Total Cross Sections Research Articles

Evaluation of 180mTa formation cross-sections in photoneutron reactions

Determining the relative production cross-sections of the short-lived (ground) and long- lived (metastable) states of 180Ta is integral in nuclear physics research. However, direct measurement of these cross-sections is challenging. In this study, we proposed a method for estimating the total flux-weighted average formation cross-section of 180m+gTa based on GEANT4 modeling to evaluate the short-lived (ground) and long-lived (metastable) states of 180Ta. A Ta target was irradiated by a bremsstrahlung photon beam (maximum electron energy: 20 MeV) obtained from the linear electron accelerator LUE-75 at the A.I. Alikhanyan National Science Laboratory (AANL), Armenia. The experiment was performed using the activation technique, and the proposed GEANT4 simulation-based method was employed to evaluate the flux-weighted average formation cross-section of 180mTa. In addition, the isomeric cross-section ratio for the 180m,gTa isomeric pair was calculated. The theoretical results obtained using the TALYS 1.96 and EMPIRE 3.2 codes were consistent with the experimental ones. To the best of the authors’ knowledge, this paper reports the estimated flux-weighted average formation cross-section of 180mTa and isomer ratio for the 180m,gTa isomeric pair, induced by the irradiation of a bremsstrahlung beam with an end-point energy of 20 MeV, for the first time. This study opens new avenues for determining the relative production cross-sections of the ground and metastable states of 180Ta, which is widely studied as a natural isomeric target in various fields, including nuclear transformation reactions, fission dynamics, etc.

CP-violating top-Higgs coupling in SMEFT

The total cross section of the process μ−μ+→νμν¯μtt¯H has strong dependence on the CP phase ξ of the top Yukawa coupling, where the ratio of ξ=π and ξ=0 (SM) grows to 670 at s=30 TeV, 3400 at 100 TeV. We study the cause of the strong energy dependence and identify its origin as the (E/mW)2 growth of the weak boson fusion sub-amplitudes, WL−WL+→tt¯H, with the two W's are longitudinally polarized. We repeat the study in the SMEFT framework where EW gauge invariance is manifest and find that the highest energy cross section is reduced to a quarter of the complex top Yukawa model result, with the same energy power. By applying the Goldstone boson (GB) equivalence theorem, we identify the origin of this strong energy growth of the SMEFT amplitudes as associated with the dimension-6 π−π+ttH vertex, where π± denotes the GB of W±. We obtain the unitarity bound on the coefficient of the SMEFT operator by studying all 2→2 and 2→3 cross sections in the J=0 channel.

Impact of the LHCb 8 [formula omitted], [formula omitted], and asymmetry data on the CT14HERA2 PDFs

First, we calculate the total cross-sections and differential cross-sections of the W and Z productions at next-to-leading order QCD using ResBos and CT14HERA2 PDFs, and compare with the measurements from the LHCb detector at a center-of-mass energy of 8 TeV and find good agreement between the experimental data and theoretical predictions. Then, we analyze the impact of LHCb 8 TeV W, Z, and asymmetry data on CT14HERA2 PDFs( g(x,Q), u(x,Q), d(x,Q), ū(x,Q), d̄(x,Q), d(x,Q)/u(x,Q) ) using the Error PDF Updating Method Package. Through this analysis, we find that the LHCb 8 TeV W and Z data prefer softer gloun and d(x,Q) at large x region, but have no significant impacts on u(x,Q) PDF.

Generalized binary-encounter-Bethe model for electron impact ionization of atoms

A generalized binary-encounter-Bethe (GBEB) model is proposed to calculate the partial ionization cross sections of all shells. The present model improves the original version of Kim et al (2000 Phys. Rev.A 62 052710) by incorporating a physically constructed effective charge felt by the ejected electron in the empirical factor, which prevents the selection of specific factors for different shells. A generalized relativistic binary-encounter-Bethe (BEB) formula is also proposed and applied to different inner shells of C, Al, Fe, Ar, Ag, Xe, Sn, Pb, and Bi atoms for impact energies from the thresholds up to 106 keV. The present model improves the partial ionization cross sections in the low-energy region compared to other relativistic BEB models. The GBEB partial and total ionization cross sections of the Xe atom are compared with the original BEB results. The present calculations, combined with the contribution from the direct multiple ionization, show good agreement with the experimental measurements in the intermediate- and high-energy ranges. We conclude that the present GBEB model, without any fitting parameters and ad hoc corrections, improves the BEB prediction of partial and total ionization cross sections for a good variety of atomic targets.

