Shape Of Angular Distribution Research Articles

Symmetry breaking due to multi-angle matter-neutrino resonance in neutron star merger remnants

Neutron star merger remnants are unique sites for exploring neutrino flavor conversion in dense media. Because of the natural excess of ν̅e over νe , the neutrino-neutrino potential can cancel the matter potential, giving rise to matter-neutrino resonant flavor conversion. Under the assumption of two (anti)neutrino flavors and spatial homogeneity, we solve the neutrino quantum kinetic equations to investigate the occurrence of the matter-neutrino resonance within a multi-angle framework. We find that isotropy is broken spontaneously, regardless of the mass ordering. Relying on a hydrodynamical simulation of a binary neutron star merger remnant with a black hole of 3 M ⊙ and an accretion torus of 0.3 M ⊙, we find that complete flavor conversion caused by the matter-neutrino resonance is unlikely, although the matter and neutrino potentials cancel at various locations above the disk. Importantly, the matter-neutrino resonant flavor conversion crucially depends on the shape of the neutrino angular distributions. Our findings suggest that an accurate modeling of the neutrino angular distributions is necessary to understand flavor conversion physics in merger remnants, its implications on the disk physics and synthesis of the elements heavier than iron.

A Novel Way of Optimizing Headlight Distributions Based on Real-Life Traffic and Eye Tracking Data Part 3: Driver Gaze Behaviour on Real Roads and Optimized Light Distribution

In order to find optimized headlight distributions based on real traffic data, a three-step approach has been chosen. The complete investigations are too extensive to fit into a single paper; this paper is the last of a three part series. Over the three papers, a novel way to optimize automotive headlight distributions based on real-life traffic and eye tracking data is presented. Across all three papers, a total of 119 test subjects participated in the studies with over 15,000 km of driving, including recordings of gaze behaviour, light data, detection distances, and other objects in traffic. In this third paper, driver gaze behaviour is recorded while driving a 128 km round course, covering urban roads, country roads, and motorways. This gaze behaviour is then analysed and compared to prior work covering driver gaze behaviour. Comparing the gaze distributions with roadway object distributions from part two of this series, Analysis of Real-World Traffic Data in Germany and combining them with the idealized baseline headlight distribution from part one, different optimized headlight distributions can be generated. These headlight distributions can be optimized for different driving requirements based on the data that is used and weighting the different road types differently. The resulting headlight distribution is then compared to a standard light distribution in terms of the required luminous flux, angular distribution, and overall shape. Nonetheless, it is the overall approach that has been taken that we see as the primary novel outcome of this investigation, even more than the actual distribution resulting from this effort.

Neutron elastic and inelastic scattering differential cross sections on carbon

Elastic and inelastic neutron scattering angular distributions were measured on natural carbon samples to confirm existing experimental data and evaluations in the fast neutron region and to guide improvements in resonance parameters, where needed. Sixty-four (n,n′) differential cross section measurements were performed at 45 incident neutron energies between 0.5 and 8.0 MeV.Experimental angle-integrated elastic scattering cross sections are consistent with ENDF/B-VIII.0 values with the exception of the region from 3.2 to 4.0 MeV where our results are ∼3% higher. In the 3.4 to 3.6 MeV region our differential cross sections are slightly lower at forward angles and somewhat higher at backward angles than the ENDF/B-VIII.0 calculations; however, our results are consistent with measured data from other research groups. The first- through fourth-order elastic scattering Legendre coefficients from fits to these experimental data are consistent with ENDF/B-VIII.0 values across this range of incident neutron energies.Inelastic scattering cross sections were measured at 12 incident neutron energies between 5.6 and 7.8 MeV. Angle-integrated cross sections agree well with the 1978 Perey and ENDF/B-VIII.0 values; however, the angular-distribution shapes deviate somewhat from the ENDF/B-VIII.0 calculations. These data will allow refinement of the resonance parameter description in this difficult energy region.

