Theoretical study of the stereodynamics for the reaction F+HBr

The vector correlation between products and reagents for exothermic reaction F + HBr → HF + Br has been studied using a quasi-classical trajectory (QCT) method on the latest extended Lond–Eyring–Polanyi–Sato (LEPS) potential energy surface at three collision energies of 0.1 eV, 0.2 eV and 0.3 eV. Four polarization- dependent generalized differential cross-sections (2π/σ)(dσ₀₀/dω _t ), (2π/σ)(dσ₂₀/dω _t ), (2π/σ)(dσ₂₂₊/dω _t ), (2π/σ)(dσ_21?/dω _t ) have been presented in the centre of mass frame, respectively. The distribution of dihedral angle P(φ _r ), the distribution of angle between k and j ′ , P(θ _r ), are calculated. Both the influence of the collision energy and the influence of the reagent rotation on the product polarization have been studied in the present work, and the results indicate that the product rotational angular momentum j ′ is not only aligned, but also oriented along the direction perpendicular to the scattering plane. The orientation of the HF product rotational angular momentum vector j ′ depends very sensitively on the reagent rotation and also effected by the collision energy.     

Disintegration of the deuteron by linearly polarized photons at low energies

The cross section and the Σ-asymmetry of the reaction d(γ^→,p) were measured in the energy interval E_γ = 5–10 MeV. Cross sections dσ and dσ_⊥ were derived from the measured quantities dσ₀ and Σ-asymmetry. The results are compared with theoretical calculations available for this energy region.     

A semi-classical model of multi-step direct and compound nuclear reactions

A semi-classical model of multi-step direct and compound nuclear reactions is proposed to describe the angular distributions of particles emitted from the inelastic scattering induced by a nucleon with an energy of several tens of MeV. The energy-angle correlation is exactly taken into account for the first few steps of the collision process (multi-step direct process) and the generalized master equation is employed for the following stages of collision process, using the energy-averaged kernelG(Ω → Ω′) (multicompound process). The calculations for¹⁹⁷Au(p, p′),¹²⁰Sn(p, p′) and⁹³Nb(n, n′) show that the model can rather nicely reproduce the experimental data of double-differential cross sections.     

The effect of the parton transverse motion in large-p⊥ reaction

The parton transverse motion within the incident hadrons cannot be neglected when calculating large-p_⊥ reaction cross sections in the framework of hard scattering models. We give a general discussion of this effect for a large class of models. The results depend strongly on the parametrization of the hard scattering cross section at small momentum transfer in the parton-parton center of mass. With reasonable assumptions, we find that the parton transverse motion enhances the hard scattering model predictions for Edσ/dp by a factor of two and reduces

$\text{E}\text{d}\text{N}\text{d}\text{p}\text{=}\text{∫}\text{d}\text{p′}\text{E′}\text{EE′}\text{d}{}^{\mathrm{(2)}}\text{σ}\text{d}\text{p}\text{d}\text{p′}\text{E′}\text{E′}\text{d}\text{σ}\text{d}\text{p′}$

by a comparable factor, in the range p_⊥ ? 2?3 GeV/c. We study the correlations between the large-p_⊥ trigger and the background low-p_⊥ secondaries and give an estimate of the encountered azimuthal asymmetry around the beam momentum with a simple model.     

Differential cross section and vector analysing power of the p pol p → {pp} s π0 reaction at 353–700 MeV

The reaction p _pol p → {pp} _s π⁰ was studied with the ANKE spectrometer at COSY-Jülich using a polarized beam with energies 353, 500, 550 and 700 MeV. The proton pairs {pp} _s were detected at low excitation energy E _pp < 3 MeV, where S-wave dominates. The angular dependences of vector analysing power A _y and differential cross section dσ/dΩ of the reaction have been obtained for the most of the angular range at 353 MeV and forward angles at the higher beam energies. The partial wave amplitude analysis, done with the 353 MeV results, is important for Chiral Perturbation Theory tests at this energy. The data at higher energies detalize the energy dependence of dσ/dΩ(0°) obtained earlier. It allows to learn about the dynamics of the Δ(1232) resonance excitation in two-nucleon systems.     