Classical-trajectory model for ionizing proton-ammonia molecule collisions: the role of multiple ionization

We use an independent electron model with semi-classical approximation to electron dynamics to investigate differential cross sections for electron emission in fast collisions of protons with ammonia molecules. An effective potential model for the electronic orbitals is introduced, and utilized in the context of the classical-trajectory Monte Carlo (CTMC) approach for single-electron dynamics. Cross sections differential in electron emission angle and energy are compared with experimental data. Compared to previous scattering-theory based quantum-mechanical results the time-dependent semi-classical CTMC approach provides results of similar quality for intermediate and high ionized electron energies. We find some discrepancies in the total cross sections for q-fold ionization between the present model and independent-atom-model calculations. The double ionization cross sections are considerably larger than recent experimental data which are derived from coincidence counting of charged fragments. The calculated triple ionization cross sections exceed the experimental coincidence data for q = 3 by several orders of magnitude at intermediate energies.

Theoretical investigations on electron-impact single-ionization cross section of Sn 11+

The total cross-section of electron-impact single ionization for the ground configuration 3d 104s 24p 64d 3 and excited configuration 3d 104s 24p 64d 24f of Sn 11+ is determined from the ionization threshold to 1000 eV. The contributions of direct ionization, excitation auto-ionization, and resonant excitation double auto-ionization to the total electron-impact single ionization cross-section are systematically demonstrated. The cross-section of direct ionization and excited auto-ionization are determined using the level-to-level method, while the cross-section of partially resonant excited double auto-ionization are determined through the configuration averaged method. To obtain convergence, excitation channels with the maximum principal quantum number up to n = 25 are considered. A comparison of the present results with the experimental data [Borovik et al. J. Phys. B 46, 175 201 (2013)] reveal considerably improved agreement when including the resonant excitation double auto-ionization in the calculation.

Thermal performance enhancement of multiple tubes latent heat thermal energy storage system using sinusoidal wavy fins and tubes geometry modification

In this paper, performance enhancement of a shell and multiple tube latent heat thermal energy storage system (LHTESS) is numerically investigated by implementing sinusoidal wavy fins and different geometrical designs of heat transfer tubes. The annular space of the shell is filled with the paraffin wax RT35 as phase change material (PCM) and absorbs heat from hot water through the multiple tubes. With the constant total cross-section area of all tubes and fins as the constraint condition, the effect of tube number and tube shape incorporated with the proposed fins on the heat transfer properties of PCM during the melting process is evaluated. The computational results demonstrate that the sinusoidal wavy fins can improve the phase change efficiency compared to the conventional straight fins. The double-pitch sinusoidal wavy fins decrease the total melting time by 9.5% compared to the straight fins for the single-tube case. As the number of HTF tubes increased from one to four, the complete PCM melting time decreased by 38.3%. Geometrical design alterations of heat transfer tubes from circular to petal-shaped are proposed to further improve the thermal performance of multiple tubes LHTESS. The melting rate of PCM is accelerated with an increase in the number of petals. The petal tubes with nine petals can save the charging time up to 24 % in comparison with the circular tubes in a four-tube case with double-pitch sinusoidal wavy fins, and up to 57% compared to the base case with a single circular HTF tube and straight fins.

Theoretical investigation of electron interaction processes for furfural (C5H4O2) and p-benzoquinone (C6H4O2)

The present study aims to quantify the electron-induced inelastic and elastic processes for molecules of industrial relevance, furfural and p-benzoquinone. We have computed inelastic cross-sections (Qinel), elastic cross-sections (Qel) and total cross-sections (QT) through spherical complex optical potential (SCOP) formalism, from ionisation energy (IE) to 5000 eV. The continuum and discrete contributions of the Qinel have been calculated in terms of ionisation (Qion) and excitation (∑Qexc) cross-sections, respectively, by employing the complex scattering potential-ionisation contribution (CSP-iC) method. A novel 2-parameter semi-empirical method (2p-SEM), a useful approach applicable for the large molecules 55 < Z < 95 for calculating QT, has been proposed and validated. Computed results are compared with previous experimental and theoretical data. We have also estimated the dielectric constant (ε) using various methods and correlations with molecular ionisation for these applied molecules.