Noncircularity-based generalized shift invariance for estimation of angular parameters of incoherently distributed sources

In this paper, a reduced-rank angular parameters estimation algorithm is proposed for incoherently distributed (ID) noncircular sources based on a uniform linear array (ULA), which addresses the problems of central direction-of-arrival (DOA) estimation and angular spread estimation. Firstly, the noncircularity property of the signals is utilized to establish an extended generalized array manifold (GAM) model based on the first-order Taylor series approximation. Then, the central DOAs of source signals are obtained based on the generalized shift invariance property of the array manifold and the reduced-rank principle. Next, the angular spreads are estimated from the central moments of the angular distribution. Compared with the existing algorithm without exploiting the noncircularity information, the proposed one can achieve a higher accuracy and handle more sources. In addition, it can deal with a general scenario where different sources have different angular distribution shapes. Furthermore, the approximate stochastic Cramer-Rao bound (CRB) of the concerned problem is derived. Simulation results are provided to demonstrate the performance of the proposed algorithm.

Study of the Mechanism of the 27Al(α, p)30Si Reaction at Eα = 30.3 MeV

The results from measuring the angular dependence of the 27Al(α, p)30Si reaction differential cross sections at 30.3 MeV α-particle energy with the formation of the final nucleus in the ground (0+) and first excited (2+; 2.235 MeV) states are presented. The experimental results are compared to calculated ones obtained by assuming there is both a mechanism of triton cluster stripping in a collective model and one of compound nucleus formation. The amplitudes of spectroscopic factors for the virtual decay of 30Si → 27Al + t are obtained using a shell model with wave functions of the 1d–2s shell nuclei in the Nilsson model, allowing for nuclear deformation and the spin–orbit interaction of nucleons. Comparison of the results from calculations and experiments shows that mechanism of triton stripping used in the FRESCO code with the obtained spectroscopic amplitudes mainly describes both the shape of angular distributions and the absolute values of the differential cross sections. The contribution from the mechanism of compound nucleus formation is notable only at large angles of proton emission.

Elastic and inelastic scattering of O16 on Al27 and Si28 at 240 MeV

The nuclear scattering at energies well above the Coulomb barrier allows for a fairly sensitive examination of the parameters of the optical potential when the relevant couplings are included into the calculations. In this work we present experimental angular distribution data for the elastic and inelastic scatterings of $^{16}\mathrm{O}$ impinging on $^{27}\mathrm{Al}$ and $^{28}\mathrm{Si}$ target nuclei at ${E}_{\mathrm{lab}}=240\phantom{\rule{0.28em}{0ex}}\mathrm{MeV}$. The experimental data were measured at ${7}^{\ifmmode^\circ\else\textdegree\fi{}}<{\ensuremath{\theta}}_{\text{c.m.}}<{16}^{\ifmmode^\circ\else\textdegree\fi{}}$ with good angular resolution. Experimental data are compared with coupled channel calculations with the inclusion of couplings to excited states in the target and projectile. We show that the shape of angular distributions are sensitive to the mass diffuseness parameter and the best agreement is achieved for $a=0.62\phantom{\rule{0.28em}{0ex}}\mathrm{fm}$.

Fast parallel factor decomposition technique for coherently distributed source localization

This paper links parallel factor (PARAFAC) analysis to the problem of nominal direction-of-arrival (DOA) estimation for coherently distributed (CD) sources and proposes a fast PARAFACbased algorithm by establishing the trilinear PARAFAC model. Relying on the uniqueness of the low-rank three-way array decomposition and the trilinear alternating least squares regression, the proposed algorithm achieves nominal DOA estimation and outperforms the conventional estimation of signal parameter via rotational technique CD (ESPRIT-CD) and propagator method CD (PM-CD) methods in terms of estimation accuracy. Furthermore, by means of the initialization via the propagator method, this paper accelerates the convergence procedure of the proposed algorithm with no estimation performance degradation. In addition, the proposed algorithm can be directly applied to the multiple-source scenario, where sources have different angular distribution shapes. Numerical simulation results corroborate the effectiveness and superiority of the proposed fast PARAFAC-based algorithm.

