Nucleus-Nucleus Scattering Based on a Modified Glauber Theory

A modified microscopic Glauber theory has been extended to investigation of the reaction and elastic differential cross sections of various projectile-target collisions at low and intermediate energies. Through a systematic study, we find that the inclusion of the finite range interaction and Coulomb modifications plays very important role in the Glauber theory to reproduce the experimental data at these energy ranges. Usually the effect of the Coulomb modification is to decrease the reaction cross sections, on the contrary that of the finite range interaction modification increases them. The angular distributions calculated by the Glauber theory including these two corrections are in good agreement with the experimental data.     

改进的Glauber理论和核–核反应总截面

利用Glauber理论系统计算了中、低能条件下核–核反应总截面.讨论了量子效应、库仑效应以及核子–核子碰撞同位旋效应对Glauber理论的修正.发现在应用Glauber理论计算中、低能核–核反应截面时,量子修正是重要的.利用修正了的Glauber理论,系统计算了从低能到高能大量稳定线附近的核–核反应总截面,在没有可调参数的情况下,都与实验结果较好地符合.     

Determining the potential based on Rutherford backscattering data and electron screening in nuclear fusion reactions

A technique for determining the interaction potentials of He⁺–W, Ta systems on the basis of experimental data on the Rutherford backscattering of accelerated particles at an angle of 165° is proposed. This method provides an opportunity to extend the range of short distances within which the experimentally determined potential is known to 0.005 au and calculate corrections for electron screening relevant to the measurement of cross sections of the d + d nuclear fusion reaction. These corrections agree closely with the experimental data.     

低能质子引起的金LX射线相对产生截面

对于能量为０．５－１ＭｅＶ的入射质子，在计算中采用ＡｕＬ１次壳层荧光产额的实验值代替相应的Ｄｉｒａｃ－Ｈａｒｔｒｅｅ－Ｓｌａｔｅｒ值时，使用ＲＰＷＢＡ－ＢＣ（经结合能和库仑歪曲修正的相对论平面波玻恩近似）电离截面计算得到的金原子ＬＸ射线相对产生截面与测量值相符。以前报道的对ＲＰＷＢＡ－ＢＣ截面的各种修正都是不需要的     

The dilepton-production cross section in principal value resummation

Using a recent calculation of the perturbative hard part for dilepton production that sums large threshold corrections to all orders in perturbative QCD, we compute the corresponding cross sections. The hard part has been evaluated using principal value resummation and contains all singular momentum-dependent corrections. We also include a resummation of large Sudakov terms, which are independent of parton momenta. We give predictions for the dilepton-mass distribution, the rapidity distribution and the rapidity-integrated K-factor at fixed-target energies and compare with various experimental results in several kinematic regimes. We find that principal value resummation produces cross sections that are finite and well-behaved. For both protons and anti-protons on fixed targets, the resummed cross sections are, in general, in excellent agreement with the data.     

Inner-shell ionization of atoms by electron,positron and photon impacts

Plane wave Born approximation with Coulomb, relativistic and exchange corrections is employed to obtain L1-, L2- and L3-subshell ionization cross sections of several atoms due to electron and positron impacts for projectile energy varying from the threshold of ionization to 60 times the threshold energy. Photoionization cross sections for all the three L-subshells of the atoms are also calculated using the hydrogenic approximation for the atomic wave functions. For L3-subshell the present cross sections due to electron impact are in good agreement with a number of experimental data for different atoms over the entire energy range investigated. For L1- and L2-subshells the present calculations yield qualitative agreement with the experimental data. The agreement between the present results and the limited experimental data for positron impact is also satisfactory. The hydrogenic approximation for the L-subshell photoionization is found to be good at small photon energies but it underestimates the cross sections at large photon energies.     

Inclusive π4He scattering and the πN interaction in the nuclear medium

Double differential cross sections for the inclusive reaction ⁴He(π, π′)X have been measured for six pion energies between 90 and 320 MeV and an angular range from 30° to 135°. The data are interpreted in terms of the Δ-hole formalism. Medium corrections to the free π-nucleon scattering operator are important for a quantitative understanding of our results. Total inelastic cross sections are obtained and estimates for the absorption cross section are given.     

15N（p,n)15O反应中子源0°角激发函数测量

利用中国原子能科学研究院HI-13串列加速器上的多探测器快中子飞行时间谱仪, 测量了38个不同入射质子能量点下15N（p, n)15O反应0°角方向的激发函数。 测量数据用蒙特卡罗方法进行了模拟, 以进行中子注量衰减和入射窗厚度的不确定度修正。 实验在入射质子能量位于6.029—8.056 MeV之间时发现了3个共振峰, 这一点与DROSG 2000评价数据及PTB数据相符合, 但三家的截面数值存在差异, 对这些差异需要作进一步深入探讨。 The excitation function of 15N（p, n)15O reaction at 0 degree was measured at 38 energy points using the fast neutron Time of Flight (TOF) spectrometer at the HI 13 Tandem Accelerator in the China Institute of Atomic Energy（CIAE）. The measured data were analyzed by Monte Carlo simulation for the corrections of neutron flux attenuation and uncertainty of the thickness of the entrance foil. Three resonance peaks were observed in this experiment in the energy range from 6.029 to 8.056 MeV,which is comparable with the DROSG 2000 evaluated data and the PTB data. However,more experimental studies are needed since the cross sections deviate with each other.     