Compton scattering of gamma rays by electrons bound in heavy atoms

The energy spectra of 661.6 keV gamma rays scattered incoherently by lead have been measured for the scattering angles 62 °, 85 °, and 135 ° using a germanium detector. The differential cross sectionsdσdΩd E _y′ obtained from the experiment have been compared with formfactor calculations using relativistics-electron wave-functions for the initial state and relativistic Coulomb wave-functions for the unbound state. A good agreement has been obtained for large energiesE _y′ of the scattered quanta.     

Isotope effect on the stereodynamics for the collision reaction H＋LiF（v = 0, j = 0） → HF＋Li

Stereodynamics for the reaction H+LiF(v=0, j=0) → HF+Li and its isotopic variants on the ground-state (1 2 A′) potential energy surface (PES) are studied by employing the quasi-classical trajectory (QCT) method. At a collision energy of 1.0 eV, product rotational angular momentum distributions P (θr), P (φr), and P (θr ,φr), are calculated in the center-of-mass (CM) frame. The results demonstrate that the product rotational angular momentum j′ is not only aligned along the direction perpendicular to the reagent relative velocity vector k, but also oriented along the negative y axis. The four generalized polarization-dependent differential cross sections (PDDCSs) are also computed. The PDDCS 00 distribution shows a preferential forward scattering for the product angular distribution in each of the three isotopic reactions, which indicates that the title collision reaction is a direct reaction mechanism. The isotope effect on the stereodynamics is revealed and discussed in detail.     

Jet analysis in lepton-hadron scattering from QCD

For deep inelastic lepton-hadron scattering we deduce from QCD perturbation theory the cross sections $\text{d}\text{σ}\text{d}\text{T}$ and $\text{d}\text{σ}\text{d}\text{S}$ in terms of the collective jet variables thrust T and spherocity S. We find that the shape of these cross sections depends mainly on the total hadronic energy W. While present data are consistent with the cross sections calculated they do not yet prove or disprove the presence of three-jet contributions. We predict that these contributions will be clearly visible for W ? 12 to 15 GeV.     

The interaction between positive pions and deuterons at 47.5 MeV

The interaction of 47.5 (±0.5) MeV positive pions with douterons was studied using a scintillation counter telescope as the pion spectrograph. With an energy resolution sufficient to separate the elastic from inelastically scattered pions, the system was used to measure the cross sections for these reactions as well as the non-radiative pion capture process over the angular range of 22.5°–157.5°. The scattering results are well-fitted by recent theoretical calculations provided appropriate pion-nucleon phase shifts are used. The protons from the non-radiative capture reaction are fitted by a differential cross section of the form: $\text{d}\text{σ/}\text{d}\text{Ω ∝ A +}\text{cos}{}^2\text{θ}$, with A = 0.31 ± 0.03.     

Properties of ψN scattering

Extracting ψN scattering from photoproduction requires vector meson dominance and diffractive assumptions. We observe that (i) kinematic corrections to standard vector dominance formulas are important; (ii) both threshold and high energy behaviors of σ_t(ψN) support the diffractive assumption; (iii) q²-dependence in the γψ coupling could imply larger ψN cross sections; (iv) in any case σ_t is bounded through the slope of dσ/dt and σ_el/σ_t remains small.     

Inclusive φ-meson production in 93 and 63 GeV hadron interactions

The inclusive reactions h+p→φ+X, (h=π^±,,K^±,p^±), are studied for 0?x_F?0.3 and p⊥ ? 1 GeV at 93 and and 63 GeV incident momentum. Differential cross sections dσ/dp_⊥² anddσ/dx_F are presented and are compared with predictions of the naive parton model.     

