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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 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Search for non-resonant Higgs boson pair production in the $2b+2\ell +{E}_{\textrm{T}}^{\textrm{miss}}$ final state in pp collisions at $\sqrt{s}$ = 13 TeV with the ATLAS detector

A search for non-resonant Higgs boson pair (HH) production is presented, in which one of the Higgs bosons decays to a b-quark pair ($b\bar{b}$) and the other decays to WW * , ZZ * , or τ + τ – , with in each case a final state with ℓ + ℓ – + neutrinos (ℓ = e, μ). The analysis targets separately the gluon-gluon fusion and vector boson fusion production modes. Data recorded by the ATLAS detector in proton-proton collisions at a centre-of-mass energy of 13 TeV at the Large Hadron Collider, corresponding to an integrated luminosity of 140 fb –1 , are used in this analysis. Events are selected to have exactly two b-tagged jets and two leptons with opposite electric charge and missing transverse momentum in the final state. These events are classified using multivariate analysis algorithms to separate the HH events from other Standard Model processes. No evidence of the signal is found. The observed (expected) upper limit on the cross-section for non-resonant Higgs boson pair production is determined to be 9.7 (16.2) times the Standard Model prediction at 95% confidence level. The Higgs boson self-interaction coupling parameter κ λ and the quadrilinear coupling parameter κ 2V are each separately constrained by this analysis to be within the ranges [–6.2, 13.3] and [–0.17, 2.4], respectively, at 95% confidence level, when all other parameters are fixed.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Search for same-charge top-quark pair production in pp collisions at $\sqrt{s}$ = 13 TeV with the ATLAS detector

A search for the production of top-quark pairs with the same electric charge ($tt$ or $\overline{tt}$) is presented. The analysis uses proton-proton collision data at $\sqrt{s}$ = 13 TeV, recorded by the ATLAS detector at the Large Hadron Collider, corresponding to an integrated luminosity of 140 fb −1 . Events with two same-charge leptons and at least two b-tagged jets are selected. Neural networks are employed to define two selections sensitive to additional couplings beyond the Standard Model that would enhance the production rate of same-sign top-quark pairs. No significant signal is observed, leading to an upper limit on the total production cross-section of same-sign top-quark pairs of 1.6 fb at 95% confidence level. Corresponding limits on the three Wilson coefficients associated with the $\mathcal{O}^{(1)}_{tu}$, $\mathcal{O}^{(1)}_{Qu}$, and $\mathcal{O}^{(8)}_{Qu}$ operators in the Standard Model Effective Field Theory framework are derived.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Search for direct pair production of sleptons and charginos decaying to two leptons and neutralinos with mass splittings near the $W$-boson mass in $\sqrt{s}$ = 13 TeV pp collisions with the ATLAS detector

A search for the electroweak production of pairs of charged sleptons or charginos decaying into two-lepton final states with missing transverse momentum is presented. Two simplified models of R-parity-conserving supersymmetry are considered: direct pair-production of sleptons ($\sim\atop{\ell}$$\sim\atop{\ell}$), with each decaying into a charged lepton and a $\sim\atop{\chi}$ $^{0}_{1}$ neutralino, and direct pair-production of the lightest charginos ($\sim\atop{\chi}$ $^{±}_{1}$ $\sim\atop{\chi}$ $^{∓}_{1}$), with each decaying into a W-boson and a $\sim\atop{\chi}$ $^{0}_{1}$. The lightest neutralino ($\sim\atop{\chi}$ $^{0}_{1}$) is assumed to be the lightest supersymmetric particle (LSP). The analyses target the experimentally challenging mass regions where $m$($\sim\atop{\ell}$) - $m$($\sim\atop{\chi}$ $^{0}_{1}$) and ($m$$\sim\atop{\chi}$ $^{±}_{1}$) – )$m$$\sim\atop{\chi}$ $^{0}_{1}$) are close to the W-boson mass (‘moderately compressed’ regions). The search uses 139 fb –1 of $\sqrt{s}$ = 13 TeV proton-proton collisions recorded by the ATLAS detector at the Large Hadron Collider. No significant excesses over the expected background are observed. Exclusion limits on the simplified models under study are reported in the ($\sim\atop{\ell}$, $\sim\atop{\chi}$ $^{0}_{1}$) and ($\sim\atop{\chi}$ $^{±}_{1}$, $\sim\atop{\chi}$ $^{0}_{1}$) mass planes at 95% confidence level (CL). Sleptons with masses up to 150 GeV are excluded at 95% CL for the case of a mass-splitting between sleptons and the LSP of 50 GeV. Chargino masses up to 140 GeV are excluded at 95% CL for the case of a mass-splitting between the chargino and the LSP down to about 100 GeV.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Vector boson pair production at one loop: analytic results for the process $q\bar{q}$$ℓ\bar{ℓ}$$ℓ'\bar{ℓ}'g$

