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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Tropical Cyclone Wind Shear-Relative Asymmetry in Reanalyses

Abstract While tropical cyclones (TCs) are axisymmetric vortices to the first order, they often exhibit noteworthy structural asymmetries. These often result from environmental vertical wind shear, which tilts the vortex and induces a wavenumber 1 pattern in the circulation and precipitation fields. Reanalyses and climate models have improved in representing the TC structure and climatology, but their relatively coarse resolution and dependence on parameterized physics cast doubt on their ability to capture the asymmetric TC structure. We perform the most comprehensive process-oriented assessment of TC asymmetry to date in reanalyses. Specifically, we analyze the composite shear-relative TC structure in ERA5 and Climate Forecast System Reanalysis (CFSR), which vary in their resolutions, physical parameterization suites, and data assimilation techniques. These structures are compared with aircraft reconnaissance radar observations. In agreement with the observations, the strongest tangential winds are usually found left-of-shear, while inner core rainfall, ascent, vortex tilt, and low-level inflow are favored directly downshear or in the downshear-left quadrant. Outer rainband convection generally peaks in the downshear-right quadrant. Thermodynamic asymmetries are also apparent, with anomalous low-level moisture right-of-shear, midlevel warmth in the upshear-right quadrant (uptilt), and cloud properties suggestive of a realistic precipitation life cycle from growth to fallout. We also decompose rainfall contributions from the convective parameterization and large-scale cloud schemes and highlight the roles of vorticity advection, buoyancy advection, and diabatic processes in driving asymmetric vertical motions in the inner core and outer rainband regions. Our results suggest that process-level studies of TC asymmetry and TC–wind shear interaction under future warming are viable using climate models. Significance Statement Asymmetries are common in tropical cyclones (TCs), influencing their intensity, track, and hazards. Vertical wind shear often plays a leading-order role in causing these asymmetries. It is uncertain how well asymmetric structures and processes are captured in reanalyses and global climate models (GCMs) with grid spacings of 0.25° and coarser. In this study, we first evaluate TC asymmetry in reanalyses, which have the benefit of being forced by observations. This helps to assess whether the resolutions associated with GCMs sufficiently capture asymmetric structures and processes and motivates upcoming work with free-running GCMs to study how TC asymmetry may change in a warming climate.

Carstens, Jacob D.↗
DOE OSTI2016

Mitigating the impact of hohlraum asymmetries in National Ignition Facility implosions using capsule shims

Here, current indirect drive implosion experiments on the National Ignition Facility (NIF) are believed to be strongly impacted by long wavelength perturbations driven by asymmetries in the hohlraum x-ray flux. To address this perturbation source, active efforts are underway to develop modified hohlraum designs with reduced asymmetry imprint. An alternative strategy, however, is to modify the capsule design to be more resilient to a given amount of hohlraum asymmetry. In particular, the capsule may be deliberately misshaped, or “shimmed,” so as to counteract the expected asymmetries from the hohlraum. Here, the efficacy of capsule shimming to correct the asymmetries in two recent NIF implosion experiments is assessed using two-dimensional radiation hydrodynamics simulations. Despite the highly time-dependent character of the asymmetries and the high convergence ratios of these implosions, simulations suggest that shims could be highly effective at counteracting current asymmetries and result in factors of a few enhancements in neutron yields. For higher compression designs, the yield improvement could be even greater.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2022

Extensions of a classical mechanics “piston-model” for understanding the impact of asymmetry on ICF implosions: The cases of mode 2, mode 2/1 coupling, time-dependent asymmetry, and the relationship to coast-time

