Total Hadronic Cross Sections

<正>(Updated September 2013,COMPAS group,fflEP,Protvino)This updated version of the total hadronic cross sections review is based on the first half of 2013 update of the database for total cross section and the ratio of the real-to-imaginary parts of the forward elastic scattering hadronic amplitudes.New data on total pp coUisions cross sections from CERN-LHC-TOTEM[1]and new data from cosmic rays experiment PAO[2]were added.We use a procedure for ranking models as described in[3]to identify the safest parameterizations for extrapolations.Incidentally,the models giving the best fit of accelerator data also reproduce the experimental cosmic ray nucleon-nucleon data extracted from nucleon-air data with no     

丰中子核8He在Si靶上的反应总截面的测量

利用HIRFL 50MeV/u ¹³C束流在Be靶上碎裂,RIBLL选择出丰中子放射性次级束流⁸He,实验测量了25—40MeV/u ⁸He在²⁸Si靶上的反应总截面.采用双参数HO密度分布形式,通过微观Glauber模型拟合⁸He实验数据,发现⁸He具有扩展的中子密度分布.实验结果与Warner反应总截面实验和Alkhazov弹性散射实验结果较好地符合.     

Calculation of Total Cross Sections for Positron-Mg Collision

Total cross sections in positron-Mg collision are calculated in the range 2.0-60.0 eV using the momentum space coupled channels optical potential approach. The target ionization continuum and the positronium formation are included in the optical potential. The present total cross sections are compared with the experiment data and the other theoretical results.     

中能8B和9C与Si反应总截面的测量

能量为75MeV/u的¹²C初级束轰击2mm厚的初级Be靶,并利用RIBLL从弹核碎片中分离出54.2MeV/u质子滴线核束8B和61.1MeV/u的⁹C,再轰击Si靶,用透射法测量了它们与Si的反应总截面σ_R.并应用Glauber模型进行理论计算,分析结果表明⁸B和⁹C都可能具有质子晕结构.     

核反应截面替代测量方法介绍

核反应截面替代测量方法是一种间接测定核反应截面的方法, 这种方法对于测定不稳定核的反应截面具有重要的意义。 详细介绍了替代方法的理论基础、 影响其精确性的重要因素, 以及基于该方法的3种变型方法: 外替代比率方法（ESRM）、 内替代比率方法（ISRM）和混合替代比率方法（HSRM）。 阐明了每一种方法的基本原理, 给出了相关的实验验证, 并且对每一种方法的优缺点进行了分析。发现在每一种方法中, 所求反应与替代反应之间的自旋 宇称不匹配始终是不可消除的一个影响因素。 但是经过实验验证, 替代方法（包括3种变型方法）也可以达到较高的精确度, 因而在不能够直接测定核反应截面的情况下, 该方法不失为一种很好的间接测量方法。The surrogate nuclear reaction approach plays an important role in the determination of nuclear reaction cross sections that are difficult to be measured directly. In this paper, we investigate its basis, factors affecting its accuracy, and its three variants: the external surrogate ratio method (ESRM), the internal surrogate ratio method (ISRM) and the hybrid surrogate ratio method (HSRM). Each method was described, and their applications or experimental tests were given, from which we could see their respective advantages and disadvantages. And it is found that the spin parity mismatch, or the (weak) Weisskopf Ewing limit equivalently, is an inherent limitation of the approach. It is also seen that the surrogate approach can reach a high accuracy, so it is a good indirect approach when the nuclear reaction cross sections are unavailable to be measured directly.     

Efficient Method for Lorentz Integral Transforms of Reaction Cross Sections

The Lorentz integral transform (LIT) method, which allows ab-initio calculations of few-body cross sections, is reformulated via the Lanczos algorithm. The new technique, being quite general, is tested on inclusive and exclusive photonuclear reactions on three- and four-body nuclei. Due to the rapid convergence of the algorithm one gains a substantial decrease in CPU time with an excellent agreement with the results of a conventional LIT calculation. The present work opens up the possibility of ab-initio calculations for inclusive and exclusive processes for systems with a number of particles N 6.     