Measurement of proton induced absolute production cross-section of 6.13, 6.92 and 7.12 MeV γ-rays from 16O(p,p ′γ )16O reaction

In this article, we report the absolute production cross-section of 6.13, 6.92 and 7.12 MeV γ-rays from the 16O(p,p ′γ )16O reaction for incident proton energy range of 8-16 MeV. Angular distributions of the three γ-rays have been measured for seven angles at 9 MeV proton energy. A detailed phenomenological optical model potential (OMP) was set up to analyse the cross-section data. The OMP parameters were optimised using elastic, polarization and total reaction data available in the literature for protons and neutrons. Low-lying states of 16O were coupled, the optical potential was deformed using deformation parameters, and several resonances were included in the calculations to account for the nuclear structure effects. The potentials so generated have been used to calculate the differential and total cross sections for both 16O(p,p ′ )16O and 16O(p,p ′γ )16O reactions. Our calculated cross-sections are in fairly good agreement with our measured data for 6.13, 6.92 and 7.12 MeV γ-rays. However, there still exist discrepancies in reproduction of the finer details of the cross sections. The comparisons of the calculations with the data bring forth the rather complex roles of channel couplings, resonances in the p+16O system and target deformation in the variation of the cross sections with projectile energy. The increased contribution of nuclear structure effects in light mass nuclei, leads to an apparent loss of predictive power of the theoretical calculation, as we approach the low-energy region of less than 10 MeV projectile energy.

Next-to-next-to-leading-order QCD corrections to double J/ψ production at the B factories

In this paper, we study the next-to-next-to-leading-order (NNLO) QCD corrections for the process e+e− → J/ψ + J/ψ at the B factories. By including the NNLO corrections, the cross section turns negative due to the poor convergence of perturbative expansion. Consequently, to obtain a reasonable estimation for the cross section, the square of the amplitude up to NNLO is used. In addition, the contributions from the bottom quark and the light-by-light part, which are usually neglected, are also included. The final cross section is obtained as 1.76−1.66+2.42\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {1.76}_{-1.66}^{+2.42} $$\\end{document} fb at a center-of-mass energy of s\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\sqrt{s} $$\\end{document} = 10.58 GeV. Our result for total cross section and differential cross section could be compared with precise experimental measurement in future at the B factories.

Absolute Photoionization Cross Section and Dissociative Ionization Pathways of Alpha-Pinene.

The absolute photoionization cross section of the monoterpenoid, alpha-pinene (AP), is presented together with the relative photoionization cross sections of its dissociative fragments for the first time. Experiments are performed via multiplexed vacuum ultraviolet (VUV) synchrotron photoionization (PI) mass spectrometry in the 8.0-11.0 eV energy range. Experimental work is conducted at the Advanced Light Source of the Lawrence Berkeley National Laboratory. Dissociative fragments were identified at m/z 121, 94, 93, 92, and 80. The photoionization cross section for the parent mass at 11.0 eV was determined to be 17±4 Mb with a total ionization cross section of 92±23 Mb at the same photon energy. Experimental appearance energies of dissociative ionization fragments and potential dissociative ionization pathways calculated at the G4 level of theory are presented as well.

Non-thermal WIMPy baryogenesis with primordial black hole

We consider the possibility that the weakly interacting massive particles produced from the evaporation of primordial black hole can explain both the relic density of dark matter and the baryon asymmetry of the Universe, through their annihilation which violate B and CP-symmetry. We find that the primordial black hole with mass less than 107g is a good candidate as an source of TeV dark matter with the total annihilation cross section 〈σaυ〉 ≲ 10-7 GeV-2 and the B-violating scattering cross section 〈σaυ〉 ≲ 2 × 10-9 GeV-2. This large annihilation cross section of dark matter in this model would make it available to search them in the indirect search for dark matter such as gamma-ray or neutrino observations.

E+e−→Λc+Λ¯c− Cross Sections and the Λc+ Electromagnetic Form Factors within the Extended Vector Meson Dominance Model

Within the extended vector meson dominance model, we investigate the e+e−→Λc+Λ¯c− reaction and the electromagnetic form factors of the charmed baryon Λc+ . The model parameters are determined by fitting them to the cross sections of the process e+e−→Λc+Λ¯c− and the magnetic form factor |G M| of Λc+ . By considering four charmonium-like states, called ψ(4500), ψ(4660), ψ(4790), and ψ(4900), we can well describe the current data on the e+e−→Λc+Λ¯c− reaction from the reaction threshold up to 4.96 GeV. In addition to the total cross sections and |G M|, the ratio |G E/G M| and the effective form factor |G eff| for Λc+ are also calculated, and found that these calculations are consistent with the experimental data. Within the fitted model parameters, we have also estimated the charge radius of the charmed Λc+ baryon.

