Interpretations of the differential cross-sections for pp → π−π+

The differential cross-sections for $\text{p}$p → π^?π⁺ in the momentum range 0.8 to 2.4 GeV/c (centre-of-mass energy 2.02 to 2.57 GeV) are analysed in terms of the possible existence of s-channel resonances. The systematics of the dip structures and the s-dependence of dσ/dt are presented.     

Experimental investigation of the angular dependence of photon-induced differential cross-sections of L X-rays from U,Th and Bi at 59.5 keV

Summary The differential cross-sections for the emission of L_ρ, L_α, L_β and L_γ groups of L X-ray lines from U, Th and Bi have been measured at different angles varying from 45° to 135° at intervals of 15°. The vacancies were created by 59.5 keV γ-rays from²⁴¹Am source and L X-rays were measured using a Si(Li) detector. It is found that the L_γ and L_β groups of L X-rays are isotropic, the L_ρ and L_α groups are anisotropic in the spatial distribution. The authors of this paper have agreed to not receive the proofs for correction.     

Modification of a double focusing mass spectrometer for angular resolution

An angle-resolving slit has been used in a double-focusing mass spectrometer to obtain energy loss spectra over a range of scattering angles. The performance of the system is defined.     

Inner and outer shell ionization for atomic iodine: calculation of cross-sections and angular distribution parameters

This work presents results relating to photoemission cross-sections and angular distribution parameters for atomic iodine, where the photon energy varies over an energy range large enough to involve the ionization of the outermost 5p⁵ Subshell, as well as the inner 5s² and 4d¹⁰ electrons. The calculations were performed with several models, of varying sophistication according to the number of channels which are coupled to describe the continuum final-state wave function. They show that it is necessary to use a model which couples all the channels opened by the multiplet structure in order to show that the 4d shape resonance of iodine looks very much like the large 4d resonance of xenon. Anisotropie effects, whose size is reflected in the splitting among the various angular distribution parameters for alternative final ionic states, are found to be negligible within the framework of the most elaborate model, which couples all the channels corresponding to the residual ion configuration 4d⁹5p⁵; this holds less true as the angular momentum of the ionized electrons decreases. Whereas a model introducing the interchannel interactions within the ionization of one single subshell is sufficient to account for the resonances shifted beyond the thresholds for both 4d and 5p ionization, another model taking intershell interactions (5s + 5p) into account is necessary to obtain a minimum in the 5s cross-section.     

心动周期性多普勒波形的平均方法

许多临床上有用的多普勒小以形都是随时产是变化的，但又近似于周期心动周期的周期信号。为准确估计这些多普靳波形，并提取主同灵敏度的特征参数，有必要对它们按心吉期进行平均。     

Quantitative assessment of motion correction for high angular resolution diffusion imaging

Several methods have been proposed for motion correction of high angular resolution diffusion imaging (HARDI) data. There have been few comparisons of these methods, partly due to a lack of quantitative metrics of performance. We compare two motion correction strategies using two figures of merit: displacement introduced by the motion correction and the 95% confidence interval of the cone of uncertainty of voxels with prolate tensors. What follows is a general approach for assessing motion correction of HARDI data that may have broad application for quality assurance and optimization of postprocessing protocols. Our analysis demonstrates two important issues related to motion correction of HARDI data: (1) although neither method we tested was dramatically superior in performance, both were dramatically better than performing no motion correction, and (2) iteration of motion correction can improve the final results. Based on the results demonstrated here, iterative motion correction is strongly recommended for HARDI acquisitions.     

Method of averaging over interaction fields for constructing the fixed-scale renormalization group transformation

The application of the method of averaging over exchange interaction fields to clusters consisting of two magnetic atoms in the Ising model using a simple lattice has been considered. A version of the fixed-scale renormalization group transformation has been constructed. The application of these methods to the square-lattice Ising magnet with anisotropic interaction has been discussed.     

The effects of single-trial averaging on the temporal resolution of functional MRI

Computer simulations and event-related functional MRI (ER-fMRI) experiments were performed to investigate the effects of single-trial averaging and the corresponding contrast-to-noise ratio (CNR) on the minimal resolvable hemodynamic timing difference between brain areas. Three ER-fMRI sessions with temporally delayed (250, 500 and 1,000 ms) visual stimulations between two hemifields, each with 70 repeated single trials, were examined on two subjects. From the computer simulation, the temporal resolution improved as the CNR increased, which reached 500 and 100 ms for CNRs of 1.55 and 6.44, respectively. In the ER-fMRI experiments, the measured CNR increased as more single trials were averaged. The detectability of temporal differences was positively correlated (P<.05) with the CNR in all sessions for one subject but only in the 1,000-ms session for the other subject. Temporal resolution of 1,000 ms was achieved when more than 10 trials were averaged. The 500- and 250-ms delays might be differentiable when more than 20 trials were averaged, but the results were subject-dependent. This study demonstrated that the CNR could be significantly improved by single-trial averaging, which led to an improved temporal resolution of ER-fMRI. Temporal resolution in the range of hundreds of milliseconds was subject-dependent, which might be attributed to the intrinsic spatial variations in the timing of the blood oxygenation level-dependent (BOLD) response.     

Triple differential cross-sections for near threshold (e, 2e) process for hydrogen

The resonance Raman (RR) spectra of nickel octaethyl porphyrin, Ni(OEP), in CH₂Cl₂ (solvent) at different excitations such as 514.5, 488.0, 441.6 and 406.7 nm are recorded and analysed. The results of the theory of distortion-induced RR intensity is applied to the observed spectra to determine the excited electronic state symmetry of porphyrin in Ni(OEP). It is concluded that the porphyrin molecule (D_4h structure) attains a non-polar distorted structure of D₂ symmetry rather than S₄ symmetry in CH₂Cl₂ solution.     

