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At least 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Inferring subhalo effective density slopes from strong lensing observations with neural likelihood-ratio estimation

ABSTRACT Strong gravitational lensing has emerged as a promising approach for probing dark matter (DM) models on sub-galactic scales. Recent work has proposed the subhalo effective density slope as a more reliable observable than the commonly used subhalo mass function. The subhalo effective density slope is a measurement independent of assumptions about the underlying density profile and can be inferred for individual subhaloes through traditional sampling methods. To go beyond individual subhalo measurements, we leverage recent advances in machine learning and introduce a neural likelihood-ratio estimator to infer an effective density slope for populations of subhaloes. We demonstrate that our method is capable of harnessing the statistical power of multiple subhaloes (within and across multiple images) to distinguish between characteristics of different subhalo populations. The computational efficiency warranted by the neural likelihood-ratio estimator over traditional sampling enables statistical studies of DM perturbers and is particularly useful as we expect an influx of strong lensing systems from upcoming surveys.

Astronomy & Astrophysics↗
DOE OSTI2021

Redshift evolution of the H2/H i mass ratio in galaxies

ABSTRACT In this paper, we present an attempt to estimate the redshift evolution of the molecular to neutral gas mass ratio within galaxies (at fixed stellar mass). For a sample of five nearby grand design spirals located on the main-sequence (MS) of star-forming galaxies, we exploit maps at 500 pc resolution of stellar mass and star formation rate (M⋆ and SFR). For the same cells, we also have estimates of the neutral (MH i) and molecular ($M_{\rm H_2}$) gas masses. To compute the redshift evolution, we exploit two relations: (i) one between the molecular-to-neutral mass ratio and the total gas mass (Mgas), whose scatter shows a strong dependence with the distance from the spatially resolved MS, and (ii) the one between $\log (M_{\rm {H_2}}/M_{\star })$ and log (MH i/M⋆). For both methods, we and that $M_{\rm H_2}$/MH i within the optical radius slightly decreases with redshift, contrary to common expectations of galaxies becoming progressively more dominated by molecular hydrogen at high redshifts. We discuss possible implications of this trend on our understanding of the internal working of high-redshift galaxies.

Morselli, Laura (ORCID:0000000307532571)↗
DOE OSTI2025

Robust ab initio predictions for dimensionless ratios of 𝐸⁢2 and radius observables. I. Electric quadrupole moments and deformation

We report that converged results for 𝐸⁢2 observables are notoriously challenging to obtain in ab initio no-core configuration interaction approaches. Matrix elements of the 𝐸⁢2 operator are sensitive to the large-distance tails of the nuclear wave function, which converge slowly in an oscillator basis expansion. Similar convergence challenges beset ab initio prediction of the nuclear charge radius. However, we exploit systematic correlations between the calculated 𝐸⁢2 and radius observables to yield meaningful predictions for relations among these observables. In particular, we examine ab initio predictions for dimensionless ratios of the form 𝑄/𝑟 2 for nuclei throughout the 𝑝 shell. Meaningful predictions for electric quadrupole moments may then be made by calibrating to the ground-state charge radius, if experimentally known, or vice versa. Moreover, these dimensionless ratios provide ab initio insight into the nuclear quadrupole deformation.

ab initio calculations↗
DOE OSTI2025

Measurement of the branching ratio of 16 N , 15 C , 12 B , and 13 B isotopes through the nuclear muon capture reaction in the Super-Kamiokande detector

The Super-Kamiokande detector has measured solar neutrinos for more than 25 years. The sensitivity for solar neutrino measurement is limited by the uncertainties of energy scale and background modeling. Decays of unstable isotopes with relatively long half-lives through nuclear muon capture, such as 16 N, 15 C, 12 B, and 13 B, are detected as background events for solar neutrino observations. Here, in this study, we developed a method to form a pair of stopping muon and decay candidate events and evaluated the production rates of such unstable isotopes. We then measured their branching ratios considering both their production rates and the estimated number of nuclear muon capture processes as Br⁡( 16 N) = (9.0 ± 0.1)%, Br⁡( 15 C) = (0.6 ± 0.1)%, Br⁡( 12 B) = (0.98 ± 0.18)%, Br⁡( 13 B) = (0.14 ± 0.12)%, respectively. The result for 16 N has world-leading precision at present and the results for 15 C, 12 B, and 13 B are the first branching ratio measurements for those isotopes.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2026

