Predictions For Cross Sections Research Articles

NLO QCD corrections to the Bc -pair hadroproduction

The Bc meson pair, including pairs of pseudoscalar states and vector states, productions in proton-proton collisions are investigated at the next-to-leading order (NLO) accuracy in the nonrelativistic quantum chromodynamics factorization formalism. The corresponding cross sections at the Large Hadron Collider (LHC) with s=14 TeV are evaluated. Numerical results indicate that the NLO corrections are substantial, and even dominate over the leading order contributions. Considering the predicted cross sections are sizable, the Bc-pair production is expected to be observable at the high-luminosity LHC experiment. Published by the American Physical Society 2024

Investigation of the cross sections for electron collision ionization of complex molecules

AbstractAn accurate and computationally efficient determination of the cross sections for electron collision ionization of molecules has various applications, such as plasma physics and atmospheric science. In the case of large molecules, ab initio calculations are often difficult and time‐consuming. Here, we develop a feed forward neural network to predict the electron impact ionization cross sections of complex molecules. The training (predicting) set in the method consists of a series of theoretical ionization cross sections for small (large) molecules obtained from the combined model, which integrates the Binary‐Encounter‐Bethe and Deutsch‐Märk models. Several complex systems or targets involving electron collision ionization are evaluated, including molecules such as CH, CH, CH, CH, C, CHO, and CHO. The root mean square errors of the trained and predicted cross sections by the neural network (compared to the values from the combined model) are found to be approximately .0086 and .0930 (in 10 cm), respectively, (using the CHO molecule as an example), indicating our results are very high accuracy. The excellent agreement between the predicted values and the actual values indicates that the neural network is a practical and powerful tool for determining the electron collision ionization cross sections of complex molecules and can provide valuable insights into the dynamics process. Apart from its fundamental importance, this study has far‐reaching implications for gas discharge, low‐temperature plasmas, and fusion edge plasmas and so forth.

ρ -meson spectroscopy and diffractive production using the holographic light-front Schrödinger equation and the ’t Hooft equation

We determine the mass spectroscopy and light-front wave functions (LFWFs) of the ρ-meson by solving the holographic Schrödinger equation of light-front chiral QCD along with the ’t Hooft equation of (1+1)-dimensional QCD in the large Nc limit. Subsequently, we utilize the obtained LFWFs in conjunction with the color glass condensate dipole cross section to calculate the cross sections for the diffractive ρ-meson electroproduction. Our spectroscopic results align well with the experimental data. Predictions for the diffractive cross sections demonstrate good consistency with the available experimental data at different energies from H1 and ZEUS collaborations. Additionally, we show that the resulting LFWFs for the ρ-meson can effectively describe various properties, including its decay constant, distribution amplitudes, electromagnetic form factors, charge radius, magnetic and quadrupole moments. Comparative analyses are conducted with experimental measurements and the available theoretical predictions. Published by the American Physical Society 2024

Assessing the impact of nuclear mass models on the prediction of synthesis cross sections for superheavy elements

Assessing the impact of nuclear mass models on the prediction of synthesis cross sections for superheavy elements

Short-range correlations in dynamical intranuclear cascade models for describing nucleon knockout reactions

Spallation and fragmentation reactions at incident energies above the Fermi momentum are considered to be the main mechanism for the production of neutron-rich nuclei at worldwide nuclear physics facilities, such as RIBF, FRIB, and GSI-FAIR. Although it is widely known that dynamical reaction models give a rather good prediction of cross sections for nuclear residues produced in spallation and fragmentation reactions, these reaction models fail in the description of peripheral collisions involving short-range nucleon-nucleon correlations (SRCs). Here, we present state-of-the-art dynamical reaction calculations based on the intranuclear cascade approach to describe spallation and fragmentation reactions. The new version of our dynamical model, including SRCs, successfully describes isotopic cross sections of neutron-rich nuclear residues and inclusive single-neutron and single-proton knockout cross sections for various stable and exotic nuclei. Finally, the results show that the systematic strong dependency of the single-knockout cross section reduction factor on the neutron-proton separation energy asymmetry parameter (ΔS) obtained by Tostevin and Gade disappears when SRCs are taken into account.