Performance analysis of distributed source parameter estimator (DSPE) in the presence of modeling errors due to the spatial distributions of sources

In this paper, the direction of arrival (DOA) localization of spatially distributed sources impinging on a sensor array is considered. The performance of the Distributed Source Parameter Estimator (DSPE) is studied in the presence of model errors due to the angular distribution shapes of the sources. Taking into account the coherently distributed source model proposed in Valaee et al.[1], we propose a definition of angular dispersion which makes DSPE robust to the angular distribution shapes of sources, and establish closed-form expressions of the DOA estimation bias and mean square error (MSE) due to both the model errors and the effects of a finite number of snapshots. The analytical results are validated by numerical simulations and allow to analyze the performance of DSPE for coherently distributed sources. The results also show the advantage of DSPE for the localization of spatially distributed sources even if the source angular distribution shape is not exactly known.

Stretched configuration of states as inferred from $ \gamma$ γ -ray angular distributions in 40Ar + 208Pb neutron transfer reactions

Angular distributions of $ \gamma$ -rays for selected transitions in 40, 41, 42Ar isotopes have been studied with the PRISMA magnetic spectrometer coupled to the CLARA $ \gamma$ array. These transitions were populated in Ar isotopes reached via neutron transfer in the 40Ar + 208Pb reaction. By comparison with the shape of the experimental angular distribution of the known E2 transitions we established more firmly the spin and parity of excited states. In particular, in 41Ar for the $ (11/2^-)$ state through the $ (11/2^-) \rightarrow 7/2^-$ transition whose structure was discussed in terms of a phonon-fermion coupled state. The comparison with the expected fully aligned spin indicated that a high level of spin alignment has been reached.

Computational Efficient Two-Dimension DOA Estimation for Incoherently Distributed Noncircular Sources With Automatic Pairing

In this paper, the problem of two-dimensional (2-D) direction-of-arrival (DOA) estimation for incoherently distributed (ID) noncircular sources is addressed. A low-complexity estimator with automatic pairing in the three-parallel uniform linear arrays (ULAs) is proposed. First, the signal non-circularity is applied to establish an extended generalized array manifold (GAM) model based on one-order Taylor series approximation. Resorting to such model, the generalized rotational invariance relationships are identified among the extended GAM matrices of the three ULAs. Thereafter, a modified propagator method is utilized to estimate the central elevation and azimuth DOAs. Without any spectrum searching, estimation or eigenvalue decomposition of the sample covariance matrix, the proposed approach is capable of considerably reducing the calculation cost in comparison with the existing methods. In addition, it can automatically pair the estimated central azimuth and central elevation DOAs. We also derive the Cramer-Rao lower bound regarding the 2-D DOA estimation of the ID noncircular source and conduct the computational complexity analysis. Numerical results demonstrate that the proposed method achieves better estimation performance than the existing methods. Furthermore, it can be applied in the multi-source scenario where different sources may have different angular distribution shapes.

The influence of a diverging conical end on the beam's angular distribution at the outlet of the capillary

A cylindrical capillary with a diverging conical end was proposed to decrease the divergence of the beam at the capillary outlet in the free molecular regime. To evaluate the effect of the conical end on the angular distribution, test particle Monte Carlo simulations based on Cercignani-Lampis (CL) reflection were conducted. Firstly, the influence of the capillary's structural parameters on the azimuth integrated flux intensity was evaluated. The peak point of the azimuth integrated flux intensity shifted to small polar angle when decreasing the half angle of the conical end, and the magnitude of the peak decreased with the half angle when it was less than 20°, but the magnitude was still larger than that of cylindrical capillary. Meanwhile, the influence range of the conical end on the distribution increased with its height, and the structural parameters of the cylindrical part had little effect on the shape of angular distribution. Then, the effect of the conical end was studied with different CL accommodation coefficients, and the results showed that the shape of the distribution barely changed except for the transmission probability. Finally, capillary with two conical structures and the effect of conical end on an atomic hydrogen beam were discussed.

