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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 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Common origin of warm dark matter and dark radiation

We consider a cosmological scenario where a relativistic particle and a stable massive particle are simultaneously produced from the decay of a late-decaying particle after Big-Bang Nucleosynthesis but before matter-radiation equality. The relativistic and massive particles behave as dark radiation and warm dark matter, respectively. Due to a common origin, the warmness and abundances are closely related. We refer to the models that lead to such a scenario as Common Origin of Warm and Relativistic Decay Products (COWaRD). We show that COWaRD predicts a correlation between the amount of dark radiation and suppression of the large scale structure, which can be tested in future precision cosmology observations. Furthermore, we demonstrate that COWaRD is realized, as an example, in a class of supersymmetric axion models and that future observations by the next generation Cosmic Microwave Background, Large Scale Structure, and 21-cm surveys can reveal the structure of the theory.

cosmology of theories beyond the SM↗
DOE OSTI2024

Dark dimension and decaying dark matter gravitons

We explore the cosmology of the dark-dimension scenario taking into account perturbations in the linear regime. In the context of the dark-dimension scenario, a natural candidate for dark matter in our Universe is the excitations of a tower of massive spin-2 Kaluza-Klein (KK) gravitons. These dark gravitons are produced in the early Universe and decay to lighter KK gravitons during the course of cosmological evolution. The decay causes the average dark matter mass to decrease as the Universe evolves. In addition, the kinetic energy liberated in each decay leads to a kick velocity for the dark matter particles, leading to a suppression of structure formation. Using current cosmic microwave background (), baryon acoustic oscillation, and cosmic shear (KiDS-1000) data, we put a bound on the dark matter kick velocity today v today ≤ 2.2 × 10 − 4 c at 95% CL. This leads to rather specific regions of parameter space for the dark-dimension scenario. The combination of the experimental bounds from cosmology, astrophysics, and table-top experiments leads to the range l 5 ∼ 1 – 10 μ m for the size of the dark dimension. The dark-dimension scenario is found to be remarkably consistent with current observations and provides signatures that are within reach of near-future experiments. Published by the American Physical Society 2024

Astronomy & Astrophysics↗
DOE OSTI2024

Novel transition dynamics of topological solitons

Continuous phase transitions can be classified into ones characterized by local-order parameters and others that need additional topological constraints. The critical dynamics near the former transitions have been extensively studied, but the latter is less understood. We fill this gap in knowledge by studying the transition dynamics to a parity-breaking topological ground state called the chiral soliton lattice in quantum chromodynamics at finite temperature, baryon chemical potential, and an external magnetic field. We find a slowing down of the soliton’s translational motion as the critical magnetic field approaches, while the local relaxation rate to the solitonic state remains finite. The time required to converge to the stationary state strongly depends on the symmetry of the initial configuration, determining whether translational motion occurs during the dynamic process. Published by the American Physical Society 2024

Nishimura, Kentaro↗
DOE OSTI2024

Data-driven and model-agnostic approach to solving combinatorial assignment problems in searches for new physics

We present a novel approach to solving combinatorial assignment problems in particle physics. The correct assignment of decay products to parent particles is achieved in a model-agnostic fashion by introducing a neural network architecture, asswd-, which combines a custom layer based on attention mechanisms and dual autoencoders. We demonstrate how the network, trained purely on background events in an unsupervised setting, is capable of reconstructing correctly hypothetical new particles regardless of their mass, decay multiplicity, and substructure, and produces simultaneously an anomaly score that can be used to efficiently suppress the background. This model allows the extension of the suite of searches for localized excesses to include nonresonant particle pair production where the reconstruction of the two resonant masses is thwarted by combinatorics. Published by the American Physical Society 2024

Astronomy & Astrophysics↗
DOE OSTI2024

Cosmology and terrestrial signals of sexaquark dark matter

We investigate the hypothesis that sexaquarks, hypothetical stable six-quark states, could be a significant component of the dark matter. We expand on previous studies of sexaquark cosmology, accounting for the possibility that some relevant interaction cross sections might be strongly suppressed below expectations based on dimensional analysis. We update direct-detection constraints on stable sexaquarks comprising a subdominant fraction of the dark matter, as well as limits on the annihilation of an antisexaquark component from Super-Kamiokande. We argue that the scenario where sexaquarks comprise a O ( 1 ) fraction of the dark matter would require either a suppression of O ( 10 − 19 ) in sexaquark interactions with baryons, combined with a very high yield of net sexaquark number from the quark-hadron transition, or else a very strong suppression of the cross section for antisexaquark annihilation on nucleons ( 24 + orders of magnitude below the QCD scale). Independently, we find that a sexaquark component comprising more than O ( 10 − 3 ) of the dark matter can be excluded from direct-detection bounds, unless its scattering cross section is severely suppressed compared to the expected scale of strong and even electromagnetic interactions. Published by the American Physical Society 2024

