Scattering Cross Section Research Articles

Bayesian inference of in-medium baryon-baryon scattering cross sections from HADES proton flow data

Within a Bayesian statistical framework using a Gaussian Process emulator for an isospin-dependent Boltzmann-Uehling-Uhlenbeck (IBUU) transport model simulator of heavy-ion reactions at intermediate energies, we infer from the HADES proton flow data the posterior probability distribution functions of in-medium baryon-baryon scattering cross section modification factor X with respect to free-space and the corresponding incompressibility K of nuclear matter as well as their correlation function. The mean value of X is found to be X=1.32−0.40+0.28 at 68% confidence level assuming the nuclear incompressibility K will not exceed 400 MeV, providing circumstantial evidence for enhanced baryon-braryon scattering cross sections in hot and dense nuclear matter.

Multipole expansion for the electron-nucleus scattering at high energies in the unified electroweak theory

The paper presents the multipole expansion for the electron-nucleus scattering cross section at high energies within the framework of the unified electroweak theory. The electroweak currents of the nucleus are expanded into the simple components with definite angular momenta, called the multipole form factors. The multipole expansion of the cross section is a consequence of the above expansion. Besides the familiar electromagnetic form factors, there are also the vector and axial form factors, respectively, related to weak interactions. To determine multipole form factors, general formulas for the calculation of reduced matrix elements are established using the fractional parentage coefficient method and the multiparticle shell model. Calculation of them enables us to obtain more detailed information about the nuclear structure and elucidate the role played by the weak interaction in the high-energy reaction mechanisms.

Investigation of light dark matter with 2beta decay experiments

Nuclei that are unstable with respect to double beta decay are investigated in this work for a novel dark matter (DM) direct detection approach. In particular, the diagram responsible for the neutrinoless double beta decay can be considered for the possible detection technique of a Majorana DM fermion inelastically scattering on a double beta unstable nucleus, stimulating its decay. The exothermic nature of the stimulated double beta decay would allow the direct detection also of a light DM fermion, a class of DM candidates that are difficult or impossible to investigate with the traditional elastic scattering techniques. The expected signal distribution for different DM masses and the upper limits on the nucleus scattering cross sections, are shown and compared with the existing data for the case of ^{136}Xe nucleus.

Quantitative studies on the microstructure of ternary CaO–Al2O3–SiO2 glasses by Raman spectroscopy, 27Al MAS NMR and quantum chemistry ab initio calculation

To investigate the structural behaviors of Al3+ in aluminosilicate systems, the microstructural characteristics of CaO–SiO2-based glassy samples with various Al2O3 contents were examined quantitatively by Raman spectroscopy and 27Al MAS NMR. A sequence of multiple model clusters of aluminosilicate systems modified with Ca2+ and Na ​+ ​cations was designed. Then quantum chemistry (QC) ab initio calculations were performed for geometric optimization, and Raman spectral simulations were carried out. The functional relationship between the Raman scattering cross section (RSCS) and stress index of silicon-oxygen tetrahedron (SIT) for aluminosilicates was established, which was successfully applied to calibrate experimental Raman spectra. Some fivefold coordinated aluminum (AlⅤ, approximately 5%) and less than 2% sixfold coordinated aluminum (AlⅥ) were detected by 27Al MAS NMR, while most aluminum remained in tetrahedral sites (AlⅣ). The ever-finer quantitative results of Raman spectroscopy and NMR showed a gradual production of AlⅣ with the addition of Al2O3, along with a significant adjustment in Qi species distribution. Specifically, Q1, Q2 decreased, fully polymerized Q4 increased and Q3 showed a nonmonotonic variation and obtained the maximum at Al2O3 ​= ​12 ​mol%. Furthermore, the effects of aluminum on bridging oxygen bond types (T-Ob, T ​= ​Si, Al) and the degree of polymerization were discussed in detail. These structural features related to composition are essential theoretic foundations for understanding the properties of these systems.

