同位旋相关的核子碰撞截面的不同形式与核子的集体流

在详细比较同位旋相关的核子-核子碰撞截面的几种常用形式的基础上,利用IBUU模型, 分别对具有相同质量的⁶⁰Ca+⁶⁰Ca和⁶⁰Ni+⁶⁰Ni的中能重离子碰撞进行了模拟计算,定量地分析了碰撞过程中不同形式的同位旋相关的核子-核子碰撞截面对于核子的快度分布和集体流的影响.结果显示: 不同形式的核子碰撞截面,可以给出相差较大的核子的快度分布和横向流, 但在同一种截面形式下,对称势的变化对横向流的影响较小.这表明在新的动量相关的对称势下, 中能重离子碰撞中集体流对于截面的敏感性依然成立;同时表明,在相同的碰撞截面和对称势形式下, 当入射能量在平衡能附近时,入射粒子的中质比对核子在平面流的影响较大,反之,影响较小.     

Proton-nucleus inelastic cross section at ultra high energy

Energy dependence of proton-nucleus reaction cross section at very high energy is discussed. It is stressed that depending on the gluon distribution near the nuclear surface, proton-nucleous total cross section increases much more rapidly compared to the usual Glauber independent nucleon estimate. The recent observation of smaller X _max than the expected value at UHECR domain can be an indication for such a mechanism.     

Total photoproduction cross section at very high energy

In this paper we apply to the photoproduction total cross section a model we have proposed for purely hadronic processes and which is based on QCD mini-jets and soft gluon re-summation. We compare the predictions of our model with the HERA data as well as with other models. For cosmic rays, our model predicts substantially higher cross sections at TeV energies than models based on factorization, but lower than models based on mini-jets alone, without soft gluons. We discuss the origin of this difference.     

中高能区电子与分子散射总截面的计算

实验表明,电子与分子碰撞总截面(TCS)与分子本身固有参数(极化率、键长等)有一定关系,所以可从理论上定量探索这种关系,找出包含这些参数的准经验公式 .理论上可根据散射截面的"低能极限为硬球势散射、高能极限为玻恩近似"的思想,参考实验上测得的一些分子的总截面与分子的极化率的定量关系,我们用分子的几何和物理参数模拟了一种准经验公式.?     

Neutrino–nucleon cross section at intermediate energy from KM3 neutrino telescopes

The capability of a KM³ neutrino telescope to bounds the neutrino–nucleon cross section in the intermediate energy range (10⁵ GeV<E<10⁷ GeV) is studied. We use an observable which only makes use of the upward-going neutrino flux, so that the Earth filters the atmospheric muons, and it is only weakly dependent on the initial astrophysical flux uncertainties and experimental systematic. In order to study the sensitivity to departures from the standard model we have considered a cross section which is a version perturbed of the standard model one, dependent of two parameters. We present the results as regions for the allowed values for both, the parameters space and the cross section.     

Some comments on the total γγ → hadron cross section at high energy

For the γγ→h total cross section we suggest approximations for the Q² dependence and the energy dependence, which are better founded than those applied nowadays. This considerably changes the results obtained in PETRA and thier relation to the Regge-pole model.     

Qualitative modification of the high energy atomic photoionization cross section

It is demonstrated that the nonrelativistic high energy omega-->infinity behavior of the photoionization cross section of an nl atomic subshell, sigma(nl)(omega), for l>0 is independent of l and is given by sigma(nl)(omega) approximately 1/omega(9/2), rather than the previously generally accepted sigma(nl)(omega) approximately 1/omega(l+7/2). Furthermore, for l = 1, although the exponent does not change, the coefficient is significantly altered. This modification of sigma(nl)(omega) is due to the interchannel interaction between ns photoionization channels and l not equal0 channels in the atom. As a result, for the photoionization of l not equal0 electrons, the single-particle approximation is never correct in the omega-->infinity limit. This has important consequences for sum rule calculations.     

Measurements of the inclusive pd breakup cross section at low and intermediate energies

Inclusive measurements of the D(p, p)pn reaction were made at incident proton energies of 248?MeV and 13?MeV, to investigate the global feature of the pd breakup reaction at intermediate and low energies. At 248?MeV, the cross section and analyzing power A _y were measured at four angles from 7° to 20°. The data largely disagree with Faddeev calculations even if 2π-exchange three-nucleon force (2π3NF) or Δ-isobar is included, and the disagreement increases at forward angles. At 13?MeV, the cross section was measured at eight angles from 10° to 70°. The data are well reproduced by a recent pd Faddeev calculation, and the effects of Δ-isobar at 13?MeV are very small.     

Asymptotic form of the high energy photoionization cross section of fullerenes

We show that the theoretical predictions on high energy behavior of the photoionization cross section of fullerenes depend crucially on the form of the function $V(r)$ which approximates the fullerene field. The shape of the high energy cross section is obtained without solving the wave equation. The cross section energy dependence is determined by the analytical properties of the function $V(r)$.     