Astronomy & Astrophysics↗
DOE OSTI2020

Musings on the current status of HEP

I give a brief review of theoretical high energy physics as we know it today in the general picture of quantum physics. Furthermore, prospects for future developments are outlined.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Baryons and tetraquarks using instanton-induced interactions

We analyze some aspects of the perturbative and nonperturbative interactions in the composition of heavy quarkonia, heavy and light baryons ( c c c and u u u ones), as well as all charm tetraquarks ( c c c ¯ c ¯ ). Using the hyperspherical approximation and effective radial potentials (in six and nine dimensions, respectively) we derive their spectra and wave functions. In all of the cases, we focus on the splittings between the S -shell levels, which are remarkably insensitive to the quark masses, but proportional to the effective interaction potentials. We use the traditional Cornell-like potentials, and the nonperturbative instanton-induced static potentials, from correlators of two, three, and four Wilson lines, and find rather satisfactory description of spectra in all cases. Published by the American Physical Society 2024

Astronomy & Astrophysics↗
DOE OSTI2024

One-dimensional reflection in the quantum mechanical bootstrap

We describe the application of the quantum mechanical bootstrap to the solution of one-dimensional scattering problems. By fixing a boundary and modulating the Robin parameter of the boundary conditions we are able to extract the reflection coefficient for various potentials and compare to physical expectations. This includes an application of semidefinite programming to solving a half line Schrodinger problem with arbitrary Robin boundary conditions. Finally, the WKB approximation is used to numerically determine the scattering behavior of the exponential potential of Liouville theory. Published by the American Physical Society 2024

Astronomy & Astrophysics↗
DOE OSTI2024

Feature selection with distance correlation

Choosing which properties of the data to use as input to multivariate decision algorithms—also known as feature selection—is an important step in solving any problem with machine learning. While there is a clear trend towards training sophisticated deep networks on large numbers of relatively unprocessed inputs (so-called automated feature engineering), for many tasks in physics, sets of theoretically well-motivated and well-understood features already exist. Working with such features can bring many benefits, including greater interpretability, reduced training and run time, and enhanced stability and robustness. We develop a new feature selection method based on distance correlation, and demonstrate its effectiveness on the tasks of boosted top- and W -tagging. Using our method to select features from a set of over 7,000 energy flow polynomials, we show that we can match the performance of much deeper architectures, by using only ten features and two orders-of-magnitude fewer model parameters. Published by the American Physical Society 2024

Astronomy & Astrophysics↗
DOE OSTI2024

Fermion mass, axion dark matter, and leptogenesis in SO(10) GUT

SO(10) grand unified theory with minimum parameters in the Yukawa sector employs the Peccei-Quinn symmetry that solves the strong C P problem. Such an economical Yukawa sector is highly appealing and has been extensively studied in the literature. However, when the running of the renormalization group equations of the Yukawa couplings are considered, this scenario shows some tension with the observed fermion masses and mixing. In this work, we propose an extension of the minimal framework that utilizes lower dimensional representations and alleviates this tension by introducing only a few new parameters. The proposed model consists of a fermion in the fundamental and a scalar in the spinorial representations. While the latter is needed to implement the Peccei-Quinn symmetry successfully, the presence of both is essential in obtaining an excellent fit to the fermion mass spectrum. In our model, axions serve the role of dark matter, and the out-of-equilibrium decays of the right-handed neutrinos successfully generate the matter-antimatter symmetry of the Universe. Published by the American Physical Society 2024