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.

Importance of physical information on the prediction of heavy-ion fusion cross sections with machine learning

Importance of physical information on the prediction of heavy-ion fusion cross sections with machine learning

Evolution of structure functions in momentum space

We formulate the momentum-space Dokshitzer–Gribov–Lipatov-Altarelli–Parisi (DGLAP) evolution equations for structure functions measurable in deeply inelastic scattering. We construct a six-dimensional basis of structure functions that allows for a full three flavor structure and thereby provides a way to calculate perturbative predictions for physical cross sections directly without unobservable parton distribution functions (PDFs) and without the associated scheme dependence. We derive the DGLAP equations to first non-zero order in strong coupling αs\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\alpha _\ extrm{s}$$\\end{document}, but the approach can be pursued to arbitrary order in perturbation theory. We also numerically check our equations against the conventional PDF formulation.

Prediction of the bead profile for wide-band laser cladding via hybrid model of mathematics and thermal simulation

Wide-band laser cladding has high deposition rate and low dilution due to the large laser spot and rectangular powder nozzle. A mathematical model was proposed to predict the track cross-section profile for wide-band laser cladding. The melt pool morphology and powder spatial concentration were taken into consideration to improve the accuracy of the model. Thermal field simulation was carried out to study the melt pool evaluation with process parameters, while infrared images were used to verify the simulation fidelity. Powder stream photographs were taken via a CCD (charge coupled device) camera to obtain the powder spot size. Single and multi-track cladding experiments were conducted, and calculated contours of the model coincide well with the experimental results. Simulated and measured melt pool width and length agree with in 2.16% and 2.36% of error, respectively. The error of predicted cross section area is less than 9.35%. The model also has good ability to predict the powder efficiency and morphology of the cladding layer.

Shell-model calculations for two-neutron transfer near the N=20 island of inversion

We describe connections between shell-model calculation results and predictions for two-nucleon transfer reactions. Measurements of the ^{30}Mg(t,p)^{32}Mg reaction were used to identify a low-lying shape-coexisting 0^+ state in ^{32}Mg. Interpretations of those early, limited data were based on simple empirical models. The cross sections for two-nucleon transfer are, however, extremely sensitive to the details of the nuclear-structure. Motivated by the possibility of new high-resolution two-nucleon transfer measurements around the N=20 Island of Inversion, we have performed shell-model calculations wave functions for states in the nuclei ^{30,32}Mg using the SDPF-M and SDPF-MU interactions, and from those calculations obtain the two-nucleon transfer amplitudes that we use to predict cross sections for the ^{28,30}Mg(t,p)^{30,32}Mg reactions. The combined results show how the nuclear structure properties influence experimental observables for the (t,p) reaction. We compare our results with the existing data.

Predictions for exclusive varUpsilon photoproduction in ultraperipheral {textrm{Pb}}+{textrm{Pb}} collisions at the LHC at next-to-leading order in perturbative QCD

We present predictions for the rapidity-differential cross sections of exclusive varUpsilon photoproduction in ultraperipheral collisions (UPCs) of lead ions at the Large Hadron Collider (LHC). We work in the framework of collinear factorization at next-to-leading order (NLO) in perturbative QCD, modeling the generalized parton distributions (GPDs) through the Shuvaev transform of nuclear parton distribution functions (nPDFs). Our direct NLO predictions depend significantly on nPDF uncertainties and on the choices of the factorization and renormalization scales, but to a much lesser degree on GPD modeling. To tame the scale dependence and to account for the fact that the NLO calculations generally underpredict the photoproduction measurements on protons, we also present alternative, data-driven predictions. In this approach the underlying photoproduction cross sections on lead are found by combining their nuclear modifications calculated at NLO with the measured photoproduction cross sections on protons. The data-driven strategy reduces the uncertainties associated with the scale choices, and essentially eliminates the effects of GPD modeling thereby leaving the cross sections sensitive mainly to the input nPDFs. Our estimates indicate that the process is measurable in {textrm{Pb}}+{textrm{Pb}} collisions at the LHC.