低碰撞能下Li+HF(v=0－3，j=0－40)→LiF+H反应的立体动力学研究

基于2003年势能面,运用准经典轨线法(QCT)研究Li+HF→LiF+H反应立体动力学.探究较低碰撞能(1.15 kcal·mol-1-5.00 kcal·mol-1)下碰撞能、振转激发对极化微分反应截面(PDDCSs)和三矢量相关的P(θr,r)分布函数的影响,将积分散射截面与已有的理论及实验结果比较.结果显示,在较低碰撞能下碰撞能、振转激发对极化微分散射截面和三矢量相关的P(θr,r)分布函数有影响,但振转激发对极化微分反应截面和P(θr,r)分布的影响更大,碰撞能的增加使产物转动角动量后向散射的极化强度增大.在计算的能量范围内积分散射截面与其它的理论及实验结果符合较好.     

Elastic and inelastic φ photoproduction

The differential cross section of the reaction (γp → pφ) has been measured in the t range 0 ? t ? 0.4 GeV² and for photon energies from 3.0 to 6.7 GeV. In particular for the small t region the measurement accuracy was better than 10%. We obtained for the slope parameter B in an exponential parametrization of the differential cross section dσ/dt = Ae^?Bt values of $\text{B ? 6 ± 0.5}\text{GeV}{}^{\mathrm{?2}}$ which are significantly larger than the slopes obtained by most other experiments at higher t values. This indicates a t dependence of B particularly in the small t region.An energy dependence of the optical point (dσ/dt)_t=0, observed in our measurements, has been explained as a kinematic effect due to the VDM relation. A fit of our measurements is in excellent agreement with all other published values of (dσ/dt)_t=0(γp → φp), this implies that σ_tot(φp) must be essentially energy independent in this energy range.Spin density matrix elements of the φ have been evaluated and an analysis of the helicity amplitudes has been carried out. This analysis confirmed s-channel helicity conservation. Moments of spherical harmonics of the $\text{K}\text{K}$ angular decay distribution have been computed for 10 MeV $\text{K}\text{K}$ mass-bins from threshold to 1.3 GeV. The mass dependence of the normalized moments is generally smooth. Contributing amplitudes have essentially only even moments. The moment 〈Y₂⁰〉/〈Y₀⁰〉 changes sign above the φ mass.Differential cross sections for the inelastic φ production γp → φX have been evaluated for the first time both with respect to t?t_min and M_K. The integrated inelastic cross sections are comparable in size with the elastic ones. The slopes of the differential cross sections dσ/dt appear to become flatter with increasing M_X.     

Analysis of experimental data on neutron-proton scattering in the energy range between 0 and 150 keV

Experimental data on neutron-proton scattering in the energy range between 0 and 150 keV are analyzed by using various sets of effective-range parameters. It is shown that, in contrast to the parameters corresponding to the phase shifts of a Nijmegen group, the parameters corresponding to the experimental phase shifts reported by a group from George Washington University (GWU group) lead to very good agreement between the calculated cross sections and their experimental counterparts in the energy region under consideration. On the basis of the experimental value of the cross section for neutron—proton scattering at an energy of 2 keV, the total cross section for neutron-proton scattering at zero energy was found to be σ ₀ = 20.428(16) b, which is in very good agreement with a value of σ ₀ = 20.423(9) b, which was obtained as the weighted mean of the cross sections presented by Houke and Hurst. It is shown that, in the energy region around several tens of keV units, the effective-range parameters matched with Dilg’s cross-section value of σ ₀ = 20.491(14) b lead to calculated cross sections whose values are in excess of their experimental counterparts.     

ω Meson photoproduction from deuterium at 3.9 GeV photon energy

Measurements are presented of the cross sections for ω meson photoproduction from deuterium at an average photon energy of 3.9 GeV. The cross section for the coherent process γd → dω is found to be 1.4 ± 0.5 μb and that for the incoherent process γd → npω is 3.3 ± 0.7 μb. The forward differential cross section for γd → dω is estimated to be (dσ/dt)_t=0 = 54 ± 20 μb/GeV². This result indicates that the value of the A₂ exchange amplitude in ω photoproduction from hydrogen is less than that predicted from the measurements of the difference between the total hadron photoproduction cross sections from neutrons and protons. We note that the world data tend to show that the A₂ exchange amplitude is more consistent with zero than with the value needed to explain these differences. Measurements are also presented of the ratio of the coupling constants of the photon to the ? and ω mesons which tend to favour the vector dominance model proposed by Das, Mathur and Okubo with exact SU(3) symmetry at infinite energies.     

