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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 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

Baryon magnetic moments in large-N{sub c} chiral perturbation theory: Effects of the decuplet-octet mass difference and flavor symmetry breaking

The magnetic and transition magnetic moments of the ground-state baryons are computed in heavy baryon chiral perturbation theory in the large-N{sub c} limit, where N{sub c} is the number of colors. SU(3) symmetry breaking is systematically studied twofold: On the one hand, one-loop nonanalytic corrections of orders m{sub q}{sup 1/2} and m{sub q} ln m{sub q} are included, with contributions of baryon intermediate states from both flavor octet and flavor decuplet multiplets, assuming degeneracy between baryon states within a given flavor multiplet but nondegeneracy between baryons of different multiplets. On the other hand, perturbative SU(3) symmetry breaking is also analyzed by including all relevant leading-order operators that explicitly break SU(3) at linear order. The resultant expressions are compared with the available experimental data and with other determinations in the context of conventional heavy baryon chiral perturbation theory for three flavors of light quarks and at the physical value N{sub c}=3. The agreement reached is quite impressive.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Illuminating new electroweak states at hadron colliders

In this paper, we propose a novel powerful strategy to perform searches for new electroweak states. Uncolored electroweak states appear in generic extensions of the Standard Model (SM) and yet are challenging to discover at hadron colliders. This problem is particularly acute when the lightest state in the electroweak multiplet is neutral and all multiplet components are approximately degenerate. In this scenario, production of the charged fields of the multiplet is followed by decay into nearly invisible states; if this decay occurs promptly, the only way to infer the presence of the reaction is through its missing energy signature. Our proposal relies on emission of photon radiation from the new charged states as a means of discriminating the signal from SM backgrounds. Lastly, we demonstrate its broad applicability by studying two examples: a pure Higgsino doublet and an electroweak quintuplet field.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

Excitation energies of particle-hole states in {sup 208}Pb and the surface delta interaction

The schematic shell model without residual interaction (SSM) assumes the same excitation energy for all spins in each particle-hole configuration multiplet. In {sup 208}Pb, more than forty states are known to contain almost the full strength of a single particle-hole configuration. The experimental excitation energy for a state with a certain spin differs from the energy predicted by the SSM by -0.2 to +0.6 MeV. The multiplet splitting is calculated with the surface delta interaction; it corresponds to the diagonal matrix element of the residual interaction in the SSM. For states containing more than 90% strength of a certain configuration and for the centroid of several completely observed configurations, the calculated multiplet splitting often approximates the experimental excitation energy within 30 keV. The strong mixing within some pairs of states containing the full strengths of two configurations is explained.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2019

(1,0) gauge theories on the six-sphere

We construct gauge theories with a vector multiplet and hypermultiplets of (1,0) ( 1 , 0 ) supersymmetry on the six-sphere. The gauge coupling on the sphere depends on the polar angle. This has a natural explanation in terms of the tensor branch of (1,0) ( 1 , 0 ) theories on the six-sphere. For the vector multiplet we give an off-shell formulation for all supersymmetries. For hypermultiplets we give an off-shell formulation for one supersymmetry. We show that the path integral for the vector multiplet localizes to solutions of the Hermitian-Yang-Mills equation, which is a generalization of the (anti-)self duality condition to higher dimensions. For the hypermultiplet, the path integral localizes to configurations where the field strengths of two complex scalars are related by an almost complex structure.

Naseer, Usman↗
NASA NTRS1992

Solar Si II line ratios from the high-resolution telescope and spectrograph

Theoretical emission-line ratios involving multiplets near 1262, 1306, and 1530 A are derived on the basis of new calculations of electron-impact excitation rates for allowed transition in Si II. A comparison of these line ratios with observational data from a quiet solar region, a sunspot, and an active region, obtained with the HIRTS on board a sounding rocket flight reveals that the 1530-A multiplet is optically thick, which is consistent with a calculation of the optical depth of these lines through a model atmosphere. The 1262- and 1306-A multiplets appear to be effectively optically thin. The average discrepancy between the theoretical and observed ratios is about 40 percent, which may not be significant, since the estimated uncertainties in both the calculated and experimental data are approximately 30 percent.