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.

Neural network predictions of inclusive electron-nucleus cross sections

We investigate whether a neural network approach can reproduce and predict the electron-nucleus cross sections in the kinematical domain of present and future accelerator-based neutrino oscillation experiments. For this purpose, we consider the large amount of data available to the community via the University of Virginia's Quasielastic Electron Nucleus Scattering Archive and use a residual, fully connected feedforward neural network. We illustrate the training performances of the neural network by comparing its results with experimental data for the electron double-differential cross section on carbon. The agreement between predictions and data is remarkable from quasielastic to deep-inelastic scattering. To test the predicting power of the neural network we consider the numerous kinematical conditions for which experimental cross sections on calcium are available. Furthermore, we show the predictions of the electron-scattering cross sections on oxygen, argon, and titanium: Nuclei of particular interest in the context of present and future accelerator-based neutrino oscillation programs. The agreement between these predictions and the data is comparable to the one of other theoretical models commonly used to calculate electron and neutrino cross sections, such as SuSAv2 and GiBUU. Results obtained with genie, a Monte Carlo event generator, are also discussed for comparison. The good performances obtained with our neural network suggest that neural networks could be exploited for theoretical and experimental investigations of electron- and neutrino-nucleus scattering.

Neutrino structure functions from GeV to EeV energies

The interpretation of present and future neutrino experiments requires accurate theoretical predictions for neutrino-nucleus scattering rates. Neutrino structure functions can be reliably evaluated in the deep-inelastic scattering regime within the perturbative QCD (pQCD) framework. At low momentum transfers (Q2 ≲ few GeV2), inelastic structure functions are however affected by large uncertainties which distort event rate predictions for neutrino energies Eν up to the TeV scale. Here we present a determination of neutrino inelastic structure functions valid for the complete range of energies relevant for phenomenology, from the GeV region entering oscillation analyses to the multi-EeV region accessible at neutrino telescopes. Our NNSFν approach combines a machine-learning parametrisation of experimental data with pQCD calculations based on state-of-the-art analyses of proton and nuclear parton distributions (PDFs). We compare our determination to other calculations, in particular to the popular Bodek-Yang model. We provide updated predictions for inclusive cross sections for a range of energies and target nuclei, including those relevant for LHC far-forward neutrino experiments such as FASERν, SND@LHC, and the Forward Physics Facility. The NNSFν determination is made available as fast interpolation LHAPDF grids, and it can be accessed both through an independent driver code and directly interfaced to neutrino event generators such as GENIE.

Towards resolving the gallium anomaly

A series of experiments studying neutrinos from intense radioactive sources have reported a deficit in the measured event rate which, in combination, has reached a statistical significance of ∼ 5σ. In this paper, we explore avenues for explaining this anomaly, both within the Standard Model and beyond. First, we discuss possible biases in the predicted cross section for the detection reaction νe + 71Ga → e− + 71Ge, which could arise from mismeasurement of the inverse process, 71Ge decay, or from the presence of as yet unknown low-lying excited states of 71Ga. The latter would imply that not all 71Ge decays go to the ground state of 71Ga, so the extraction of the ground state-to-ground state matrix element relevant for neutrino capture on gallium would be incorrect. Second, we scrutinize the measurement of the source intensity in gallium experiments, and we point out that a ∼ 2% error in the branching ratios for 51Cr decay would be enough to explain the anomaly. Third, we investigate the calibration of the radiochemical germanium extraction efficiency as a possible origin of anomaly. Finally, we outline several new explanations beyond the Standard Model, including scenarios with sterile neutrinos coupled to fuzzy dark matter or to dark energy, as well as a model with decaying sterile neutrinos. We critically assess the viability of these scenarios, and others that have been proposed, in a summary table.

