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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 559 records · Page 31
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DOE OSTI2011

QCD Analysis of the Polarized Deep-Inelastic World Data

The results of a recent next-to-leading order QCD analysis of the world data on polarized deep inelastic scattering are reported. New parameterizations are derived for the quark and gluon distributions, accounting for the massive Wilson coefficient for the charm quarks, and the value of {alpha}{sub s}(M{sub z}{sup 2}) is determined with correlated errors. We obtain {alpha}{sub s}{sup NLO}(M{sub Z}{sup 2}) = 0.1132{sub -0.0095}{sup +0.0056}. Limits on potential higher twist contributions to the structure function g{sub 1}(x,Q{sup 2}) are derived. We also compare to the results obtained by other groups.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

Global phase diagram of a doped Kitaev-Heisenberg model

The global phase diagram of a doped Kitaev-Heisenberg model is studied using an $SU(2)$ slave-boson mean-field method. Near the Kitaev limit, $p$-wave superconducting states which break the time-reversal symmetry are stabilized as reported by You {\it et al.} [Phys. Rev. B {\bf 86}, 085145 (2012)] irrespective of the sign of the Kitaev interaction. By further doping, a $d$-wave superconducting state appears when the Kitaev interaction is antiferromagnetic, while another $p$-wave superconducting state appears when the Kitaev interaction is ferromagnetic. This $p$-wave superconducting state does not break the time-reversal symmetry as reported by Hyart {\it et al.} [Phys. Rev. B {\bf 85}, 140510 (2012)], and such a superconducting state also appears when the antiferromagnetic Kitaev interaction and the ferromagnetic Heisenberg interaction compete. This work, thus, demonstrates the clear difference between the antiferromagnetic Kitaev model and the ferromagnetic Kitaev model when carriers are doped while these models are equivalent in the undoped limit, and how novel superconducting states emerge when the Kitaev interaction and the Heisenberg interaction compete.

novel superconductivity↗
DOE OSTI2016

Dual origin of pairing in nuclei

The pairing correlations of the nucleus {sup 120}Sn are calculated by solving the Nambu–Gor’kov equations, including medium polarization effects resulting from the interweaving of quasiparticles, spin and density vibrations, taking into account, within the framework of nuclear field theory (NFT), processes leading to self-energy and vertex corrections and to the induced pairing interaction. From these results one can not only demonstrate the inevitability of the dual origin of pairing in nuclei, but also extract information which can be used at profit to quantitatively disentangle the contributions to the pairing gap Δ arising from the bare and from the induced pairing interaction. The first is the strong {sup 1}S{sub 0} short-range NN potential resulting from meson exchange between nucleons moving in time reversal states within an energy range of hundreds of MeV from the Fermi energy. The second results from the exchange of vibrational modes between nucleons moving within few MeV from the Fermi energy. Short- (v{sub p}{sup bare}) and long-range (v{sub p}{sup ind}) pairing interactions contribute essentially equally to nuclear Cooper pair stability. That is to the breaking of gauge invariance in open-shell superfluid nuclei and thus to the order parameter, namely to the ground state expectation value of the pair creation operator. In other words, to the emergent property of generalized rigidity in gauge space, and associated rotational bands and Cooper pair tunneling between members of these bands.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2026

Topological freeze-out by semi-annihilation

We point out that a QCD-like dark sector can be coupled to the Standard Model by gauging the topological Skyrme current, which measures the dark baryon number in the infrared, to give a technically natural model for dark matter. This coupling allows for a semi-annihilation process χχ → χX μ , where X μ is the gauge boson mediator and χ a dark pion field, which plays the dominant role in setting the dark matter relic abundance. The topological interaction is purely p-wave and so free from indirect detection constraints. We show that the dark matter pion mass needs to be in the range 10 MeV ≲ m χ ≲ 1 TeV; towards the lighter end of this range, there can moreover be significant self-interactions. We discuss prospects for probing this scenario at collider experiments, ranging from the LHC to low-energy e + e − colliders, future Higgs factories, and beam-dump experiments.

