The total photon-proton cross section for hadron production

The total hadronic cross section, σ_T has been measured for tagged γ-rays, using electron beams in the GeV range, and narrow energy bins. Preliminary data are given covering the γ-energy region 275 MeV-1850 MeV, where interesting structure characteristics are observed.     

A semi-empirical formula for the neutron total cross section and the interpretation of the empirical formula forA ⩾ 40

Weaknesses in Angeli and Csikai’s interpretation of their empirical formula for the neutron total cross section (σ _T) are pointed out. Using the Fourier-Bessel re-presentation of the scattering amplitude a semi-empirical formula forσ _T is obtained which has greater applicability and also explains the success of the empirical formula for mass numberA ⩾ 40 in terms of the established trends in neutron optical potential parameters.     

On the Thomson cross section of light scattering by a moving particle

The Thomson cross section of light scattering is calculated for a moving particle within classical electrodynamics.     

Study of the total reaction cross section via QMD

This paper presents a new empirical formula to calculate the average nucleon-nucleon (N-N) collision number for the total reaction cross sections (σ_R). Based on the initial average N-N collision number calculated by quantum molecular dynamics (QMD), quantum correction and Coulomb correction are taken into account within it. The average N-N collision number is calculated by this empirical formula. The total reaction cross sections are obtained within the framework of the Glauber theory. σ_R of ²³Al+¹²C, ²⁴Al+¹²C, ²⁵Al+¹²C, ²⁶Al+¹²C and ²⁷Al+¹²C are calculated in the range of low energy. We also calculate the σ_R of ²⁷Al+¹²C with different incident energies. The calculated σ_R are compared with the experimental data and the results of Glauber theory including the σ_R of both spherical nuclear and deformed nuclear. It is seen that the calculated σ_R are larger than σ_R of spherical nuclear and smaller than σ_R of deformed nuclear, whereas the results agree well with the experimental data in low-energy range.     

The total cross section for the production of heavy quarks in hadronic collisions

We present the results of a full calculation of the QCD O(α_S³) radiative corrections to the total cross section for the production of a heavy quark pair. We find large contributions for parton subenergies near threshold and well above threshold. The implications for the production of top and bottom quarks at collider energies are discussed.     

An experimental limit on the coupling of a light neutral pseudoscalar particle to hadrons

Detailed results of an experiment, looking for a short-lived neutral particle decaying by ane ⁺ e ⁻ pair in the decay of the 3.68 MeV (3/2) state in¹³C, whose decay is predominantly M1, are presented. An upper limit of 7 × 10⁻⁵ has been placed on the branching ratio for decay through such a particle with a mass in the range 1.7 to 1.9 MeV/c². This leads to an upper limit of 10⁻⁶ for the coupling of such a particle to nucleons. Such a limit rules out the explanation of thee ⁺ ande ⁻ peaks recently observed in heavy ion collisions, as due to the decay of a neutral particle.     

A semi-empirical formula for total cross sections of electron scattering from diatomic molecules

A fitting formula based on the Born approximation is used to fit the total cross sections for electron scattering by diatomic molecules (CO, N₂, NO, O₂ and HCl) in the intermediate- and high-energy range. By analyzing the fitted parameters and the total cross sections, we found that the internuclear distance of the constituent atoms plays an important role in the e-diatomic molecule collision process. Thus a new semi-empirical formula has been obtained. There is no free parameter in the formula, and the dependence of the total cross sections on the internuclear distance has been reflected clearly. The total cross sections for electron scattering by CO, N₂, NO, O₂ and HCl have been calculated over an incident energy range of 10–4000 eV. The results agree well with other available experimental and calculation data.     

Temperature effects on the absorption cross section of a small conductive particle

Temperature effects on the absorption cross section of a small conductive spherical particle were investigated. Calculations were performed in terms of the kinetic approach for the case where the contribution of eddy currents to the absorption dominated and provided that the particle size was small compared to the skin depth. The latter condition allows the skin effect to be disregarded.     

