hydrogen production, allowing for more efficient development of new water-splitting materials. Methods: Holmium tetranitrato ([Ho(NO3)4]-) clusters were generated in gas-phase using the electrospray ionization source of a Bruker (Billerica, MA, USA) micrOTOF-Q II quadrupole time-of-flight mass spectrometer. Spray solutions consisted of aqueous holmium (Ho) nitrate solutions (at nominally 3 mM) diluted to 30 µM in acetonitrile. The holmium (Ho) tetranitrato clusters were isolated using the quadrupole and were subsequently activated and allowed to react with background water in the collision cell. High resolution, high mass accuracy spectra were recorded using the time-of-flight. Mass accuracy was ensured using external calibration with Agilent (Santa Clara, CA, USA) ESI-L Low Concentration tuning mix. Preliminary data: Collisional activation of the holmium tetranitrato complexes ([Ln(NO3)4]-) resulted in an expected series of ions resulting from the loss of ·NO and ·NO2. This included an ion at m/z = 382.885 assigned as [HoO2(NO3)3]- (theoretical m/z=382.884, error=-1.2 ppm), resulting from loss of ·NO, and an ion at m/z=366.890 assigned as [HoO(NO3)3]- (theorical m/z=366.889, error=-1.8 ppm), resulting from loss of ·NO2. Additional ions were detected that would result from more complicated losses from [Ho(NO3)4]-, including ions at m/z=320.898 assigned as [HoO2(NO3)2]- (theoretical m/z=320.896, error=-4.9 ppm), at m/z=304.904 assigned as [HoO(NO3)2]- (theoretical m/z=304.901, error=-8.1 ppm, very low signal), and at m/z=288.908 assigned as [Ho(NO3)2]- (theoretical m/z=288.907, error=-3.4 ppm). This ion series would arise from loss of some combination of ·NO, ·NO2, and ·NO3, although it is not known whether these losses occur sequentially (e.g. loss of ·NO and ·NO3 to yield [HoO2(NO3)2]-) or as a single species (e.g. direct loss of N2O4). These ions were accompanied by a complementary series representing addition of a single water molecule. This included an ion at m/z=338.908 assigned as [HoO2(NO3)2H2O]- (theoretical m/z=338.907, error=-4.1 ppm), an ion at m/z=322.912 assigned as [HoO(NO3)2H2O]- (theoretical m/z=322.912, error=1.2 ppm), and an ion at m/z=306.918 assigned as [Ho(NO3)2H2O]-, (theoretical m/z=306.918, error=-3.7 ppm). An additional hydrated ion was observed at m/z=276.921 assigned as [HoO2(NO3) H2O]- (theoretical m/z=276.919, error=-7.3 ppm), although corresponding dehydrated ion was not observed. An additional ion was observed at m/z=367.898 that has been assigned as [Ho(NO3)3OH]- (theoretical m/z=367.897, error=-2.5 ppm). It is hypothesized that this ion arises from addition of water to [Ho(NO3)3]- followed by elimination of a hydrogen radical. Neither [Ho(NO3)3]- nor [Ho(NO3)3H2O]- were detected, suggesting that, if the hypothesis is correct, addition of water to [Ho(NO3)3]- and its subsequent splitting is rapid. Elimination of HNO3 from [Ho(NO3)4H2O]- could also yield [Ho(NO3)3OH]-; however, no [Ho(NO3)4H2O]- ions were observed. Novelty: Potential evidence of water splitting on gas-phase lanthanide clusters offers a way to study the intrinsic reactivity of hydrogen-generation materials.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