Measurement of the ratio of the $𝐵^+_𝑐 → 𝐽/𝜓⁢𝜏^+⁢𝜈_𝜏$ and $𝐵^+_𝑐 → 𝐽/𝜓⁢𝜇^+⁢𝜈_𝜇$ branching fractions using three-prong 𝜏 lepton decays

The ratio between the $𝐵^+_𝑐 → 𝐽/𝜓⁢𝜏^+⁢𝜈_𝜏$ and $𝐵^+_𝑐 → 𝐽/𝜓⁢𝜇^+⁢𝜈_𝜇$ branching fractions is measured using a data sample of proton-proton collisions collected by CMS at a center-of-mass energy of 13 TeV in the years 2016–2018 and corresponding to an integrated luminosity of 138 fb −1 . The 𝐽/𝜓 meson is identified through its 𝐽/𝜓 → 𝜇 + ⁢𝜇 − decay and the tau lepton is reconstructed in the hadronic three-prong final state. The measured ratio of branching fractions in this tau decay mode, ℛ had 𝐽/𝜓 = $1.0⁢4^{+0.50}_{−0.44}$, is combined with the previous analysis based on the 𝜏 + $→ 𝜇^+⁢𝜈_𝜇\bar{𝜈}_𝜏$ leptonic decay channel, leading to ℛ 𝐽/𝜓 = 0.49 ± 0.26. As this result is consistent with the standard model prediction of 0.258 ± 0.004, no evidence of lepton flavor universality violation is found.

Chekhovsky, V. [Yerevan Physics Institute]↗
DOE OSTI2020

Analysis of THz generation by multicolor laser pulses with various frequency ratios

Here, terahertz (THz) generation in a gas medium is simulated by quantum calculations with multicolor intense laser pulses of various frequency ratios. By correlating THz radiation with the above-threshold-ionization photoelectron spectrum, we confirm that our previously proposed free-free transition model for the generation of THz radiation is also applicable to multicolor pulses. THz photon emissions can proceed through transitions between continuous states with similar energies that have opposite parities. This mechanism predicts that THz waves can be efficiently generated at special two-color laser frequency ratios when the multiphoton mixing condition is satisfied. Applying this model to multicolor fields (sawtooth wave shape), we provide a quantum-mechanical interpretation for the reason for THz radiation enhancement. A scheme combining multiple lasers to raise THz radiation satisfying multiphoton mixing conditions is also proposed.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2021

Examination of the universal behavior of the η-to-π 0 ratio in heavy-ion collisions

We demonstrate that the pT dependence of the η/π 0 ratio at midrapidity is universal within a few percent for high-energy p+p, p+A, and d+A collisions, over a broad range of collision energies. The η/π 0 ratio increases with p T up to 4 to 5 GeV/c where it saturates at a nearly constant value of 0.487±0.024. Above p T =5 GeV/c, the same constant value is also observed in A+A collisions independent of collision system, energy, and centrality. At lower p T , where accurate η/π 0 data are absent for A+A collisions, we estimate possible deviations from the universal behavior, which could arise due to the rapid radial hydrodynamic expansion of the A+A collision system. For A+A collisions at the BNL Relativistic Heavy Ion Collider we find that possible deviations are limited to the p T range from 0.4 to 3 GeV/c and remain less than 20% for the most central collisions.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2023

Measurement of the mass and width of the Λ c ⁢(2625) + charmed baryon and the branching ratios of Λ c ⁢(2625) + → Σ$^{0}_{c}$π + and Λ c ⁢(2625) + → Σ$^{++}_{c}$π -

