Energy Dependence Of Cross Section Research Articles

Study of electron and positron elastic scattering cross-sections of astro molecule H2S

Abstract The elastic, integrated, momentum transfer, viscosity, energy-dependent, and differential cross-sections and the Sherman function for electron and positron H2S scattering are reported at impact energies ranging from 1 eV to 1 MeV. The average orientations of the polar molecule H2S are considered, and the electron and positron elastic scattering cross-sections of H2S are typically calculated using single scattering-independent atom approximation. The relativistic Dirac equation is solved using the free atom optical potential, which includes the electrostatic interaction potential, exchange potential, correlation polarization potential, and imaginary absorption potential. The present computed cross-section results are compared with the available experimental and theoretical results, and a reasonable agreement is observed.

Measurement of the e+e−→KSKL cross section near the ϕ(1020) resonance with the SND detector

The cross section for the e+e−→KSKL process is measured in the center-of-mass energy range from 1000 to 1100 MeV in the experiment with the SND detector at the VEPP-2000 e+e− collider. The measurement is carried out in the KS→2π0 decay mode. Data with an integrated luminosity of 20 pb−1 recorded in 2018 at 18 energy points are used in the analysis. The systematic uncertainty in the measured cross section at the maximum of the ϕ resonance is 0.9%. The mass, width of the ϕ meson, and the product of the branching fractions B(ϕ→KSKL)B(ϕ→e+e−) are determined from the fit to the cross section energy dependence. Published by the American Physical Society 2024

Enthalpy of the Cerium (Ce) Chemi-Ionization Reaction and CeO+, CeC+, and CeCO+ Bond Energies Determined by Energy-Resolved Guided Ion Beam Mass Spectrometry Experiments.

Cerium (Ce) oxide, carbide, and carbonyl cation bond energies and the exothermicity of the Ce chemi-ionization (CI) reaction with atomic oxygen were investigated using guided-ion beam tandem mass spectrometry (GIBMS). The kinetic energy dependent product cross sections for reactions of Ce+ with O2, CO, and CO2 and CeO+ with O2, CO, Xe, and Ar were measured using GIBMS. For the reactions of Ce+ with O2 and CO2, CeO+ is formed through an exothermic reaction, whereas CeO+ formation is endothermic in the reaction with CO. This reaction also forms CeC+ and CeCO+ is formed in the reaction of Ce+ with CO2, both in endothermic processes. Reactions of CeO+ with all four gases led to endothermic collision-induced dissociation as well as exchange reactions to form CeO2+ for the O2 and CO reactants. Bond dissociation energies (BDEs) at 0 K were determined through analyses of the kinetic energy dependent cross sections for all endothermic reactions. We determined that the BDEs of CeO+, CeC+, and CeCO+ are 8.46 ± 0.15, 3.93 ± 0.16, and ≥0.25 ± 0.07 eV, respectively, where the CeO+ BDE is a weighted average of 6 independent 0 K threshold measurements. The CeO+ BDE is combined with the ionization energy (IE) of Ce to determine an exothermicity of 2.91 ± 0.15 eV for the Ce + O → CeO+ + e- chemi-ionization reaction. Combined with neutral BDEs from the literature, the thermochemistry determined here also provides IE(CeO) = 5.03 ± 0.12 eV and IE(CeC) = 6.50 ± 0.16 eV. Theoretical calculations for ground and some excited states were performed for CeO+, CeC+, and CeCO+ to provide insight into the bonding and a comparison with the experimentally determined BDEs for each molecule.

Physics of near-threshold resonances

In this paper, we present our approach to the treatment of final-state interaction of hadrons. It is based on the assumption that quark–antiquark pairs are produced at small distances, while the interaction of hadrons takes place at larger distances. As a result, the effects of final-state interaction are determined by the wave function of produced hadronic system. The account for final-state interaction within this approach allows us to successfully describe the energy dependence of cross-sections of many processes, as well as electromagnetic form factors of hadrons.