The nucleon-induced deuteron breakup process as a laboratory for chiral dynamics

The nucleon-induced deuteron breakup reaction is studied within the Faddeev approach at incoming nucleon laboratory energies of 135 and 200 MeV. The chiral semilocal momentum-space (SMS) potential developed up to N4LO+, supplemented by the N2LO three-nucleon interaction, is used. Our investigation is focused on the determination of theoretical uncertainties in a predicted cross section related to its dependence on the value of the cutoff parameter of the regulator. We also compare predictions based on the complete N2LO potential with those based on the two-nucleon force upgraded to the N4LO+ order and augmented with the N2LO three-nucleon force. In addition, we study the three-nucleon force effects predicted by this model of interaction. Our systematic study covers the entire kinematically allowed phase space; however, our main results are obtained when additional restrictions on energies and cross section values are imposed. In such a case, we observe that the dependence of the differential cross sections on the regulator cutoff is moderate at 135 MeV and much stronger at 200 MeV. For the latter energy, it can amount to up to 45% in specific kinematic configurations. Taking into account terms beyond, N2LO in a two-body interaction changes the cross section up to 20% (27%) at E = 135(200) MeV. The inclusion of the three-nucleon force leads to effects of approximately 27% at both energies. We illustrate these dependencies with a few examples of the exclusive cross section as a function of the arc length of the S-curve.

Flux-integrated semiexclusive cross sections for charged-current quasielastic and neutral-current elastic neutrino scattering off Ar40 and a sterile neutrino oscillation study

Flux-integrated semiexclusive differential cross sections for charged-current quasielastic and neutral-current elastic neutrino scattering on argon are analyzed. The cross sections are calculated using the relativistic distorted-wave impulse approximation with values of the nucleon axial mass ${M}_{A}=1\text{ }\text{ }\mathrm{GeV}$ and 1.2 GeV. The elastic scattering cross sections are also computed for different strange quark contributions to the neutral-current axial form factor. The flux-integrated differential cross sections as functions of reconstructed neutrino energy are evaluated for the far detector of the SBN experiment. The effects of the short baseline neutrino oscillations are taken into account in a $3+1$ framework. We found that cross sections depend on oscillation parameters and the ratio of the measured and predicted cross sections can be used in a sterile neutrino oscillation study.

Determination of 170,172Yb(α,n)173,175Hf reaction cross sections in a stacked-target experiment