As long suspected, low mode asymmetry in inertially confined fusion (ICF) implosions has been implicated as a performance limiting factor [Casey et al., “Evidence of three-dimensional asymmetries seeded by high-density carbon-ablator nonuniformity in experiments at the national ignition facility,” Phys. Rev. Lett. 126, 025002 (2021)]. Recently a non-linear, but solvable, theory [Hurricane et al., “An analytic asymmetric-piston model for the impact of mode-1 shell asymmetry on ICF implosions,” Phys. Plasmas 27, 062704 (2020)] based upon the simple picture of a pair of asymmetric pistons has generated new insights and provided some practical formulas for estimating the degradation of an implosion due to mode-1 asymmetry and demonstrated a previously unrecognized connection between measured hot-spot drift velocity, nuclear down-scatter ratio asymmetry, and the concept of residual kinetic energy (RKE). Asymmetry of the implosion “shell,” as opposed to asymmetry of the hot-spot, was key to the classical mechanics model because the majority of the kinetic energy in an implosion is carried by the shell. Herein, the two-piston model is extended to a six-piston model in order to capture mode-2 asymmetry and coupling between mode-1 and mode-2. A key result of this new six-piston model is that the weighted harmonic mean of shell areal density is the fundamental quantity that determines the RKE and performance degradations for a three-dimensional implosion. Agreement is found between the scalings coming from the theory and ICF implosion data from the National Ignition Facility and to large ensembles of detailed simulations. The connection between the piston model's dependence upon the radius of peak velocity and coast-time is also highlighted in this paper. Finally, by extending the two-piston model to include time-dependent “swing,” it is shown in the Appendix that the shell asymmetry at the time of stagnation dominates the solution for RKE.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2016

Target and beam-target spin asymmetries in exclusive π + and π - electroproduction with 1.6- to 5.7-GeV electrons

Beam-target double-spin asymmetries and target single-spin asymmetries in exclusive pi(+) and quasiexclusive pi(-) electroproduction were obtained from scattering of 1.6- to 5.7-GeV longitudinally polarized electrons from longitudinally polarized protons (for pi(+)) and deuterons (for pi(-)) using the CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Lab. The kinematic range covered is 1.1 < W < 2.6 GeV and 0.05 < Q(2) < 5 GeV2, with good angular coverage in the forward hemisphere. The asymmetry results were divided into approximately 40 000 kinematic bins for pi(+) from free protons and 15 000 bins for pi(-) production from bound nucleons in the deuteron. The present results are found to be in reasonable agreement with fits to previous world data for W < 1.7 GeV and Q(2) < 0.5 GeV2, with discrepancies increasing at higher values of Q(2), especially for W > 1.5 GeV. Very large target-spin asymmetries are observed for W > 1.6 GeV. When combined with cross-section measurements, the present results can provide powerful constraints on nucleon resonance amplitudes at moderate and large values of Q(2), for resonances with masses as high as 2.3 GeV.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2017

Beam-target double-spin asymmetry in quasielastic electron scattering off the deuteron with CLAS

The deuteron plays a pivotal role in nuclear and hadronic physics, as both the simplest bound multinucleon system and as an effective neutron target. Quasielastic electron scattering on the deuteron is a benchmark reaction to test our understanding of deuteron structure and the properties and interactions of the two nucleons bound in the deuteron. The experimental data presented here can be used to test state-of-the-art models of the deuteron and the two-nucleon interaction in the final state after two-body breakup of the deuteron. Focusing on polarization degrees of freedom, we gain information on spin-momentum correlations in the deuteron ground state (due to the D-state admixture) and on the limits of the impulse approximation (IA) picture as it applies to measurements of spin-dependent observables like spin structure functions for bound nucleons. Information on this reaction can also be used to reduce systematic uncertainties on the determination of neutron form factors or deuteron polarization through quasielastic polarized electron scattering. Furthermore, we measured the beam-target double-spin asymmetry (A || ) for quasielastic electron scattering off the deuteron at several beam energies (1.6–1.7, 2.5, 4.2, and 5.6–5.8GeV), using the CEBAF Large Acceptance Spectrometer (CLAS) at the Thomas Jefferson National Accelerator Facility. The deuterons were polarized along (or opposite to) the beam direction. The double-spin asymmetries were measured as a function of photon virtuality Q 2 (0.13–3.17(GeV/c) 2 ), missing momentum (p m =0.0–0.5GeV/c), and the angle between the (inferred) spectator neutron and the momentum transfer direction (θ nq ). We compare our results with a recent model that includes final-state interactions (FSI) using a complete parametrization of nucleon-nucleon scattering, as well as a simplified model using the plane wave impulse approximation (PWIA). We find overall good agreement with both the PWIA and FSI expectations at low to medium missing momenta (p m ≤0.25GeV/c), including the change of the asymmetry due to the contribution of the deuteron D state at higher momenta. At the highest missing momenta, our data clearly agree better with the calculations including FSI. Final-state interactions seem to play a lesser role for polarization observables in deuteron two-body electrodisintegration than for absolute cross sections. Our data, while limited in statistical power, indicate that PWIA models work reasonably well to understand the asymmetries at lower missing momenta. In turn, this information can be used to extract the product of beam and target polarization (P b P t ) from quasielastic electron-deuteron scattering, which is useful for measurements of spin observables in electron-neutron inelastic scattering. But, at the highest missing (neutron) momenta, FSI effects become important and must be accounted for.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2016

