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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 577 records · Page 32
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Search for a light charged Higgs boson in $t \rightarrow H^{\pm } b$ decays, with $H^{\pm } \rightarrow cs$, in $pp$ collisions at $\sqrt{s}={13}\hbox { TeV}$ with the ATLAS detector

A search for a light charged Higgs boson produced in decays of the top quark, $t \rightarrow H^{\pm } b$ with $H^{\pm } \rightarrow cs$, is presented. This search targets the production of top-quark pairs $t\bar{t} \rightarrow WbH^{\pm } b$, with $W \rightarrow ℓv(ℓ = e, μ)$, resulting in a lepton-plus-jets final state characterised by an isolated electron or muon and at least four jets. The search exploits b-quark and c-quark identification techniques as well as multivariate methods to suppress the dominant $t\bar{t}$ background. The data analysed correspond to 140 fb -1 of $pp$ collisions at $\sqrt{s}$ = 13 TeV recorded with the ATLAS detector at the LHC between 2015 and 2018. Observed (expected) 95% confidence-level upper limits on the branching fraction $\mathscr{B}(t \rightarrow H^{\pm } b)$, assuming $\mathscr{B}(t \rightarrow Wb) + \mathscr{B}(t \rightarrow H^{\pm }(\rightarrow cs)b$, are set between 0.066% (0.077%) and 3.6% (2.3%) for a charged Higgs boson with a mass between 60 and 168 GeV.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Measurement of correlations among net-charge, net-proton, and net-kaon multiplicity distributions in Pb-Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV

Correlations among conserved quantum numbers, such as the net-electric charge, the net-baryon, and the net-strangeness in heavy-ion collisions, are crucial for exploring the QCD phase diagram. In this paper, these correlations are investigated using net-proton number (as a proxy for the net-baryon), net-kaon number (for the net-strangeness), and net-charged particle number in Pb-Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV with the ALICE detector. The observed correlations deviate from the Poissonian baseline, with a more pronounced deviation at LHC energies than at RHIC. Theoretical calculations of the Thermal-FIST hadron resonance gas model, HIJING, and EPOS LHC event generators are compared with experimental results, where a significant impact of resonance decays is observed. Thermal-FIST calculations under the grand canonical and canonical ensembles highlight significant differences, underscoring the role of local charge conservation in explaining the data. Recent lattice QCD studies have demonstrated that the magnetic field generated by spectator protons in heavy-ion collisions affects susceptibility ratios, in particular those related to the net-electric charge and the net-baryon numbers. The experimental findings are in qualitative agreement with the expectations of lattice QCD.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2025

First measurement of D* + vector meson spin alignment in Pb–Pb collisions at $\sqrt{{s}_{\text{NN}}}={5}.0{2}$ TeV

The first measurement of prompt D *+ -meson spin alignment in ultrarelativistic heavy-ion collisions with respect to the direction orthogonal to the reaction plane is presented. The spin alignment is quantified by measuring the element ρ 00 of the diagonal spin-density matrix for prompt D *+ mesons with 4 < p T < 30 GeV/c in two rapidity intervals, |y| < 0.3 and 0.3 < |y| < 0.8, in central (0–10%) and midcentral (30–50%) Pb–Pb collisions at $\sqrt{{s}_{\text{NN}}}={5}.0{2}$ TeV. Evidence of spin alignment ρ 00 > 1/3 has been found for p T > 15 GeV/c and 0.3 < |y| < 0.8 with a significance of 3.1σ. The measured spin alignment of prompt D *+ mesons is compared with the one of inclusive J/ψ mesons measured at forward rapidity (2.5 < y < 4).

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2025

Multiplicity-dependent inclusive J/ ψ production at forward rapidity in pp collisions at $\sqrt{s}$ = 13 TeV

This paper presents a study of the inclusive forward J/ψ yield as a function of forward charged-particle multiplicity in pp collisions at $\sqrt{s}$ = 13 TeV using data collected by the ALICE experiment at the CERN LHC. The results are presented in terms of relative J/ψ yields and relative charged-particle multiplicities with respect to these quantities obtained in inelastic collisions having at least one charged particle in the pseudorapidity range |η| < 1. The J/ψ mesons are reconstructed via their decay into μ + μ − pairs in the forward rapidity region (2.5 < y < 4). The relative multiplicity is estimated in the forward pseudorapidity range which overlaps with the J/ψ rapidity region. The results show a steeper-than-linear increase of the J/ψ yields versus the multiplicity. They are compared with previous measurements and theoretical model calculations.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2025