We present compact analytic results for the one-loop amplitude for the process 0 → $q\bar{q}$$ℓ\bar{ℓ}$$ℓ'\bar{ℓ}'g$, relevant for both the production of a pair of Z and W-bosons in association with a jet. We focus on the gauge-invariant contribution mediated by a loop of quarks. We explicitly include all effects of the loop-quark mass m, appropriate for the production of a pair of Z-bosons. In the limit m → 0, our results are also applicable to the production of W-boson pairs, mediated by a loop of massless quarks. Implemented in a numerical code, the results are fast. The calculation uses novel advancements in spinor-helicity simplification techniques, for the first time applied beyond five-point massless kinematics. We make use of primary decompositions from algebraic-geometry, which now involve non-radical ideals, and p-adic numbers from number theory. We show how to infer whether numerator polynomials belong to symbolic powers of non-radical ideals through numerical evaluations.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Combination of inclusive top-quark pair production cross-section measurements using ATLAS and CMS data at $ \sqrt{s} $ = 7 and 8 TeV

A combination of measurements of the inclusive top-quark pair production cross-section performed by ATLAS and CMS in proton–proton collisions at centre-of-mass energies of 7 and 8 TeV at the LHC is presented. The cross-sections are obtained using top-quark pair decays with an opposite-charge electron–muon pair in the final state and with data corresponding to an integrated luminosity of about 5 fb$^{−1}$ at $ \sqrt{s} $ = 7 TeV and about 20 fb$^{−1}$ at $ \sqrt{s} $ = 8 TeV for each experiment. The combined cross-sections are determined to be 178.5 ± 4.7 pb at $ \sqrt{s} $ = 7 TeV and $ {243.3}_{-5.9}^{+6.0} $ pb at $ \sqrt{s} $ = 8 TeV with a correlation of 0.41, using a reference top-quark mass value of 172.5 GeV. The ratio of the combined cross-sections is determined to be R$_{8/7}$ = 1.363 ± 0.032. The combined measured cross-sections and their ratio agree well with theory calculations using several parton distribution function (PDF) sets. The values of the top-quark pole mass (with the strong coupling fixed at 0.118) and the strong coupling (with the top-quark pole mass fixed at 172.5 GeV) are extracted from the combined results by fitting a next-to-next-to-leading-order plus next-to-next-to-leading-log QCD prediction to the measurements. Using a version of the NNPDF3.1 PDF set containing no top-quark measurements, the results obtained are $ {m}_t^{\textrm{pole}}={173.4}_{-2.0}^{+1.8} $ GeV and $ {\alpha}_{\textrm{s}}\left({m}_Z\right)={0.1170}_{-0.0018}^{+0.0021} $.[graphic not available: see fulltext]

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2026

Search for Higgs boson pair production in the $\mathrm{b}\overline{\mathrm{b}}\mathrm{WW}$ decay channel with two leptons in the final state using proton-proton collision data at $\sqrt{s}=13.6$ TeV

A search for Higgs boson pair production is presented, targeting final states where one Higgs boson decays to a bottom quark-antiquark pair and the other Higgs boson decays to two W bosons, both of which decay leptonically, to an electron or a muon, and a neutrino. For the first time, the search is conducted with proton-proton collision data from the LHC at $\sqrt{s}=13.6$ TeV, recorded with the CMS detector in 2022 and 2023 and corresponding to an integrated luminosity of 62 fb −1 . The results are consistent with the standard model predictions. An upper limit of 12.0 times the standard model prediction at 95% confidence level is set on the Higgs boson pair production cross section, with an expected limit of 18.5. The results are also used to constrain the strength of the trilinear self-coupling of the Higgs boson, as well as of the quartic coupling between two Higgs bosons and two vector bosons.

Hadron-Hadron Scattering↗
DOE OSTI2025

A search for dark matter produced in association with a dark Higgs boson decaying into a Higgs boson pair in 3b or 4b final states using pp collisions at $\sqrt{s}=13$ TeV with the ATLAS detector

A search is performed for dark matter particles produced in association with a resonant pair of Higgs bosons using 140 fb −1 of proton-proton collisions at a centre-of-mass energy of 13 TeV recorded by the ATLAS detector at the Large Hadron Collider. This signature is expected in some extensions of the Standard Model predicting the production of dark matter particles, and is interpreted in terms of a dark Higgs model containing a Z′ mediator in which the dark Higgs boson s decays into a pair of Higgs bosons. The dark Higgs boson is reconstructed through final states with at least three b-tagged jets, produced by the pair of Higgs boson decays, in events with significant missing transverse momentum consistent with the presence of dark matter. The observed data are found to be in good agreement with Standard Model predictions, constraining scenarios with dark Higgs boson masses within the range of 250 to 400 GeV and Z′ mediators up to 2.3 TeV.