Models for Dark Matter↗
DOE OSTI2015

Asymmetric dark matter and CP violating scatterings in a UV complete model

We explore possible asymmetric dark matter models using CP violating scatterings to generate an asymmetry. In particular, we introduce a new model, based on DM fields coupling to the SM Higgs and lepton doublets, a neutrino portal, and explore its UV completions. We study the CP violation and asymmetry formation of this model, to demonstrate that it is capable of producing the correct abundance of dark matter and the observed matter-antimatter asymmetry. Crucial to achieving this is the introduction of interactions which violate CP with a T{sup 2} dependence.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Sizable NSI from the SU(2) L scalar doublet-singlet mixing and the implications in DUNE

Here, we propose a novel and simple mechanism where sizable effects of non-standard interactions (NSI) in neutrino propagation are induced from the mixing between an electrophilic second Higgs doublet and a charged singlet. The mixing arises from a dimensionful coupling of the scalar doublet and singlet to the standard model Higgs boson. In light of the small mass, the light mass eigenstate from the doublet-singlet mixing can generate much larger NSI than those induced by the heavy eigenstate. We show that a sizable NSI ε eτ (~0.3) can be attained without being excluded by a variety of experimental constraints. Furthermore, we demonstrate that NSI can mimic effects of the Dirac CP phase in the neutrino mixing matrix but they can potentially be disentangled by future long-baseline neutrino experiments, such as the Deep Underground Neutrino Experiment (DUNE).

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

Effective field theory of weakly coupled inflationary models

The application of Effective Field Theory (EFT) methods to inflation has taken a central role in our current understanding of the very early universe. The EFT perspective has been particularly useful in analyzing the self-interactions determining the evolution of co-moving curvature perturbations (Goldstone boson modes) and their influence on low-energy observables. However, the standard EFT formalism, to lowest order in spacetime differential operators, does not provide the most general parametrization of a theory that remains weakly coupled throughout the entire low-energy regime. Here we study the EFT formulation by including spacetime differential operators implying a scale dependence of the Goldstone boson self-interactions and its dispersion relation. These operators are shown to arise naturally from the low-energy interaction of the Goldstone boson with heavy fields that have been integrated out. We find that the EFT then stays weakly coupled all the way up to the cutoff scale at which ultraviolet degrees of freedom become operative. This opens up a regime of new physics where the dispersion relation is dominated by a quadratic dependence on the momentum ω ∼ p{sup 2}. In addition, provided that modes crossed the Hubble scale within this energy range, the predictions of inflationary observables — including non-Gaussian signatures — are significantly affected by the new scales characterizing it.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

Oscillating asymmetric dark matter

We study the dynamics of dark matter (DM) particle-antiparticle oscillations within the context of asymmetric DM. Oscillations arise due to small DM number-violating Majorana-type mass terms, and can lead to recoupling of annihilation after freeze-out and washout of the DM density. Asymmetric DM oscillations 'interpolate' between symmetric and asymmetric DM freeze-out scenarios, and allow for a larger DM model-building parameter space. We derive the density matrix equations for DM oscillations and freeze-out from first principles using nonequilibrium field theory, and our results are qualitatively different than in previous studies. DM dynamics exhibits particle-vs-antiparticle 'flavor' effects, depending on the interaction type, analogous to neutrino oscillations in a medium. 'Flavor-sensitive' DM interactions include scattering or annihilation through a new vector boson, while 'flavor-blind' interactions include scattering or s-channel annihilation through a new scalar boson. In particular, we find that flavor-sensitive annihilation does not recouple when coherent oscillations begin, and that flavor-blind scattering does not lead to decoherence.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2011

Hidden Higgs boson at the LHC and light dark matter searches

Recent LHC searches have not found a clear signal of the Higgs boson h of the standard model (SM) with three or four families in the mass range m{sub h}=120-600 GeV. If the Higgs had an unexpectedly large invisible branching ratio, the excluded m{sub h} regions would shrink. This can be realized in the simplest weakly interacting massive particle dark matter (DM) model, which is the SM plus a real gauge-singlet scalar field D as the DM, via the invisible mode h{yields}DD. Current data allow this decay to occur for D-mass values near, but below, m{sub h}/2 and those compatible with the light DM hypothesis. For such D masses, h{yields}DD can dominate the Higgs width depending on m{sub h}, and thus sizable portions of the m{sub h} exclusion zones in the SM with three or four families may be recovered. Increased luminosity at the LHC may even reveal a Higgs having SM-like visible decays still hiding in the presently disallowed regions. The model also accommodates well the new possible DM hints from CRESST-II and will be further tested by improved data from future DM direct searches.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Precision Electroweak Measurements and Constraints on the Standard Model

This note presents constraints on Standard Model parameters using published and preliminary precision electroweak results measured at the electron-positron colliders LEP and SLC. The results are compared with precise electroweak measurements from other experiments, notably CDF and D0 at the Tevatron. Constraints on the input parameters of the Standard Model are derived from the results obtained in high-Q{sup 2} interactions, and used to predict results in low-Q{sup 2} experiments, such as atomic parity violation, Moller scattering, and neutrino-nucleon scattering. The main changes with respect to the experimental results presented in 2007 are new combinations of results on the W-boson mass and width and the mass of the top quark.

