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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 1,009 records · Page 56
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DOE OSTI2013

Methods and Results for Standard Model Event Generation at $\sqrt{s}$ = 14 TeV, 33 TeV and 100 TeV Proton Colliders (A Snowmass Whitepaper)

This document describes the novel techniques used to simulate the common Snowmass 2013 En- ergy Frontier Standard Model backgrounds for future hadron colliders. The purpose of many Energy Frontier studies is to explore the reach of high luminosity data sets at a variety of high energy collid- ers. The generation of high statistics samples which accurately model large integrated luminosities for multiple center-of-mass energies and pile-up environments is not possible using an unweighted event generation strategy | an approach which relies on event weighting was necessary. Even with these improvements in e ciency, extensive computing resources were required. This document de- scribes the speci c approach to event generation using Madgraph5 to produce parton-level processes, followed by parton showering and hadronization with Pythia6, and pile-up and detector simulation with Delphes3. The majority of Standard Model processes for pp interactions at √s = 14, 33, and 100 TeV with 0, 50, and 140 additional pile-up interactions are publicly available.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Three relativistic neutrons in a finite volume

We generalize the relativistic field-theoretic (RFT) three-particle finite-volume formalism to systems of three identical, massive, spin-1/2 fermions, such as three neutrons. This allows, in principle, for the determination of the three-neutron interaction from the finite-volume spectrum of three-neutron states, which can be obtained from lattice QCD calculations.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Recent developments in neutrino-nucleus interactions in 1 GeV energy region

Neutrino interactions in 1 GeV energy region are discussed. A role of nucleon-nucleon correlations in understanding recent quasi-elastic cross section measurements on nuclear target is explained. An importance of a correct treatment of two-body current contribution to the neutrino inclusive cross section is addressed.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Exploring the parameter space of warm-inflation models

Warm inflation includes inflaton interactions with other fields throughout the inflationary epoch instead of confining such interactions to a distinct reheating era. Previous investigations have shown that, when certain constraints on the dynamics of these interactions and the resultant radiation bath are satisfied, a low-momentum-dominated dissipation coefficient ∝T{sup 3}/m{sub χ}{sup 2} can sustain an era of inflation compatible with CMB observations. In this work, we extend these analyses by including the pole-dominated dissipation term ∝√(m{sub χ}T)exp (−m{sub χ}/T). We find that, with this enhanced dissipation, certain models, notably the quadratic hilltop potential, perform significantly better. Specifically, we can achieve 50 e-folds of inflation and a spectral index compatible with Planck data while requiring fewer mediator field (O(10{sup 4}) for the quadratic hilltop potential) and smaller coupling constants, opening up interesting model-building possibilities. We also highlight the significance of the specific parametric dependence of the dissipative coefficient which could prove useful in even greater reduction in field content.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

Benchmarking a nonequilibrium approach to photon emission in relativistic heavy-ion collisions

In this study, the production of photons through binary scattering processes is investigated for equilibrated hadronic systems. More precisely, a nonequilibrium hadronic transport approach to describe relativistic heavy-ion collisions is benchmarked with respect to photon emission. Cross sections for photon production in π + ρ → π + γ and π + π → ρ + γ scattering processes are derived from an effective chiral field theory and implemented into the hadronic transport approach, SMASH (Simulating Many Accelerated Strongly-interacting Hadrons). The implementation is verified by systematically comparing the thermal photon rate to theoretical expectations. Further, the impact of form factors is discussed, scattering processes mediated by ω mesons are found to contribute significantly to the total photon production. Several comparisons of the yielded photon rates are performed: to parametrizations of the very same rates as used in hydrodynamic simulations, to previous works relying on different cross sections for the production of direct photons from the hadronic stage, and to partonic rates. Finally, the impact of considering the finite width of the ρ meson is investigated, where a significant enhancement of photon production in the low-energy region is observed. This benchmark is the first step toward a consistent treatment of photon emission in hybrid hydrodynamics + transport approaches and toward a genuine dynamical description.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