Using the entire data sample of 980 fb -1 collected at or near the Y⁡(4⁢S) resonance with the Belle detector operating at the KEKB asymmetric-energy e + ⁢e - collider, we report the measurement of the mass, width, and the branching ratios of the Λ c (2625) + charmed baryon. The mass difference between Λ c ⁢(2625) + and Λ$^{+}_{c}$ is measured to be M⁡(Λ c ⁢(2625) + )-M⁡(Λ$^{+}_{c}$)=341.518±0.006±0.049 MeV/c 2 . The upper limit on the width is measured to be Γ⁡(Λ c ⁢(2625) + )<0.52 MeV/c 2 at 90% confidence level. Based on a full Dalitz plot fit, branching ratios with respect to the mode Λ c⁢ (2625) + →Λ$^{+}_{c}$π + ⁢π - are measured to be $\frac{\mathscr{B}⁡(Λ_c(2625)^+ → Σ^{0}_{c}π^+)} {\mathscr{B}⁡(Λ_c(2625)^+ → ^{+}_{c}⁢π^+⁢π^-)}$ = (5.19±0.23±0.40)% and $\frac{\mathscr{B}(Λ_c (2625)^+ → Σ{_c^+}^+ π^-)}{\mathscr{B}(Λ_c (2625)^+ → Λ{_c^+} π^+π^-)}$ = (5.13±0.26±0.32)%, where the first and second uncertainties are statistical and systematic, respectively. These measurements can be used to further constrain the parameters of the underlying theoretical models.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Measurement of the B + /B 0 production ratio in e + e - collisions at the $\Upsilon$ (4S) resonance using B → J/Ψ($\ell\ell$)K decays at Belle

We measure the ratio of branching fractions for the $\Upsilon$ (4S) decays to B + B - and B 0 $\bar{B}$ 0 using B + → J/Ψ($\ell\ell$)K + and B 0 → J/Ψ($\ell\ell$)K 0 samples, where J/Ψ($\ell\ell$) stands for J/Ψ → $\ell$ + $\ell$ - ($\ell$ = e or μ), with 711 fb -1 of data collected at the $\Upsilon$ (4S) resonance with the Belle detector. We find the decay rate ratio of $\Upsilon$ (4S) → B + B - over $\Upsilon$ (4S) → B 0 $\bar{B}$ 0 to be 1.065 ± 0.012 ± 0.019 ± 0.047, which is the most precise measurement to date. The first and second uncertainties are statistical and systematic, respectively, and the third uncertainty is due to the assumption of isospin symmetry in B → J/Ψ($\ell\ell$) K.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2024

Measurement of Ω c 0 baryon production and branching-fraction ratio BR ( Ω c 0 → Ω - e + ν e ) / BR ( Ω c 0 → Ω - π + ) in p p collisions at s = 13 TeV

The inclusive production of the charm-strange baryon $Ω^0_c$ is measured for the first time via its semileptonic decay into $Ω$ - e + ν e at midrapidity (|y| < 0.8) in proton-proton (pp) collisions at the center-of mass energy $\sqrt{s}$ = 13 TeV with the ALICE detector at the LHC. The transverse momentum (p T ) differential cross section multiplied by the branching ratio is presented in the interval 2 < p T < 12 GeV=c. The branching-fraction ratio BR($Ω^0_c$ → $Ω$ - e + ν e )/BR($Ω^0_c$→ Ω - π + ) is measured to be 1.12 ± 0.22 (stat) ± 0.27 (syst). Comparisons with other experimental measurements, as well as with theoretical calculations, are presented

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Measurements of the charge ratio and polarization of cosmic-ray muons with the Super-Kamiokande detector

