Total Cross Section Data Research Articles

Measurement of the neutron total cross section of 9Be at the Back-n white neutron source of CSNS* *Supported by the National Key Research and Development Plan (2016YFA0401603), the National Natural Science Foundation of China (11675155, 11790321) and Foundation of President of China Academy of Engineering Physics (YZJJLX2016003)

The neutron total cross section data of 9Be are essential in the nuclear structure model research of light nuclei and nuclear power installations. The neutron total cross section of 9Be in the 0.3 eV−120 MeV energy region has been measured using time-of-flight and transmission methods with the Neutron Total Cross Sectional Spectrometer (NTOX) based on the multi-cell fast fission chamber at the China Spallation Neutron Source (CSNS)-Back-n white neutron source (Back-n). The fission count-neutron energy distributions of 235U and 238U without samples and with Be samples with three thicknesses were measured in the double-bunch operation mode for a beam power of 100 kW. The Bayesian method was used to eliminate the influence of the double-bunch problem on neutron measurement in the energy region above 10 keV. The neutron total cross section of 9Be results was consistent with ENDF/B-VIII.0 evaluation library data in the 0.3 eV−20 MeV energy region. In the energy ranges of 0.3 eV to 10 keV and 0.01 to 20 MeV, the deviations between our results and the evaluation results of ENDF/B-VIII.0 were within 2.5% and 15%, respectively. In the resonance energy region, the measured resonance energies in our experiment were 0.63, 0.82, and 2.8 MeV, respectively. The results showed that the total cross section uncertainties of three Be samples were within 2.2% in the energy region below 1 MeV. The total cross section uncertainty of 30 mm Be from 235U was the smallest and less than 5% in the energy region of 0.3 eV−120 MeV. The results of this experiment can provide technical support for further data analysis and related nuclear data evaluation.

Neutron Total Cross Sections of 232Th, 237Np, 235,238U, and 239Pu from 3 to 230 MeV

Neutron total cross-section data for 232Th, 237Np, 235,238U, and 239Pu were measured over the energy range of a few MeV up to 230 MeV at the Weapons Neutron Research Facility of the Los Alamos Neutron Science Center. The results for 235U, 237Np, and 239Pu are the first to be reported over this full energy range. Our data are compared to the ENDF/B-VIII.0 and JENDL-5 evaluations and to selected previous data sets. These results provide neutron cross sections with small statistical uncertainties and low systematic errors to improve theoretical modeling and data evaluation for these nuclei.

Integral Electron Scattering Cross Sections from N2O for Impact Energies Ranging from 1 to 1000 eV.

Accurate total cross sections (TCS), within 5%, for electron scattering by N2O molecules have been measured with a magnetically confined electron transmission apparatus for impact energies ranging from 1 to 200 eV. For higher energies, these measurements have been complemented with our independent atom-based screening corrected additivity rule, including interference (IAM-SCAR + I) method to determine a complete reference TCS data set in the energy range (1-1000 eV). After a critical discussion that includes our calculated integral elastic and ionization cross sections and the theoretical and experimental data available in the literature, a complete set of integral elastic and inelastic (rotational, vibrational, and electronic excitation, ionization and electron attachment) cross sections, consistent with the reference TCS data, have been derived. This update on the N2O collisional database may help to improve the accuracy of radiation-induced transport models.

Holographic description of elastic photon-proton and photon-photon scattering

We investigate the elastic photon-proton and photon-photon scattering in a holographic QCD model, focusing on the Regge regime. Considering contributions of the Pomeron and Reggeon exchange, the total and differential cross sections are calculated. While our model involves several parameters, by virtue of the universality of the Pomeron and Reggeon, for most of them the values determined in the preceding study on the proton-proton and proton-antiproton scattering can be employed. Once the two adjustable parameters, the Pomeron-photon and Reggeon-photon coupling constant, are determined with the experimental data of the total cross sections, predicting the both cross sections in a wide kinematic region, from the GeV to TeV scale, becomes possible. We show that the total cross section data can be well described within the model, and our predictions for the photon-proton differential cross section are consistent with the data.