Measurement of the high energy two-body deuteron photodisintegration differential cross section

The first measurements of the d(gamma,p)n differential cross section at forward angles and photon energies above 4 GeV were performed at the Thomas Jefferson National Accelerator Facility (JLab). The results indicate evidence of an angular dependent scaling threshold. Results at straight theta(cm) = 37 degrees are consistent with the constituent counting rules for E(gamma) greater, similar 4 GeV, while those at 70 degrees are consistent with the constituent counting rules for E(gamma) greater, similar 1.5 GeV.     

Compton-scattering cross section on the proton at high momentum transfer

Cross-section values for Compton scattering on the proton were measured at 25 kinematic settings over the range s=5-11 and -t=2-7 GeV2 with a statistical accuracy of a few percent. The scaling power for the s dependence of the cross section at fixed center-of-mass angle was found to be 8.0+/-0.2, strongly inconsistent with the prediction of perturbative QCD. The observed cross-section values are in fair agreement with the calculations using the handbag mechanism, in which the external photons couple to a single quark.     

利用中-质微分流探测对称能的高密行为

基于同位旋和动量依赖的强子输运模型IBUU04，研究了¹³²Sn+¹²⁴Sn在三种不同碰撞能量、两种不同对称能作用下，中-质微分流随快度的变化关系. 发现中-质微分流的强度随碰撞能量的增大而增强. 在碰撞能量为400 MeV每核子时，中-质微分流对对称能最为敏感. 关键词： 重离子碰撞 中-质微分流 对称能     

Double-spin asymmetries in the cross section of \rho^0 and \phi production at intermediate energies

Double-spin asymmetries in the cross section of electroproduction of and mesons on the proton and deuteron are measured at the HERMES experiment. The photoabsorption asymmetry in exclusive electroproduction on the proton exhibits a positive tendency. This is consistent with theoretical predictions that the exchange of an object with unnatural parity contributes to exclusive electroproduction by transverse photons. The photoabsorption asymmetry on the deuteron is found to be consistent with zero. Double-spin asymmetries in and meson electroproduction by quasi-real photons were also found to be consistent with zero; the asymmetry in the case of the meson is compatible with a theoretical prediction which involves knockout from the nucleon. Received: 11 February 2003 / Published online: 11 June 2003     

Time-independent values of the differential cross section and overlap functions at high energies

The extremal values, obtained previously [1, 2], of the differential cross section for elastic scattering in the region of the diffraction cone are generalized to other angles and reduced to a form suitable for comparison with experiment. Similar results are also found in the case of inelastic binary reactions and overlap functions. Comparison with experiment indicates that the time-independent values are extremely close to the measured ones.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 73–79, August, 1973.     

The intermediate weak boson and weak interactions at high energy

The high-energy pire-leptonic weak interaction is investigated based on the assumption of the existence of a charged vector boson which mediates the weak processes. With the aid of the fixed-t dispersion relation the following relation is obtained: The weak boson mass m_W should satisfy $\text{m}{}_{\mathrm{<mtext>W</mtext>}}\text{? G}{}^{\mathrm{<mtext>?</mtext><mtext>1</mtext><mtext>2</mtext>}}$, with G the Fermi coupling constant, if the asymptotic value of the cross section becomes of the order of the strong interaction in the energy region observable in cosmic rays, etc.The scattering processes $\text{e}\text{+ν→}\text{e}\text{+ν}\text{and}\text{e}\text{+}\text{ν}\text{→}\text{e}\text{+}\text{ν}$ are examined by the aid of the N/D method. For a large vector-boson mass $\text{m}{}_{\mathrm{<mtext>W</mtext>}}\text{?100}\text{GeV}$, an S-wave resonance should exist for the process e+ν→e+ν while for $\text{e}\text{+}\text{ν}\text{→}\text{e}\text{+}\text{ν}$ there should exist a P-wave resonance which corresponds to the intermediate weak boson. The neutral current is then estimated. It is shown that the neutral current produced as a higher-order effect is not inconsistent with the present experiments on the pure-leptonic weak interaction if m_W?1 TeV.     

中高能电子被氟代甲烷散射的总截面计算

利用可加性规则,使用Hartree-Fock 波函数,采用被束缚原子概念修正过的复光学势,首次在100～5 000eV内对电子被具有较多电子数的氟代甲烷分子散射的总截面进行了计算,且将计算值与实验值及经验公式进行了比较,得出了被束缚原子概念修正过的复光学势可成功用于"电子-氟代甲烷"散射总截面计算的结论;研究了"电子-氟代甲烷"的散射总截面与目标分子总电子数及电子入射能量间的关系,初步分析了结构因子与总电荷数相关的原因,并指出了对复光学势进行进一步修正时应遵循的原则.