Dark Energy and Dark Matter↗
DOE OSTI2024

Analytic amplitudes for a pair of Higgs bosons in association with three partons

The pair production of Higgs bosons at the LHC can give information about the triple Higgs boson coupling. We perform an analytic one-loop calculation of the amplitudes for a pair of Higgs bosons in association with three partons, retaining the exact dependence on the quark mass circulating in the loop. These amplitudes constitute the real radiation corrections in the calculation of Higgs boson pair production at next-to-leading order in the strong coupling. The results of an analytic generalised-unitarity computation are simplified via analytic reconstruction in spinor variables. Compact ansätze for kinematic pole residues are iteratively fitted via p-adic evaluations near said poles and subtracted until no pole remains. A new ansatz construction is introduced to minimally parametrise coefficients of amplitudes with multiple massive external legs. The simplified expressions are faster to evaluate than automatic codes and can lead to more stable results near singular regions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Pairing Ga/Al-Zeolites with tailored acidity as tandem catalysts for the conversion of alcohols to olefins

Zeolites are versatile catalysts owing to their tunable acidity where the active site(s) can be placed within the crystal framework or as extra-framework species in confined pores. A common approach to tailor Brønsted acidity is heteroatom exchange involving the replacement of framework aluminum with alternative elements. Introduction of heteroatoms often results in less acidic catalysts that can be used in tandem reactions for targeted reactive intermediates. Here, in this study, we prepare a series of three different zeolites with MWW, CHA, and MFI frameworks as aluminosilicates and gallosilicates to demonstrate their performance in alcohol dehydration reactions. The two reactions examined in this study are methanol conversion to dimethyl ether and ethanol conversion to ethylene. Our findings reveal that Ga-zeolites exhibit superior performance with Ga-MCM-22 (MWW) achieving nearly 100% alcohol conversion and selectivity to desired products at contact times that are significantly less than most dehydration catalysts reported in literature. The unique properties of Ga-zeolites are attributed to their reduced acid site strength via a direct (one-pot) synthesis that avoids conventional time-intensive, multi-step post-synthesis modifications of Al-zeolites. Here we demonstrate the use of Ga-zeolites as tandem catalysts when paired with a downstream Al-zeolite in a dual-bed reactor configuration to convert cheaper reagents (alcohols) upstream to more desired intermediates as feeds for downstream catalysts to produce light olefins. We demonstrate that dual beds using Ga-zeolite – Al-ZSM-5 (upstream–downstream) pairings outperform single bed configurations with Al-ZSM-5 or a physical mixture (Ga-/Al-zeolite) for methanol to hydrocarbons reactions, with notable improvements in catalyst lifetime and increased light olefins selectivity. Similarly, dual beds using Ga-zeolite – Al-SSZ-13 (upstream–downstream) pairings result in improved performance for ethanol to propylene reactions with significant increases in propylene selectivity (>20 %) compared to a conventional single bed configuration of Al-SSZ-13. Overall, this study offers a new perspective on the use of heteroatom-exchanged zeolite catalysts in tandem reactions as a means of capitalizing on their reduced acid site strength and suggests differences in the intrinsic acidity of zeolite crystal structures.

42 ENGINEERING↗
DOE OSTI2020

Semiclassical model for calculating exciton and polaron pair energetics at interfaces

Exciton and polaron pair dissociation is a key functional aspect of photovoltaic devices. To improve upon the current state of interfacial transport models, we augment the existing classical models of dielectric interfaces by incorporating results from ab initio calculations, allowing us to calculate exciton and polaron binding energies more accurately. We demonstrate the predictive capabilities of this new model using two interfaces: (i) the boron subphthalocyanine chloride (SubPc) and C60 interface, which is an archetype for many organic photovoltaic devices; and (ii) pentacene and silicon (1 0 0), which represents a hybrid between organic and inorganic semiconductors. Overall, our calculations predict that the insertion of molecular dipoles at interfaces can be used for improving polaron pair dissociation and that sharp transitions in dielectric permittivity can have a stronger effect on the polaron pair dissociation than even the electron-hole Coulomb interaction.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Dedicated beam position monitor pair for model-independent lattice characterization at NSLS-II