Measurement of target and double-spin asymmetries for the $\vec e\vec p\to e\pi^+ (n)$ reaction in the nucleon resonance region at low $Q^2$

We report measurements of target- and double-spin asymmetries for the exclusive channel $\vec e\vec p\to e\pi^+ (n)$ in the nucleon resonance region at Jefferson Lab using the CEBAF Large Acceptance Spectrometer (CLAS). These asymmetries were extracted from data obtained using a longitudinally polarized NH$_3$ target and a longitudinally polarized electron beam with energies 1.1, 1.3, 2.0, 2.3 and 3.0 GeV. The new results are consistent with previous CLAS publications but are extended to a low $Q^2$ range from $0.0065$ to $0.35$ (GeV$/c$)$^2$. The $Q^2$ access was made possible by a custom-built Cherenkov detector that allowed the detection of electrons for scattering angles as low as $6^\circ$. These results are compared with the unitary isobar models JANR and MAID, the partial-wave analysis prediction from SAID and the dynamic model DMT. In many kinematic regions our results, in particular results on the target asymmetry, help to constrain the polarization-dependent components of these models.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2017

Measurement of the B ± production asymmetry and the C P asymmetry in B ± → J / ψ K ± decays

The B ± meson production asymmetry in pp collisions is measured using B + →¯D 0 π + decays. The data were recorded by the LHCb experiment during Run 1 of the LHC at center-of-mass energies of √s = 7 and 8 TeV. The production asymmetries, integrated over transverse momenta in the range 2 < p T < 30 GeV/c, and rapidities in the range 2.1 < y < 4.5 are measured to be A prod (B + ,√s = 7 TeV)=(–0.41±0.49±0.10)×10 –2 , A prod (B + ,√s = 8 TeV)=(–0.53±0.31±0.10)×10 –2 , where the first uncertainties are statistical and the second are systematic. These production asymmetries are used to correct the raw asymmetries of B + →J/ψK + decays, thus allowing a measurement of the CP asymmetry, A CP (B + →J/ψK + )=(0.09±0.27±0.07)×10 –2 .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Long-lived Dust Asymmetries at Dead Zone Edges in Protoplanetary Disks

A number of transition disks exhibit significant azimuthal asymmetries in thermal dust emission. One possible origin for these asymmetries is dust trapping in vortices formed at the edges of dead zones. We carry out high-resolution, two-dimensional hydrodynamic simulations of this scenario, including the effects of dust feedback. We find that, although feedback weakens the vortices and slows down the process of dust accumulation, the dust distribution in the disk can nonetheless remain asymmetric for many thousands of orbits. We show that even after 10{sup 4} orbits, or 2.5 Myr when scaled to the parameters of Oph IRS 48 (a significant fraction of its age), the dust is not dispersed into an axisymmetric ring, in contrast to the case of a vortex formed by a planet. This is because accumulation of mass at the dead zone edge constantly replenishes the vortex, preventing it from being fully destroyed. We produce synthetic dust emission images using our simulation results. We find that multiple small clumps of dust may be distributed azimuthally. These clumps, if not resolved from one another, appear as a single large feature. A defining characteristic of a disk with a dead zone edge is that an asymmetric feature is accompanied by a ring of dust located about twice as far from the central star.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

