Simple approximation of cross sections for nuclear reactions involving Z = 3–12, 14 nuclei

A compact cross section data base is obtained for almost 5000 nonresonance nuclear reactions involving stable and unstable Be, B, C, N, O, F, Ne, Na, Mg, and Si isotopes. The calculations are performed using the Sãn Paulo potential and the barrier penetration formalism. The calculated cross sections are approximated by simple analytical formulas. The results are necessary for simulating nuclear burning in neutron stars.     

A simplified Glauber model for hadron–nucleus cross sections

A model for hadron–nucleus cross sections based on a simplified Glauber approach is proposed. The predictions of the model are compared with experimental data for the inelastic and the total hadron–nucleus cross sections from available databases. The model has been implemented in the framework of the Gent4 toolkit.     

Complex scattering potential – ionization contribution (CSP-ic) method for calculating total ionization cross sections on electron impact

In this article, we report calculations of total ionization cross sections, Q _ion , for simple atoms (C, N, O, F) and molecules (NO and NH₃)_{3}) of atmospheric interest on electron impact at energies from threshold to 2000 eV. We have employed the complex scattering potential – ionization contribution (CSP-ic) method for the present study. Attempt has been made to improve the method by computing the parameter that involves the ratio of sum of the total excitation cross sections (Σ Q _exc ) and total inelastic cross section (Q _inel ) at the peak of the inelastic cross section. The present study not only provided a better estimation of the parameter involved in the CSP-ic method but also provided better agreement with the available experimental and theoretical data on the ionization cross sections of the simple atomic and molecular targets studied here.     

M_(αβ) X-ray production cross sections of Pb and B iby 9–40 keV electron impact

The experimental data of Mαβ X-ray production cross sections for Pb and Bi by 9–40 keV electron impact have been given. Thin films with thick carbon substrates are used in the experiment. The effects of target structure on the Mαβ X-ray production cross sections are corrected by using the Monte Carlo method. The corrected experimental data are compared with calculated cross sections in terms of the distorted-wave Born approximation(DWBA) theory. The measured Mαβ X-ray production cross sections for Pb and Bi are lower than the DWBA calculations. The atomic relaxation parameters used in comparing the DWBA values with experimental results affect the degree of difference.     

Electron impact ionization cross sections for Li-like Al ion in ground and excited states

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Temperature-dependent cross sections for meson–meson nonresonant reactions in hadronic matter

We present a potential of which the short-distance part is given by one gluon exchange plus perturbative one- and two-loop corrections and of which the large-distance part exhibits a temperature-dependent constant value. The Schrödinger equation with this temperature-dependent potential yields a temperature dependence of the mesonic quark–antiquark relative-motion wave function and of meson masses. The temperature dependence of the potential, the wave function and the meson masses brings about temperature dependence of cross sections for the nonresonant reactions $\pi \pi \to \rho \rho$ for $I=2$, $KK\to K^{*}{K}^{*}$ for $I=1$, $K{K}^{*}\to K^{*}{K}^{*}$ for $I=1$, $\pi K\to \rho K^{*}$ for $I=3/2$, $\pi K^{*}\to \rho K^{*}$ for $I=3/2$, $\rho K\to \rho K^{*}$ for $I=3/2$ and $\pi K^{*}\to \rho K$ for $I=3/2$. As the temperature increases, the rise or fall of peak cross sections is determined by the increased radii of initial mesons, the loosened bound states of final mesons, and the total-mass difference of the initial and final mesons. The temperature-dependent cross sections and meson masses are parametrized.     

Double-hump resonance structure of the cross sections for electron impact ionization of Ar5+

Configuration-average distorted-wave calculations are carried out for electron-impact ionization of Ar5+. Both direct ionization and the indirect excitation autoionization processes are included in our calculations. Our theoretical values are in quite reasonable agreement with the experimental data. The indirect processes contribute up to 50% to the total ionization cross sections. The possible origin of double-hump resonance structure of the cross sections is demonstrated and the contributions of metastable states are also taken into account.     