Particle production as a function of charged-particle flattenicity in 𝑝⁢𝑝 collisions at $\sqrt{s}$ = 13 TeV

This paper reports the first measurement of the transverse momentum (𝑝 T ) spectra of primary charged pions, kaons, (anti)protons, and unidentified particles as a function of the charged-particle flattenicity in pp collisions at $\sqrt{s}$ =13 TeV. Flattenicity is a novel event shape observable that is measured in the pseudorapidity intervals covered by the V0 detector, 2.8 < 𝜂 < 5.1 and −3.7 < 𝜂 < −1.7. According to QCD-inspired phenomenological models, it shows sensitivity to multiparton interactions and is less affected by biases toward larger 𝑝 T due to local multiplicity fluctuations in the V0 acceptance than multiplicity. The analysis is performed in minimum-bias (MB) as well as in high-multiplicity events up to 𝑝 T = 20 GeV/⁢𝑐. The event selection requires at least one charged particle produced in the pseudorapidity interval |𝜂| < 1. The measured 𝑝 T distributions, average 𝑝 T , kaon-to-pion and proton-to-pion particle ratios, presented in this paper, are compared to model calculations using pythia 8 based on color strings and EPOS LHC. The modification of the 𝑝 T -spectral shapes in low-flattenicity events that have large event activity with respect to those measured in MB events develops a pronounced peak at intermediate 𝑝 T (2 < 𝑝 T < 8 GeV/𝑐), and approaches the vicinity of unity at higher 𝑝 T . The results are qualitatively described by pythia, and they show different behavior than those measured as a function of charged-particle multiplicity based on the V0M estimator.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Delivering laser performance conditions to enable fusion ignition, and beyond at the National Ignition Facility

On December 5th, 2022, controlled fusion ignition was demonstrated for the first time at the National Ignition Facility (NIF), a major achievement in the field of Inertial Confinement Fusion (ICF) requiring a multi-decadal effort involving broad national and international collaborations. To drive the fusion ignition reaction with the compressed fuel capsule, that yielded 3.15 MJ of nuclear energy [1], the NIF laser delivered a high-precision pulse shape with 2.05 MJ of ultra-violet (UV) laser energy and a peak power of 440 TW. This laser energy was an increase of ~8 % compared to that delivered on the previous “threshold of ignition” record yield experiment (1.37 MJ of yield for 1.89 MJ of laser energy) on August 8th, 2021. Here we explain how the results of our extensive research in laser technology and UV optics damage mitigation led to major improvements in the NIF laser, enabling this energy increase along with additional accuracy, precision, and power balance enhancements. Furthermore, we will discuss on-going efforts that have enabled operations at 2.2 MJ of UV energy as well as potential new initiatives to push the laser performance –accuracy and delivered energy– to even higher levels in the future as previously demonstrated on a small subset of NIF beams.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2020

Study of CMOS strip sensor for future silicon tracker

Monolithic silicon sensors developed with High-Voltage CMOS (HV-CMOS) processes have become highly attractive for charged particle tracking. Compared with the standard CMOS sensors, HV-CMOS sensors can provide larger and deeper depletion regions that lead to larger signals and faster charge collection. They can provide high position resolution, low material budget, high radiation hardness and low cost that are desirable for high performance tracking in harsh collision environment. Various studies have been conducted to explore the technology feasibility for the large-area tracking systems at future collider experiments. CHESS (CMOS HV/HR Evaluation for Strip Sensor) sensor series have been developed as an alternative solution to the conventional silicon micro-strip detectors for the ATLAS inner tracker upgrade. The first prototype (named CHESS1) was to evaluate the diode geometry and the in-pixel analog electronics. Obtained test results were used to optimize the second prototype (named CHESS2). CHESS2 was implemented with a full digital readout architecture and realized as a full reticle sized monolithic sensor. Here, the basic characteristics of the CHESS2 prototype sensors and their performance in response to different input signals are presented.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2023