Measurement of the branching fraction and C P asymmetry in B 0 → π 0 π 0 decays, and an improved constraint on φ 2

Here, we measure the branching fraction and C P violation asymmetry in the decay B 0 → π 0 π 0 , using a data sample of 752 × 10 6 B B ¯ pairs collected at the Υ ( 4 S ) resonance with the Belle detector at the KEKB e + e - collider. The obtained branching fraction and direct C P asymmetry are B ( B → π 0 π 0 ) = [ 1.31 ± 0.19 ( stat ) ± 0.19 ( syst ) ] × 10 - 6 and A C P = + 0.14 ± 0.36 ( stat ) ± 0.10 ( syst ) , respectively. The signal significance, including the systematic uncertainty, is 6.4 standard deviations. Furthemore, we combine these results with Belle’s earlier measurements of B 0 → π + π - and B ± → π ± π 0 to exclude the C P -violating parameter φ 2 from the range 15.5 ° < φ 2 < 75.0 ° at 95% confidence level.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

Improved limits on Fierz interference using asymmetry measurements from the Ultracold Neutron Asymmetry (UCNA) experiment

The Ultracold Neutron Asymmetry (UCNA) experiment was designed to measure the β-decay asymmetry parameter, A 0 , for free neutron decay. In the experiment, polarized ultracold neutrons are transported into a decay trap, and their β-decay electrons are detected with ≈4π acceptance into two detector packages which provide position and energy reconstruction. The experiment also has sensitivity to b n , the Fierz interference term in the neutron β-decay rate. In this work, we determine bn from the energy dependence of A 0 using the data taken during the UCNA 2011–2013 run. In addition, we present the same type of analysis using the earlier 2010 A dataset. Furthermore, motivated by improved statistics and comparable systematic errors compared to the 2010 data-taking run, we present a new b n measurement using the weighted average of our asymmetry dataset fits, to obtain b n = 0.066 ± 0.041 stat ± 0.024 syst which corresponds to a limit of -0.012 < b n < 0.144 at the 90% confidence level.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2018

Measurement of the beam asymmetry Σ and the target asymmetry T in the photoproduction of ω mesons off the proton using CLAS at Jefferson Laboratory

Here, the photoproduction of $\omega$ mesons off the proton has been studied in the reaction $\gamma p\to p\,\omega$ using the CEBAF Large Acceptance Spectrometer (CLAS) and the frozen-spin target (FROST) in Hall B at the Thomas Jefferson National Accelerator Facility. For the first time, the target asymmetry, $T$, has been measured in photoproduction from the decay $\omega\to\pi^+\pi^-\pi^0$, using a transversely-polarized target with energies ranging from just above the reaction threshold up to 2.8 GeV. Significant non-zero values are observed for these asymmetries, reaching about 30-40% in the third-resonance region. New measurements for the photon-beam asymmetry, $\Sigma$, are also presented, which agree well with previous CLAS results and extend the world database up to 2.1 GeV. These data and additional $\omega$-photoproduction observables from CLAS were included in a partial-wave analysis within the Bonn-Gatchina framework. Significant contributions from $s$-channel resonance production were found in addition to $t$-channel exchange processes.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Dependence of nuclear quadrupole resonance transitions on the electric field gradient asymmetry parameter for nuclides with half-integer spins