43 PARTICLE ACCELERATORS↗
DOE OSTI2024

Bosenovae with quadratically-coupled scalars in quantum sensing experiments

Abstract Ultralight dark matter (ULDM) particles of massm ϕ ≲ 1 eV can form boson stars in DM halos. Collapse of boson stars leads to explosive bosenova emission of copious relativistic ULDM particles. In this work, we analyze the sensitivity of terrestrial and space-based experiments to detect such relativistic scalar ULDM particles interacting through quadratic couplings with Standard Model constituents, including electrons, photons, and gluons. We highlight key differences with searches for linear ULDM couplings. Screening of ULDM with quadratic couplings near the surface of the Earth can significantly impact observations in terrestrial experiments, motivating future space-based experiments. We demonstrate excellent ULDM discovery prospects, especially for quantum sensors, which can probe quadratic couplings orders below existing constraints by detecting bosenova events in the ULDM mass range 10 −23 eV ≲m ϕ ≲ 10 −5 eV. We also report updated constraints on quadratic couplings of ULDM in case it comprises cold DM.

Physics↗
DOE OSTI2011

Negative-parity {Lambda}{sub Q} baryons in the baryon-meson continuum

The negative-parity charmed baryons are investigated by employing the quark model as well as the effective baryon meson model with a bound state embedded in the continuum. Especially the mass difference between the J{sup P} 1/2{sup -} and 3/2{sup -}{Lambda}{sub c}{sup +} baryons is discussed. The observed value of this mass splitting is almost the same as that of {Xi}{sub c}, about 30 MeV. It is found that most of this splitting can be reproduced by assuming a simple qqQ configuration. The coupling to the baryon-meson scattering state may enlarge the splitting as it does for the {Lambda}(1405)(1/2{sup -}) and {Lambda}(1520)(3/2{sup -}) case. We investigate this coupling effect and find that with an appropriately modified coupling or the pole energy, the peak can be reproduced.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Search for WH Associated Production in the l upsilon b-bbar Final State Using the DØ Detector at the Tevatron

The Standard Model is the framework which allows to describe interactions between particles and their dynamics. The Higgs mechanism is a solution to naturally introduce a mass term in the theoretical description of this model. After electroweak spontaneous symmetry breaking, a new massive scalar particle is introduced, the Higgs boson. Since it hasn’t been discovered yet, the search for the Higgs boson is carried at the Tevatron, which is a p$\bar{p}$ collider at a center-of-mass of 1.96 TeV. For M H <115 GeV, the dominant decay mode is H → b$\bar{b}$ . The analysis presented in this document is focused on the 100< M H <150 GeV mass range, in the channel where the Higgs boson is produced in assocation with a W boson which decays either to an electron or muon and a neutrino. The study of this final state relies on informations collected from all parts of the DØ detector. A result based on 5.3 fb -1 of RunII Tevatron collisions is presented here. In order to increase the sensitivity to the signal, the analysis is separated in different sub-channels according to the lepton flavour, number of jets in the final state, number of jets identified as originated from b quarks and data taking periods. After selecting events, a multivariate analysis technique is used to separate signal-like events from the expected physics and instrumental backgrounds. A good agreement between data and simulation is observed. As no signal excess is observed in data, an observed (expected) upper limit of 4.5 (4.8) for M H = 115 GeV is set on the ratio of the WH cross section multiplied by the H → b$\bar{b}$ branching fraction to its standard model prediction, at 95% confidence level. Since the final Tevatron dataset is soon to be analyzed, an effort is brought to achieve the maximum sensitivity. A preliminary analysis updated in Summer 2011 is presented as well as future improvements to be considered in the final publication for the search in the WH → ℓνb$\bar{b}$ channel. Since the dijet invariant mass is the most discriminant single variable, a correction based on jet shapes is derived to improve the mass resolution, hence the analysis sensitivity. Moreover, a different usage of b-jets identification tools and optimization studies on the final discriminant yields a significant improvement. This result is part of the Tevatron Higgs combination.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2012

