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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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At least 991 records · Page 55
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Multi-track event reconstruction to constrain the p ̄ background in Mu2e

Mu2e experiment will search for the neutrinoless, coherent conversion of μ − → e − in the field of an Al nucleus. One of the expected backgrounds is p ̄ ’s annihilating in the stopping target to produce signal-like e − ’s. Although not a dominant background, it has a large uncertainty and cannot be suppressed by the timing cuts used to reduce the prompt background. However, at Mu2e energies, p p ̄ annihilation is the only source of events with multiple, simultaneous particles coming from the stopping target. We utilized this unique feature and developed a novel way to reconstruct multi-track events and estimate the p ̄ background.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2027

Conceptual design of highly-constrained splitters for the FFA@CEBAF energy upgrade study

The Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab is investigating a significant energy upgrade utilizing Fixed-Field Alternating-gradient (FFA) recirculating arcs. This upgrade requires the design of complex horizontal beam splitters to manage up to six concurrent beam passes. This paper presents the conceptual design of these splitters, which are subject to severe physical constraints imposed by the existing accelerator tunnel and multifaceted beam dynamics requirements for matching into the permanent-magnet FFA arcs. The design methodology, centered on multi-pass simulations in the Bmad toolkit, is detailed from the initial geometric layout through the advanced optics matching. Key results include a robust geometric arrangement that fits within the spatial boundaries and the development of multiple, flexible optics matching solutions. Furthermore, the design integrates a viable scheme for extracting high-energy beams for the experimental halls, a critical operational requirement. This work establishes a comprehensive and viable conceptual design, forming a baseline for future engineering and performance optimization studies.

Bodenstein, R.M. [Thomas Jefferson National Accele↗
DOE OSTI2020

Distinct Assembly Processes and Microbial Communities Constrain Soil Organic Carbon Formation

Soil stores more carbon (C) than all vegetation and the atmosphere combined. Soil C stocks are broadly shaped by temperature, moisture, soil physical characteristics, vegetation, and microbial-mediated metabolic processes. The efficiency with which microorganisms use soil C regulates the balance between C storage in soil and the atmosphere. In this review, we discuss how microbial physiology and community assembly processes determine microbial growth rate and efficiency and, in turn, soil organic C cycling through the lens of community ecology. We introduce a conceptual framework cataloging life history (i.e., growth rate, resource acquisition, and stress tolerance) and assembly traits (i.e., competition, facilitation, and dispersal) that correspond with different growth efficiencies. We also compare how dominant mycorrhizal fungal type affects growth efficiency. We propose that further development and inclusion of specific community parameters in microbial-explicit Earth system models are needed for accurately predicting soil organic C responses to global change.

carbon sequestration↗
DOE OSTI2024

Iterative methods in GPU-resident linear solvers for nonlinear constrained optimization

Linear solvers are major computational bottlenecks in a wide range of decision support and optimization computations. The challenges become even more pronounced on heterogeneous hardware, where traditional sparse numerical linear algebra methods are often inefficient. For example, methods for solving ill-conditioned linear systems have relied on conditional branching, which degrades performance on hardware accelerators such as graphical processing units (GPUs). To improve the efficiency of solving ill-conditioned systems, our computational strategy separates computations that are efficient on GPUs from those that need to run on traditional central processing units (CPUs). Our strategy maximizes the reuse of expensive CPU computations. Iterative methods, which thus far have not been broadly used for ill-conditioned linear systems, play an important role in our approach. In particular, we extend ideas from Arioli et al., (2007) to implement iterative refinement using inexact LU factors and flexible generalized minimal residual (FGMRES), with the aim of efficient performance on GPUs. In conclusion, we focus on solutions that are effective within broader application contexts, and discuss how early performance tests could be improved to be more predictive of the performance in a realistic environment.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2019

Constraining unintegrated gluon distributions from inclusive photon production in proton–proton collisions at the LHC

We compute the leading order (LO) qg → qγ and next-to-leading order (NLO) gg → qq¯γ contributions to inclusive photon production in proton–proton (p+p) collisions at the LHC. These channels provide the dominant contribution at LO and NLO for photon transverse momenta k γ⟂ corresponding to momentum fractions of x ≤ 0.01 in the colliding protons. Our computations, performed in the dilute–dense framework of the Color Glass Condensate effective field theory (CGC EFT), show that the NLO contribution dominates at small-x because it is sensitive to k γ⟂ -dependent unintegrated gluon distributions in both of the protons. We predict a maximal 10% modification of the cross section at low k γ⟂ as a direct consequence of the violation of k ⟂ -factorization. The coherence effects responsible for this modification are enhanced in nuclei and can be identified from inclusive photon measurements in proton–nucleus collisions. We provide numerical results for the isolated inclusive photon cross section for k γ⟂ ≤ 20 GeV in p+p collisions that can be tested in the future at the LHC.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2019

Constraining the symmetry energy with heavy-ion collisions and Bayesian analyses

Efficiency corrected single ratios of neutron and proton spectra in central Sn 112 + 112 Sn and Sn 124 + 124 Sn collisions at 120 MeV/u are combined with double ratios to provide constraints on the density and momentum dependencies of the isovector mean-field potential. Bayesian analyses of these data reveal that the isoscalar and isovector nucleon effective masses, m s ⁎ − m v ⁎ are strongly correlated. The linear correlation observed in m s ⁎ − m v ⁎ yields a nearly independent constraint on the effective mass splitting Δ m n p ⁎ = ( m n ⁎ − m p ⁎ ) / m N = − 0.05 − 0.09 + 0.09 δ . The correlated constraint on the standard symmetry energy, $S_0$ and the slope, L at saturation density yields the values of symmetry energy S ( ρ s ) = 16.8 − 1.2 + 1.2 MeV at a sensitive density of ρ s / ρ 0 = 0.43 − 0.05 + 0.05 .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