Double-hump resonance structure of the cross sections for electron impact ionization of Ar^5 ＋

Configuration-average distorted-wave calculations are carried out for electron-impact ionization of Ar^5 ＋ .Both direct ionization and the indirect excitation autoionization processes are included in our calculations. Our theoretical values are in quite reasonable agreement with the experimental data. The indirect processes contribute upto 50% to the total ionization cross sections. The possible origin of double-hump resonance structure of the crcessections is demonstrated and the contributions of metastable states are also taken into account.     

Infrared absorption cross sections for acetone (propanone) in the 3 μm region

Infrared absorption cross sections for acetone (propanone), CH₃C(O)CH₃, have been determined in the 3 μm spectral region from spectra recorded using a high-resolution FTIR spectrometer (Bruker IFS 125 HR) and a multipass cell with a maximum optical path length of 19.3 m. The spectra of mixtures of acetone with dry synthetic air were recorded at 0.015 cm⁻¹ resolution (calculated as 0.9/MOPD using the Bruker definition of resolution) at a number of temperatures and pressures (50-760 Torr and 195-296 K) appropriate for atmospheric conditions. Intensities were calibrated using three acetone spectra (recorded at 278, 293 and 323 K) taken from the Pacific Northwest National Laboratory (PNNL) IR database.     

Cross sections for leptophobic topcolor Z′ decaying to top–antitop

We present numerical calculations of the production cross section of a heavy Z?? resonance in hadron?Chadron collisions with subsequent decay into top?Cantitop pairs. In particular, we consider the leptophobic topcolor Z?? discussed under Model IV of hep-ph/9911288, which has predicted cross sections large enough to be experimentally accessible at the Fermilab Tevatron and the Large Hadron Collider at CERN. This article presents an updated calculation valid for the Tevatron and all proposed LHC collision energies. Cross sections are presented for various Z?? widths, in $p\bar{p}$ collisions at $\sqrt{s}=2\mbox{~TeV}$ , and in pp collisions at $\sqrt{s}=7, 8, 10 \mbox{ and } 14\mbox{~TeV}$ .     

Electron impact total(elastic+inelastic) cross sections with simple molecules consisting of N & O atoms at 100-1600eV

A model complex optical potential rewritten by the conception of bonded atom, which considers the overlapping effect of electron cloud, is employed to calculate the total (elastic + inelastic) cross sections with simple molecules (N2, O2, NO2, NO, N2O) consisting of N & O atoms over an incident energy range of 100 - 1600 eV by the use of additivity rule at Roothaan-Hartree-Fock level. In the study, the complex optical potential composed of static, exchange, correlation polarization plus absorption contributions firstly uses bonded-atom conception. The qualitative results are compared with experimental data and other calculations wherever available and good agreement is obtained. The total cross sections of electron-molecule scattering above 100 eV can be successfully calculated.     

On next-to-eikonal corrections to threshold resummation for the Drell–Yan and DIS cross sections

We study corrections suppressed by one power of the soft gluon energy to the resummation of threshold logarithms for the Drell–Yan cross section and for Deep Inelastic structure functions. While no general factorization theorem is known for these next-to-eikonal (NE) corrections, it is conjectured that at least a subset will exponentiate, along with the logarithms arising at leading power. Here we develop some general tools to study NE logarithms, and we construct an ansatz for threshold resummation that includes various sources of NE corrections, implementing in this context the improved collinear evolution recently proposed by Dokshitzer, Marchesini and Salam (DMS). We compare our ansatz to existing exact results at two and three loops, finding evidence for the exponentiation of leading NE logarithms and confirming the predictivity of DMS evolution.     

Differential elastic and quenching cross sections for Ar*(3P) and CO2(X1 ∑ g +)

The energy dependence of the differential scattering of metastable Ar*(³P) by ground-state CO₂(X¹ ∑ _g ⁺) has been studied at relative kinetic energies from 58 to 126 meV over an angular range of 5–160° c.m. using crossed molecular beams. The position and curvature of rainbow maxima, which are observed at each energy, are used to obtain parameters for a Lennard-Jones (12, 6) spherically symmetric potential. The position of the minimum, r _m = 5·02 ± 0·65 Å, is identical to that for K + CO₂ and the well depth, ε = 16·3 ± 0·8 meV, is about 10 per cent greater. The scattered intensity shows a distinct fall-off on the dark side of the rainbow compared to that expected for elastically scattered Ar*. This depletion, caused primarily by the quenching of Ar*, is analysed in terms of the optical-shadow model to determine the energy dependence of the observed quenching cross section, which is predicted to have a maximum of 67 Ų at 193 meV.     