17C反应截面和去中子截面

利用日本理化学研究所的放射性束流线RIPS, 测量了能量为79A MeV的¹⁷C在¹²C反应靶上的反应截面, 并同时得到了¹⁷C的移去1个、2个及3个中子的截面; 分别利用有限力程Glauber模型和少体Glauber模型结合壳模型的谱因子分析了反应截面和移去1个中子截面, 研究了¹⁷C的密度分布、结构和价中子布居. 反应截面和中子移去截面是两个相互独立的量, 通过对两者的分析, 都可以得出¹⁷C由芯核¹⁶C和价中子组成, 并且价中子主要处于d_5/2轨道的结论. 总结了现有的碳同位素的反应截面和相互作用截面的工作.     

Resonances and Fluctuations in Nuclear Reaction Cross Sections

On the basis of the continuum shell model, an expression for the S-matrix is derived. The external mixing between shape resonances and resonance states of complicated nuclear structure is investigated. It is shown that the doorway properties of the shape resonances may lead to an l-dependent transparency of the optical potential and, consequently, to an energy dependence of large back angle scattering if the unitarity of the S-matrix is taken into account.     

中子与52Cr反应截面的理论分析

根据中子与天然核Cr及其同位素反应的总截面,去弹性散射截面和弹性散射角分布的实验数据,获得了入射中子能量从1MeV—250MeV的一组普适中子与Cr及其同位素反应的光学模型势参数.应用光学模型,扭曲波玻恩近似理论,宽度涨落修正的Hauser-Feshbach理论,和预平衡反应的激子模型,计算和分析了中子与⁵²Cr反应的所有截面、角分布、能谱和双微分截面.理论计算与实验数据进行了分析比较.     

The Reaction Cross Section and Neutron Removal Cross Sections of 17C

The reaction cross section, together with the one-, two- and three neutron removal cross sections, of ¹⁷C with the energy of 79A MeV on carbon target were measured using the radioactive beam line RIPS of RIKEN. The reaction cross section and the one-neutron removal cross section were analyzed within the frame of Glauber model. Both the analyses favor the dominant configuration of a ¹⁶C core (2⁺) plus a d_5/2 valence neutron for ¹⁷C. The work for the neutron-rich carbon isotope on the reaction cross section σ_R and the interaction cross section σ_I on ^{12C target are summarized.}     

New Data on Photoneutron Reaction Cross Sections for 76,78,80,82Se Nuclei

The problem of reliability of the cross section data obtained for partial photoneutron reactions on ^76,78,80,82Se nuclei in beams of quasimonoenergetic annihilation photons by means of neutron multiplicity sorting is discussed by employing objective physical criteria. It is shown that, because of substantial systematic uncertainties, experimental data on the (γ, 1n) and (γ, 2n) cross sections are unreliable. New data satisfying the reliability criteria are obtained for the partial photoneutron reaction cross sections for ^76,78,82Se nuclei by an experimental—theoretical method for evaluating such cross sections and are compared with experimental data and with data evaluated earlier for the isotope ⁸⁰Se. The evaluated integrated cross sections for the total photoneutron reactions on ^76,78,80,82Se nuclei are compared with the predictions of the Thomas-Reiche-Kuhn classical dipole sum rule.

     

Total Cross Sections at High Energies - An Update

Current and future measurements for the total cross sections at E-811, PP2PP, CSM, FELIX, and TOTEMhave been analyzed using various models. In the light of this study an attempt has been made to focus on the behaviorof total cross section at very high energies.     

27,28P+28Si总反应截面增强及可能相关的机制

测量了27,28P和相应同中子异位素在28Si靶上的中能反应截面.测得N=12和13同中子异位素的反应截面在Z=15处突然增大.对Z≤14同中子异位素和28P的实验数据结果可以用改进的光学极限近似的Glauber理论很好地描述.28P的反应截面能够用扩大核芯以改进的Glauber理论来解释.但是,用改进光学极限和少体近似的Glauber理论却低估了27P的实验数据.理论分析表明,扩大的核芯加质子晕可能是响应27P+28Si反应截面增强的机制. The reaction cross sections of~(27,28)P and the corresponding isotones on Si target were measured at intermediate energies. The measured reaction cross sections of the N=12 and 13 isotones show an abrupt increase at Z=15. The experimental results for the isotones with Z≤14 and~(28)P can be described well by the modified Glauber theory of the optical limit approach. The enhancement of the reaction cross section for~(28)P could be explained by the modified Glauber theory with an enlarged core. Theoretical ana...     

