Total Cross Section Data Research Articles

Cross sections for electron collision with five-membered ring heterocycles

The absolute total cross-section (TCS) for electron scattering from isoxasole, (CH)3NO, molecule has been measured using the linear transmission technique for impact energies ranging from 1 to 400 eV. The measured TCS energy dependence appears typical for highly polar targets; over whole energy range applied, the magnitude of TCS generally decreases as the energy increases. Some narrow features located near 1.2 and 2.7 eV have been observed in the TCS curve as well as a broad enhancement spanned between 5 and 15 eV. The TCS for electron-isoxazole scattering has been compared with TCS data for furan, (CH)4O; differences and similarities in the appearance of both TCSs energy functions are indicated and discussed. In addition, for several five-membered ring heterocycle molecules: isoxazole, pyrrole [(CH)4NH] and tiophene [(CH)4S], integral elastic (ECS) and ionization (ICS) cross sections have been calculated at intermediate and high electron-impact energies in the additivity rule approximation and the binary-encounter-Bethe approach, respectively. For isoxazole and furan the sums of ECS and ICS are in very good agreement with the respective measured TCSs above 50 − 60 eV.

Total and partial photoneutron reactions cross sections – new analysis and evaluation

The well-known problems of significant disagreements between partial photoneutron reactions ( γ , n ), ( γ ,2 n ) and ( γ ,3 n ) cross sections data obtained in various experiments are discussed. Using new objective criteria of data reliability it was shown that majority of data under discussion contains significant distortions because of definite shortcomings of experimental photoneutron multiplicity sorting methods used – the majority of experimental data obtained such methods are not reliable. These criteria were transitional photoneutron multiplicity functions F i = σ ( γ ,in)/ σ ( γ , x n) having values not higher than 1.00, 0.50, 0.33, 0.25, 0.20…., correspondingly for i = 1, 2, 3, 4, 5,…New experimentally-theoretical method was proposed to evaluate reliable data free from shortcomings of neutron multiplicity sorting. For partial reaction cross section evaluation the only experimental data for total neutron yield reaction cross section σ exp ( γ , x n) = σ exp [( γ ,n) + 2( γ ,2n) + 3( γ ,3n) + …] free from the mentioned shortcomings are used together with functions F i theor calculated within the modern model for photonuclear reactions − σ eval ( γ ,in) = F i theor · σ exp ( γ ,xn). Many new reliable data for 90 Zr, 115 In, 112,114,116,117,118,119,120,122,124 Sn, 159 Tb, 181 Ta, 197 Au, and 208 Pb were evaluated. Deviations of evaluated data from experimental ones are analysed and the physical consequences are discussed.

Simulation calculations of transmissions for neutron total cross-section measurements of MAs and LLFPs by complementary use of a compact accelerator-driven neutron source

We performed simulation calculations of neutron transmission spectra for minor actinide and long-lived fission product samples with pulsed neutron beams produced by the two neutron sources: the Accurate Neutron-Nucleus Reaction measurement Instrument (ANNRI) at the Japan Spallation Neutron Source (JSNS) that provides the world's most intense pulsed neutron beam, and a compact accelerator-driven neutron source. For the both cases, we assumed to put a neutron detector at downstream of the sample and took into account the detector efficiency of neutrons to estimate statistics. ANNRI gives high statistical neutron transmission spectra. Therefore, it is useful for obtaining the total cross-section data through the transmission spectra for the small amount sample or the small cross-section regions between the resonances not only for monitoring the beam condition during the neutron capture-reaction measurements at ANNRI. On the other hand, a compact neutron source shows transmission spectra at resonances with less deformation by its single bunch beam. This implies that the compact neutron source is useful for assigning the resonances and the resonance analysis.