Ionization of CH[formula omitted] under fast He-like Si-ion impact

We have studied the absolute double differential cross section (DDCS) of electrons ejected from the methane molecule (CH4) under the impact of highly charged fast projectile ions. The energy and angular distributions of electrons have been measured in interactions with 70 MeV Si12+ ions. These DDCS data together with the derived single differential cross sections and the total cross section (TCS) have been compared with predictions of the continuum distorted wave-eikonal initial state model using different approaches for the molecular orbitals. It has been found that the theories overestimate the measured DDCS values at low ejection energies, which may indicate shortcomings of the model in the case of strong perturbation. At the same time, applying the model to a previous measurement using fast C ions having a lower perturbation strength, excellent agreements have been obtained with the experimental data. Considering the scaling properties, the available TCS data have been plotted with a scaled parameter, namely the perturbation strength, q/v (where q= charge state, v=velocity of the projectile). The KLL Auger e-emission as well as the KLL hyper-satellite peaks are analyzed for different emission angles. The double K-vacancy production shows a considerable enhancement i.e. 37% of the single production cross section which is consistent with some of the recent experiments on K-ionization using x-ray techniques.

Elastic proton–neutron and antiproton–neutron scattering in holographic QCD

The total and differential cross sections of the elastic proton–neutron and antiproton–neutron scattering are studied in a holographic QCD model, focusing on the Regge regime. Taking into account the Pomeron and Reggeon exchange, which are described by the Reggeized spin-2 glueball and vector meson propagator respectively, those cross sections are obtained. It is presented that the currently available experimental data of the total cross sections can be well described within the model. Once a single adjustable parameter is determined with the total cross section data, the differential cross sections can be calculated without any additional parameters. Although the available differential cross section data are limited, it is found that our predictions are consistent with those.

Constraining the top-quark mass within the global MSHT PDF fit

We examine the ability of experimental measurements of top-quark pair production to constrain both the top-quark mass and the strong coupling within the global MSHT parton distribution function (PDF) fit. Specifically, we consider ATLAS and CMS measurements of differential distributions taken at a centre-of-mass energy of 8 TeV, as well as tbar{t} total cross section data taken at a variety of experiments, and compare to theoretical predictions including next-to-next-to-leading order corrections. We find that supplementing the global fit with this additional information results in relatively strong constraints on the top-quark mass, and is also able to bound the strong coupling in a limited fashion. Our final result is m_t=173.0pm 0.6~textrm{GeV} and is compatible with the world average pole mass extracted from cross section measurements of 172.5pm 0.7~textrm{GeV} by the Particle Data Group. We also study the effect of different top-quark masses on the gluon parton distribution function, finding changes at high x which nonetheless lie within the large PDF uncertainties in this region.

On sequential single-pion production in double-pionic fusion

Recently a two-step process has been proposed for the double-pionic fusion to deuterium pn(I=0)→dπ+π−. Its calculation is solely based on total cross section data for the two sequential single-pion production steps pn(I=0)→ppπ− followed by pp→dπ+. Though this sequential process was aimed to explain the dibaryon resonance d⁎(2380) peak in double-pionic fusion, we demonstrate that this is not the case. It rather fits to a possible broad bump at 2.31 GeV in the energy dependence of the pn→dπ0π0 reaction, which was recently interpreted as a consequence of dibaryonic excitations in isoscalar single-pion production.

Geant4model for neutrino nucleon/nucleus integral cross sections

The Geant4model for neutrino nucleon/nucleus integral cross sections, based on selection of the existing physical models, is discussed. The comparison of the model predictions with experimental data for quasi-elastic, inelastic and total neutrino nucleon cross sections is presented.