Sulfur-Ligated [2Fe-2C] Clusters as Synthetic Model Systems for Nitrogenase

Metal clusters featuring carbon and sulfur donors have coordination environments comparable to the active site of nitrogenase enzymes. Here, we report a series of di-iron clusters supported by the dianionic yldiide ligands, in which the Fe sites are bridged by two μ 2 -C atoms and four pendant S donors. The [L 2 Fe 2 ] (L = {[Ph 2 P(S)] 2 C} 2– ) cluster is isolable in two oxidation levels, all-ferrous Fe 2 II and mixed-valence Fe II Fe III . The mixed-valence cluster displays two peaks in the Mössbauer spectra, indicating slow electron transfer between the two sites. The addition of the Lewis base 4-dimethylaminopyridine to the Fe2 II cluster results in coordination with only one of the two Fe sites, even in the presence of an excess base. Conversely, the cluster reacts with 8 equiv of isocyanide t BuNC to give a monometallic complex featuring a new C–C bond between the ligand backbone and the isocyanide. The electronic structure descriptions of these complexes are further supported by X-ray absorption and resonant X-ray emission spectroscopies.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Why Are There so Few Reports of High-Energy Electron Drift Resonances? Role of Radial Phase Space Density Gradients

Models of monochromatic Pc5 (2–7 mHz) ultralow frequency (ULF) wave interactions with high energy (greater than ~1 MeV) electrons predict drift resonant interactions that can cause rapid radial transport and acceleration. There are few reports of electron drift resonance at energies greater than ~1 MeV, in contrast to lower energies; moreover, all previous reports occur in the aftermath of interplanetary shocks. These two facts are difficult to reconcile with theory and numerical simulations predicting that greater than ~1 MeV drift resonances should occur more often and in a wider variety of driving conditions. In this study, we show that a combination of observational sampling biases and nominal radial phase space density gradients is one explanation for this discrepancy between theory and observations. In particular, we examine electron dynamics in two case studies with very similar satellite coverage, solar wind conditions, and Pc5 wave properties, yet with different radial phase space density profiles. Using global wave and particle observations, we show that the events have vastly different particle responses despite having similar wave properties. Placing these results in context with past studies, we further show here that nominal radial PSD gradients near geostationary orbit can mask the expected drift resonance particle response and explain (1) the small number of past greater than ~1 MeV drift resonance reports and (2) the restriction of these reports to interplanetary shock events. We argue that future observational studies characterizing radial transport via drift resonance should examine global particle dynamics, including observations of the radial phase space density profile.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2024

Time-resolved Auger–Meitner spectroscopy of the photodissociation dynamics of CS 2

The photodissociation dynamics of UV excited CS 2 are investigated using time-resolved Auger–Meitner (AM) spectroscopy. AM decay is initiated by inner-shell ionisation with a femtosecond duration x-ray (179.9 eV) probe generated by the FERMI free electron laser. The time-delayed x-ray probe removes an electron from the S(2p) orbital leading to secondary emission of a high energy electron through AM decay. We monitor the electron kinetic energy of the AM emission as a function of pump-probe delay and observe time-dependent changes in the spectrum that correlate with the formation of bound, excited-state CS 2 molecules at early times, and CS + S fragments on the picosecond timescale. The results are analysed based on a simplified kinetic scheme that provides a time constant for dissociation of approximately 1.2 ps, in agreement with previous time-resolved x-ray photoelectron spectroscopy measurements (Gabalski, et al 2023 J. Phys. Chem. Lett. 14 7126–7133).

Auger spectroscopy↗
DOE OSTI2021

The Hi-GAL compact source catalogue – II. The 360° catalogue of clump physical properties

ABSTRACT We present the 360° catalogue of physical properties of Hi-GAL compact sources, detected between 70 and 500 $\mu$m. This release not only completes the analogous catalogue previously produced by the Hi-GAL collaboration for −71° ≲ ℓ ≲ 67°, but also meaningfully improves it because of a new set of heliocentric distances, 120 808 in total. About a third of the 150 223 entries are located in the newly added portion of the Galactic plane. A first classification based on detection at 70 $\mu$m as a signature of ongoing star-forming activity distinguishes between protostellar sources (23 per cent of the total) and starless sources, with the latter further classified as gravitationally bound (pre-stellar) or unbound. The integral of the spectral energy distribution, including ancillary photometry from λ = 21 to 1100 $\mu$m, gives the source luminosity and other bolometric quantities, while a modified blackbody fitted to data for $\lambda \ge 160~\mu$m yields mass and temperature. All tabulated clump properties are then derived using photometry and heliocentric distance, where possible. Statistics of these quantities are discussed with respect to both source Galactic location and evolutionary stage. No strong differences in the distributions of evolutionary indicators are found between the inner and outer Galaxy. However, masses and densities in the inner Galaxy are on average significantly larger, resulting in a higher number of clumps that are candidates to host massive star formation. Median behaviour of distance-independent parameters tracing source evolutionary status is examined as a function of the Galactocentric radius, showing no clear evidence of correlation with spiral arm positions.