Energy efficient F atom generation and control in CF4 capacitively coupled plasmas driven by tailored voltage waveforms

Abstract Neutral radicals generated by electron impact dissociation of the background gas play important roles in etching and deposition processes in low pressure capacitively coupled plasmas (CCPs). The rate and energy efficiency of producing a given radical depend on the space- and time-dependent electron energy distribution function (EEDF) in the plasma, as well as the electron energy dependent cross sections of the electron-neutral collisions that result in the generation of the radical. For the case of a CCP operated in CF4 gas, we computationally demonstrate that the energy efficiency of generating neutral radicals, such as F atoms can be improved by controlling the EEDF by using tailored voltage waveforms (TVW) instead of single-frequency driving voltage waveforms and that separate control of the radical density and the ion energy can be realized by adjusting the waveform shape at constant peak-to-peak voltage. Such discharges are often used for industrial etching processes, in which the F atom density plays a crucial role for the etch rate. Different voltage waveform shapes, i.e. sinusoidal waveforms at low (13.56 MHz) and high (67.8 MHz) frequencies, peaks- and sawtooth-up TVWs, are used to study their effects on the energy cost / energy efficiency of F atom generation by PIC/MCC simulations combined with a stationary diffusion model. The F atom density is enhanced by increasing the voltage amplitude in the single frequency cases, while the energy cost per F atom generation increases, i.e. the energy efficiency decreases, because more power is dissipated to the ions, as the sheath voltages and the ion energy increase simultaneously. In contrast, using TVWs can result in a lower energy cost and provide separate control of the F atom density and the ion energy. This is explained by the fact that tailoring the waveform shape in this way allows to enhance the high-energy tail of the EEDF during the sheath expansion phase by inducing a non-sinusoidal sheath motion, which results in acceleration of more electrons to high enough energies to generate F atoms via electron-neutral collisions compared to the single frequency cases. Similar effects of TVWs are expected for the generation of other neutral radicals depending on the electron energy threshold and the specific consequences of TVWs on the EEDF under the discharge conditions of interest.

Quantifying the U 5f covalence and degree of localization in U intermetallics

A procedure for quantifying the U 5f electronic covalency and degree of localization in U intermetallic compounds is presented. To this end, bulk sensitive hard and soft x-ray photoelectron spectroscopy were utilized in combination with density-functional theory (DFT) plus dynamical mean-field theory (DMFT) calculations. The energy dependence of the photoionization cross sections allows the disentanglement of the U 5f contribution to the valence band from the various other atomic subshells so the computational parameters in the DFT+DMFT can be reliably determined. Applying this method to UGa2 and UB2 as model compounds from opposite ends of the (de)localization range, we have achieved excellent simulations of the valence band and core-level spectra. The width in the distribution of atomic U 5f configurations contributing to the ground state, as obtained from the calculations, quantifies the correlated nature and degree of localization of the U 5f. The findings permit answering the longstanding question why different spectroscopic techniques give seemingly different numbers for the U 5f valence in intermetallic U compounds. Published by the American Physical Society 2024

Energy-dependent boosted dark matter from diffuse supernova neutrino background

Diffuse neutrinos from past supernovae in the Universe present us with a unique opportunity to test dark matter (DM) interactions. These neutrinos can scatter and boost the DM particles in the Milky Way halo to relativistic energies allowing us to detect them in terrestrial laboratories.Focusing on generic models of DM-neutrino and electron interactions, mediated by a vector or a scalar boson, we implement energy-dependent scattering cross-sections and perform detailed numerical analysis of DM attenuation due to electron scattering in-medium while propagating towards terrestrial experiments. We set new limits on DM-neutrino and electron interactions for DM with masses in the range ∼ (0.1, 104) MeV, using recent data from XENONnT, LUX-ZEPLIN, and PandaX-4T direct detection experiments. We demonstrate that consideration of energy-dependent cross-sections for DM interactions can significantly affect constraints previously derived under the assumption of constant cross-sections, modifying them by multiple orders of magnitude.

Cross section measurement of e+e−→ηψ(2S) and search for e+e−→ηX˜(3872)

The energy-dependent cross section for e+e−→ηψ(2S) is measured at 18 center of mass energies from 4.288 to 4.951 GeV using the BESIII detector. Using the same data samples, we also perform the first search for the reaction e+e−→ηX˜(3872), but no evidence is found for the X˜(3872) in the π+π−J/ψ mass distribution. At each of the 18 center of mass energies, upper limits at the 90% confidence level on the cross section for e+e−→ηψ(2S) and on the product of the e+e−→ηX˜(3872) cross section with the branching fraction of X˜(3872)→π+π−J/ψ are reported. Published by the American Physical Society 2024