MEND——-—个计算250 MeV以下中重核数据的程序(英文)

基于球型光学模型、 预平衡发射和Hauser Feshbach统计等理论, 编制了MEND程序（Medium Energy Nuclear Data）, 该程序适用于中重原子核在入射粒子能量低于250 MeV的中低能区的全套核数据计算。对于中子和质子在250 MeV以下诱发的核反应, 其全截面、 反应截面、 弹性散射微分截面、 双微分截面和能谱等理论计算值与相应的实验值基本一致。MEND是计算中低能核反应的基础程序, 在我国已被广泛用于核数据计算及建立中能核数据库Based on the spherical optical model, pre equilibrium statistical theory, and Hauser Feshbach theory, etc., the code MEND (Medium Energy Nuclear Data) is written for calculating the complete set of nuclear data of medium heavy nuclei in medium low energy region (≤250 MeV). For the reactions induced by neutron and proton below 250 MeV, the total cross sections, reaction cross sections, elastic scattering differential cross sections, double differential cross sections and energy spectra, etc. calculated by the code MEND, generally agree with those corresponding experimental data. MEND is a foundational program for nuclear reaction in medium low energy region and is wildely used for nuclear data calculation and establishing ENDF/B6 format files of medium low energy region in China.     

微扰QCD对Drell-Yan过程能量损失效应的修正

利用Glauber模型以及DGLAP方程下的核内核子的部分子分布函数, 在次领头阶QCD下计算了Drell-Yan过程中的能量损失效应, 计算表明QCD修正并不能改善理论结果与试验结果的符合, 尤其是p-W与p-Be以x₁为变量的微分截面比. 原因是所用的核内核子部分子的分布函数是以领头阶近似为基础并通过演化方程得到的. 于是利用在次领头阶微扰QCD下得到的核遮蔽效应核内核子的部分子分布函数重新计算了次领头阶QCD修正对Drell-Yan过程能量损失的贡献. 计算结果表明康普顿散射过程与湮没过程中应该有更多的能量损失.     

用直接中子法测量（n, 2n）反应截面的实验方法研究

在中国原子能科学研究院HI-13 串列加速器上的非常规多探测器快中子飞行时间谱仪上,采用直接中子法测量了14.3 MeV 中子与169Tm作用的(n,2n) 反应截面。用蒙特卡罗方法模拟了次级中子的产生,以对实验数据进行中子注量率衰减、多次散射和有限几何修正,同时结合SUNF 方法得到的评价能谱,给出了(n,2n) 反应截面的实验测量结果。测量截面以中子弹性散射微分截面作为标准截面来归一,并用反冲质子望远镜测量n-p 反应的反冲质子,以监视中子注量率。用直接中子法测量得到的结果与评价数据进行了比较,讨论了采用这种方法测量(n,2n) 反应截面的可行性。(n,2n) reaction cross section from 169Tm at 14.3 MeV was measured with the direct emittedneutron coincidence detecting method, using abnormal fast neutron TOF spectrometer on the HI-13 Tandem Accelerator at CIAE. Monte-Carlo method was used to simulate the generation of secondary neutron and correct the experimental data considering neutron flux attenuation, multiple scattering and finite geometry correction. Combining with evaluated spectra given by SUNF program, the experimental measurement results of the (n,2n) reaction cross sections were given. Cross sections of measurements were normalized by using neutron elastic scattering differential cross section as a standard section, and a recoil proton telescope was used to measure recoiling proton from the n-p reaction to monitor neutron flux rate. After comparing the experimental results with evaluated data, the feasibility of the direct emitted-neutron coincidence detecting method is discussed.     

Cross sections of partial photoneutron reactions for the 115In nucleus and the neutron multiplicity sorting

A joint analysis of the experimental data on cross sections of total and partial photoneutron reactions is performed for the ¹¹⁵In isotope. The data are obtained by using the quasimonoenergetic photons generated upon the annihilation of relativistic positrons. Well-known systematic discrepancies between the results of various experiments are analyzed using objective absolute criteria of data reliability and authenticity. Methods for taking these discrepancies into account are considered. New reliable and authentic evaluations for cross sections of the σ(γ, n), σ(γ2n), and σ(γ, 3n) reactions are obtained using the data on the cross section of the reaction of photoneutron total yields σ(γ,xn) in the context of a new experimental-theoretical approach to evaluating the cross sections of partial reactions. These data are free from the shortcomings of experimental methods for the photoneuron multiplicity sorting.     