New determination of the production cross section for γ rays in the Galaxy

The flux of $\gamma$ rays is measured with unprecedented accuracy by the $\textit{Fermi}$ Large Area Telescope from 100 MeV to almost 1 TeV. In the future, the Cherenkov Telescope Array will have the capability to measure photons up to 100 TeV. To accurately interpret this data, precise predictions of the production processes, specifically the cross section for the production of photons from the interaction of cosmic-ray protons and helium with atoms of the ISM, are necessary. In this study, we determine new analytical functions describing the Lorentz-invariant cross section for $\gamma$-ray production in hadronic collisions. We utilize the limited total cross section data for $\pi^0$ production channels and supplement this information by drawing on our previous analyses of charged pion production to infer missing details. In this context, we highlight the need for new data on $\pi^0$ production. Our predictions include the cross sections for all production channels that contribute down to the 0.5% level of the final cross section, namely $\eta$, $K^+$, $K^-$, $K^0_S$, and $K^0_L$ mesons as well as $\Lambda$, $\Sigma$, and $\Xi$ baryons. We determine the total differential cross section $d\sigma(p+p\rightarrow \gamma+X)/dE_{\gamma}$ from 10 MeV to 100 TeV with an uncertainty of 10% below 10 GeV of $\gamma$-ray energies, increasing to 20% at the TeV energies. We provide numerical tables and a script for the community to access our energy-differential cross sections, which are provided for incident proton (nuclei) energies from 0.1 to $10^7$ GeV (GeV/n).

A new 103Rh Unresolved Resonance Region evaluation

A new evaluation in the Unresolved Resonance Region has been performed for 103Rh, an important fission product. The evaluation was done in coordination with and is consistent with a new Resolved Resonance Region evaluation. It was determined using measured total cross section data that there is significant structure in the underlying dilute-average cross section within the unresolved resonance energy range of the evaluation (8–40.146 keV). Energy-dependent strength functions are provided to more accurately represent this structure. A covariance matrix for the average parameters that represent the entire Unresolved Resonance Region is provided to comply with the current ENDF-6 format. This new evaluation more closely matches the experimental data available when compared to the current evaluations.

Performance of machine learning algorithms on neutron activations for Germanium isotopes

In the studies of nuclear physics, one of the important parameters for nuclear reactions is the reaction cross-section. It can be obtained from experimental data or by different theoretical models. In this study, we implement machine learning (ML) algorithms to the regression analysis of the nuclear cross-section of neutron-induced nuclear reactions of Germanium isotopes. The data for the training of the machine was borrowed from the TENDL-2019 library for the total cross-section data of possible nuclear reactions after the bombardment of the different target materials by neutrons. Three ML models, Artificial Neural Networks (ANN), K-Nearest Neighbors (KNN) and, Support Vector Machines (SVM), were developed to fit nuclear data from the TENDL-2019 database in order to predict neutron induce reaction cross sections. The performance of each algorithm is determined and compared by evaluating the mean square error (MSE) and the correlation coefficient (R2). According to the results obtained, we demonstrate that cross-section information can be obtained safely with ML techniques and the regression curve generated by our models is in good agreement with the evaluated nuclear data library. From our study, ANN and KNN are found to be better compared to SVM algorithm. ML models can enhance classical physics-guided models and play a role in nuclear data analyses. They can be used as an alternative to the estimation of cross-sections for neutron energies of an unknown energy value.

The calculation of light element impurity ([formula omitted], n) yield curves in a PuO[formula omitted] matrix and associated specific yield coefficients: Influence of the reaction cross sections

Most of the Pu separated from irradiated commercial nuclear fuel is stored as PuO 2. The primary quantitative nondestructive measurement technique used to verify the amount of Pu in storage containers is passive neutron correlation counting. An important physical property of the oxide material is the ratio, α, of the rate of (α, n) neutrons produced inside the item to the rate of neutrons produced by spontaneous fission. This ratio influences the precision of the correlated counting method and affects the interpretation of the data because of how it changes both the primary total neutron production rate and the rate of induced fission events taking place inside the item. In addition to the main O(α, n) contribution, additional contributions come from α-particle interactions with light element impurities that are inevitably present. In this work, we calculate specific (α, n) yield coefficients, expressed in units of neutrons per second per gram of α-emitting nuclide per part per million by mass of the specified impurity element distributed in a pure PuO 2 matrix, for some key α-emitting actinides commonly present in reprocessed Pu (238–242Pu+241Am). These coefficients are directly applicable to nuclear safeguards verification work in which the α ratio is often calculated from the Pu-isotopic composition and chemical information obtained by other means. They also provide a convenient up-to-date reference set against which values generated by other methods can be compared. Results are presented for impurities with atomic number from 3 to 17 inclusive, plus K and Fe. In most cases, these coefficients are not expected to change by more than 5%–10% at any time in the future. However, as new data become available, changes as large as 20% may be needed for some targets (e.g., F). The present yield calculations are limited by the general shortage of quality experimental total (α, n) reaction cross section data, which, together with unexplained variation between determinations, means that an objective and coherent evaluation is not possible. The situation is even less satisfactory for the partial differential cross section needed to calculate neutron spectra.