New color-octet axial vector boson revisited

In this paper we reexamine how to utilize the previous proposed color-octet axial-vector boson ${Z}_{\mathrm{C}}$ to explain the $3.4\ensuremath{\sigma}$ anomaly of $t\overline{t}$ forward-backward (FB) asymmetry ${A}_{\mathrm{FB}}$ for ${m}_{t\overline{t}}>450\text{ }\text{ }\mathrm{GeV}$ observed by CDF. Our numerical results indicate that the best-fit parameters are ${g}_{A}^{q}=0.07$, ${g}_{A}^{Q}=3$, and ${M}_{\mathrm{C}}=440\text{ }\text{ }\mathrm{GeV}$, which are obtained by fitting the mass dependent ${A}_{\mathrm{FB}}$ and total cross section data provided by a recent CDF measurement. Here ${g}_{A}^{q}({g}_{A}^{Q})$ and ${M}_{\mathrm{C}}$ are the axial couplings among ${Z}_{\mathrm{C}}$ with the first two (the third) generation quarks, and ${Z}_{\mathrm{C}}$ mass, respectively. We also calculate one-side forward-backward asymmetry ${A}_{\mathrm{OFB}}$ for top and bottom quark pair production at the LHC, focusing on the new contributions from ${Z}_{\mathrm{C}}$. Our studies show that ${A}_{\mathrm{OFB}}$ can be utilized to measure the properties of new particle ${Z}_{\mathrm{C}}$.

Relativistic Descriptions of Final-State Interactions in Charged-Current Quasielastic Neutrino-Nucleus Scattering at MiniBooNE Kinematics

The results of two relativistic models with different descriptions of the final-state interactions are compared with the MiniBooNE data of charged-current quasielastic cross sections. The relativistic mean field model uses the same potential for the bound and ejected nucleon wave functions. In the relativistic Green's function model, the final-state interactions are described in the inclusive scattering consistently with the exclusive scattering using the same complex optical potential. The relativistic Green's function results describe the experimental data for total cross sections without the need to modify the nucleon axial mass.

Calculation of the Complete Sets of Nuclear Data for n + 32,34S Below 20 MeV

Based on the available experimental data for total cross section, nonelastic cross section, and elastic scattering angular distribution of n + 32,natS, a set of neutron optical potential parameters is obtained. The complete sets of nuclear data for n + 32,34S < 20 MeV are calculated. These sets include cross sections, angular distributions of elastic scattering, energy spectra and/or double-differential cross sections of all emitted particles, and gamma production data (production cross sections and multiplicity, energy spectra) in all kinds of reactions. The calculated results are generally in good accordance with experimental data and are compared with JENDL-3.3.

Helium-3 global optical model potential with energies below 250 MeV

A new set of global phenomenological optical model potential parameters has been obtained for helium-3 projectile, by simultaneously fitting the experimental data of helium-3 total reaction cross sections and elastic scattering angular distributions in the mass range of target nuclei 20⩽A⩽209 at incident energies below 250 MeV. A comparison has been made between the extracted helium-3 global optical model potential parameters and the existing ones. The calculated results of total reaction cross sections and elastic scattering angular distributions are also compared with experimental data with their satisfactory agreement.

Total cross section prediction of the collisions of positrons and electrons with alkali atoms using Gradient Tree Boosting

A relatively new computational technique, namely gradient tree boosting (GTB), is presented for modeling the total cross sections of the scattering of positrons and electrons by alkali atoms in the low and intermediate energy regions. The calculations have been performed in the framework of gradient tree boosting (GTB). The GTB has been running based on the experimental data of the total collisional cross sections to produce the total cross sections for each alkali atom as a function of the incident energy of the projectile as well as the atomic number and the static dipole polarizability of the atom. Moreover our GTB model is used to predict the experimental data for total collisional cross sections that are not used in the training session. The calculated and predicted total collisional cross sections are compared with the experimental data. We find that the GTB technique shows a good match to the experimental data. To our knowledge, this is the first application of the GTB technique to the data of positron and electron collisions with alkali atoms at low and intermediate energies.

Total Cross Sections for Neutron Nucleus Scattering

Systematics of neutron scattering cross sections on various materials for neutron energies up to several hundred MeV are important for ADSS applications. Ramsauer model is well known and widely applied to understand systematics of neutron nucleus total cross sections. In this work, we examined the role of nuclear effective radius parameter (r$_0$) on Ramsauer model fits of neutron total cross sections. We performed Ramsauer model global analysis of the experimental neutron total cross sections reported by W. P. Abfalterer, F. B. Bateman, {\it et. al.,}, from 20MeV to 550MeV for nuclei ranging from Be to U . The global fit functions which can fit total cross section data over periodic table are provided along with the required global set of parameters. The global fits predict within $\pm 8%$ deviation to data, showing the scope for improvement. It has been observed that a finer adjustment of r$_0$ parameter alone can give very good Ramsauer model description of neutron total scattering data within $\pm 4%$ deviation. The required r$_0$ values for Ramsauer model fits are shown as a function of nuclear mass number and an empirical formula is suggested for r$_0$ values as a function of mass number. In optical model approach for neutron scattering, we have modified the real part of Koning-Deleroche potentails to fit the neutron total cross sections using SCAT2 code. The modified potentails have a different energy dependence beyond 200MeV of neutron energy and fit the total cross sections from Al to Pb.