Elia, Davide↗
DOE OSTI2020

Search for elements 119 and 120

In this work, a search for production of the superheavy elements with atomic numbers 119 and 120 was performed in the 50 Ti + 249 Bk and 50 Ti + 249 Cf fusion-evaporation reactions, respectively, at the gas-filled recoil separator TASCA at GSI Darmstadt, Germany. Over four months of irradiation, the 249 Bk target partially decayed into 249 Cf, which allowed for a simultaneous search for both elements. Neither was detected at cross-section sensitivity levels of 65 and 200 fb for the 50 Ti + 249 Bk and 50 Ti + 249 Cf reactions, respectively, at a midtarget beam energy of E lab = 281.5 MeV. The nonobservation of elements 119 and 120 is discussed within the concept of fusion-evaporation reactions including various theoretical predictions on the fission-barrier heights of superheavy nuclei in the region of the island of stability.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2025

Investigating Λ baryon production in 𝑝-Pb collisions in jets and the underlying event using angular correlations

First measurements of hadron-Λ (ℎ−Λ) azimuthal angular correlations in 𝑝-Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV using the ALICE detector at the Large Hadron Collider are presented. These correlations are used to separate the production of associated Λ baryons into three different kinematic regions, namely those produced in the direction of the trigger particle (near side), those produced in the opposite direction (away side), and those whose production is uncorrelated with the jet axis (underlying event). The per-trigger associated Λ yields in these regions are extracted, along with the near- and away-side azimuthal peak widths, and the results are studied as a function of associated particle 𝑝 T and event multiplicity. Comparisons with the dpmjet event generator and previous measurements of the 𝜙⁡(1020) meson are also made. The final results indicate that strangeness production in the highest multiplicity 𝑝-Pb collisions is enhanced relative to low multiplicity collisions in both the jetlike regions and the underlying event. The production of Λ relative to charged hadrons is also enhanced in the underlying event when compared to the jetlike regions. Additionally, the results hint that strange quark production in the away-side of the jet is modified by soft interactions with the underlying event.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2025

LHCspin: a Polarized Gas Target for LHC

The goal of the LHCspin project is to develop innovative solutions for measuring the 3D structure of nucleons in high-energy polarized fixed-target collisions at LHC, exploring new processes and exploiting new probes in a unique, previously unexplored, kinematic regime. A precise multi-dimensional description of the hadron structure has, in fact, the potential to deepen our understanding of the strong interactions and to provide a much more precise framework for measuring both Standard Model and Beyond Standard Model observables. This ambitious task poses its basis on the recent experience with the successful installation and operation of the SMOG2 unpolarized gas target in front of the LHCb spectrometer. Besides allowing for interesting physics studies ranging from astrophysics to heavy-ion physics, SMOG2 provides an ideal benchmark for studying beam-target dynamics at the LHC and demonstrates the feasibility of simultaneous operation with beam-beam collisions. With the installation of the proposed polarized target system, LHCb will become the first experiment to simultaneously collect data from unpolarized beam-beam collisions at $\sqrt{s}$=14 TeV and polarized and unpolarized beam-target collisions at $\sqrt{s_{NN}}\sim$100 GeV. LHCspin has the potential to open new frontiers in physics by exploiting the capabilities of the world's most powerful collider and one of the most advanced spectrometers. This document also highlights the need to perform an R&D campaign and the commissioning of the apparatus at the LHC Interaction Region 4 during the Run 4, before its final installation in LHCb. This opportunity could also allow to undertake preliminary physics measurements with unprecedented conditions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Light neutral-meson production in pp collisions at $\sqrt{\text{s}}$ = 13 TeV