Keenan, F. P.↗
NASA NTRS1994

Oscillator strengths of selected resonance transitions in neutral sulfur

Mean lives and branching ratios for the 4s (3)S(sup 0 sub 1) and 4s(double prime) (3)P(sup 0 sub 1, 2) levels of neutral sulfur were determined at the Toledo Heavy Ion Accelerator using beam-foil spectroscopic techniques. The mean lives obtained for the 4s (3)S(sup 0 sub 1) 4s(double prime) (3)P(sup 0 sub 1), and (3)P(sup 0 sub 2) levels, 1.875 +/- 0.094 ns, 2.034 +/- 0.102 ns, and 2.146 +/- 0.129 ns, respectively, represent the most accurate results available to date. Oscillator strengths for the transitions 3p(sup 4)(3)P(sub 2, 1, 0)-4s (3)S(sup 0 sub 1) and 3p(sup 4)(3)P(sub 2, 1, 0)-4s(double prime) (3)P(sup 0 sub 1, 2) were derived from these mean lives together with the measured branching ratios. For comparison with published results which present only multiplet f-values, such f-values were computed from the measured individual line oscillator strengths. The value obtained for the 3p(sup 4)(3)P-4s(sup 3)S(sup 0) multiplet at 1814 A is 0.088 +/- 0.005, in good agreement with the mean of previous experimental measurements and theoretical calculations. With the mean life for the 4s(double prime) 3P(sup 0 sub 0) level set equal to the mean of our determination for the other two 4s(double prime) (3)P(sup 0) levels (a valid assumption for LS coupling conditions, and consistent with the observed equality of the mean lives within the accuracy of our measurement), an oscillator strength for the 1299 A multiplet of 0.121 +/- 0.004 was found. Both results are in good agreement with recent large-scale theoretical calculations that incorporate the effects of configuration interaction.

Beideck, D. J.↗
NASA NTRS2006

Lifetimes and Oscillator Strengths for Ultraviolet Transitions in P II, Cl II and Cl III

Oscillator strengths for transitions in P II, Cl II and Cl III are derived from lifetimes and branching factions measured with beam-foil techniques. The focus is on the multiplets with a prominent interstellar line at 1153 A in P II which is seen in spectra of hot stars, and the lines at 1071 A in Cl II and 1011 A in Cl III whose lines are seen in spectra of diffuse interstellar clouds and the Io torus acquired with the Far Ultraviolet Spectroscopic Explorer. These data represent the first complete set of experimental f-values for the lines in the multiplets. Our results for P II (lambda)1153 agree well with Curtis semi-empirical predictions, as well as the large scale computations by Hibbert and by Tayal. The data for Cl II (lambda)1071 also agree very well with the most recent theoretical effort and with Morton s newest recommendations. For Cl III, however, our f-values are significantly larger than those given by Morton; instead, they are more consistent with recent large-scale theoretical calculations. Extensive tests provide confirmation that LS coupling rules apply to the transitions for the multiplets in Cl II and Cl III.

Cheng, S.↗
NASA NTRS2011

Searching for Soft Relativistic Jets in Core-Collapse Supernovae with the IceCube Optical Follow-up Program

Context. Transient neutrino sources such as Gamma-Ray Bursts (GRBs) and Supernovae (SNe) are hypothesized to emit bursts of high-energy neutrinos on a time-scale of < or approx.100 s. While GRB neutrinos would be produced in high relativistic jets, core-collapse SNe might host soft-relativistic jets, which become stalled in the outer layers of the progenitor star leading to an efficient production of high-energy neutrinos. Aims. To increase the sensitivity to these neutrinos and identify their sources, a low-threshold optical follow-up program for neutrino multiplets detected with the IceCube observatory has been implemented. Methods. If a neutrino multiplet, i.e. two or more neutrinos from the same direction within 100 s, is found by IceCube a trigger is sent to the Robotic Optical Transient Search Experiment, ROTSE. The 4 ROTSE telescopes immediately start an observation program of the corresponding region of the sky in order to detect an optical counterpart to the neutrino events. Results. No statistically significant excess in the rate of neutrino multiplets has been observed and furthermore no coincidence with an optical counterpart was found. Conclusions. The search allows, for the first time, to set stringent limits on current models predicting a high-energy neutrino flux from soft relativistic hadronic jets in core-collapse SNe. We conclude that a sub-population of SNe with typical Lorentz boost factor and jet energy of 10 and 3 x 10(exp 51) erg, respectively, does not exceed 4:2% at 90% confidence.