Asymmetry dependence of nucleon correlations in spherical nuclei extracted from a dispersive-optical-model analysis

Neutron elastic-scattering angular distributions were measured at beam energies of 11.9 and 16.9 MeV on 40,48 Ca targets. These data plus other elastic-scattering measurements, total and reaction cross-sections measurements, (e, ep) data, and single-particle energies for magic and doubly magic nuclei have been analyzed in the dispersive optical-model (DOM), generating nucleon self-energies (optical-model potentials) that can be related, via the many-body Dyson equation, to spectroscopic factors and occupation probabilities. It is found that, for stable nuclei with N Z, the imaginary surface potential for protons exhibits a strong dependence on the neutron-proton asymmetry. This result leads to a more modest dependence of the spectroscopic factors on asymmetry. The measured data and the DOM analysis of all considered nuclei clearly demonstrate that the neutron imaginary surface potential displays very little dependence on the neutron-proton asymmetry for nuclei near stability (N Z).

Self-consistent continuum random-phase approximation calculations with finite-range interactions

We present a technique that treats, without approximations, the continuum part of the excitation spectrum in random phase approximation calculations with finite-range interactions. The interaction used in Hartree-Fock calculations to generate the single-particle basis is also used in continuum random phase approximation calculations. We show results for electric dipole and quadrupole excitations in $^{16}\mathrm{O}$, $^{22}\mathrm{O}$, $^{24}\mathrm{O}$, $^{40}\mathrm{Ca}$, $^{48}\mathrm{Ca}$, and $^{52}\mathrm{Ca}$ nuclei. We compare our results with those of the traditional discrete random phase approximation, with continuum independent-particle model results, and with results obtained by a phenomenological random phase approximation approach. We study the relevance of the continuum, of the residual interaction, and of the self-consistency. We also compare our results with the available total photoabsorption cross-section data.

High-energy strong interactions: from ‘hard’ to ‘soft’

We discuss the qualitative features of the recent data on multiparticle production observed at the LHC. The tolerable agreement with Monte Carlos based on LO DGLAP evolution indicates that there is no qualitative difference between `hard' and `soft' interactions; and that a perturbative QCD approach may be extended into the soft domain. However, in order to describe the data, these Monte Carlos need an additional infrared cutoff k_min with a value k_min ~ 2-3 GeV which is not small, and which increases with collider energy. Here we explain the physical origin of the large k_min. Using an alternative model which matches the `soft' high-energy hadron interactions smoothly on to perturbative QCD at small x, we demonstrate that this effective cutoff k_min is actually due to the strong absorption of low k_t partons. The model embodies the main features of the BFKL approach, including the diffusion in transverse momenta, lnk_t, and an intercept consistent with resummed next-to-leading log corrections. Moreover, the model uses a two-channel eikonal framework, and includes the contributions from the multi-Pomeron exchange diagrams, both non-enhanced and enhanced. The values of a small number of physically-motivated parameters are chosen to reproduce the available total, elastic and proton dissociation cross section (pre-LHC) data. Predictions are made for the LHC, and the relevance to ultra-high-energy cosmic rays is briefly discussed. The low x inclusive integrated gluon PDF, and the diffractive gluon PDF, are calculated in this framework, using the parameters which describe the high-energy pp and p\bar{p} `soft' data. Comparison with the PDFs obtained from the global parton analyses of deep inelastic and related `hard' scattering data, and from diffractive deep inelastic data looks encouraging.

Forward $${{\bar p} d}$$ Elastic Scattering and Total Spin-Dependent pd Cross Sections

Glauber theory is applied to \({{\bar p} d}\) scattering at beam energies 20–300 MeV using the \({{\bar N} N}\) amplitudes of the Julich models. The available data for unpolarized differential and total cross section are well described within this approach. The polarized total \({{\bar p} d}\) cross sections are calculated within the single-scattering approximation using the optical theorem.