The momentum-differential invariant cross sections of π 0 and η mesons are reported for pp collisions at $\sqrt{s}$ = 13 TeV at midrapidity (|y| < 0.8). The measurement is performed in a broad transverse-momentum range of 0.2 < p T < 200 GeV/c and 0.4 < p T < 60 GeV/c for the π 0 and η, respectively, extending the p T coverage of previous measurements. Transverse-mass-scaling violation of up to 60% at low transverse momentum has been observed, agreeing with measurements at lower collision energies. Transverse Bjorken x (x T ) scaling of the π 0 cross sections at LHC energies is fulfilled with a power-law exponent of n = 5.01 ± 0.05, consistent with values obtained for charged pions at similar collision energies. The data are compared to predictions from next-to-leading order perturbative QCD calculations, where the π 0 spectrum is best described using the CT18 parton distribution function and the NNFF1.0 or BDSS fragmentation function. Expectations from PYTHIA8 and EPOS LHC overestimate the spectrum for the π 0 and are not able to describe the shape and magnitude of the η spectrum. The charged-particle multiplicity dependent π 0 and η p T spectra show the expected change of the spectral shape, characterized by a flatter slope with increasing multiplicity. This is demonstrated across a broad transverse-momentum range and up to events with a charged-particle multiplicity exceeding five times the mean value in minimum bias collisions. The η/π 0 ratio depends on the charged-particle multiplicity for p T < 4 GeV/c. PYTHIA8 and EPOS LHC qualitatively explain this behavior with an increasing contribution from the feed-down of heavier particles to the π 0 spectrum.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2026

Advances in 3D transient plasma dynamics and control through MHD and hybrid fluid-kinetic simulations with JOREK

Transient phenomena and their control are of high relevance in magnetic confinement fusion plasmas to guarantee a stable and safe plasma operation. Interpretative simulations can maximize the insights gained from experiments on present machines and predictive simulations can help in the preparation of design, mitigation techniques and operational scenarios for future devices. In this article, we provide an overview of recent advances and novel scientific results obtained with the 3D non-linear hybrid fluid-kinetic code JOREK, covering physics of plasma transients from the core to the scrape-off layer (SOL) both for tokamak and stellarator devices. Substantial progress was made in the physics understanding, model validation with experiments and experiment interpretation, thus, giving confidence for predictions to devices like DTT, ITER and DEMO. The topics addressed comprise a wide range: the edge physics of new operation scenarios and edge localized mode suppression; major disruptions with a focus on runaway electrons and vertical displacement events as well as disruption mitigation by shattered pellet injection; the physics mechanisms and operational limits of the flux pumping regime for sawtooth control; MHD limits of stellarators and work towards incorporating advanced edge/SOL/exhaust dynamics; continuing improvements of the code for more efficient hybrid simulations on conventional and accelerated high performance computing architectures.

disruptions↗
DOE OSTI2024

Investigating strangeness enhancement in jet and medium via 𝜙⁡(1020) production in 𝑝-Pb collisions at √ s NN = 5.02TeV

This work aims to differentiate strangeness produced from hard processes (jetlike) and softer processes (underlying event) by measuring the angular correlation between a high-momentum trigger hadron (ℎ) acting as a jet proxy and a produced strange hadron [𝜙⁡(1020) meson]. Measuring ℎ−𝜙 correlations at midrapidity in 𝑝-Pb collisions at √ s NN = 5.02TeV as a function of event multiplicity provides insight into the microscopic origin of strangeness enhancement in small collision systems. The jetlike and the underlying-event-like strangeness production are investigated as a function of event multiplicity. They are also compared between a lower and higher momentum region. The evolutions of the per-trigger yields within the near-side (aligned with the trigger hadron) and away-side (in the opposite direction of the trigger hadron) jets are studied separately, allowing for the characterization of two distinct jetlike production regimes. Furthermore, the ℎ−𝜙 correlations within the underlying event give access to a production regime dominated by soft production processes, which can be compared directly to the in-jet production. Comparisons between ℎ−𝜙 and dihadron correlations show that the observed strangeness enhancement is largely driven by the underlying event, where the 𝜙/ℎ ratio is significantly larger than within the jet regions. As multiplicity increases, the fraction of the total 𝜙⁡(1020) yield coming from jets decreases compared to the underlying event production, leading to high-multiplicity events being dominated by the increased strangeness production from the underlying event.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

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↗