Scattering Properties of Non-Gaussian Ocean Surface with the SSA Model Applied to GNSS-R

Global Navigation Satellite System Reflectometry (GNSS-R) is an emerging earth observation method for remote sensing of feature parameters using reflected signals from navigation satellites, and is a purely specular bistatic forward scattering observation means with special right-handed circular polarization incident wave. In this paper, the small-slope approximation model of non-Gaussian sea surface is used as the basis to construct the scattering model for the observation geometry of GNSS-R as well as the L-band characteristics, and the fully-polarization normalized bistatic radar scattering cross section (NBRCS) are simulated by the method of polarization synthesis to analyze the scattering characteristics under different wind speeds and directions on the ocean surface, which highlights the variation of NBRCS with wind direction, and the scattering modeling accuracy is improved by comparing with the data of CYGNSS. In addition, we adopt the observation geometry deviating from purely specular geometry, discuss the scattering azimuth angle, scattering influence, and the relative relationship between different polarizations of the scattering angle under the non-specular geometry.

Improved treatment of dark matter capture in compact stars

Compact stellar objects are promising cosmic laboratories to test the nature of dark matter (DM). DM captured by the strong gravitational field of these stellar remnants transfers kinetic energy to the star during the collision. This can have various effects such as anomalous heating of old compact stars. The proper calculation of the DM capture rate is key to derive bounds on DM interactions in any scenario involving DM accretion in a star. We improve former calculations, which rely on approximations, for both white dwarfs (WDs) and neutron stars (NSs). We account for the stellar structure, gravitational focusing, relativistic kinematics, Pauli blocking, realistic form factors, and strong interactions (NSs). Considering DM capture by scattering off either ions or degenerate electrons in WDs, we show that old WDs in DM-rich environments could probe the elusive sub-GeV mass regime for both DM-nucleon and DM-electron scattering. In NSs, DM can be captured via collisions with strongly interacting baryons or relativistic leptons. We project the NS sensitivity to DM-nucleon and DM-lepton scattering cross sections which greatly exceeds that of direct detection experiments, especially for low mass DM.

Scattering of Positive Muons by Atoms of Inert Gases

In the present work, the cross sections of elastic and inelastic scattering of positive muons by He and Ar atoms at low and medium kinetic energies are calculated by the methods of many-body theory with the use of the ATOM-M software package. For comparison, the results of elastic and inelastic positron scattering at the same energies are also given. The dependence of the phases and scattering cross sections on the charge of the particle and its mass, as well as on the charge of the nucleus of the scattering atom, is discussed.

Erratum to: Approximation of Differential Cross Sections for Elastic Proton-Nucleus Scattering

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Cored dark matter halos in the cosmic neutrino background

We study the impact of the interaction between DM and the cosmic neutrino background on the evolution of galactic dark matter halos. The energy transfer from the cosmic background neutrinos to galactic dark matter can heat the center of the galaxy and make it cored. The core formation is efficient for the small galaxies such as the satellite galaxies of the Milky Way and we can put a conservative constraint on the non-relativistic elastic scattering cross section as σχν ≲ 10-31 cm2 for 0.1 keV dark matter.

Blazar boosted dark matter — direct detection constraints on σeχ : role of energy dependent cross sections

Elastic collisions with relativistic electrons from the blazar's jet can accelerate dark matter (DM) particles in the DM spike surrounding the supermassive black hole at its center. This can allow one to set stringent limits on the DM-electron scattering cross section (σ̅eχ ) for DM masses less than 100 MeV. We consider DM particles boosted by energetic electrons in the jets of the blazars TXS 0506+056 and BL Lacertae. Both vector and scalar mediators for the scattering of electron and electrophilic fermionic DM are studied. We highlight that the ensuing energy dependence of the S-matrix for the corresponding Lorentz structure of the vertex significantly modifies the constraints. We find that the revised exclusion limits are orders of magnitude stronger than the equivalent results for the simple constant cross section assumption. Our limits are also assessed for the less cuspy spike.