We present the results of the charge ratio (𝑅) and polarization (𝑃$^{𝜇}_{0}$) measurements using decay electron events collected between September 2008 and June 2022 with the Super-Kamiokande detector. Because of its underground location and long operation, we are able to perform high-precision measurements by accumulating cosmic-ray muons. We measured the muon charge ratio to be 𝑅 = 1.32 ± 0.02⁢(stat +syst) at 𝐸 𝜇 ⁢cos⁡𝜃 Zenith = 0.7$^{+0.3}_{−0.2}$ TeV, where 𝐸 𝜇 is the muon energy and 𝜃 Zenith is the zenith angle of incoming cosmic-ray muons. This result is consistent with the Honda flux model while indicating a tension with the 𝜋⁢𝐾 model of 1.9⁢𝜎. We also measured the muon polarization at the production location to be 𝑃$^{𝜇}_{0}$ = 0.52 ± 0.02 (stat+syst) at the muon momentum of 0.9$^{+0.6}_{−0.1}$ TeV/𝑐 at the surface of the mountain; this also suggests a tension with the Honda flux model of 1.5⁢𝜎. This is the most precise measurement ever to experimentally determine the cosmic-ray muon polarization near 1 TeV/𝑐. These measurement results are useful to improve atmospheric neutrino simulations.

Atmospheric neutrino oscillations↗
DOE OSTI2020

Direct Measurement of the Be 7 L / K Capture Ratio in Ta-Based Superconducting Tunnel Junctions

We report a high-statistics measurement of the L / K orbital electron capture ratio in 7 Be embedded in cryogenic Ta. The thin Ta film formed part of a high-resolution superconducting tunnel junction radiation detector that was used to identify the signals from different decay channels. The measured L/K capture ratio of 0.070(7) is significantly larger than the only previous measurement of this quantity and the theoretical predictions that include in-medium effects. This value is a uniquely sensitive probe of the 1s and 2s orbital overlaps with the nucleus and is of relevance to nuclear and atomic physics, as well as Li production in novae and other astrophysical scenarios. Furthermore, this is the first experiment that uses superconducting tunnel junctions for nuclear-recoil detection, opening a new experimental avenue for low-energy precision measurements with rare isotopes.

6 ≤ A ≤ 19↗
DOE OSTI2025

Operation of AlGaN Channel HEMTs at 850 °C With ON/OFF Ratio >10 4

Here, we report 850 ° C operation of ultrawide bandgap (UWBG) Al-rich Al 0.68 Ga 0.32 N channel high electron mobility transistors (HEMTs) at atmospheric pressure in nitrogen ambient. Temperature dependent DC electrical characteristics were measured in situ up to 850 ° C, after exposure to 850 ° C for 60 minutes, and at 25 ° C after high temperature testing. At 850 ° C (time, t = 0 min), all HEMTs tested maintained an on/off ratio greater than 10 4 (maximum of 4.6 × 10 4 ). The threshold voltage demonstrated excellent stability with less than ±10% deviation. After returning to 25 ° C, the devices showed negligible degradation. In fact, the off-state gate current decreased and on/off ratio slightly increased. The robustness of these UWBG AlGaN transistors at temperatures up to 850 ° C demonstrates their viability for extreme environment applications.

AlGaN↗
DOE OSTI2023

Experimental and computational studies of load ratio effect on fatigue crack growth rates in Alloy 709 at elevated temperatures

Abstract Experimental testing and finite element simulations of fatigue crack growth were performed in austenitic 20Cr‐25Ni (Alloy 709) steel at different load ratios and elevated temperatures. The experimental tests were performed using compact tension specimens, and crack growth rates were measured at stress intensity factors ranging between 5 and 35 MPa√m. Fractographic analysis using scanning electron microscopy indicated crack surface roughness and secondary cracking depending on testing temperature and load ratio. Finite element simulations of fatigue crack growth were performed to compute plasticity‐induced crack opening loads and predict crack growth rates. Predictions of fatigue crack growth rates using finite element simulations were performed using the computed crack‐tip opening loads, and they are shown to match well the experimental measurements.