Abbasi, R.↗
DOE OSTI2013

Analysis of Lattice Baryon Masses in 1/Nc expansion

The 1/Nc expansion of QCD is a perturbative and successful framework for the phenomenology of ground state and excited state baryons. As proposed in [1], it is a systematic expansion in powers of 1/Nc and a good approximation, qualitatively and quantitatively, when Nc=3. The 1/Nc expansion has been applied to the ground state baryons including studies of SU(6) spin-flavor symmetry in [2]. A framework was suggested in [3] for excited baryons based on the 1/Nc expansion was implemented and analyzed with the physical masses from the Particle Data Group. And a successful calculation of the spin identified spectrum of Nucleons and Deltas has been carried out in lattice QCD [4]. Using mass operators organized according to the 1/Nc expansion, the analysis of lattice baryon masses has been completed for the negative parity baryons in the multiplet [70,1]? of the SU(6)×O(3) representation, and results for that multiplet and the rest of the multiplets will be presented in this talk.\\[4pt] [1] G. 'tHooft Nucl.Phys.B72, 461(1974).\\[0pt] [2] R.F. Dashen, E.E. Jenkins, and A.V. Manohar Phys.Rev.D51 (1995).\\[0pt] [3] C.E. Carlson, C.D. Carone, J.L. Goity, R.F. Lebed Phys.Rev.D59 (1999).\\[0pt] [4] R.G. Edwards, J.J. Dudek, D.G. Richards, S.J. Wallace Phys.Rev.D84 (2011).

Fernando, Ishara↗
DOE OSTI2011

Heavy quark spin symmetry and heavy hadronic molecules

In the heavy quark limit there is heavy quark spin symmetry. As a consequence, heavy hadrons or heavy quarkonia form spin multiplets. We argue that due to the symmetry, also heavy flavor hadronic molecules form spin multiplets, and the hyperfine splittings are the same as those between the heavy hadrons which are components of the molecules. Hence it provides a method to identify the nature of heavy hadronic molecules. As an example, we give predictions of the properties of an {eta}{sub c}{sup '}f{sub 0}(980) bound state assuming the Y(4660) to be an S-wave {psi}{sup '}f{sub 0}(980) shallow bound state. We also show that the enhancement observed in the {Lambda}{sub c}{sup +}{Lambda}{sub c}{sup -} invariant mass distribution might be the Y(4660).

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Kβ X-ray Emission Spectra Analysis Using Bayesian Optimization

The Kβ X-ray emission spectrum of 3 d transition metals is rich with electronic and structural information due to strong exchange interactions with the valence shell of the metal, and has become crucial for understanding their spin and oxidation states. The spectrum is commonly treated using crystal-field multiplet theory, a semi-empirical theory that uses tunable parameters to control the strength of the effects present in X-ray emission spectroscopy (XES). However, determining the experimental values of these parameters remains a challenge. We present a methodology that applies Bayesian optimization to crystal-field multiplet theory to determine parameter values. The algorithm is tested on the X-ray emission spectra of a collection of Mn, Co, and Ni oxides. We are able to find optimal values for the four most impactful parameters: Slater−Condon reduction factors F dd , F pd , and G pd , and crystal field splitting 10 Dq . The algorithm produces significantly improved accuracy compared to current analysis methods, and probes interparameter dependencies by modeling the error landscape. This advancement enhances XES analysis by offering an approach of obtaining quantitative electronic structural information on 3 d transition metal valence shells, facilitating applications across various scientific fields.