Estimation of the proportions of aluminum-fluorine species in NaF-AlF3 mixtures by in situ Raman spectroscopy and theoretical simulations

The quantitative distribution of different types of clusters in a binary NaF-AlF3 molten salt system with a series of cryolite ratios (CR, NaF/AlF3 molar ratio) was explored by in situ high-temperature Raman spectroscopy in conjunction with quantum chemistry (QC) ab initio calculations. Density functional theory (DFT) was used to simulate the Raman spectra of solid crystalline Na5Al3F14 (CR = 1.67) and Na3AlF6 (CR = 3.00). Aluminum-fluorine molecular model clusters containing species with typical characteristic microstructures were built in a molten NaF-AlF3 system. Deconvolution of the major stretching vibrational bands of Al-F-Al and Al-F bonds was carried out by using the Voigt function. The anionic fractions of different species present in the molten NaF-AlF3 system were quantitatively analyzed by a function of the microstructure dependent on Raman scattering cross sections (RSCS). AlF63-, AlF52-, and AlF4- were the dominant species in the aluminum-fluorine molten salt system. As the NaF in the melt increased, the content of AlF52- reached the maximum concentration when CR = 2.00. Apart from the recognized existence of both AlF4- and AlF63-, the aluminum bridging fluorine species of Al2F7- has been proven to exist in molten systems when CR ≤ 1.00. The relationship between the viscosity and various (n-3)Na+·AlFn(n-3)- species distributions has been investigated. The results showed that the contribution of different (n-3)Na+·AlFn(n-3)- to viscosity was essentially the same, and simply depended on the number of different species.

а- бөлшектердің 9Be ядросымен соқтығысу кезіндегі серпімді шашырауының жаһандық заңдылықтары

The article investigates the characteristics of the experimental data of the elastic scattering cross section in the low-energy range of the a+9Be nuclear system. General regularities depending on the change in the energy of accelerated ions of the parameters of the obtained cross sections are established. Based on the analysis in the framework of the optical model (OM), energy-dependent optical interaction potentials in a wide range of energies were found.The energy regularity of potentials, revealed as a result of systematic analysis, makes it possible to predict with sufficient accuracy the cross-section of processes at energies at which experimental measurements were not carried out.The potential, which is a complex function of the interaction between nuclei, is an empirical measurement that describes the interaction in the scattering process.Studies of the dependence of the potential on external factors should be carried out individually for each nuclear system. Such analyses carried out in order to improve the accuracy of phenomenological theories should be based on a large array of experimental data. To clarify the truthfulness of the results of phenomenological approaches, it would be theoretically more correct to determine the global patterns of potentials and energy dependences of the full reaction cross-section.The article defines the energy dependence of the potentials and the total cross-section of the reaction based on a systematic analysis of the experimental data set in the energy range of laboratory Elab=30 - 60 MeV for the α+9Be process.Optimal values of the cross-section parameters satisfying global laws depending on the energy of the accelerating beam are found.

Endothermic self-interacting dark matter in Milky Way-like dark matter haloes

ABSTRACT Self-interacting dark matter (SIDM) offers the potential to mitigate some of the discrepancies between simulated cold dark matter (CDM) and observed galactic properties. We introduce a physically motivated SIDM model to understand the effects of self interactions on the properties of Milky Way and dwarf galaxy sized haloes. This model consists of dark matter with a nearly degenerate excited state, which allows for both elastic and inelastic scattering. In particular, the model includes a significant probability for particles to up-scatter from the ground state to the excited state. We simulate a suite of zoom-in Milky Way-sized N-body haloes with six models with different scattering cross sections to study the effects of up-scattering in SIDM models. We find that the up-scattering reaction greatly increases the central densities of the main halo through the loss of kinetic energy. However, the physical model still results in significant coring due to the presence of elastic scattering and down-scattering. These effects are not as apparent in the subhalo population compared to the main halo, but the number of subhaloes is reduced compared to CDM.

Absolute Stimulated Raman Cross Sections of Molecules

Stimulated Raman scattering (SRS) is a fundamental optical process that was discovered more than 60 years ago. While the early SRS spectroscopy studies have provided valuable insights into materials systems, the advent of SRS microscopy has launched a rapidly growing field in biological imaging. However, a fundamental understanding of the molecular response under SRS is still lacking. Herein we present a new framework to introduce molecule-intrinsic stimulated Raman scattering cross sections, σSRS, in the unit of Göppert-Mayer (GM). The absolute SRS cross sections determined for real molecular systems challenge the conventional wisdom that Raman spectroscopy is always a weak process. The enormous rate acceleration of SRS, captured by an apparent SRS cross section, stems from a synergistic effect between the field and the molecule. Our new framework goes beyond the conventional optics-centric view and presents a molecule-inclusive perspective, thus offering a comprehensive foundation for the future growth of SRS spectroscopy and microscopy.