Four-fermion interaction in relativistic heavy ion collisions

A (nearly) perfect liquid discovered in experiments with ultrarelativistic heavy ion collisions is investigated by studying the quark ensembles with four-fermion interaction considered as a fundamental theoretical approach. A comparative analysis of several quantum liquid models is performed, allowing one to conclude that the presence of gas-liquid phase transition is a characteristic feature of those models. The problem of the instability of the quark droplets with the small number of quarks, related with a possible formation of a chiral soliton, is discussed. A mixed phase of vacuum and baryon matter, as a possible scenario of its stability, is studied. Some aspects of the color superconductivity are considered. In addition, a recently proposed nontrivial thermodynamic state, called the fermion condensate, is studied. An analysis of unexpected opportunity to link the bare and effective coupling constants is performed within the framework of a simple model. It is pointed out that a simple subtraction procedure leads to the finite result without a typical logarithmic singularity for the observed coupling constant as a function of the transferred energy.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Mixing effects on spectroscopy and partonic observables of heavy mesons with logarithmic confining potential in a light-front quark model

Using the variational principle, we systematically investigate the mass spectra and wave functions of both 1⁢𝑆 and 2⁢𝑆 state heavy pseudoscalar (𝑃) and vector (𝑉) mesons within the light-front quark model. This approach incorporates a Coulomb plus logarithmic confinement potential to accurately describe the constituent quark and antiquark dynamics. Additionally, spin hyperfine interactions are introduced perturbatively to compute the masses of pseudoscalar and vector mesons. The present analyses of the 1⁢𝑆 and 2⁢𝑆 states require the consideration of mixing between them to account for empirical constraints. These constraints include the mass gap Δ⁢𝑀 𝑃 >Δ⁢𝑀 𝑉 , where Δ⁢𝑀 𝑃⁡(𝑉) =𝑀$^{2⁢𝑆}_{𝑃⁡(𝑉)}$−𝑀$^{1⁢𝑆}_{𝑃⁡(𝑉)}$ and the hierarchy of the decay constants 𝑓 1⁢𝑆 >𝑓 2⁢𝑆 . We find the optimal value of the mixing angle to be 𝜃 =1⁢8°, significantly enhancing the consistency between our spectroscopic predictions and the experimental data compiled by the Particle Data Group. Furthermore, based on the predicted mass, the newly observed resonance 𝐵 𝐽⁡ (5840) could be assigned as a 2 1⁢ 𝑆 0 state in the 𝐵 meson family. The study also reports various pertinent observables, including twist-two distribution amplitudes, electromagnetic form factors, charge radii, 𝜉 moments, and transition form factors that are found to be consistent with both available lattice simulations and experimental data. In addition, our predicted branching ratios for the channels of 𝐵 + →𝜏 + ⁢𝜈 𝜏 as well as rare decays of 𝐵 0 and 𝐵$^0_𝑠$ appear in accordance with experimental data.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Neutrino masses and scalar singlet dark matter

Here We propose a simple extension of the Standard Model (SM) which has a viable dark matter (DM) candidate and can explain the generation of tiny neutrino masses. The DM is an electroweak (EW) singlet scalar S, odd under an imposed exact Z 2 symmetry, that interacts with the SM through the “Higgs portal” coupling, while all other particles are even under Z 2 . The model also has an EW isospin 3/2 scalar Δ and a pair of EW isospin vectors Σ and $\bar{Σ}$, which are responsible for generating tiny neutrino mass via the effective dimension-seven operator. Thanks to the additional interactions with Δ, the scalar singlet DM S survives a large region of parameter space by relic density constraints from WMAP/Planck and direct search bounds from updated LUX data. Constraints on the model from the LHC are also discussed.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Lambda-Nucleon Potential Calculated from Lattice QCD

