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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 505 records · Page 28
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Many-body chaos in the antiferromagnetic quantum critical metal

Here, we compute the scrambling rate at the antiferromagnetic (AFM) quantum critical point, using the fixed point theory found by Schlief, Lunts, and Lee. At this strongly coupled fixed point, there is an emergent control parameter $w \ll 1$ that is a ratio of natural parameters of the theory. The strong coupling is unequally felt by the two degrees of freedom: the bosonic AFM collective mode is heavily dressed by interactions with the electrons, while the electron is only marginally renormalized. We find that the scrambling rates act as a measure of the “degree of integrability” of each sector of the theory: the Lyapunov exponent for the boson $λ^{(B)}_L \sim \mathcal{O} (\sqrt{w})k_BT/ℏ$ is significantly larger than the fermion one $λ^{(F)}_L \sim \mathcal{O}(w^2)k_BT/ℏ$, where $\textit{T}$ is the temperature. Although the interaction strength in the theory is of order unity, the larger Lyapunov exponent is still parametrically smaller than the universal upper bound of $λ_L = 2πk_BT/ℏ$. We also compute the spatial spread of chaos by the boson operator, whose low-energy propagator is highly nonlocal. We find that this nonlocality leads to a scrambled region that grows exponentially fast at intermediate distances, giving an infinite “butterfly velocity” of the chaos front, a result that has also been found in lattice models with long-range interactions.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Search for dark matter produced in association with a Higgs boson decaying to γγ or τ + τ – at $ \sqrt{s}=13 $ TeV

A search for dark matter particles is performed by looking for events with large transverse momentum imbalance and a recoiling Higgs boson decaying to either a pair of photons or a pair of τ leptons. The search is based on proton-proton collision data at a center-of-mass energy of 13 TeV collected at the CERN LHC in 2016 and corresponding to an integrated luminosity of 35.9 fb$^{-1}$. No significant excess over the expected standard model background is observed. Upper limits at 95% confidence level are presented for the product of the production cross section and branching fraction in the context of two benchmark simplified models. For the Z$^{'}$-two-Higgs-doublet model (where Z$^{'}$ is a new massive boson mediator) with an intermediate heavy pseudoscalar particle of mass m$_{A}$ = 300 GeV and m$_{DM}$ = 100 GeV, the Z$^{'}$ masses from 550 GeV to 1265 GeV are excluded. For a baryonic Z$^{'}$ model, with m$_{DM}$ = 1 GeV, Z$^{'}$ masses up to 615 GeV are excluded. Results are also presented for the spin-independent cross section for the dark matter-nucleon interaction as a function of the mass of the dark matter particle. In conclusion, this is the first search for dark matter particles produced in association with a Higgs boson decaying to two τ leptons.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

High Energy Physics at Tufts University Final Report

In this Final Report, we the researchers of the high energy physics group at Tufts University summarize our works and achievements in three frontier areas of elementary particle physics: (i) Neutrino physics at the Intensity Frontier, (ii) Collider physics at the Energy Frontier, and (iii) Theory investigations of spin structure and quark-gluon dynamics of nucleons using quantum chromodynamics. With our Neutrino research we completed, or else brought to a useful state, the following: Data-taking, physics simulations, physics analysis, physics reporting, explorations of matter effects, and detector component fabrication. We conducted our work as participants in the MINOS, NOvA, and LBNE neutrino oscillation experiments and in the MINERvA neutrino scattering experiment. With our Collider research we completed or else brought to a useful state: Data-taking, development of muon system geometry and tracking codes, software validation and maintenance, physics simulations, physics analysis, searches for new particles, and study of top-quark and B-quark systems. We conducted these activities as participants in the ATLAS proton-proton collider experiment at CERN and in the CDF proton-antiproton collider experiment at Fermilab. In our Theory research we developed QCD-based models, applications of spin phenomenology to fundamental systems, fitting of models to data, presenting and reporting of new concepts and formalisms. The overarching objectives of our research work have always been: 1) to test and clarify the predictions of the Standard Model of elementary particle physics, and 2) to discover new phenomena which may point the way to a more unified theoretical framework.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Search for Excited Leptons in Proton-Proton Collisions at $\sqrt{s}$ = 8 TeV