Engineering↗
DOE OSTI2021

Effects of Al:Si and (Al+Na):Si ratios on the static corrosion of sodium‐boroaluminosilicate glasses

Abstract Understanding alteration mechanisms of borosilicate glasses in aqueous media is essential to nuclear waste performance assessments to ensure radioisotopes are contained for extended durations. Aluminum is typically added to glass compositions to reduce the extent of alteration. However, previous work on 7‐day durability tests has suggested that Al has a nonlinear relationship with extent of alteration. The effects of Al:Si and (Al+Na):Si substitutions on glass durability were evaluated using series of glasses based on the International Simple Glass corroded in static conditions up to 13 months in deionized water at 90°C. The alteration behavior was determined by measurement of element release in solution. The ⁓7‐day alteration trends across the series were consistent with predicted trends. The 13‐month results indicated overall alteration decreased as Al:Si ratios increased and was unaffected by changes in (Al+Na):Si except for the glass with the highest (Al+Na):Si ratio (ISG‐A23N), which completely altered within 14 days. Frequent sampling and in situ Raman measurements of solutions revealed ISG‐A23N experienced several distinguishable alteration rate regimes within 7 days, forming a ⁓100 µm alteration layer and a NaSiAlO 4 zeolite.

Reiser, Joelle T.↗
DOE OSTI2024

Excitation functions and isomeric cross-section ratios of (d,xn) reactions on 86 Sr

Excitation functions of the 86 Sr(d,n) 87m,87g Y, 86 Sr(d,2n) 86m,86g Y and 86 Sr(d,3n) 85m,85g Y reactions on enriched 86 Sr target were measured by the activation technique up to deuteron energies of 49 MeV. The isomeric cross-section ratios as a function of projectile energy were deduced from the measured data for 87m Y, 87g Y(cum), 86m Y, 86g Y(cum), 85m Y and 85g Y pairs for the same energy range. All measurements are reported for the first time. The experimental data were compared with the data from the TENDL library which is based on TALYS calculation with default parameters. No satisfactory agreement was observed. Nuclear model calculations were then performed using the codes TALYS and EMPIRE with some parameter adjustments, and compared with the experimental data. The quality of the agreement between experimental data and model calculations was numerically quantified. In general, the data as well as the isomeric cross-section ratios are partially reproduced by the model calculations, provided the input model parameters are properly chosen and the level structure of the product nucleus is thoughtfully considered.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

From pole parameters to line shapes and branching ratios

Abstract Resonances are uniquely characterized by their complex pole locations and the corresponding residues. In practice, however, resonances are typically identified experimentally as structures in invariant mass distributions, with branching fractions of resonances determined as ratios of count rates. To make contact between these quantities it is necessary to connect line shapes and resonance parameters. In this work we propose such a connection and illustrate the formalism with detailed studies of the $$\rho (770)$$ ρ ( 770 ) and $$f_0(500)$$ f 0 ( 500 ) resonances. Based on the line shapes inferred from the resonance parameters along these lines, expressions for partial widths and branching ratios are derived and compared to other approaches in the literature.

Physics↗
DOE OSTI2022

Measurements of $W$ and $Z/γ^*$ cross sections and their ratios in $pp$ collisions at STAR

While the unpolarized parton distribution functions of the valence quarks ( d d and u u ) are well determined from DIS experiments, the sea quark counterparts, \bar{d} d ‾ and \bar{u} u ‾ , are much less constrained, in particular, near the valence region. Measurements of W^+/W^- W + / W − production ratio in pp p p collider experiments, such as the STAR experiment at RHIC, can probe the \bar{d}/\bar{u} d ‾ / u ‾ ratio at a large Q^2 Q 2 set by the W W mass. These proceedings will discuss recent results of W W and Z Z cross-section measurements using the STAR pp p p collision data at a center-of-mass energy of \sqrt{s} = 500/510\;\mathrm{GeV} s = 500 / 510 G e V collected in 2011, 2012, 2013 and 2017.

Nam, Jae↗