Allowed transition energies and eigenstate expansions have been calculated and tabulated in numerical form as functions of the electric field gradient asymmetry parameter for the zero field Hamiltonian of quadrupolar nuclides with I=3/2,5/2,7/2, and 9/2. These results are essential to interpret nuclear quadrupole resonance (NQR) spectra and extract accurate values of the electric field gradient tensors. Applications of NQR methods to studies of electronic structure in heavy element systems are proposed.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2017

Target and double spin asymmetries of deeply virtual π 0 production with a longitudinally polarized proton target and CLAS

The target and double spin asymmetries of the exclusive pseudoscalar channel e→p→→epπ0 were measured for the first time in the deep-inelastic regime using a longitudinally polarized 5.9 GeV electron beam and a longitudinally polarized proton target at Jefferson Lab with the CEBAF Large Acceptance Spectrometer (CLAS). The data were collected over a large kinematic phase space and divided into 110 four-dimensional bins of Q2, xB, -t and Φ. Large values of asymmetry moments clearly indicate a substantial contribution to the polarized structure functions from transverse virtual photon amplitudes. The interpretation of experimental data in terms of generalized parton distributions (GPDs) provides the first insight on the chiral-odd GPDs H˜T and ET, and complement previous measurements of unpolarized structure functions sensitive to the GPDs HT and E¯T. These data provide a crucial input for parametrizations of essentially unknown chiral-odd GPDs and will strongly influence existing theoretical calculations based on the handbag formalism.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Measurement of branching fractions, C P asymmetry, and isospin asymmetry for B → ρ γ decays using Belle and Belle II data

We present measurements of B + → ρ + γ and B 0 → ρ 0 γ decays using a combined data sample of 772 × 10 6 B B ¯ pairs collected by the Belle experiment and 387 × 10 6 B B ¯ pairs collected by the Belle II experiment in e + e − collisions at the ϒ ( 4 S ) resonance. After an optimized selection, a simultaneous fit to the Belle and Belle II datasets yields 114 ± 12 B + → ρ + γ and 99 ± 12 B 0 → ρ 0 γ decays. The measured branching fractions are ( 13.1 − 1.9 − 1.2 + 2.0 + 1.3 ) × 10 − 7 and ( 7.6 ± 1.3 − 0.8 + 1.0 ) × 10 − 7 for B + → ρ + γ and B 0 → ρ 0 γ decays, respectively, where the first uncertainty is statistical and the second is systematic. We also measure the isospin asymmetry A I ( B → ρ γ ) = ( 10.9 − 11.7 − 7.3 + 11.2 + 7.8 ) % and the direct C P asymmetry A C P ( B + → ρ + γ ) = ( − 8.2 ± 15.2 − 1.3 + 2.0 ) % . Published by the American Physical Society 2025

Adachi, I. (ORCID:0000000322870173)↗
DOE OSTI2016

Measurements of the charge asymmetry in top-quark pair production in the dilepton final state at s = 8 TeV with the ATLAS detector

We presented measurements of the top-antitop quark pair production charge asymmetry in the dilepton channel, characterized by two high- pT leptons (electrons or muons), using data corresponding to an integrated luminosity of 20.3 fb $-$1 from pp collisions at a center-of-mass energy $\sqrt{s}$ = 8 TeV collected with the ATLAS detector at the Large Hadron Collider at CERN. Inclusive and differential measurements as a function of the invariant mass, transverse momentum, and longitudinal boost of the $t\bar{t}$ system are performed both in the full phase space and in a fiducial phase space closely matching the detector acceptance. Two observables are studied: A $ℓℓ\atop{C}$ based on the selected leptons and A$t\bar{t}\atop{C}$ based on the reconstructed $t\bar{t}$ final state. The inclusive asymmetries are measured in the full phase space to be A $ℓℓ\atop{C}$ = 0.008 ± 0.006 and A$t\bar{t}\atop{C}$= 0.021 ± 0.016 , which are in agreement with the Standard Model predictions of A $ℓℓ\atop{C}$ = 0.0064 ± 0.0003 and A$t\bar{t}\atop{C}$ = 0.0111 ± 0.0004 .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