Imaging of a spatial distribution of preferred orientation of crystallites by pulsed neutron Bragg edge transmission

A pulsed neutron transmission coupled with a two-dimensional position sensitive neutron detector gives a time-of-flight spectrum at each pixel of the detector, which depends on the total cross-sections of materials. In order to extract quantitative information of the preferred orientation included in the Bragg scattering total cross-section data, a spectral analysis software for the 2D imaging has been developed, and the transmission data of an unbent iron plate were analyzed. The 2D images with respect to the preferred orientation were successfully obtained, and the effectiveness of spectroscopic neutron transmission imaging was indicated.

High resolution study of the Λp final state interaction in the reaction [formula omitted

The reaction pp→K++(Λp) was measured at Tp=1.953 GeV and Θ=0° with a high missing mass resolution in order to study the Λp final state interaction. The large final state enhancement near the Λp threshold can be described using the standard Jost-function approach. The singlet and triplet scattering lengths and effective ranges are deduced by fitting simultaneously the Λp invariant mass spectrum and the total cross section data of the free Λp scattering.

Cross-sections from scalar field theory

A scalar quantum field theory method is used to calculate differential and total cross-sections for elastic and inelastic scattering in proton–proton collisions. When Mandelstam variables are used, the resulting formulas are simple and can be written in closed form. They display features very typical of elastic and inelastic scattering. The results show good agreement with total cross-section data for η meson production. Thus for this particular example, a simple scalar model can be used in place of a more complicated field theory with spin.

Electron correlations in single-electron capture from helium by fast protons andαparticles

Single-electron capture from heliumlike atomic systems by bare projectiles is investigated by means of the four-body boundary-corrected first Born approximation (CB1-4B). The effect of the dynamic electron correlation is explicitly taken into account through the complete perturbation potential. The quantum-mechanical post and prior transition amplitudes for single charge exchange encompassing symmetric and/or asymmetric collisions are derived in terms of two-dimensional real integrals in the case of the prior form and five-dimensional quadratures for the post form. An illustrative computation is performed for single-electron capture from helium by protons and {alpha} particles at intermediate and high impact energies. The role of dynamic correlations is examined as a function of increased projectile energy. The validity and utility of the proposed CB1-4B method is critically assessed in comparison with the existing experimental data for total cross sections, and excellent agreement is obtained.

Total cross sections for positron scattering fromH2at low energies

This paper revisits positron scattering from molecular hydrogen, in an attempt to provide accurate total cross-section data against which theoretical calculations might be benchmarked. The present data were measured over the energy range 0.1--50 eV and, where possible, are compared to results from previous experiments and calculations. Agreement with the earlier data was typically very good at energies above 10 eV but becomes progressively more marginal as we go to lower energies. None of the current theories quantitatively reproduce our measurements over the entire energy range, although at a qualitative level the main features driving the scattering dynamics are apparent.

Photoproduction of hypernuclei within the quark–meson coupling model

We study the photoproduction of the 12ΛB hypernucleus within a fully covariant effective Lagrangian based model, employing Λ bound state spinors derived from the latest quark–meson coupling model. The kaon production vertex is described via creation, propagation and decay of N∗(1650), N∗(1710), and N∗(1720) intermediate baryonic resonant states in the initial collision of the photon with a target proton in the incident channel. The parameters of the resonance vertices are fixed by describing the total and differential cross section data on the elementary γp→ΛK+ reaction in the energy regime relevant to the hypernuclear production. It is found that the hypernuclear production cross sections calculated with the quark model based hyperon bound state spinors differ significantly from those obtained with the phenomenological Dirac single particle wave functions.

Dynamical coupled-channels study ofπN→ππNreactions

As a step toward performing a complete coupled-channels analysis of the world data of pi N, gamma^* N --> pi N, eta N, pi pi N reactions, the pi N --> pi pi N reactions are investigated starting with the dynamical coupled-channels model developed in Phys. Rev. C76, 065201 (2007). The channels included are pi N, eta N, and pi pi N which has pi Delta, rho N, and sigma N resonant components. The non-resonant amplitudes are generated from solving a set of coupled-channels equations with the meson-baryon potentials defined by effective Lagrangians. The resonant amplitudes are generated from 16 bare excited nucleon (N^*) states which are dressed by the non-resonant interactions as constrained by the unitarity condition. The available total cross section data of pi^+ p --> pi^+ pi^+ n, pi^+ pi^0 and pi^- p --> pi^+ pi^- n, pi^- pi^0 n, pi^0 pi^0 n can be reproduced to a very large extent both in magnitudes and energy-dependence. Possible improvements of the model are investigated, in p