Weak-triplet, color-octet scalars and the CDF dijet excess

We extend the standard model to include a weak-triplet and color-octet scalar. This 'octo-triplet' field consists of three particles, two charged and one neutral, whose masses and renormalizable interactions depend only on two new parameters. The charged octo-triplet decay into a W boson and a gluon is suppressed by a loop factor and an accidental cancellation. Thus, the main decays of the charged octo-triplet may occur through higher-dimensional operators, mediated by a heavy vectorlike fermion, into quark pairs. For an octo-triplet mass below the tb¯ threshold, the decay into Wb b¯ through an off-shell top quark has a width comparable to that into cs¯ or cb¯. Pair production with one octo-triplet decaying to two jets and the other decaying to a W and two soft b jets may explain the dijet-plus-W excess reported by the CDF Collaboration. The same higher-dimensional operators lead to CP violation in B s -B¯ s mixing.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Improving the Top Quark Forward-Backward Asymmetry Measurement at the LHC

At the LHC, top quark pairs are dominantly produced from gluons, making it difficult to measure the top quark forward-backward asymmetry. To improve the asymmetry measurement, we study variables that can distinguish between top quarks produced from quarks and those from gluons: the invariant mass of the top pair, the rapidity of the top-antitop system in the lab frame, the rapidity of the top quark in the top-antitop rest frame, the top quark polarization and the top-antitop spin correlation. We combine all the variables in a likelihood discriminant method to separate quark-initiated events from gluon-initiated events. We apply our method on models including G-prime's and W-prime's motivated by the recent observation of a large top quark forward-backward asymmetry at the Tevatron. We have found that the significance of the asymmetry measurement can be improved by 10% to 30%. At the same time, the central values of the asymmetry increase by 40% to 100%. We have also analytically derived the best spin quantization axes for studying top quark polarization as well as spin-correlation for the new physics models.

43 PARTICLE ACCELERATORS↗
DOE OSTI2012

Chiral color quark symmetry and possible constraints on the G Prime -boson mass from tevatron and LHC data

A gauge model featuring a chiral color symmetry of quarks was considered, and possible manifestations of this symmetry in proton-antiproton and proton-proton collisions at the Tevatron and LHC energies were studied. The cross section {sigma}{sub tt}-bar for the production of tt-bar quark pairs at the Tevatron and the forward-backward asymmetry A{sub FB}{sup pp}-bar in this process were calculated and analyzed with allowance for the contributions of the G Prime -boson predicted by the chiral color symmetry of quarks, the G Prime -boson massm{sub G Prime} and the mixing angle {theta}{sub G} being treated as free parameters of the model. Limits on m{sub G Prime} versus {theta}{sub G} were studied on the basis of data from the Tevatron on {sigma}{sub tt}-bar and A{sub FB}{sup pp}-bar, and the region compatible with these data within one standard deviation was found in the m{sub G Prime }-{theta}{sub G} plane. The region ofm{sub G Prime }-mass values that is appropriate for observing the G Prime -boson at LHC is discussed.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

Thermal production of ultrarelativistic right-handed neutrinos: complete leading-order results

The thermal production of relativistic right-handed Majorana neutrinos is of importance for models of thermal leptogenesis in the early Universe. Right-handed neutrinos can be produced both by 1↔2 decay or inverse decay and by 2 → 2 scattering processes. In a previous publication we have studied the production via 1↔2 (inverse) decay processes. There we have shown that multiple scattering mediated by soft gauge boson exchange also contributes to the production rate at leading order and gives a strong enhancement. Here we complete the leading order calculation by adding 2 → 2 scattering processes involving either electroweak gauge bosons or third-generation quarks. We find that processes with gauge interactions give the most important contributions. We also obtain a new sum rule for the Hard Thermal Loop resummed fermion propagator.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Atomic entanglement mediated by various non-classical cavity fields

In this paper several non-classical properties are described such as the entanglement of bipartite system in the multimode cavities, described by the Jaynes-Cummings as well as the Tavis-Cummings model. The modes are described quantum mechanically, which helps to bring out the non-classical features emerging from the interaction of atoms with the cavity modes. Effects such as the growth of the magnitude of atomic entanglement with the increase of the cavity photon number, arising out of the intensity dependent atom-cavity coupling lead to interesting dissimilarities from the case of entanglement generated by the standard Jaynes-Cummings interaction. The dynamics of a single Rydberg atom in an n-mode cavity are also described by oscillations at the rate of the interaction strength of the atom-field interaction, Finally, we investigate the entanglement dynamics in the presence of cavity dissipation under single mode Tavis-Cummings interaction. The atom-photon interactions and the generation of entanglement mediated through them are expected to play an important role in possible future practical realizations in the field of quantum communications for various atom-photon interaction models considered under single or multimode cavity.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