On the scale variation of the total cross section for Higgs production at the LHC and at the Tevatron

We present a detailed study of the total pp cross section for scalar Higgs production to next-to-next-to-leading order in α_s at LHC energies, and of the pp̄ cross section at the Tevatron, combining an implementation of the solutions of the parton evolution equations at the three-loop order with the corresponding hard scatterings, evaluated at the same perturbative order. Our solutions of the DGLAP equations are implemented directly in x-space and allow for the study of the dependence of the results on the factorization (μ_F) and renormalization scales (μ_R) typical of a given process, together with the stability of the perturbative expansion. The input sets for the parton evolutions are those given by Martin, Roberts, Stirling and Thorne and by Alekhin. Results for K-factors are also presented. The NNLO corrections can be quite sizeable at typical collider energies. The stability region of the perturbative expansion is found when μ_R>m_H∼μ_F.     

Experimental cross section for dimuon production and the Drell-Yan model

We have measured the absolute cross section for dimuon production in hadron collisions at 200 GeV/c in the continuum region M = 4–8.5 GeV. In all the channels studied (pN, $\text{p}$N, π^±N and π^?H₂) the experimental cross section is significantly larger by a factor of 2.3 ± 0.5 than expected from the Drell-Yan model. Furthermore, our proton-nucleon data allow a determination of the nucleon valence structure function which agrees with the deep inelastic lepton scattering data.     

The pomeron-particle total cross section and diffractive production of showers at very high energies

The experimental data of ISR and NAL for the process pp → pX are used for the determination of the pomeron-particle total cross section and the triple-pomeron vertex. Estimates of the cross sections of the diffractive production of one and several showers of particles are given. It is shown that at s ～ 10³ GeV² the cross section of all inelastic diffractive processes is ～ 6 mb and grows with energy. A theoretical estimate of the amplitude of pomeron-pomeron scattering is given.     

General derivation of the total electromagnetic cross sections for an arbitrary particle

This work concerns a common problem in electromagnetic scattering; calculation of the total scattering, extinction, and absorption cross sections for an arbitrary particle. Typical expressions for the cross sections are obtained in terms of the vector spherical wave function expansions for the incident and scattered waves. The unique aspect of this work is that the derivation is carried out specifically without use of the far-field zone approximation. The resulting expressions, valid at any distance, exactly match those obtained from the far-field approximation. This demonstrates that the cross sections are independent of the distance from the particle at which they are calculated as one would expect from energy conservation. Numerical simulations of the near and far-field zone energy flows due to a spherical particle are presented to illustrate several implications of this result.     

Double differential cross sections of light charged particle production for the n+~(238)U reaction

Production of light complex particles from the n+~(238) U reaction is analyzed with the exciton model including the improved Iwamoto-Harada pickup mechanism for the preequilibrium process. It is allowed that some of the nucleons forming the complex ejectile come from levels below the Fermi energy, and the intrinsic structure of the emitted particle is taken into account. The equilibrium-state emissions are also considered by using HauserFeshbach theory with the width fluctuation correction and the evaporation model. Moreover, all cross sections,angular distributions, energy spectra and double differential cross sections of neutron, proton, deuteron, triton and alpha emissions for the n+~(238) U reaction are consistently calculated and analyzed with nuclear theoretical models in the energy range En 150 MeV. ENDF-formatted nuclear data including information about the production of light charged particles are obtained.     

A model for πp,Kp and ψp total cross section ratios

We calculate the ratios of πp, Kp and ψp total cross sections utilizing coupled homogeneous linear integral equations supplemented with SU(4) symmetry for the couplings. Kinematic effects arising from mass splitting and t_min effects are crucial. We obtain $\text{σ}{}_{\mathrm{<mtext>\pi </mtext><mtext>p</mtext>}}\text{σ}{}_{\mathrm{<mtext>Kp</mtext>}}\text{≈ 1.7}\text{and}\text{σ}{}_{\mathrm{<mtext>\psi </mtext><mtext>p</mtext>}}\text{σ}{}_{\mathrm{<mtext>\pi </mtext><mtext>p</mtext>}}\text{≈}\text{1}\text{50}$.     

Watson representation for the amplitude of lepton-pair production in nucleus-nucleus collisions

An expression for the amplitude of lepton pair production in nucleus-nucleus collisions is obtained in terms of the amplitudes of lepton-nucleus scattering. By using this representation an approximate compact expression for this amplitude valid to terms of the order (Zα)⁵ is obtained.