This paper reports recent lattice characterization results obtained at the National Synchrotron Light Source II (NSLS-II) storage ring, conducted without reliance on a lattice model. A pair of beam position monitors (BPMs) with bunch-by-bunch (B$\times$B) resolution, were recently installed in a section of the storage ring free of magnetic fields. The new BPM pair measured the beam, or bunch’s transverse Poincaré map precisely after the beam was excited. Linear one-turn-matrices (OTM) were then derived, and from these, the 4-dimensional coupled Twiss parameters were extracted at the locations of the BPM pair. By normalizing beam oscillation amplitudes with the Twiss parameters, the global action-variables were obtained. Additionally, these action-variables facilitated the measurement of the local Twiss parameters observed by other BPMs independent on lattice model. This method is general, and particularly useful in certain scenarios such as a round beam mode in a diffraction-limited light source ring. We applied it to assess both weakly and strongly coupled lattices at the NSLS-II ring. Through analysis of the strongly coupled lattice, the quadrupole tilt errors were estimated to be less than 400 μrad. Utilizing the BPMs’ B$\times$B resolution, for the first time we observed the variations of the linear lattice along a long bunch-train.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Search for pair production of boosted Higgs bosons via vector-boson fusion in the $b$$\overline{b}$$b$$\overline{b}$ final state using $pp$ collisions at $\sqrt{s}$ = 13 TeV with the ATLAS detector

A search for Higgs boson pair production via vector-boson fusion is performed in the Lorentz-boosted regime, where a Higgs boson candidate is reconstructed as a single large-radius jet, using 140 fb−1 of proton–proton collision data at $\sqrt{s}$ = 13 TeV recorded by the ATLAS detector at the Large Hadron Collider. Only Higgs boson decays into bottom quark pairs are considered. The search is particularly sensitive to the quartic coupling between two vector bosons and two Higgs bosons relative to its Standard Model prediction, K 2V . This study constrains K 2V to 0.55 < K 2V < 1.49 at the 95% confidence level. The value K 2V = 0 is excluded with a significance of 3.8 standard deviations with other Higgs boson couplings fixed to their Standard Model values. A search for new heavy spin-0 resonances that would mediate Higgs boson pair production via vector-boson fusion is carried out in the mass range of 1–5 TeV for the first time under several model and decay-width assumptions. No significant deviation from the Standard Model hypothesis is observed and exclusion limits at the 95% confidence level are derived.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

On the co-nucleation of adjoining twin pairs at grain boundaries in hexagonal close-packed materials

Here this work addresses the formation of adjoining twin pairs (ATPs) at grain boundaries (GBs) in hexagonal close-packed (hcp) metals from the perspective of the co-nucleation (CN) of pairs of deformation twins. A continuum defect mechanics model is proposed to investigate the energetic feasibility of the CN of ATPs resulting from the dissociation of GB dislocations. Application of the model to a set of GBs in Mg reveals that CN is largely preferred over the nucleation of a single twin variant for low misorientation angle GBs, which is consistent with previous experimental analyses. The CN events are subsequently analyzed considering the GB character, and the twin system alignment ($m$') and Schmid factors to obtain better insights into the conditions governing the formation of ATPs via CN. The likelihood of CN even at low $m$' values reveals that CN events could be responsible for the formation of ATP pairs in these scenarios.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Annihilation-gamma-based diagnostic techniques for magnetically confined electron–positron pair plasma

Efforts are underway to magnetically confine electron–positron pair plasmas to study their unique behaviour, which is characterized by significant changes in plasma time and length scales, supported waves and unstable modes. However, use of conventional plasma diagnostics presents challenges with these low-density and annihilating matter–antimatter plasmas. To address this problem, we propose to develop techniques based on the distinct emission provided by annihilation. This emission exhibits two spatial correlations: the distance attenuation of isotropic sources and the back-to-back propagation of momentum-preserving 2 $\gamma$ annihilation. We present the results of our analysis of the $\gamma$ emission rate and the spatial profile of the annihilation in a magnetized pair plasma from direct pair collisions, from the formation and decay of positronium as well as from transport processes. In order to demonstrate the effectiveness of annihilation-based techniques, we tested them on annular $\gamma$ emission profiles produced by a $\beta ^+$ radioisotope on a rotating turntable. Direct and positronium-mediated annihilation result in overlapping volumetric $\gamma$ sources, and the 2 $\gamma$ emission from these volumetric sources can be tomographically reconstructed from coincident counts in multiple detectors. Transport processes result in localized annihilation where field lines intersect walls, limiters or internal magnets. These localized sources can be identified by the fractional $\gamma$ counts on spatially distributed detectors.