Elastic pion-proton and pion-pion scattering at high energies in holographic QCD

The total and differential cross sections of high energy pion-proton and pion-pion scattering are investigated in a holographic QCD model, focusing on the Regge regime in which the Pomeron exchange gives the dominant contribution to those cross sections. The Pomeron is described by the Reggeized spin-2 particle propagator, and the hadron-Pomeron couplings are given by gravitational form factors of the hadrons, which are obtained from the bottom-up AdS/QCD models. Since the parameters, which characterize the Pomeron trajectory, have been determined in a preceding study of the proton-proton scattering, the pion-proton cross sections can be expressed with a single adjustable parameter. Once this parameter is determined by the experimental data of the pion-proton total cross section, its differential cross section and the pion-pion cross sections can be calculated without any additional parameter. Although the currently available data are limited, it is found that our calculation is consistent with those. Our predictions are explicitly shown, and the present model can be tested at the future experimental facilities.

Photoproduction in an effective Lagrangian approach * *Partially supported by the National Natural Science Foundation of China (12175240, 11475181, 11635009), the Fundamental Research Funds for the Central Universities, the China Postdoctoral Science Foundation (2021M693141, 2021M693142), and the Key Research Program of Frontier Sciences of Chinese Academy of Sciences (Y7292610K1)

A gauge-invariant model is constructed for the reaction within a tree-level effective Lagrangian approach to understand the underlying production mechanisms and study the resonance contributions in this reaction. In addition to the t-channel K and exchanges, s-channel nucleon exchange, and interaction current, the s-channel nucleon resonance exchanges are included in constructing the reaction amplitudes to describe the data. It is found that the contributions from the s-channel exchange are required to describe the most recently measured total cross-section data for from the CLAS Collaboration. Further analysis indicates that the interaction current dominates the reaction near the threshold as a result of gauge invariance. The t-channel K exchange contributes significantly, while the contributions from the t-channel exchange and s-channel nucleon exchange are ultimately negligible. The contributions from the s-channel exchange are found to be responsible for the bump structure shown in the CLAS total cross-section data above the center-of-mass energy GeV. The predictions of the differential cross sections for are presented and discussed, which can provide theoretical guidance for future experiments.

Improvements in the particle and heavy-ion transport code system (PHITS) for simulating neutron-response functions and detection efficiencies of a liquid organic scintillator

ABSTRACT In this study, we simulated the neutron-response functions and detection efficiencies of a liquid organic scintillator using the particle and heavy-ion transport code system (PHITS). We incorporated the algorithm and database of the neutron-response simulation code SCINFUL–QMD into PHITS. Then, we updated the total, elastic, and inelastic cross-section data of the hydrogen and carbon nuclei for neutrons and developed a new scorer to analyze the light outputs from a scintillator. The calculation results of the neutron-response functions and the detection efficiencies were compared with results of SCINFUL–QMD, the previous PHITS with the new scorer, and the reported measurements. It was found that the improved PHITS successfully reproduced the results calculated by SCINFUL–QMD, except for around 150 MeV where a discontinuity in the detection-efficiency curve was observed in the SCINFUL–QMD values. Our results showed better agreement with the measured data than the results of the previous PHITS. The uncertainties of the detection efficiencies calculated by PHITS using the present extensions were estimated to be approximately 15% for neutrons in the energy region below 100 MeV.