About the effect of a bound state on ionization cross sections in ion-atom collisions

The cross sections σ_nl for ionization of hydrogen-like ions by heavy particles from the nl = 3s, 3p, 3d, 4s and 4p states have been calculated in the Born approximation. A structure in the energy dependence of the cross sections σ_nl and the ratios of the cross sections σ_nl/σ_1s due to the radial wave function of a bound state is discussed.     

Elektron-Bremsstrahlungswirkungsquerschnitte von 180- und 380 keV-EIektronen

The bremsstrahlung cross sections, differential in photon energy and angle have been determined by measuring the x-rays emitted from thin targets (Al₂O₃: 56,5 and 113 μg/ cm²; Au: 9,7 and 24,4 μg/cm²) for incident electron energies of 180 and 380 keV with a 5×5 inch NaI scintillation spectrometer at angles from 0 to 150 degrees. A response matrix is used to convert the measured pulse height distribution into the spectrum of photons incident on the spectrometer. The results show that in this energy region the Bethe-Heitler-Sauter (Born approximation) theory underestimates the cross sectionsd ² σ/dk · dΩ anddσ/dk. The application of the Elwert factor gives a considerable improvement. For Al₂O₃ the Elwert corrected Born approximation gives values which are generally within the limits of error of the measurements. The experimental values of theHeitler parameter\(\Phi _{rad} /\bar \Phi \) are 5,0 (Al₂O₃) and 6,7 (Au) for 180 keV and 5,6 (A1₂O₃) and 7,3 (Au) for 380 keV. The angular distribution of the radiation has been compared with some characteristic angles predicted by the theory ofSommerfeldKulenkampff. Special consideration has been given to the high frequency limit. The cross sections at this energy have been derived from the correctedSauter-Fano theory and are in good agreement with the measurements.     

Coulomb deexcitation of muonic hydrogen within the quantum close-coupling method

The Coulomb deexcitation of muonic hydrogen in collisions with the hydrogen atom has been studied in the framework of the fully quantum-mechanical close-coupling method for the first time. The calculations of the l-averaged cross sections of the Coulomb deexcitation are performed for (μp)_n and (μd)_n atoms in the initial states with the principal quantum number n = 3–9 and at relative energies E = 0.1–100 eV. The obtained results for the n and E dependences of the Coulomb deexcitation cross sections drastically differ from the semiclassical results. An important contribution of the transitions with Δn > 1 to the total Coulomb deexcitation cross sections (up to ～37%) is predicted.     

Calculations of double-differential triton emission cross sections at 62-MeV proton-induced reactions

Double-differential cross sections (d ² σ/dΩd?) have been calculated and analyzed for triton production in proton-induced reactions on ²⁷Al, ^54,56Fe, ¹⁹⁷Au, and ²⁰⁸Pb target nuclei at incident energy of 62 MeV. Calculations of double-differential cross sections have been performed using nuclear models implemented in the TALYS 1.2 code. The calculated results of the double-differential cross sections for triton emission have been compared with the existing experimental data.     

K0 production in e+e− annihilations at 30 GeV center of mass energy

Inclusive K⁰-production has been measured in e⁺e^- annihilation at a center of mass energy of about W = 30 GeV. The ratio of K⁰ + K⁰ production to μ⁺μ^- production is R_K0 = 5.6 ± 1.1 (statist. error) ± 0.8 (system.error) This value is about a factor of three higher than R_K0 at W = 7 GeV. The cross sections (s/β) dσ/dx is consistent with a scaling behaviour.