Lensfree Air-Quality Monitoring of Fine and Ultrafine Particulate Matter Using Vapor-Condensed Nanolenses.

Current commercial air-quality monitoring devices lack a large dynamic range, especially at the small, ultrafine size scale. Furthermore, there is a low density of air-quality monitoring stations, reducing the precision with which local particulate matter hazards can be tracked. Here, we show a low-cost, lensfree, and portable air-quality monitoring device (LPAQD) that can detect and measure micron-sized particles down to 100 nm-sized particles, with the capability to track and measure particles in real time throughout a day and the ability to accurately measure particulate matter densities as low as 3 μg m-3. A vapor-condensed film is deposited onto the coverslip used to collect particles before the LPAQD is deployed at outdoor monitoring sites. The vapor-condensed film increases the scattering cross section of particles smaller than the pixel size, enabling the sub-pixel and sub-diffraction-limit-sized particles to be detected. The high dynamic range, low cost, and portability of this device can enable citizens to monitor their own air quality to hopefully impact user decisions that reduce the risk for particulate matter-related diseases.

Intrinsic thermal conductivity of ZrC from low to ultrahigh temperatures: A critical revisit

Current phonon transport theory based on ground-state calculations has been successful in predicting thermal conductivity at room and medium temperatures but may misrepresent behavior at high temperatures. In this work, we predict the thermal conductivity ($\ensuremath{\kappa}$) of ZrC including electronic and phonon contributions from 300 to 3500 K, by including high-order phonon scattering; lattice expansion; temperature-dependent (TD) second-, third-, and fourth-order force constants (2FC, 3FC, and 4FC); and interband phonon conduction by using first principles. For the phonon transport, we find that four-phonon scattering (4ph) significantly reduces the phonon thermal conductivity (${\ensuremath{\kappa}}_{\mathrm{ph}}$), by as much as $\ensuremath{\sim}75%$ at 3500 K. After including 4ph scattering and all other factors, ${\ensuremath{\kappa}}_{\mathrm{ph}}$ shows a $\ensuremath{\sim}{T}^{\ensuremath{-}1.5}$ rather than $\ensuremath{\sim}{T}^{\ensuremath{-}1}$ dependence. TD 2FC decreases three-phonon scattering rates but increases 4ph rates by decreasing and increasing the scattering phase spaces, respectively. For 4ph phase space, the TD 2FC flattens phonon bands, and allows more redistribution-4ph processes $(1+2\ensuremath{\rightarrow}3+4)$ to happen. The combination effect of TD 2FC and TD 4FC reduces 4ph rates of acoustic modes but increases those of optical modes. The TD 3FC and 4FC decrease the phonon scattering cross section and increase the ${\ensuremath{\kappa}}_{\mathrm{ph}}$ significantly (by 52% at 3500 K). The contribution from interband (Wigner) phonon conduction is small, even at ultrahigh temperatures. For electronic thermal transport, we find that it is sensitive to and can be changed by 20% by the TD lattice constants. The Lorenz number varies from 1.6 to $3.3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}8}\phantom{\rule{0.16em}{0ex}}\mathrm{W}\phantom{\rule{0.16em}{0ex}}\mathrm{\ensuremath{\Omega}}\phantom{\rule{0.16em}{0ex}}{\mathrm{K}}^{\ensuremath{-}2}$ at different temperatures. The theoretical prediction in the literature overpredicts ${\ensuremath{\kappa}}_{\mathrm{ph}}$ (e.g., $\ensuremath{\sim}28%$) and underpredicts the ${\ensuremath{\kappa}}_{\mathrm{el}}$ (e.g., $\ensuremath{\sim}38%$), resulting in an overall underprediction of $\ensuremath{\kappa}$ ($\ensuremath{\sim}26%$ at 1500 K). The impacts of grain size and defects are found to be strong, leading to the lower observed thermal conductivity in experiments.

Study of Electron Collisions with Isoprene, 1,2-Butadiene, and Their Isomers.