Bayesian optimization↗
DOE OSTI2014

Far-ultraviolet observations of comet C/2001 Q4 (NEAT) with FIMS/SPEAR

We present the results of far-ultraviolet observations of comet C/2001 Q4 (NEAT) that were made with the Far-Ultraviolet Imaging Spectrograph on board the Korean satellite STSAT-1. The observations were conducted in two campaigns during its perihelion approach between 2004 May 8 and 15. Based on the scanning mode observations in the wavelength band of 1400-1700 Å, we have constructed an image of the comet with an angular size of 5°×5°, which corresponds to the central coma region. Several important fluorescence emission lines were detected including S I multiplets at 1429 and 1479 Å, C I multiplets at 1561 and 1657 Å, and the CO A{sup 1}Π-X{sup 1}Σ{sup +} Fourth Positive system; we have estimated the production rates of the corresponding species from the fluxes of these emission lines. The estimated production rate of CO was Q {sub CO} = (2.65 ± 0.63) × 10{sup 28} s{sup –1}, which is 6.2%-7.4% of the water production rate and is consistent with earlier predictions. The average carbon production rate was estimated to be Q{sub C} = ∼1.59 × 10{sup 28} s{sup –1}, which is ∼60% of the CO production rate. However, the observed carbon profile was steeper than that predicted using the two-component Haser model in the inner coma region, while it was consistent with the model in the outer region. The average sulfur production rate was Q{sub S} = (4.03±1.03) × 10{sup 27} s{sup –1}, which corresponds to ∼1% of the water production rate.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

On helium 1083 nm line polarization during the impulsive phase of an X1 flare

We analyze spectropolarimetric data of the He i 1083 nm multiplet (1s2s{sup 3}S{sub 1}−1s2p{sup 3}P{sub 2,1,0}{sup o}) during the X1 flare SOL2014-03-29T17:48, obtained with the Facility Infrared Spectrometer (FIRS) at the Dunn Solar Telescope. While scanning active region NOAA 12017, the FIRS slit crossed a flare ribbon during the impulsive phase, when the helium line intensities turned into emission at ≲twice the continuum intensity. Their linear polarization profiles are of the same sign across the multiplet including 1082.9 nm, intensity-like, at ≲5% of the continuum intensity. Weaker Zeeman-induced linear polarization is also observed. Only the strongest linear polarization coincides with hard X-ray (HXR) emission at 30–70 keV observed by RHESSI. The polarization is generally more extended and lasts longer than the HXR emission. The upper J = 0 level of the 1082.9 nm component is unpolarizable; thus, lower-level polarization is the culprit. We make non-LTE radiative transfer calculations in thermal slabs optimized to fit only intensities. The linear polarizations are naturally reproduced, through a systematic change of sign with wavelength of the radiation anisotropy when slab optical depths of the 1082.9 component are ≲1. Neither are collisions with beams of particles needed, nor can they produce the same sign of polarization of the 1082.9 and 1083.0 nm components. The He i line polarization merely requires heating sufficient to produce slabs of the required thickness. Widely different polarizations of Hα, reported previously, are explained by different radiative anisotropies arising from slabs of different optical depths.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

Submillimeter/THz rotational spectroscopy of SH{sup +} (X{sup 3}Σ{sup −}): The complete N = 1←0 transition

The N = 1 ← 0 transition of SH{sup +} (X{sup 3}Σ{sup −}) in its complete fine structure multiplet (J = 0 ← 1, 2 ← 1, and 1 ← 1) has been measured using submillimeter/THz direct absorption spectroscopy in the frequency range near 346–683 GHz. This work is the first direct laboratory measurement of the J = 0 ← 1 and 1 ← 1 spin components. This molecular ion was created in the gas phase from a mixture of H{sub 2}S and argon in an AC discharge. Hyperfine components, arising from the nuclear spin of H (I = 1/2), were resolved in every fine structure multiplet. The data have been analyzed using a Hund’s case b{sub βJ} Hamiltonian, resulting in further improvement in the accuracy of the rotational, spin–rotation, spin–spin, and magnetic hyperfine constants for SH{sup +}. From these new data, frequency predictions have been made for the N = 2 → 1 and 3 → 2 transitions, with an estimated uncertainty of less than 1 MHz. These data also confirm the recent detection of the two hyperfine components of the N = 1 → 0, J = 0 → 1 transition of SH{sup +} in the Orion Bar, as well as the J = 1 → 1 component of this molecular ion near 683 GHz toward Sgr B2.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