A search for compositeness of electrons and muons is presented using a data sample of proton-proton collisions at a center-of-mass energy of $ \sqrt{s} = 8 $ TeV collected with the CMS detector at the LHC and corresponding to an integrated luminosity of 19.7 fb$^{−1}$. Excited leptons (ℓ$^{*}$) produced via contact interactions in conjunction with a standard model lepton are considered, and a search is made for their gauge decay modes. The decays considered are ℓ$^{*}$ → ℓγ and ℓ$^{*}$ → ℓZ, which give final states of two leptons and a photon or, depending on the Z-boson decay mode, four leptons or two leptons and two jets. The number of events observed in data is consistent with the standard model prediction. Exclusion limits are set on the excited lepton mass, and the compositeness scale Λ. For the case M$_{ℓ*}$ = Λ the existence of excited electrons (muons) is excluded up to masses of 2.45 (2.47) TeV at 95% confidence level. Neutral current decays of excited leptons are considered for the first time, and limits are extended to include the possibility that the weight factors f and f′, which determine the couplings between standard model leptons and excited leptons via gauge mediated interactions, have opposite sign.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Direct detection of light dark matter charged under a 𝐿 𝜇 − 𝐿 𝜏 symmetry

A possible extension of the Standard Model able to explain the recent measurement of the anomalous magnetic moment of the muon consists in adding a gauged 𝑈⁢(1) 𝐿𝜇−𝐿𝜏 symmetry. If the dark matter particle is charged under this symmetry, then the kinetic mixing between the new gauge boson and the photon induces dark matter-electron interactions. We derive direct detection constraints on light dark matter charged under a 𝑈⁢(1) 𝐿𝜇−𝐿𝜏 symmetry with electron recoil experiments and explore prospects with XLZD and OSCURA to close in the parameter space able to explain simultaneously the recent measurement on the anomalous magnetic moment of the muon and the observed relic density of dark matter. We further discuss the spin-dependent scattering contribution arising in this model, which was ignored previously in the literature.

extensions of gauge sector↗
DOE OSTI2011

Engineering interactions for quasiperfect transfer of polariton states through nonideal bosonic networks of distinct topologies

We present a scheme for quasiperfect transfer of polariton states from a sender to a spatially separated receiver, both composed of high-quality cavities filled by atomic samples. The sender and the receiver are connected by a nonideal transmission channel --the data bus-- modelled by a network of lossy empty cavities. In particular, we analyze the influence of a large class of data-bus topologies on the fidelity and transfer time of the polariton state. Moreover, we also assume dispersive couplings between the polariton fields and the data-bus normal modes in order to achieve a tunneling-like state transfer. Such a tunneling-transfer mechanism, by which the excitation energy of the polariton effectively does not populate the data-bus cavities, is capable of attenuating appreciably the dissipative effects of the data-bus cavities. After deriving a Hamiltonian for the effective coupling between the sender and the receiver, we show that the decay rate of the fidelity is proportional to a cooperativity parameter that weighs the cost of the dissipation rate against the benefit of the effective coupling strength. The increase of the fidelity of the transfer process can be achieved at the expense of longer transfer times. We also show that the dependence of both the fidelity and the transfer time on the network topology is analyzed in detail for distinct regimes of parameters. It follows that the data-bus topology can be explored to control the time of the state-transfer process.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Matter power spectrum in hidden neutrino interacting dark matter models: a closer look at the collision term

Dark Matter (DM) models providing possible alternative solutions to the small-scale crisis of the standard cosmology are nowadays of growing interest. We consider DM interacting with light hidden fermions via well-motivated fundamental operators showing the resultant matter power spectrum is suppressed on subgalactic scales within a plausible parameter region. Our basic description of the evolution of cosmological perturbations relies on a fully consistent first principles derivation of a perturbed Fokker-Planck type equation, generalizing existing literature. The cosmological perturbation of the Fokker-Planck equation is presented for the first time in two different gauges, where the results transform into each other according to the rules of gauge transformation. Furthermore, our focus lies on a derivation of a broadly applicable and easily computable collision term showing important phenomenological differences to other existing approximations. As one of the main results and concerning the small-scale crisis, we show the equal importance of vector and scalar boson mediated interactions between the DM and the light fermions.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2024

Observational prospects of self-interacting scalar superradiance with next-generation gravitational-wave detectors

Abstract Current- and next-generation gravitational-wave observatories may reveal new, ultralight bosons. Through the superradiance process, these theoretical particle candidates can form clouds around astrophysical black holes and result in detectable gravitational-wave radiation. In the absence of detections, constraints—contingent on astrophysical assumptions—have been derived using LIGO-Virgo-KAGRA data on boson masses. However, the searches for ultralight scalars to date have not adequately considered self-interactions between particles. Self-interactions that significantly alter superradiance dynamics are generically present for many scalar models, including axion-like dark matter candidates and string axions. We implement the most complete treatment of particle self-interactions available to determine the gravitational-wave signatures expected from superradiant scalar clouds and revisit the constraints obtained in a past gravitational-wave search targeting the black hole in Cygnus X-1. We also project the reach of next-generation gravitational-wave observatories to scalar particle parameter space in the mass-coupling plane. We find that while proposed observatories have insufficient reach to self-interactions that can halt black hole spin-down, next-generation observatories are essential for expanding the search beyond gravitational parameter space and can reach a mass and interaction scale of ∼ 10 − 13 –10 −12 eV / c 2 and ≳ 10 17 GeV, respectively.