Astronomy & Astrophysics↗
DOE OSTI2024

Longer-lived mediators from charged mesons and photons at neutrino experiments

Since many of the dark-sector particles interact with Standard Model (SM) particles in multiple ways, they can appear in experimental facilities where SM particles appear in abundance. In this study, we explore a particular class of longer-lived mediators that are dominantly produced from photons and charged mesons that arise in proton-beam fixed-target-type neutrino experiments. This class of mediators encompasses light scalars that appear in theories like extended Higgs sectors, muon(electro)philic scalars, etc. We evaluate the sensitivities of these mediators at beam-based neutrino experiments such as the finished ArgoNeuT, ongoing MicroBooNE, SBND, ICARUS, and the upcoming DUNE experiment. We find that muonphilic scalars are more enhanced while produced from three-body decay of charged mesons. The above-mentioned experiments can probe unexplored regions of parameter space that can explain the current discrepancy in the anomalous magnetic moment of muons. We further find that Compton-like scattering of photons is the largest source of electrophilic scalars. By utilizing this, the DUNE Near Detector can explore new regions in the sensitivity space of electrophilic scalars. We also show that Bethe-Heitler scattering processes can be used to probe flavor-specific lepton final states even for the mediator masses below twice the lepton mass. Published by the American Physical Society 2024

Astronomy & Astrophysics↗
DOE OSTI2024

Primary observables for gauge boson collider signals

In this paper, we determine a basis for the on-shell four-point amplitudes V V V V for Standard Model gauge bosons V = W ± , Z , γ , g . Following previous work, this completes the analysis of three- and four-point amplitudes for the Standard Model and could be used for model-independent searches for beyond the Standard Model physics at colliders. Our results include a Lagrangian parametrization for the “primary” amplitudes, where including additional derivatives leads to the Mandelstam “descendant” amplitudes, and upper bounds on the coupling constants from imposing unitarity. We also perform an estimate for the sensitivity for new Z decays at the High-Luminosity LHC, finding that Z → γ ℓ ¯ ℓ could be searched for, but that other decay modes, like Z → ( γ γ γ , γ g g ) , are too small to be discovered after imposing unitarity constraints. Published by the American Physical Society 2024

Astronomy & Astrophysics↗
DOE OSTI2024

Chaos in inhomogeneous neutrino fast flavor instability

In dense neutrino gases, the neutrino-neutrino coherent forward scattering gives rise to a complex flavor oscillation phenomenon not fully incorporated in simulations of neutron star mergers (NSM) and core collapse supernovae (CCSNe). Moreover, it has been proposed to be chaotic, potentially limiting our ability to predict neutrino flavor transformations in simulations. To address this issue, we explore how small flavor perturbations evolve in the nonlinear regime of the neutrino quantum kinetic equation within a narrow centimeter-scale region inside a NSM and a toy neutrino distribution. Our findings reveal that paths in the flavor state space of solutions with similar initial conditions diverge exponentially, exhibiting chaos. This inherent chaos makes the microscopic scales of neutrino flavor transformations unpredictable. However, the domain-averaged neutrino density matrix remains relatively stable, with chaos minimally affecting it. This particular property suggests that domain-averaged quantities remain reliable despite the exponential amplification of errors. Published by the American Physical Society 2024

Astronomy & Astrophysics↗
DOE OSTI2024

Asymmetric reheating via inverse symmetry breaking

Asymmetric reheating is a generic requirement for models of dark sectors with light species, but its implementation is usually in tension with unique phenomenologies otherwise possible in compelling theories containing dark copies of the Standard Model. We present a simple module to implement asymmetric reheating during a Z 2 -breaking phase above some critical temperature. This reinvigorates the possibility of an exactly degenerate mirror sector and the striking phenomenology of composite particles oscillating into their mirror counterparts. Published by the American Physical Society 2024

Astronomy & Astrophysics↗
DOE OSTI2024

Quantum duality in electromagnetism and the fine structure constant

We describe the interplay between electric-magnetic duality and higher symmetry in Maxwell theory. When the fine structure constant is rational, the theory admits noninvertible symmetries which can be realized as composites of electric-magnetic duality and gauging a discrete subgroup of the one-form global symmetry. These noninvertible symmetries are approximate quantum invariances of the natural world which emerge in the infrared below the mass scale of charged particles. We construct these symmetries explicitly as topological defects and illustrate their action on local and extended operators. We also describe their action on boundary conditions and illustrate some consequences of the symmetry for Hilbert spaces of the theory defined in finite volume. Published by the American Physical Society 2024

Astronomy & Astrophysics↗