SPECTRAL OPTICAL MONITORING OF THE NARROW-LINE SEYFERT 1 GALAXY Ark 564

We present the results of a long-term (1999-2010) spectral optical monitoring campaign of the active galactic nucleus (AGN) Ark 564, which shows a strong Fe II line emission in the optical. This AGN is a narrow-line Seyfert 1 (NLS1) galaxy, a group of AGNs with specific spectral characteristics. We analyze the light curves of the permitted H{alpha}, H{beta}, optical Fe II line fluxes, and the continuum flux in order to search for a time lag between them. Additionally, in order to estimate the contribution of iron lines from different multiplets, we fit the H{beta} and Fe II lines with a sum of Gaussian components. We find that during the monitoring period the spectral variation (F{sub max}/F{sub min}) of Ark 564 is between 1.5 for H{alpha} and 1.8 for the Fe II lines. The correlation between the Fe II and H{beta} flux variations is of higher significance than that of H{alpha} and H{beta} (whose correlation is almost absent). The permitted-line profiles are Lorentzian-like and do not change shape during the monitoring period. We investigate, in detail, the optical Fe II emission and find different degrees of correlation between the Fe II emission arising from different spectral multiplets and the continuum flux. The relatively weak and different degrees of correlations between permitted lines and continuum fluxes indicate a rather complex source of ionization of the broad-line emission region.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

Non-perturbative effect and PAMELA limit on electro-weak dark matter

We discuss the non-perturbative effects on the annihilation cross section of an Electro-Weak Dark Matter (EWDM) particle belonging to an electroweak multiplet when the splittings between the masses of the DM component and the other charged or neutral component(s) of the multiplet are treated as free parameters. Our analysis shows that EWDM exhibits not only the usual Sommerfeld enhancement with resonance peaks but also dips where the cross section is suppressed. Moreover, we have shown that the non-perturbative effects become important even when the EWDM mass is below the TeV scale, provided that some of the mass splittings are reduced to the order of a few MeV. This extends the possibility of observing sizeable non-perturbative effects in the dark matter annihilation to values of the dark matter mass significantly smaller than previously considered, since only electroweak-induced mass splittings larger than 100 MeV have been discussed in the literature so far. We have then used the available experimental data on the cosmic antiproton flux to constrain the EWDM parameter space. In our calculation of the expected signal we have included the effect of the convolution of the cross section with the velocity distribution of the dark matter particles in the Galaxy, showing that it can alter the non-perturbative effects significantly. In the case of EWDM with non-zero hypercharge, we have shown that the mass splitting in the Dirac dark matter fermion can be chosen so that the inelastic cross section of the EWDM off nuclei is allowed by present direct detection constraints and at the same time is within the reach of future experiments.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

Millicharge or decay: a critical take on Minimal Dark Matter

Minimal Dark Matter (MDM) is a theoretical framework highly appreciated for its minimality and yet its predictivity. Of the two only viable candidates singled out in the original analysis, the scalar eptaplet has been found to decay too quickly to be around today, while the fermionic quintuplet is now being probed by indirect Dark Matter (DM) searches. It is therefore timely to critically review the MDM paradigm, possibly pointing out generalizations of this framework. We propose and explore two distinct directions. One is to abandon the assumption of DM electric neutrality in favor of absolutely stable, millicharged DM candidates which are part of SU(2){sub L} multiplets with integer isospin. Another possibility is to lower the cutoff of the model, which was originally fixed at the Planck scale, to allow for DM decays. We find new viable MDM candidates and study their phenomenology in detail.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

Influence of the Wavefunction Distribution on Exciton Dissociation in Electric Field

We show that the dissociation threshold of an exciton, a bound electron-hole pair, by an electric field is mainly determined by its energy: as expected, the dissociation voltage decreases with increasing exciton energy. However, within the multiplet of states belonging to a particular principal quantum number n, the dissociation voltage rises with increasing state energy, in contrast to the expectations based on energy arguments. This behavior is demonstrated for the yellow exciton states of Cu{sub 2}O and is attributed to the distribution of the wavefunction in the potential landscape, where the lower (higher) lying state in the multiplet is shifted away (towards) the tunnel barrier.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