Closed-form expression for the Goos-Hänchen lateral displacement

The Artmann formula provides an accurate determination of the Goos-Haenchen lateral displacement in terms of the light wavelength, refractive index and incidence angle. In the total reflection region, this formula is widely used in the literature and confirmed by experiments. Nevertheless, for incidence at critical angle, it tends to infinity and numerical calculations are needed to reproduce the experimental data. In this paper, we overcome the divergence problem at critical angle and find, for Gaussian beams, a closed formula in terms of modified Bessel functions of the first kind. The formula is in excellent agreement with numerical calculations and reproduces, for incidence angles greater than critical ones, the Artmann formula. The closed form also allows one to understand how the breaking of symmetry in the angular distribution is responsible for the difference between measurements done by considering the maximum and the mean value of the beam intensity. The results obtained in this study clearly show the Goos-Haenchen lateral displacement dependence on the angular distribution shape of the incoming beam. Finally, we also present a brief comparison with experimental data and other analytical formulas found in the literature.

Rainbow channeling of protons in very short carbon nanotubes with aligned Stone–Wales defects

In this paper proton channeling through armchair single-walled-carbon-nanotubes (SWCNTs) with aligned Stone–Wales defects has been investigated. The energy of the proton beam was 1GeV, while the lengths of the SWCNTs have been varied from 200nm up to 1000nm. The linear density of aligned defects has been varied in the whole range, from minimally up to maximally possible values. Here are presented results of a detailed morphological analysis concerning: the formation, evolution and interaction of the nanotube rainbows.The potential of the SWCNT has been constructed from Molère’s expression of the Thomas–Fermi’s proton–carbon interaction-energy, using the approximation of the continuous atomic string. Trajectories of the channeled protons were obtained by solving the corresponding classical equations of motions. Distributions of the transmitted protons were obtained by the Monte-Carlo simulation. The shape of angular distributions has been explained in the framework of the theory of nanotube rainbows. The aim of this study is also to investigate the applicability of the proton rainbow channeling for the characterization of nanotubes with aligned Stone–Wales defects.

Differential Cross Sections and Product Rovibrational Distributions for (16)O + (32)O2 and (18)O + (36)O2 Collisions.

We report rotationally resolved opacity functions, product rotational distributions, and differential cross sections for the (16)O + (16)O(16)O (v = 0,j = 1) → (16)O(16)O (v' = 0,j') + (16)O and (18)O + (18)O(18)O (v = 0,j = 1) → (18)O(18)O (v' = 0,j') + (18)O collisions calculated by a time-independent quantum mechanical method employing one of the latest potential energy surface of ozone [ Dawes ; et al. J. Chem. Phys. 2013 , 139 , 201103 ]. The results obtained for both collisional systems in the energy range 0.001-0.2 eV are examined, and interesting mass scaling effects have been discovered. The shapes of product angular distributions suggest a transition from an indirect to a direct scattering, via an osculating intermediate complex.

Angular asymmetries as a probe for anomalous contributions toHZZvertex at the LHC

In this article, the prospects for studying the tensor structure of the HZZ vertex with the LHC experiments are presented. The structure of tensor couplings in Higgs di-boson decays is investigated by measuring the asymmetries and by studing the shapes of the final state angular distributions. The expected background contributions, detector resolution, and trigger and selection efficiencies are taken into account. The potential of the LHC experiments to discover sizeable non-Standard Model contributions to the HZZ vertex with $300\;{\rm fb}^{-1}$ and $3000\;{\rm fb}^{-1}$ is demonstrated.