Background: For understanding the synthesis of elements in the universe, precise knowledge of reaction rates and cross sections is paramount. This is especially true for the $p$ process because its study requires large network calculations including thousands of nuclei and nuclear reactions with little room for simplification. Therefore, robust theoretical methods for predicting cross sections are needed which are usually based on Hauser-Feshbach calculations. These calculations use physics input in the form of $\ensuremath{\gamma}$-ray strength functions, nuclear level densities, and particle $+$ nucleus optical-model potentials. These have to be constrained using experimental results.Purpose: To constrain the $\ensuremath{\alpha}$ optical-model potential $\ensuremath{\alpha}$-induced reactions are well suited. The ytterbium isotopic chain not only offers multiple stable isotopes on which cross sections can be measured and insights into the evolution of the $\ensuremath{\alpha}$ optical-model potential with the neutron-to-proton ratio can be gained but also includes the $p$ nucleus $^{168}\mathrm{Yb}$. Its abundance is significantly impacted by the $^{164,166}\mathrm{Yb}(\ensuremath{\alpha},\ensuremath{\gamma})$ reactions and is, therefore, also affected by the constraints resulting from the experiment presented in this paper.Method: To study the $^{170,172}\mathrm{Yb}(\ensuremath{\alpha},n)^{173,175}\mathrm{Hf}$ reaction cross sections the activation method was used. During irradiation the targets were arranged in stacks of four to reduce the required irradiation time. Aluminum degrader foils served as backings. The average interaction energy inside each ytterbium layer was determined via geant4 simulations. A third layer, consisting of manganese, was used to verify the simulations by comparing the measured $^{55}\mathrm{Mn}(\ensuremath{\alpha},(2)n)^{57,58}\mathrm{Co}$ reaction cross sections to previous results. For irradiation the 10 MV FN tandem accelerator located at the University of Cologne was used and the activation measurement was performed utilizing the Cologne Clover Counting setup consisting of two clover-type high-purity germanium detectors in a face-to-face geometry.Results: For the $^{170}\mathrm{Yb}(\ensuremath{\alpha},n)$ reaction seven cross sections at center-of-mass energies between 12.7 and 16.5 MeV were measured. For the $^{172}\mathrm{Yb}(\ensuremath{\alpha},n)$ reaction six cross sections for center-of-mass energies of 13.1 to 16.5 MeV could be determined with an additional upper limit at ${E}_{\mathrm{c}.\mathrm{m}.}=12.3$ MeV.Conclusion: Comparisons to theoretical models show that state-of-the-art $\ensuremath{\alpha}$-optical model potentials reproduce the measured cross sections very well. The ratios of $(\ensuremath{\alpha},n)$ reaction cross sections in the ytterbium isotopic chain can be accurately reproduced as well.

Cross sections of the Rb83(p,γ)Sr84 and Kr84(p,γ)Rb85 reactions at energies characteristic of the astrophysical γ process

We have measured the cross section of the $^{83}\mathrm{Rb}(p,\ensuremath{\gamma})^{84}\mathrm{Sr}$ radiative capture reaction in inverse kinematics using a radioactive beam of $^{83}\mathrm{Rb}$ at incident energies of 2.4 and $2.7\phantom{\rule{0.16em}{0ex}}A$ MeV. Prior to the radioactive beam measurement, the $^{84}\mathrm{Kr}(p,\ensuremath{\gamma})^{85}\mathrm{Rb}$ radiative capture reaction was measured in inverse kinematics using a stable beam of $^{84}\mathrm{Kr}$ at an incident energy of $2.7A$ MeV. The effective relative kinetic energies of these measurements lie within the relevant energy window for the $\ensuremath{\gamma}$ process in supernovae. The central values of the measured partial cross sections of both reactions were found to be $0.17--0.42$ times the predictions of statistical model calculations. Assuming the predicted cross section at other energies is reduced by the same factor leads to a slightly higher calculated abundance of the $p$ nucleus $^{84}\mathrm{Sr}$, caused by the reduced rate of the $^{84}\mathrm{Sr}(\ensuremath{\gamma},p)^{83}\mathrm{Rb}$ reaction derived from the present measurement.

Associated $$\phi $$ and $$J/\Psi $$ photoproduction in ultraperipheral PbPb collisions at the Large Hadron Collider and Future Circular Collider

In this paper we analyze the associated $\phi$ and $J/\Psi$ photoproduction in ultraperipheral $PbPb$ collisions through the double scattering mechanism for the energies of the Large Hadron Collider (LHC) and Future Circular Collider (FCC). Our results complement a previous analysis for the $\rho\rho$, $J/\Psi J/\Psi$ and $\rho J/\Psi$ production. We present our predictions for the total cross sections and rapidity distributions considering the rapidity ranges covered by the ALICE and LHCb detectors, which indicate that a future experimental analysis of $\phi J/\Psi$ final state is feasible. These results point out that the study of the double vector meson photoproduction in heavy ion collisions can be useful to constrain the double scattering mechanism and improve our understanding of the QCD dynamics at high energies.