Oscillations in Total Photodetachment Cross Sections of a Triatomic Anion

The total photodetachment cross section of a linear triatomic anion is derived for arbitrary laser polarization direction. The cross section is ,shown to be strongly oscillatory when the laser polarization direction is parallel to the axis of the system; the oscillation amplitude decreases and vanishes as the angle between the laser polarization and the anion axis increases and becomes perpendicular to the axis. The average cross section over the orientations of the triatomie system is also obtained. The cross section of the triatomic anion is compared with the cross section of a two-center system. We find there are two oscillation frequencies in the triatomie anion in contrast to only one oscillation frequency in the two-center case. Closed-orbit theory is used to explain the oscillations.     

中子与裂变核238U反应双微分截面的理论分析

根据中子与原子核U及其同位素反应的总截面,去弹性散射截面和弹性散射角分布的实验数据,获得了入射中子能量0.1—20MeV的一组普适中子与U及其同位素反应的光学模型势参数.应用光学模型,核裂变理论,耦合道理论,扭曲波玻恩近似理论,宽度涨落修正的Hauser-Feshbach理论和预平衡反应的激子模型,计算和分析了中子与²³⁸U反应的所有截面、角分布、能谱和双微分截面.理论计算与实验数据进行了分析比较     

An Empirical Formula Approach to Total Cross Sections for Electron Scattering on Polyatomic Molecules

Considering the real experimental process of e-molecule scattering a new empirical formula has been developed to calculate the total cross sections （TOSs） for electron scattering on polyatomic molecules （CH4, C2H2, CH3OH and CH3F）. The present results are compared with other available theoretical results and experimental data. The new formula incorporates an energy factor f（E） to represent the elastic and inelastic changing process during experiments. It depends on no adjustable parameters and has also extended the validity of the empirical approaches to lower energy range further.     

Note on Resonant and Non-resonant Peaks in Electron-Atom Total Scattering Cross Sections

Certain broad low-energy peaks caused by a single partial wave in total cross sections are explained in terms of phase shifts. Such peaks have been associated with the real part of a Regge pole trajectory, having a maximum near an integer value of the angular momentum quantum number. At the peak energies, the pertinent partial-wave phase shift was shown to have a local maximum near a value π/2 modulo π. This implies no time delay in the semiclassical context. The phenomenon is a quantum effect, lacking a semiclassical interpretation.     

Analysis of Neutron Double-Differential Cross Sections for n + 12C Reaction Below 30 MeV

Based on the light nucleus reaction model (Nucl. Sci. Eng. l33 (1999) 218), four aspects (neutron incident energy region, reaction channel analysis, the renewed level schemes and the optical model parameters) of n 12 C reaction are improved to calculate total outgoing neutron double-differential cross sections with modified LUNF code below 30 MeV. The calculated results agree fairly well with the experimental data at En = 14.1 MeV and 18 MeV. The analysis shows that the pre-equilibrium mechanism, which is exactly considered the conservation of energy, momentum and parity, dominates the whole reaction process. The contribution of the neutron emission from 5He to total energyangular spectra is also considered properly. This modified LUNF code will be a useful tool to set up the file of neutron double-differential cross sections below 30 MeV in the neutron evaluation nuclear data library.     

State-Selective and Total Single-Capture Cross Sections for Fast Collisions of Multiply Charged Ions with Helium Atoms

The four-body boundary corrected first Born approximation (CB1-4B) is used to calculate the single electron capture cross sections for collisions between fully stripped ions (He²⁺, Be⁴⁺, B⁵⁺ and C⁶⁺) and helium target at intermediate and high impact energies. The main goal of this study is to assess the usefulness of the CB1-4B method at intermediate and high impact energies for these collisions. Detailed comparisons with the measurements are carried out and the obtained theoretical cross sections are in reasonable agreement with the available experimental data.     

Theoretical Analysis of Double Differential Cross Sections for n+ 238U Reaction

Based on the new measurements of total, nonelastic, elastic cross section and elastic scattering angular distributions for n+U reactions, a set of neutron optical model potential parameters is obtained in the region of incident neutron energy from 0.1 to 20 MeV. The cross sections, angular distributions, energy spectra and double differential cross sections are calculated and analyzed by optical model, nuclear fission theory, distorted wave Born approximation theory, coupled channel theory, the unified Hauser-Feshbach theory, as well as exciton model. The results indicate that our theoretical model can reasonably analysis n+ ²³⁸U reaction data with neutron energy lower than 20 MeV.