Positron scattering from neon and argon

The relativistic optical potential method has been used to calculate a complete set of cross sections for positron scattering from neon and argon in the energy range from zero to 1 keV. Elastic, positronium formation, excitation, direct ionization, and grand total cross sections are presented and compared to the recommended results of Ratnavelu et al. (J Phys Chem Ref Data 48:023102, 2019). Here, positronium formation is modeled as an ionization process by successively lowering the ionization thresholds. This process was carried out for the four lowest energy levels of positronium.Graphical abstract

Positron scattering from krypton and xenon

A cross section set is reported for positron scattering from krypton and xenon over the energy range from zero to 1 keV using the relativistic optical potential method. This set includes elastic, positronium formation, excitation, direct ionization, and grand total cross sections. They are compared to the recommended results of Ratnavelu et al. (J Phys Chem Ref Data 48:023102, 2019). The positronium formation cross section reported is represented by the sum obtained by successively lowering the ionization threshold to coincide with those for formation into the four lowest energy levels of positronium.Graphical

Measurement of the neutron-induced total cross sections of $$^\text {nat}$$Pb from 0.3 eV to 20 MeV on the Back-n at CSNS

Measurement of the neutron-induced total cross sections of $$^\text {nat}$$Pb from 0.3 eV to 20 MeV on the Back-n at CSNS

Tumor margin irregularity degree is an important preoperative predictor of adverse pathology for clinical T1/2 renal cell carcinoma and the construction of predictive model.

To explore the critical role of the tumor margin irregularity degree (TMID) of renal tumors in predicting adverse pathology of patients with clinical T1/2 (cT1/2) renal cell carcinoma (RCC). A total of 821 patients with cT1/2 RCC undergoing nephrectomy in the Second Hospital of Tianjin Medical University between January 2017 and December 2020 were reviewed. The tumor margin irregularity (TMI) was classified into renal mass with locally raised protrusion and smooth margin called 'lobular', sharply and unsmooth nodular margin called 'spiculation', blurred margins between tumor and renal parenchyma or a completely irregular and non-elliptical shape. The ratio between the number of irregular cross-sections (X) and the number of total cross-sections from top to bottom occupied (Y) was defined as TMID (X/Y). The logistic regression was performed to determine the independent predictors of adverse pathology, and the Kaplan-Meier curve and log-rank test were used to analyze the survival outcomes. Among 821 cT1/2 RCC patients, 245 (29.8%) had adverse pathology. The results of the univariate and multivariate logistic regressions showed that the age, tumor size, hemoglobin, and TMID were the independent predictors of adverse pathology. Incorporation of TMID could increase the discrimination of the predictive model with the area under curve (AUC) of ROC curves increasing from 0.725 to 0.808. Patients with adverse pathology or higher TMID both had significantly shorter recurrence-free survival (RFS). The nomogram model incorporated with TMID for predicting adverse pathology could increase its discrimination, calibration, and clinical application values, compared with the models without TMID.

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.

Nuclear radii from total reaction cross section measurements at intermediate energies with complex turning point corrections to the eikonal model

Nuclear radii from total reaction cross section measurements at intermediate energies with complex turning point corrections to the eikonal model

Analysis of the cross section and characteristic of fluorescence emission of the He atom confined in the plasma conditions

The structural properties, angle-integrated total and magnetic sublevel excitation cross sections, alignments of the residual ion, and polarization properties of the line emission are investigated for the plasma-embedded atomic system. This is done using the developed distorted wave approach which solves the Dirac equation by employing a modified Debye potential to represent the screened interaction in plasmas. The effective Hamiltonian is employed to obtain the level energies as functions of the screening parameters. The Coulomb interaction is replaced by shielded Coulomb interaction during the collision dynamics. As an illustrating example, detailed calculations are carried out for the 1s2→1s2p3,1P1 excitations of the plasma-embedded He atom by electron impact. Our results suggest that the energy levels are pushed towards continuum as the effect of (plasma) confinement increases. The cross sections decreases monotonically if the screening effect is enhanced continuously, while the alignments of the residual He+ ion and polarizations of the fluorescence emission change slightly for the corresponding screening parameters. A comparison of our results in the absence of the screening potential with other available experimental and theoretical data shows satisfactory agreement. The present study not only provides a helpful approach to study the influence of plasma effect, but also has important applications in laser produced plasmas, stellar atmospheres, fusion research plasmas and so on.