We present our studies of Lambda-Nucleon ({Lambda}N) interaction by using lattice QCD. The equal-time Nambu-Bethe-Salpeter (NBS) amplitude of the lowest energy scattering state of a proton-{Lambda} system is calculated from lattice QCD. In this report, two different types of gauge configurations are employed: (i) Quenched QCD configurations at {beta} = 5.7 (a = 0.1416(9) fm) on a 32{sup 3}x48 lattice, whose spatial volume is (4.5 fm){sup 3}.(ii)2+1 flavor full QCD configurations generated by the PACS-CS collaboration at {beta} = 1.9 (a = 0.0907(13) fm) on a 32{sup 3}x64 lattice, whose spatial volume is (2.90 fm){sup 3}. The spin-singlet central potential is calculated from the NBS wave function for the spin J = 0 state, whereas the spin-triplet central potential as well as the tensor potential are deduced simultaneously from the NBS wave function for the spin J = 1 state by dividing it into the S-wave and the D-wave components.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Early Career: The search for weakly interacting dark matter with liquid xenon

We report results from a search for weakly interacting dark matter particles obtained with the LUX experiment. LUX was located at a depth of 4850 feet at the Sanford Underground Research Facility in Lead, South Dakota from 2013 through 2016. It found no evidence for dark matter particle interactions and set new constraints on the properties of such particles for masses between 6 GeV and 100 TeV. The work reported here also characterized the performance of such experiments by developing a new calibration technique based upon a tritium beta decay source.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Thermodynamic origin of the pressure-induced Invar effect: General criterion and experimental study of Fe 68 ⁢Pd 32

Synchrotron X-ray diffraction measurements were performed on 57 Fe 68 Pd 32 at multiple pressures and two temperatures in a diamond-anvil cell. Between 4 and 11GPa, the thermal expansion was zero or slightly negative. This pressure-induced Invar effect was studied further with 57 Fe nuclear forward scattering and nuclear resonant inelastic X-ray scattering to obtain information on the pressure-induced changes in both the magnetization and the phonon density of states. Magnetic entropy and phonon entropy were obtained from these results, the latter with additional measurements from inelastic neutron scattering to account for the contributions from Pd atoms. The dependencies of these entropies on pressure gave the magnetic and phonon contributions to thermal expansion. These canceled in the region of pressure-induced Invar behavior, even though they individually increased by more than a factor of 2 below the Curie pressure. The behavior of phonons gives evidence for spin-phonon interactions in Fe 68 Pd 32 . A general explanation of the pressure-induced Invar effect is presented, showing that Invar behavior is typically expected at a pressure P* below a magnetic transition at pressure PC. The difference in pressure P C − P* scales with the fractional reduction in magnetic exchange interaction divided by the average Gr¨uneisen parameter.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2021

Self-interacting neutrinos, the Hubble parameter tension, and the cosmic microwave background

Here, we perform a comprehensive study of cosmological constraints on nonstandard neutrino self-interactions using cosmic microwave background and baryon acoustic oscillation data. We consider different scenarios for neutrino self-interactions distinguished by the fraction of neutrino states allowed to participate in self-interactions and how the relativistic energy density, N eff , is allowed to vary. Specifically, we study cases in which all neutrino states self-interact and N eff varies; two species free-stream, which we show alleviates tension with laboratory constraints, while the energy in the additional interacting states varies; and a variable fraction of neutrinos self-interact with either the total N eff fixed to the Standard Model value or allowed to vary. In no case do we find compelling evidence for new neutrino interactions or nonstandard values of N eff . In several cases, we find additional modes with neutrino decoupling occurring at lower redshifts z dec ~ 10 3–4 . We do a careful analysis to examine whether new neutrino self-interactions solve or alleviate the so-called H 0 tension and find that, when all Planck 2018 CMB temperature and polarization data are included, none of these examples eases the tension more than allowing a variable N eff comprised of free-streaming particles. Although we focus on neutrino interactions, these constraints are applicable to any light relic particle.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Post-inflationary dark matter bremsstrahlung