Low energy electron scattering from pyridine using a Surko trap and beam

This paper presents measurements of low energy electron scattering from pyridine. The low energy positron beamline at the Australian National University was used for these measurements, with a change in operational parameters allowing for the measurement of electron scattering processes. We have collected data for the low energy total cross section for electron scattering, as well as measurements of the differential cross sections for electrons up to 3 eV impact energy. The operation of the beamline will be briefly outlined and data are compared to R-matrix and Schwinger multichannel theoretical calculations, as well as previous experimental data.

Electron emission from fluorene (C13H10) upon 3.5 MeV/u Si8+ ion impact: double differential distributions

We have studied the electron emission from one of the polycyclic aromatic hydrocarbon (PAH) molecules namely, fluorene (C13H10), upon 3.5 MeV/u Si8+ ion impact. The experimentally measured absolute double differential cross sections (DDCS) are compared with the continuum distorted wave-eikonal initial state (CDW-EIS) model and the first Born approximation including correct boundary conditions (CB1). The measurements are carried out in the ejected e−-energy range of 1 eV–400 eV and in the angular range of 20°–160°. We have obtained the single differential and the total cross sections (TCSs) of e−-emission as well. The CB1 calculation largely underestimates the data. The CDW-EIS model, which is applied for the PAH molecule for the first time, provides an overall better agreement with the double differential, single differential and TCS data. The DDCS data for fluorene has also been compared with that for CH4 molecule, at a few angles. The forward–backward angular asymmetry shows a relatively flatter distribution compared to the theoretical predictions. The contribution due to the giant plasmon resonance could not be clearly observed except a mild indication in the asymmetry parameter. The angular distribution of the carbon KLL Auger electron cross section shows certain variations. The study of the KLL hyper-satellite component indicates the double K-ionization cross section is about 8.6% of the single K-ionization one.

Theoretical investigations of structural, spectroscopic and electron collision data of acetone

ABSTRACT Comprehensive computational studies are carried out for the structural, spectroscopic and electron collision data of acetone. The time-dependent density functional theory (TDDFT) is employed to compute singlet and triplet vertical excitation energies and to determine their valence/Rydberg character. Excellent correlation is obtained between the predicted spectral features with the available experimentally observed spectral features. We also report a detailed study on the e-acetone interactions for the comprehensive energy range starting from 0.1 to 5000 eV. We found a smooth matching of R-matrix and SCOP data for total cross sections at 17 eV and hence are able to estimate the total cross sections over such a wide energy range. Moreover, the study is augmented with additional data on Eigenphase sum, differential cross sections (DCS), momentum transfer cross sections (MTCS), electronic excitation cross-sections, symmetry decomposition of elastic cross sections, inelastic cross sections, etc. Ionisation cross-sections are computed using Complex scattering Potential-ionisation contribution (CSP-ic) and Binary Encounter Bethe (BEB) formalisms. Transport coefficients such as mean free path, diffusion and mobility coefficients are calculated from the effective collision frequency and the rate coefficients are estimated over a wide electron temperature range for elastic and inelastic processes. Importantly, we have been able to identify new resonances (; and ) from the present study. The theoretical data obtained here will be of great use in varieties of applications involving acetone.

Proton Electromagnetic Form Factors Data Are in Disagreement with New Electron-Positron Annihilation into Proton-Antiproton Pair Total Cross Section Measurements

In this paper a consistency of new very precise data on electron-positron annihilation into proton-antiproton pair total cross section with existing proton and neutron electromagnetic form factors data is investigated. First, the result is represented by a theoretically predicted dashed line for the total cross section obtained in the simultaneous analysis of the proton and neutron form factors data by the advanced nucleon electromagnetic structure Unitary and Analytic model, and then, as the neutron data are always less precise from objective reasons than the proton data, the result is also represented by a theoretically predicted full line for the total cross section obtained in the analysis of only the proton form factors data in space-like and time-like regions by the advanced proton electromagnetic structure Unitary and Analytic model. In both cases one finds disagreement between the electron-positron annihilation into proton-antiproton pair total cross section data and the corresponding form factors data, which is demonstrated by a disagreement of the dashed and full curves representing theoretically predicted electron-positron annihilation into proton-antiproton pair total cross sections behaviors.