Physical criteria for the reliability of data on the photodisintegration of the <Superscript>89</Superscript>Y nucleus

Experimental photonuclear reaction cross sections obtained in experiments using quasimonoenergetic annihilation, monoenergetic tagged photons, and bremsstrahlung γ-radiation are analyzed using physical criteria for the reliability of data on the ⁸⁹Y nucleus. It is found that the reliability of data on the cross sections of partial reactions (γ, 1n) and (γ, 2n), obtained by means of photoneutron multiplicity sorting, is highly doubtful. Reliable cross sections of reactions (γ, 1n) and (γ, 2n) are obtained using the experimental–theoretical method (ETM) for evaluating using both experimental cross sections of neutron yield reaction σ^exp(γ, xn) that are free of neutron multiplicity problems, and theoretically calculated F _i ^theor ratios of the cross sections of definite (i) partial reactions to cross section σ^theor(γ, xn). It is shown that the evaluated cross sections differ noticeably from the experimental data.     

Contribution of inverse gluon emission to QCD corrections to the Drell-Yan process for experiments at the large hadron collider (LHC)

The contributions of inverse gluon emission to the lowest order QCD corrections to the Drell-Yan process for future experiments at LHC are calculated. The use of fully differential cross sections makes it possible to apply readily the results of these calculations for experimental purposes (in correcting data from future experiments at LHC). It is shown analytically that the present results are independent of the quark mass. A numerical analysis of respective radiative effects is performed by means of the READY FORTRAN code with allowance for the experimental cuts used at the Compact Muon Solenoid (CMS) detector.     

质子与~(52)Cr反应数据理论计算与分析

在质子与48Ti,51V和52Cr反应的去弹截面、弹性散射角分布实验数据的基础上,获得了一组入射质子能量在150 MeV以下的质子与52Cr反应的光学势参数。应用光学模型、扭曲波玻恩近似理论、核内级联模型、蒸发模型、带宽度涨落修正的Hauser-Feshbach理论以及激子模型(含改进的Iwamoto–Harada模型)计算得到了质子与52Cr反应的所有截面、角分布、能谱和双微分截面。对理论计算结果与实验数据以及TENDL中的数据进行了比较分析,结果显示,理论计算结果与实验数据符合较好,且反应道截面优于TENDL的结果。     

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.

     

Effects of relativistic kinematics in heavy ion elastic scattering

Relativistic corrections to the reaction kinematic parameters were made for elastic scattering of ⁶Li, ¹²C and ⁴⁰Ar from ⁴⁰Ca, ⁹⁰Zr and ²⁰⁸Pb targets at incident energies between 20 and 100 MeV/nucleon. The results of optical model calculations show that the effects of such corrections are important when describing the angular distributions of elastic scattering cross sections for heavy ion scattering at incident energies as low as around 40 MeV/nucleon. The effects on the total reaction cross sections on the other hand, were found to be small within the energy range studied when the optical model potential is fixed.     

Energy dependence of optical-model parameters for the interaction of 6Li and 7Li Ions with 28Si nuclei at low energies

The results of a joint analysis of experimental data (angular distributions for scattering and total reaction cross sections) are presented for the case of the interaction of ^6,7Li ions with ²⁸Si nuclei at energies between 7.5 and 32 MeV. The respective calculations were performed on the basis of a deformed potential of the optical model by using the SPI-GENOA code. The energy dependences of the parameters of the macroscopic optical model and the total cross section for the (^6,7Li+²⁸Si) reactions were obtained over the energy interval from 7.5 to 32 MeV. The calculated angular distributions and total reaction cross sections are in good agreement with experimental data.     

反应窗理论的适用性研究

基于低能离子与原子碰撞的分子库仑过垒模型，简要描述了与入射离子速度相关的反应窗理论.根据这一理论，计算了不同碰撞速度时O⁸⁺-H，Ar⁸⁺-H，Ar⁸⁺-He，Ne¹⁰⁺-He及Ar¹⁸⁺-He等碰撞体系单电子俘获过程的微分截面，还计算了碰撞速度为0.53 a.u.时¹⁵N⁷⁺-Ne碰撞体系单电子、双电子及三电子俘获过程的微分截面，并与他人的实验结果作了比较.研究发现，反应窗理论预言的末态电子分布与实验结果符合较好.理论和实验研究表明，随着碰撞速度的增加反应窗变宽；反应窗理论所预言的微分截面，当Q值较小时比实验结果偏大，当Q值较大时比实验结果偏小. 关键词： 反应窗理论 态选择微分截面 分子库仑过垒模型 离子与原子碰撞     

Description of the continuous spectrum of a three-body Coulomb system within the <Emphasis Type="Italic">J</Emphasis>-matrix approach

The contribution of the continuous spectrum of two-body Coulomb sybsystems to reaction matrix elements is studied. The respective Faddeev-Merkuriev differential equations are solved within the J-matrix approach. The differential cross sections for the double ionization of a helium atom by a direct electron impact is calculated by way of example. The results agree well with experimental data both in shape of the cross sections and in magnitude.