Ratio of J/Ψ and Ψ(2s) exclusive photoproduction cross sections as an indicator for the presence of nonlinear QCD evolution

We investigate the proposal that the rise with energy of the ratio of the exclusive photoproduction cross sections of vector mesons Ψ(2s) and J/Ψ can serve as an indicator for the presence of high gluon densities and associated nonlinear high energy evolution; we study this proposal for both photoproduction on a proton and a lead nucleus. While previous studies were based on unintegrated gluon distributions subject to linear (Balitsky-Fadin-Kuraev-Lipatov) and nonlinear (Balitsky-Kovchegov) evolution equations, the current study is based on the Golec-Biernat Wüsthoff and Bartels Golec-Biernat Kowalski models, which allows us to assess more directly the relevance of nonlinear corrections for the description of the energy dependence of the photoproduction cross section. We find that the rise of the ratio is directly related to the presence of a node in the Ψ(2s) wave function and only manifests itself for the complete nonlinear models, while it is absent for their linearized versions. We further provide predictions based on leading order collinear factorization and examine to which extent such an approach can mimic a ratio rising with energy. We also provide a description of recent ALICE data on the energy dependence of the photonuclear J/Ψ production cross section and give predictions for the energy dependence of the ratio of Ψ(2s) and J/Ψ photoproduction cross sections for both scattering on a proton and a lead nucleus. Published by the American Physical Society 2024

Nuclear reaction cross sections and the optical potentials and for the n-12C and N-12C scattering

In this talk we first discuss total cross sections for the system n-12C in the incident energy range 20-500 MeV, calculated with a phenomenological optical potential and the optical model. We compare with calculations done with the eikonal model using the same potential and a single folding potential in the optical limit. Several single folding potentials are obtained using 12C densities from different models. These potentials are sensitive to the density used and none of them reproduces the characteristics of the phenomenological potential nor the cross section results. We then discuss nucleus-nucleus potentials and reaction cross sections for some projectiles on 12C within the eikonal formalism. We find that single folded projectile-target imaginary potentials and double folded potentials can produce similar energy dependence of the reaction cross sections but the single folding results agree better with experimental data provided the radius parameter of the phenomenological n-target potential is allowed to be energy dependent. We conclude that a single folding nucleusnucleus potential build on a phenomenological nucleon-nucleus potential can constitute an interesting and useful alternative to double folding potentials.

Electron-induced ionization cross-sections for C5H5N

The secondary electron energy-dependent partial differential ionization cross sections at fixed incident electron energies 100 and 200 eV and their integral or total ionization cross sections in the incident electron energy range ionization threshold to 5 keV for C5H5N Bio-molecule due to electron impact corresponding to the produced major cations are calculated by employing revisited Jain-Khare semiempirical approach. The averaged secondary electron energy and the ionization rate coefficients are calculated from the ionization threshold to 5 keV. The present results are compared with available experimental and theoretical results and are found to be in satisfactory agreement.

Measurement of e+e−→pK−Λ¯+c.c.\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {e}^{+}{e}^{-}\ o p{K}^{-}\\overline{\\Lambda}+c.c. $$\\end{document} cross sections between 4.009 GeV and 4.951 GeV

Using e+e− collision datasets corresponding to a total integrated luminosity of 21.7 fb−1 collected with the BESIII detector at the BEPCII collider at center-of-mass energies ranging from 4.009 GeV to 4.951 GeV, the energy-dependent cross sections of e+e−→pK−Λ¯+c.c.\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {e}^{+}{e}^{-}\ o p{K}^{-}\\overline{\\Lambda}+c.c. $$\\end{document} are measured for the first time. By fitting these energy-dependent cross sections, we search for the excited ψ states ψ(4160) and ψ(4415), and the vector charmonium-like states ψ(4230), ψ(4360), and ψ(4660). No evidence for these is observed and the upper limits on the branching fractions of these states decaying into pK−Λ¯+c.c.\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ p{K}^{-}\\overline{\\Lambda}+c.c. $$\\end{document} are set at the 90% confidence level.

Precise Measurement of the e^{+}e^{-}→D_{s}^{*+}D_{s}^{*-} Cross Sections at Center-of-Mass Energies from Threshold to 4.95GeV.