Isoprene, 1,2-butadiene, and their isomers play an important role in aerosols in the atmosphere, interstellar media, and extraterrestrial life. Since electrons are everywhere, studying how electrons interact with these molecules is an important part of studying such environments. To date, however, little investigation has been conducted in this area. Bearing this in mind, we conducted a thorough investigation to report the various electron scattering cross sections of isoprene, 1,2-butadiene, and their isomers. The methods used for this purpose are reliable within the limits of adopted model potentials. The optical potential method was used to get the total elastic and inelastic cross sections, while the complex scattering potential ionization contribution method was used to get the total ionization cross section from the inelastic contribution. The results from these approximations are pretty close to the results from earlier experiments and theories. Furthermore, most of these isomers are being explored for the first time. Besides, their isomeric effect is also discussed. A correlation between the cross sections of molecules is demonstrated, which can be used to predict cross sections of those molecules where previous data are not available.

A Monte Carlo method for 3D radiative transfer equations with multifractional singular kernels

We propose in this work a Monte Carlo method for three dimensional scalar radiative transfer equations with non-integrable, space-dependent scattering kernels. Such kernels typically account for long-range statistical features, and arise for instance in the context of wave propagation in turbulent atmosphere, geophysics, and medical imaging in the peaked-forward regime. In contrast to the classical case where the scattering cross section is integrable, which results in a non-zero mean free time, the latter here vanishes. This creates numerical difficulties as standard Monte Carlo methods based on a naive regularization exhibit large jump intensities and an increased computational cost. We propose a method inspired by the finance literature based on a small jumps - large jumps decomposition, allowing us to treat the small jumps efficiently and reduce the computational burden. We demonstrate the performance of the approach with numerical simulations and provide a complete error analysis. The multifractional terminology refers to the fact that the high frequency contribution of the scattering operator is a fractional Laplace-Beltrami operator on the unit sphere with space-dependent index.

The method of fundamental solutions for electromagnetic scattering by a perfect conductor in chiral environment

The electromagnetic scattering problem for a time-harmonic plane wave by a perfectly conductive body embedded in a chiral medium is considered. Potentials in terms of the fundamental solution in dyadic form for chiral media are defined. The well-posedness of the scattering problem is studied using defined potentials in terms of the fundamental solution for chiral environment and the boundary integral operators associated with them. An extension of the method of fundamental solutions for electromagnetic scattering in chiral media is applied in order to approximate the solution. The electric scattered field is approximated by a finite linear combination of the dyadic fundamental solutions of the equation governing the problem for singularities placed on an auxiliary surface outside the domain of the problem and for unknown coefficients determined by the boundary conditions. Density properties on the surface of the scatterer are proven for a defined system of functions consisting of the tangential components of the dyadic fundamental solution. These density properties together with the well-posedness of the scattering problem are used to reduce the approximation of the solution to the approximation of the known boundary data. The linear system obtained from the boundary conditions in order to determine the appropriate unknown coefficients of the finite linear combination is presented. Using these results we approximate the far-field patterns and the scattering cross section. Numerical results for the special case of a spherical scatterer and an ellipsoidal scatterer are presented.

Implications on cosmology from Dirac neutrino magnetic moments

The mechanism for generating neutrino masses remains a puzzle in particle physics. If neutrino masses follow from a Dirac mass term, then neutrino states exist with opposite chirality compared to their weakly-interacting counterparts. These inactive states do not interact with their active counterparts at measurable scales in the standard model. However, the existence of these states can have implications for cosmology as they contribute to the radiation energy density at early times, and the matter energy density at late times. How Dirac neutrinos may populate thermal states via an anomalous magnetic moment operator is the focus of this work. A class of models where all neutrinos have a magnetic moment independent of flavor or chirality is considered. Subsequently, the cross sections for neutrinos scattering on background plasma particles are calculated so that the relic inactive neutrino energy is derived as a function of plasma temperature. To do so, one needs cross sections for scattering on all electrically charged standard-model particles. Therefore, the scattering cross section between a neutrino and $W$-boson via the magnetic moment vertex is derived. Current measurements put a constraint on the size of the neutrino magnetic moment from the cosmological parameter $N_{\rm eff}$ and light-element primordial abundances. Finally, how the extra Dirac states contribute to the matter energy density at late times is investigated by examining neutrino free-streaming.