Electron impact total cross section calculations for CH3SH (methanethiol) from threshold to 5 keV

We report calculated total elastic cross sections Q_el, total ionisation cross sections, Q_ion, summed total excitation cross sections ∑Q_exc and total cross sections Q_T for CH₃SH upon electron impact for energies from ionisation threshold to 5 keV. We have employed Spherical Complex Optical Potential (SCOP) formalism to calculate total elastic cross section Q_el, and total inelastic cross section Q_inel and used Complex Scattering Potential – the ionisation contribution (CSP-ic) method to extract the ionisation cross sections, Q_ion, from the calculated Q_inel. The calculated total cross sections are examined as functions of incident electron energy and are compared with available data wherever possible and overall good agreement is observed. In this work Q_el, Q_ion, and ∑Q_exc are reported for the first time for CH₃SH in this energy range.     

Total cross sections for photoabsorption on light nuclei in the energy range 600–1500 MeV

Experimental data of the GRAAL Collaboration on the total cross sections for photoabsorption on deuterium and carbon targets at gamma-ray energies in the range between 600 and 1500 MeV are presented. The experiment was performed in a beam of photons obtained by the method of the Compton backscattering of laser photons at the electron storage ring of the European Synchrotron Radiation Facility (ESRF, Grenoble, France) by using a wide-aperture detector covering a solid angle close to 4π. The total photoabsorption cross sections were determined by two independent methods: by subtracting the emptytarget background and by summing partial cross sections for meson photoproduction. The total cross sections for photoabsorption on quasifree protons and neutrons are shown to agree both in magnitude and in shape within a 5% precision of the measurements. In contrast to data previously available in the literature, both cross sections show distinctly the F ₁₅(1680) resonance at a photon energy of about 1 GeV. Data obtained in the present experiment for the cross sections for photoabsorption on a free and a bound nucleon are compared. This comparison reveals a substantial role of two-nucleon correlations in estimating the nuclear-medium effect on meson photoproduction.     

A mean-field description of (γ, pi) cross sections at medium energies

Differential (γ, p_i) cross sections on ¹⁶O and ⁴⁰Ca have been calculated within a single-particle direct knock-out model, for photon energies between 40 and 400 MeV. It is shown that generating the bound and scattered states in a Skyrme Hartree-Fock (HF) mean-field, one can account for the global features of the data. Hereby, the role of the velocity-dependent part of the nucleon-nucleon interaction is emphasized.     

Systematical law of (n, γ) reaction cross sections of even-even nuclei

We have derived a formula for the neutron radiative capture cross section in the framework of a statistical model approach to nuclear reactions. Based on this formula, new systematics are established between the (n, γ) reaction cross section and the energy level density of a compound nucleus or a relative neutron excess of an even-even target nucleus for neutron incident energy above the resonance region to MeV. Good agreement with experimental data suggests that this new systematical law is helpful to analyze the experimental data.     

On the possibility for precision measurements of differential cross sections for elastic proton–proton scattering at the Protvino accelerator

Elastic-scattering data were analyzed, and it was concluded on the basis of this analysis that precisionmeasurements of differential cross sections for elastic proton–proton scattering at the accelerator of the Institute for High Energy Physics (IHEP, Protvino, Russia) over a broad momentum-transfer range are of importance and topical interest. The layout of the respective experimental facility detecting the scattered particle and recoil proton and possessing a high momentum-transfer resolution was examined along with the equipment constituting this facility. The facility in question is able to record up to a billion events of elastic proton–proton scattering per IHEP accelerator run (20 days). Other lines of physics research with this facility are briefly discussed.