The process e^{+}e^{-}→D_{s}^{*+}D_{s}^{*-} is studied with a semi-inclusive method using data samples at center-of-mass energies from threshold to 4.95GeV collected with the BESIII detector operating at the Beijing Electron Positron Collider. The Born cross sections of the process are measured for the first time with high precision in this energy region. Two resonance structures are observed in the energy-dependent cross sections around 4.2 and 4.4GeV. By fitting the cross sections with a coherent sum of three Breit-Wigner amplitudes and one phase-space amplitude, the two significant structures are assigned masses of (4186.8±8.7±30) and (4414.6±3.4±6.1) MeV/c^{2}, widths of (55±15±53) and (122.5±7.5±8.1) MeV, where the first errors are statistical and the second ones are systematic. The inclusion of a third Breit-Wigner amplitude is necessary to describe a structure around 4.79GeV.

Coupled channels and production of near-threshold [formula omitted] resonances in e+e− annihilation

The effects of final-state interaction of hadrons, produced in e+e− annihilation near the threshold, are discussed. If there is a loosely bound state or a virtual state in a system of produced hadrons, then the energy dependence of hadroproduction cross section is very strong. Our approach is based on the use of the effective potentials accounting for the interaction between hadrons in the final state. The cases of a few channels with nonzero transition amplitudes between them are considered. It is shown that these transitions drastically change the energy dependence of the cross sections. In particular, a narrow resonance below the threshold in one channel leads to a broad peak in another channel. We explained the non-trivial energy dependence of the production cross sections of BB¯, B⁎B¯, BB¯⁎, B⁎B¯⁎ near the thresholds in e+e− annihilation and obtained good agreement between our predictions and the experimental data available.

Exclusive Photo-production of J/Ψ and Ψ(2s) as a tool to explore the transition to high and saturated gluon densities at the LHC.


 
 
 We study the energy dependence of the cross-section for exclusive photo-production of vector mesons J/Ψ and Ψ(2s) and search for signs for the onset of non-linear QCD dynamics in this observable. Our study is based on two dipole models: the Golec-Biernat, Wuesthoff Model (GBW) and the Bartels, Golec-Biernat, Kowal- ski Model (BGK). We find that differences between linear and non-linear implementations of these models are relatively small in the kinematic region probed by both HERA and LHC experiments if the energy dependence of the photo-production cross-section is being considered. We however find that the ratio of both cross-sections grows with energy in the presence of non-linear effects, while it remains approximately constant in the linearized case. The ratio of photo-production cross-sections might therefore provide a suitable tool to characterize the size of non-linear QCD effects at current collider energies.
 
 

Amplitudes of 3H, 3He Two-Particle Photo-Breakup in Non-Local QED Approach

Three-nucleon systems are essential for the investigation of many-body forces in nuclear physics. Well-grounded parametrization of their vertex functions with further application for the calculation of cross-sections in nonlocal QED approach provides the ground for investigation of the variety of multi-particle systems. In present paper we describe the process of parametrization of two-particle photo-breakup amplitudes of three-nucleon systems (3H, 3He). We provide the general description of the wave function construction for three-nucleon systems as well as the parametrization of their vertex functions accounting two- and three-nucleon interactions based on meson exchange current formalism. In our calculations we account first and second order one-pion exchange terms and the term related to the exchange of ω and ρ mesons. The three-nucleon interaction potential is given as a sum of attraction (two-pion exchange) term andappropriate repulsive part. Based on the variational ”Urbana + Model VII” amplitudes we provide the results for energy dependence of differential cross-section of 3He(γ, p)d reaction at proton angle θ = 90◦ from the threshold up to Eγ = 40 MeV and compare theoretical predictions with the available experimental data. The investigation is also provided for angular cross-section distributions at high photon energies (Eγ = 305 ± 5 MeV; 365 ± 5 MeV; 450 ± 10 MeV and 675 ± 50 MeV). Correct description of 3H, 3He photo-disintegration processes in a unified approach based on the gauge nature of the electromagnetic field implies application of this model for other multi-particle systems.

Spin-orbit charge transfer from guanine and 9-methylguanine radical cations to nitric oxide radicals and the induced triplet-to-singlet intersystem crossing.