Dark matter may only interact with the visible sector efficiently at energy scales above the inflaton mass, such as the Planck scale or the grand unification scale. In such a scenario, the dark matter is mainly produced out of equilibrium during the period of reheating, often referred to as UV freeze-in. Here, we evaluate the abundance of the dark matter generated from bremsstrahlung off the inflaton decay products assuming no direct coupling between the inflaton and the dark matter. This process generally dominates the production of dark matter for low reheating temperatures where the production through the annihilations of particle in the thermal plasma becomes inefficient. We find that the bremsstrahlung process dominates for reheating temperatures T RH ≲ 10 10 GeV, and produces the requisite density of dark matter for a UV scale ≃ 10 16 GeV. As examples, we calculate numerically the yield of the dark matter bremsstrahlung through gravitation and dimension-6 vector portal effective interactions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Effect of final state interactions on particle production in d+Au collisions at energies available at the BNL Relativistic Heavy Ion Collider

We show that particle species dependence of enhanced hadron production at intermediate transverse momentum (p{sub T}) for d+Au collisions at RHIC can be understood in terms of the hadronization from string fragmentation and the subsequent hadronic rescatterings in the final state. A multiphase transport model (AMPT) with two different hadronization mechanisms, string fragmentation or parton coalescence, is used in our study. When the hadrons are formed from string fragmentation, the subsequent hadronic rescatterings will result in particle mass dependence of the nuclear modification factor R{sub CP}, which is consistent with the present experimental data. On the other hand, in the framework of parton coalescence, the mass dependence disappears and the strangeness plays an important role in hadron production.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2023

Non-standard neutrino interactions in light mediator models at reactor experiments

Compared to other neutrino sources, the huge anti-neutrino fluxes at nuclear reactor based experiments empower us to derive stronger bounds on non-standard interactions of neutrinos with electrons mediated by light scalar/vector mediators. At neutrino energy around 200 keV reactor anti-neutrino flux is at least an order of magnitude larger compared to the solar flux. The atomic and crystal form factors of the detector materials related to the details of the atomic structure becomes relevant at this energy scale as the momentum transfers would be small. Non-standard neutrino-electron interaction mediated by light scalar/vector mediator arises naturally in many low-scale models. We also propose one such new model with a light scalar mediator. Here, we investigate the parameter space of such low-scale models in reactor based neutrino experiments with low threshold Ge and Si detectors, and find the prospect of probing/ruling out the relevant parameter space by finding the projected sensitivity at 90% confidence level by performing a $χ$ 2 -analysis. We find that a detector capable of discriminating between electron recoil and nuclear recoil signal down to a very low threshold such as 5 eV placed in reactor based experiment would be able to probe a larger region in parameter space compared to the previously explored region. A Ge (Si) detector with 10 kg-yr exposure and 1 MW reactor anti-neutrino flux would be able to probe the scalar and vector mediators with masses below 1 keV for coupling products $\sqrt{g_vg_e}$ ~ 1 × 10 -6 (9.5 × 10 -7 ) and 1 × 10 -7 (8 × 10 -8 ), respectively.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Models for SIMP dark matter and dark photon

We give a review on the SIMP paradigm and discuss a consistent model for SIMP dark mesons in the context of a dark QCD with flavor symmetry. The Z′-portal interaction is introduced being compatible with stable dark mesons and is responsible for making the SIMP dark mesons remain in kinetic equilibrium with the SM during the freeze-out process. The SIMP parameter space of the Z′ gauge boson can be probed by future collider and direct detection experiments.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Studying the interaction between charm and light-flavor mesons

The two-particle momentum correlation functions between charm mesons ( D * ± and D ± ) and charged light-flavor mesons ( π ± and K ± ) in all charge combinations are measured for the first time by the ALICE Collaboration in high-multiplicity proton–proton collisions at a center-of-mass energy of s = 13 TeV . For DK and D * K pairs, the experimental results are in agreement with theoretical predictions of the residual strong interaction based on quantum chromodynamics calculations on the lattice and chiral effective field theory. In the case of D π and D * π pairs, tension between the calculations including strong interactions and the measurement is observed. For all particle pairs, the data can be adequately described by Coulomb interaction only, indicating a shallow interaction between charm and light-flavor mesons. Finally, the scattering lengths governing the residual strong interaction of the D π and D * π systems are determined by fitting the experimental correlation functions with a model that employs a Gaussian potential. The extracted values are small and compatible with zero. © 2024 CERN, for the ALICE Collaboration 2024 CERN

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