Collaviti, Spencer (ORCID:0009000372808236)↗
DOE OSTI2012

Electroweak bremsstrahlung for wino-like Dark Matter annihilations

If the Dark Matter is the neutral Majorana component of a multiplet which is charged under the electroweak interactions of the Standard Model, its main annihilation channel is into W{sup +}W{sup −}, while the annihilation into light fermions is helicity suppressed. As pointed out recently, the radiation of gauge bosons from the initial state of the annihilation lifts the suppression and opens up an s-wave contribution to the cross section. We perform the full tree-level calculation of Dark Matter annihilations, including electroweak bremsstrahlung, in the context of an explicit model corresponding to the supersymmetric wino. We find that the fermion channel can become as important as the di-boson one. This result has significant implications for the predictions of the fluxes of particles originating from Dark Matter annihilations.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Higgs quadruplet impact on W mass shift, dark matter, and LHC signatures

The addition of a Higgs quadruplet to the standard model (SM) of quarks and leptons would shift the W -boson mass upward. It could also facilitate the production of dark matter through the conventional thermal freeze-out scenario via Yukawa interaction with the Higgs quadruplet or freeze-in production from the decay of SM Higgs. We investigate the same-sign lepton smoking gun signature of the double-charged scalar component of the quadruplet Higgs at the LHC. Published by the American Physical Society 2024

Astronomy & Astrophysics↗
DOE OSTI2022

Sachdev-Ye-Kitaev models and beyond: Window into non-Fermi liquids

In this work is a review of the Sachdev-Ye-Kitaev (SYK) model of compressible quantum many-body systems without quasiparticle excitations, and its connections to various theoretical studies of non-Fermi liquids in condensed matter physics. The review is placed in the context of numerous experimental observations on correlated electron materials. Strong correlations in metals are often associated with their proximity to a Mott transition to an insulator created by the local Coulomb repulsion between the electrons. The phase diagrams of a number of models of such a local electronic correlation are explored, employing a dynamical mean-field theory in the presence of random spin exchange interactions. Numerical analyses and analytical solutions, using renormalization group methods and expansions in large spin degeneracy, lead to critical regions that display SYK physics. The models studied include the single-band Hubbard model, the t–J model, and the two-band Kondo-Heisenberg model in the presence of random spin exchange interactions. Also examined are non-Fermi liquids obtained by considering each SYK model with random four-fermion interactions to be a multiorbital atom, with the SYK atoms arranged in an infinite lattice. Connections are made to theories of sharp Fermi surfaces without any low-energy quasiparticles in the absence of spatial disorder, obtained by coupling a Fermi liquid to a gapless boson; a systematic large-N theory of such a critical Fermi surface, with SYK characteristics, is obtained by averaging over an ensemble of theories with random boson-fermion couplings. Finally, an overview of the links between the SYK model and quantum gravity is presented, and the review ends with an outlook on open questions.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

Extended Brueckner-Hartree-Fock Theory with Pionic Correlation and Chiral Symmetry

We present a nuclear many-body theory with explicit treatment of strong tensor correlation induced by the pion-exchange interaction. For this purpose, the Hartree-Fock variational model space is extended to include 2-particle 2-hole (2p-2h) states, which are able to handle the tensor correlation with high momentum components originating from pseudo-scalar nature of the pion. We take a variational principle of the total energy, and obtain an extended Brueckner-Hartree-Fock equation with inclusion of the effect of the pion exchange and short-range repulsive interaction. This framework has a similar structure as the Brueckner theory and we call this framework extended Brueckner-Hartree-Fock theory.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Modelling Z→TT processes in ATLAS with T-embedded Z →μμ data

We describe the concept, technical realisation and validation of a largely data-driven method to model events with Z→ττ decays. In Z→μμ events selected from proton-proton collision data recorded at √s=8 TeV with the ATLAS experiment at the LHC in 2012, the Z decay muons are replaced by τ leptons from simulated Z →ττ decays at the level of reconstructed tracks and calorimeter cells. The τ lepton kinematics are derived from the kinematics of the original muons. Thus, only the well-understood decays of the Z boson and τ leptons as well as the detector response to the τ decay products are obtained from simulation. All other aspects of the event, such as the Z boson and jet kinematics as well as effects from multiple interactions, are given by the actual data. This so-called τ-embedding method is particularly relevant for Higgs boson searches and analyses in ττ final states, where Z→ττ decays constitute a large irreducible background that cannot be obtained directly from data control samples. In this paper, we discuss the relevant concepts based on the implementation used in the ATLAS Standard Model H→ττ analysis of the full datataset recorded during 2011 and 2012.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