Nitric oxide (●NO) participates in many biological activities, including enhancing DNA radiosensitivity in ionizing radiation-based radiotherapy. To help understand the radiosensitization of ●NO, we report reaction dynamics between ●NO and the radical cations of guanine (a 9HG●+ conformer) and 9-methylguanine (9MG●+). On the basis of the formation of 9HG●+ and 9MG●+ in the gas phase and the collisions of the radical cations with ●NO in a guided-ion beam mass spectrometer, the charge transfer reactions of 9HG●+ and 9MG●+ with ●NO were examined. For both reactions, the kinetic energy-dependent product ion cross sections revealed a threshold energy that is 0.24 (or 0.37) eV above the 0K product 9HG (or 9MG) + NO+ asymptote. To interrogate this abnormal threshold behavior, the reaction potential energy surface for [9MG + NO]+ was mapped out at closed-shell singlet, open-shell singlet, and triplet states using density functional and coupled cluster theories. The results showed that the charge transfer reaction requires the interaction of a triplet-state surface originating from a reactant-like precursor complex 3[9MG●+(↑)⋅(↑)●NO] with a closed-shell singlet-state surface evolving from a charge-transferred complex 1[9MG⋅NO+]. During the reaction, an electron is transferred from π∗(NO) to perpendicular π∗(9MG), which introduces a change in orbital angular momentum. The latter offsets the change in electron spin angular momentum and facilitates intersystem crossing. The reaction threshold in excess of the 0K thermochemistry and the low charge-transfer efficiency are rationalized by the vibrational excitation in the product ion NO+ and the kinetic shift arising from a long-lived triplet intermediate.

Enhanced Deuteron Coalescence Probability in Jets.

The transverse-momentum (p_{T}) spectra and coalescence parameters B_{2} of (anti)deuterons are measured in p-p collisions at sqrt[s]=13 TeV for the first time in and out of jets. In this measurement, the direction of the leading particle with the highest p_{T} in the event (p_{T}^{lead}>5 GeV/c) is used as an approximation for the jet axis. The event is consequently divided into three azimuthal regions, and the jet signal is obtained as the difference between the toward region, that contains jet fragmentation products in addition to the underlying event (UE), and the transverse region, which is dominated by the UE. The coalescence parameter in the jet is found to be approximately a factor of 10 larger than that in the underlying event. This experimental observation is consistent with the coalescence picture and can be attributed to the smaller average phase-space distance between nucleons in the jet cone as compared with the underlying event. The results presented in this Letter are compared to predictions from a simple nucleon coalescence model, where the phase-space distributions of nucleons are generated using pythia8 with the Monash 2013 tuning, and to predictions from a deuteron production model based on ordinary nuclear reactions with parametrized energy-dependent cross sections tuned on data. The latter model is implemented in pythia8.3. Both models reproduce the observed large difference between in-jet and out-of-jet coalescence parameters, although the almost flat trend of the B_{2}^{Jet} is not reproduced by the models, which instead give a decreasing trend.

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

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

Bond Energies of UO+ and UC+: Guided Ion Beam and Quantum Chemical Studies of the Reactions of Uranium Cation with O2 and CO

AbstractGuided ion beam tandem mass spectrometry was used to examine the kinetic energy dependent reactions of U+ with O2 and CO. In the reaction of U+ with O2, the UO+ product is formed in a barrierless and exothermic process with a reaction efficiency at low energies of k/kcol=1.1±0.2, but increases at higher collision energies. Formation of both UO+ and UC+ in the reaction of U+ with CO is endothermic. 0 K bond dissociation energies (BDEs) of D0(U+‐O)=7.88±0.09 eV and D0(U+‐C)=4.03±0.13 eV were determined by analyzing the kinetic energy dependent cross sections in the latter endothermic reactions. These values are within experimental uncertainty of previously reported experimental values. Additionally, the electronic states of UO+ and UC+ and the potential energy surfaces for the reactions were explored by quantum chemical calculations. The former include a full Feller‐Peterson‐Dixon composite approach with correlation contributions up to CCSDT(Q) for UO and UO+, yielding D0(U‐O)=7.82 eV and D0(U+‐O)=7.99 eV, as well as more approximate CCSD(T) calculations where a semi‐empirical model was used to estimate spin‐orbit energy contributions, which are generally found to improve the agreement with experiment. Both experimental BDEs are observed to be close to those of their transition metal congeners, ScL+, YL+, and GdL+ (L=O and C).