Jπof6He(5.3 MeV)

Consideration of its energy, angular-distribution shape, and magnitude of a cross section in the reaction He(p,t) leads me to conclude that the 5.3-MeV state is likely 0+.Received 25 November 2013DOI:https://doi.org/10.1103/PhysRevC.89.014326©2014 American Physical Society

An apparatus to study the energy and angular distributions of electron-bremsstrahlung photons from gaseous targets

An apparatus is developed to measure the energy- and angular distributions of bremsstrahlung generated from collisions of energetic electrons with isolated atoms and molecules. A considerable reduction of thick target bremsstrahlung (TTB) background produced by scattered electrons from the chamber wall is achieved. Details of the experimental setup with regard to design of its components, experimental technique, data acquisition and analysis etc. are given and discussed. The reliability and performance of the setup are demonstrated by obtaining some test results on angular- and energy distributions of bremsstrahlung produced in collisions of 4.0keV electrons with free argon atoms. These results are compared with the theoretical predictions of the ordinary- and the polarization bremsstrahlung emissions. In this comparison, the experimental data for energy distributions of BS photons are found to be in reasonable agreement while they are found to have noticeable differences in shape of angular distributions.

Experimental observations ofs−pcoupling in copper dimer anions

The photoelectron velocity-map image technique was employed to examine the one-photon detachment of Cu monomer and dimer anions using a linearly polarized infrared femtosecond laser. While the photoelectron angular distribution (PAD) in a single-photon detachment experiment of Cu${}^{\ensuremath{-}}$ shows no dependence on photon energy, the dimer anion PAD does show a strong dependence on photon energy. As the laser wavelength increases from 532 to 817 nm, the photoelectron angular distributions of the main one-photon detachment channel of the prominent detachment channel of Cu${}_{2}$${}^{\ensuremath{-}}$ changes its direction from parallel to the direction of polarization for the 532-nm laser to perpendicular to the direction of polarization for the 817-nm laser. Based upon a numerical analysis of the anisotropy parameters, the relative contributions of the $s$, $p$, and $d$ orbitals are obtained. The fully occupied $d$ orbitals contribute less to the detachment amplitude. The contribution of the $p$ waves to the detachment amplitude increases with the photon energy, while that of $s$ waves decreases, which is in agreement with the prediction of the Wigner threshold law. The relative contributions of the different partial waves, $s$ and $p$, to the detachment amplitude are altered by the excess energy of the detached electron, resulting in the determined shape of the photoelectron angular distributions. Our one-photon photodetachment experiments on the energy-dependent angular distributions of the copper anionic dimers indicate that $s$-$p$ coupling is important to the photodetachment of copper dimer anions, especially at increased photon energies.

Low-Complexity Estimation of the Nominal Azimuth and Elevation for Incoherently Distributed Sources

This paper develops a new technique for estimating the two-dimensional direction-of-arrivals (DOAs) of incoherently distributed (ID) sources, which can estimate effectively the nominal azimuth and nominal elevation of multiple ID sources at the cost of less computational complexity. Using a pair of parallel uniform linear arrays (ULAs), a new approach for 2D DOA estimation of multiple ID sources is proposed. The proposed method firstly estimates the nominal elevation by the modified TLS-ESPRIT method, which is based on the approximate rotational invariance property with respect to the nominal elevation between two closely parallel ULAs. And then with the help of the nominal elevation estimates, the nominal azimuth is estimated by one-dimensional searching. Without multi-dimensional searching, the proposed method has significantly reduced the computational cost compared with the existing methods. Simulation results indicate that the proposed method can exhibit a good performance and be applied to the multisource scenario where different sources may have different angular distribution shapes.

Electron impact excitation of the ã 3B1u electronic state in C2H4: An experimentally benchmarked system?

We report on differential and integral cross section measurements for the electron impact excitation of the lowest-lying triplet electronic state (ã (3)B(1u)) in ethylene (C(2)H(4)). The energy range of the present experiments was 9 eV-50 eV, with the angular range of the differential cross section measurements being 15°-90°. As the ground electronic state of C(2)H(4) is a (1)A(g) state, this singlet → triplet excitation process is expected to be dominated by exchange scattering. The present angular distributions are found to support that assertion. Comparison, where possible, with previous experimental results from the University of Fribourg group shows very good agreement, to within the uncertainties on the measured cross sections. Agreement with the available theories, however, is generally marginal with the theories typically overestimating the magnitude of the differential cross sections. Notwithstanding that, the shapes of the theoretical angular distributions were in fact found to be in good accord with the corresponding experimental results.