{pi}N transition distribution amplitudes: Their symmetries and constraints from chiral dynamics

Baryon to meson transition distribution amplitudes (TDAs) extend the concept of generalized parton distributions. Baryon to meson TDAs appear as building blocks in the collinear factorized description of amplitudes for a class of hard exclusive reactions, prominent examples of which being hard exclusive meson electroproduction off a nucleon in the backward region and baryon-antibaryon annihilation into a meson and a lepton pair. We study the general properties of these objects following the underlying symmetries of QCD. In particular, the Lorentz symmetry results in the polynomiality property of the Mellin moments in longitudinal momentum fractions. We present a detailed account of the isotopic and permutation symmetry properties of nucleon to pion ({pi}N) TDAs. This restricts the number of independent leading twist {pi}N TDAs to eight functions, providing description of all isotopic channels. Using chiral symmetry and the crossing relation between {pi}N TDAs and {pi}N generalized distribution amplitudes, we establish soft pion theorems for {pi}N TDAs, which determine the magnitude of {pi}N TDAs. Finally, we build a simple resonance exchange model for {pi}N TDAs considering N and {Delta}(1232) exchange contributions into the isospin-(1/2) and isospin-(3/2) {pi}N TDAs.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2014

Self-interacting scalar dark matter with local Z{sub 3} symmetry

We construct a self-interacting scalar dark matter (DM) model with local discrete Z{sub 3} symmetry that stabilizes a weak scale scalar dark matter X. The model assumes a hidden sector with a local U(1){sub X} dark gauge symmetry, which is broken spontaneously into Z{sub 3} subgroup by nonzero VEV of dark Higgs field φ{sub X} ((φ{sub X})≠0). Compared with global Z{sub 3} DM models, the local Z{sub 3} model has two new extra fields: a dark gauge field Z{sup '} and a dark Higgs field φ (a remnant of the U(1){sub X} breaking). After imposing various constraints including the upper bounds on the spin-independent direct detection cross section and thermal relic density, we find that the scalar DM with mass less than 125 GeV is allowed in the local Z{sub 3} model, in contrary to the global Z{sub 3} model. This is due to new channels in the DM pair annihilations open into Z{sup '} and φ in the local Z{sub 3} model. Most parts of the newly open DM mass region can be probed by XENON1T and other similar future experiments. Also if φ is light enough (a few MeV ∼<m{sub φ}∼< O(100) MeV), it can generate a right size of DM self-interaction and explain the astrophysical small scale structure anomalies. This would lead to exotic decays of Higgs boson into a pair of dark Higgs bosons, which could be tested at LHC and ILC.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

Magnon–magnon interactions in O(3) ferromagnets and equations of motion for spin operators

The method of equations of motion for spin operators in the case of O(3) Heisenberg ferromagnet is systematically analyzed starting from the effective Lagrangian. It is shown that the random phase approximation and the Callen approximation can be understood in terms of perturbation theory for type B magnons. Also, the second order approximation of Kondo and Yamaji for one dimensional ferromagnet is reduced to the perturbation theory for type A magnons. An emphasis is put on the physical picture, i.e. on magnon–magnon interactions and symmetries of the Heisenberg model. Calculations demonstrate that all three approximations differ in manner in which the magnon–magnon interactions arising from the Wess–Zumino term are treated, from where specific features and limitations of each of them can be deduced.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2026

William A. Bardeen: A life in physics and the legacy of the chiral anomaly

William Allan Bardeen (September 15, 1941 − November 18, 2025) was an American theoretical physicist who worked at the Fermi National Accelerator Laboratory. He is renowned for his foundational work on the chiral anomaly, the Adler-Bardeen theorem, the non-Abelian anomaly and gravitational anomalies. He was instrumental in the development of quantum chromodynamics and its applications, such as semileptonic decays and the Λ $\overline{MS}$ scheme frequently used in perturbative analysis of high energy processes involving strong interactions. Bardeen also played a major role in developing a theory of dynamical breaking of electroweak symmetry via top quark condensates, leading to one of the first composite Brout-Englert-Higgs boson models. His work on the chiral symmetry dynamics of heavy-light quark bound states correctly predicted abnormally long-lived resonances which are chiral symmetry partners of the ground state.

Hill, Christopher T. [Fermi National Accelerator L↗
DOE OSTI2011

Theoretical update of the charm structure function of the proton

We present a theoretical update for the inclusive charm production in deep inelastic scattering. From the soft-gluon resummation at the threshold we derive all the threshold-enhanced contributions of the gluon coefficient function for the charm structure function F{sub 2}{sup c} at the next-to-next-to-leading order. Some numerical results are presented.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