Physics↗
DOE OSTI2026

Transfer Learning Meets Embedded Correlated Wavefunction Theory for Chemically Accurate Molecular Simulations: Application to Calcium Carbonate Ion Pairing

Achieving chemical accuracy for molecular simulations remains a central challenge in computational chemistry. Here, we present an embedded correlated wavefunction transfer learning (ECW-TL) framework for accurately simulating molecular dynamics in the condensed phase. ECW-TL incorporates high-level electron exchange and correlation effects in ECW theory while preserving the training and computational efficiency of machine-learned interatomic potentials. We demonstrate the framework on Ca 2+ –CO 3 2– ion pairing in aqueous solution, a key process underlying CO 2 mineralization in seawater. As proof of principle, we first show that fine-tuning a DFT-revPBE-D3(BJ) baseline model with embedded-DFT-SCAN data reproduces the DFT-SCAN free-energy surface within 1 kcal/mol across all solvation states. Extending the framework to embedded MP2 and localized natural-orbital CCSD(T) further refines the free-energy profile, revealing the crucial role of exact electron exchange and correlation in determining ion-pair stability and structure. The computed ion-pair association free energy is in quantitative agreement with experimental measurements, further validating the accuracy of the ECW-TL framework. ECW-TL thus provides a general, data-efficient route for transferring CW accuracy to efficient simulations of complex aqueous and interfacial chemical processes.

cluster chemistry↗
DOE OSTI2021

Specific Ion Solvation and Pairing Effects in Glycerol Carbonate

Identifying the driving forces behind the solvation of inorganic salts by nonaqueous solvents is an important step in the development of green solvents. Here we focus on one promising solvent: glycerol carbonate (GC). Using ab initio molecular dynamics simulations, we build upon our previous work by detailing glycerol carbonate’s interactions with a series of anions, a lithium ion, and the LiF ion pair. Through these investigations, we highlight the changes in solvation behavior as the anion size increases, the competition of binding shown by lithium for the oxygens of GC, and the behavior of the LiF ion pair in a GC solution. These results in this work indicate the importance of the cation’s identity in ion-pairing structure and dynamics and lend insight into the key factors behind the specific ion effects seen in GC.

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

Uniform Diffusion of Cooper Pairing Mediated by Hole Carriers in Topological Sb 2 Te 3 /Nb

Spin-helical Dirac Fermions at a doped topological insulator’s boundaries can support Majorana quasiparticles when coupled with s-wave superconductors, but in n-doped systems, the requisite induced Cooper pairing in topological states is often buried at heterointerfaces or complicated by degenerate coupling with bulk conduction carriers. Rarely probed are p-doped topological structures with nondegenerate Dirac and bulk valence bands at the Fermi level, which may foster long-range superconductivity without sacrificing Majorana physics. Using ultrahigh-resolution photoemission, we report proximity pairing with a large decay length in p-doped topological Sb 2 Te 3 on superconducting Nb. Despite no momentum-space degeneracy, the topological and bulk states of Sb 2 Te 3 /Nb exhibit the same isotropic superconducting gaps at low temperatures. Furthermore, our results unify principles for realizing accessible pairing in Dirac Fermions relevant to topological superconductivity.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Bridge Connectivity Dictates Spin Interactions and Triplet Pair Dynamics in Intramolecular Singlet Fission

Electron spin plays a critical role in determining the structure, dynamics, and reactivities of molecular excited states, including multiexciton processes such as singlet fission. These systems exhibit triplet pair states whose excited state dynamics can be widely tuned through molecular engineering. For example, the electronic coupling between covalently linked chromophores can be readily modulated using chemical bridges to control proximity, quantum interference, or resonance effects. However, less is known about how spin coupling interactions are impacted by chromophore architecture, and how this influences triplet pair recombination dynamics. Here, in this study, we investigate the role of bridge connectivity and chromophore identity in modulating interchromophore exchange and dipolar coupling interactions for a series of pentacene and tetracene dimers bridged by alternant hydrocarbons (phenylene, naphthalene, anthracene). Using both time-resolved electron paramagnetic resonance and transient absorption spectroscopy, we find that the boundedness and recombination pathways of the triplet pair spins are highly sensitive to molecular architecture and chromophore-specific magnetic dipolar interactions. Notably, nominally ferromagnetic and antiferromagnetic eigenstates result in distinct spin state orderings, consistent with predictions from quantum interference-based graphical models. These findings establish new design principles for tuning spin dynamics in iSF materials, with implications for photonic and quantum information applications.

He, Guiying [City Univ. of New York (CUNY), NY (Un↗