Anomalous hyperfine fields detected with the differential angular correlation method

Time differential perturbed angular distributions of nanosecond-levels of some rare earth nuclei embedded in a ferromagnetic host lattice have been measured. Coulomb excitation with 4–10 MeV α-particles and recoil implantation technique have been used. Some evidences have been found for anomalous hyperfine fields acting on the nucleus in a time period which cannot be resolved. On a time scale starting at about 1 nsec where details can be resolved, the hypothesis of a static hyperfine field parallel to the external polarizing field seems to be justified.     

Total and differential cross-sections for the pp\rightarrow pp\eta^\prime reaction near threshold

The -meson production in the reaction has been studied at excess energies of Q = 26.5, 32.5 and 46.6 MeV using the internal beam facility COSY-11 at the cooler synchrotron COSY. The total cross-sections as well as one angular distribution for the highest Q-value are presented. The excitation function of the near-threshold data can be described by a pure s-wave phase space distribution with the inclusion of the proton-proton final-state interaction and Coulomb effects. The obtained angular distribution of the -mesons is also consistent with pure s-wave production.Received: 11 August 2003, Revised: 14 November 2003, Published online: 6 April 2004PACS: 13.60.Le Meson production - 13.75.-n Hadron-induced low- and intermediate-energy reactions and scattering (energy GeV) - 13.85.Lg Total cross-sections - 25.40.-h Nucleon-induced reactions     

Triple differential cross-sections for the ionization of metastable 2P-state hydrogen atoms by electrons with exchange effects

In this paper, triple differential cross-sections for the ionization of metastable 2P-state hydrogen atoms by 250 eV electron energy with exchange effects for various kinematic conditions are calculated. Multiple scattering theory proposed by Das and Seal in Phys. Rev. A 47, 2978 (1993) is utilized here. The computational results provide significant peak features that show good qualitative agreement with the hydrogenic ground-state experimental data and theoretical results and the present first Born results. In addition, physical origin of the peaks of the cross-section curves is investigated.     

Calculation of triple differential cross-sections ofK-shell ionization of medium-heavy atoms by electrons for symmetric geometry

Triple differential cross-section forK-shell ionization of medium-heavy atoms by relativistic electrons has been calculated for coplanar symmetric geometry. In this calculation the final state is described by a non-relativistic wave function of Das and Seal [Phys. Rev. A47 (1993) 2978] multiplied with suitable spinors. Results of the present calculation are compared with the available experimental data and with other theoretical calculations.     

共面双对称几何条件下电子碰撞Na原子单电离的三重微分截面

应用参数化的最佳有效势方法, 推广三体库仑波模型(3C)及动力学屏蔽的三体库仑波模型(DS3C模型)于Na原子, 计算了共面双对称几何条件下, 电子碰撞Na原子单电离的三重微分截面(TDCS), 与最近Murray的测量数据、Hitawala等人的扭曲波近似(DWBA)及考虑极化 的扭曲波近似(DWBAP)的理论结果进行了比较. 发现, DWBA在低入射能量反映了实验结果, 而3C计算在低入射能量时失效, DS3C计算对其有所改善. 入射能量较高时DS3C及3C结果的角度分布优于DWBA, 能够较好地定性描述上述碰撞过程. 说明对于共面双对称几何条件下的电子碰撞多电子原子单电离过程, 出射道三粒子间的动力学关联效应是比较强的.     

Increasing the frequency resolution in the processing of acoustic signals by sliding complex weighted averaging

We investigated the possibilities of estimating the transient impedance of an emitter and receiver in a free field, and we present our results, which are based on sliding complex weighted averaging of the frequency dependence of emitter and receiver’s transient impedance in a nonanechoic bath. We show that the procedure makes it possible to reduce reflection effects and to form free-field conditions in baths with various reflections that differ sharply in shape and many times in size. We suggest a procedure of repeat use of sliding complex weighted averaging together with spectrometry of reflection functions, which makes it possible to increase the frequency resolution of the method.     

On the effect of incident angular resolution in high-energy fixed-target collision experiments

A general calculation of the correction to the measured cross section in fixed-target experiments, due to the angular resolution of the incident beam, is carried out. A first-order expression in the incident solid angle ΔΩ is explicity given, and shows that, in the TeV region, angular resolutions as accurate as 10^?1 mrad are required for measurements within the cross-section forward peak.     

Triple differential cross-sections for the fast electron/positron impact ionization of hydrogen and helium in the Glauber approximation

Triple differential cross-section for electron and positron impact ionization of hydrogen and helium are calculated by using the Glauber approximation along with post-collision interaction effects which are estimated classically. The present results are compared with the recent absolute data of Ehrhardt, Jung and coworkers for the electron impact case. The positron impact case is found to lead to a larger binary to recoil peak maxima ratio (compared to the electron impact case) which further increases when post-collision interaction effects are included.     

共面双对称几何条件下Ne原子(e,2e)反应的三重微分截面

利用标准一阶扭曲波玻恩近似方法(DWBA)计算了共面双对称几何条件下不同能量电子碰撞电离Ne原子的三重微分截面(TDCS),与Nixon和Murray[1]最新的实验测量数据进行比较.当入射电子能量较低时,理论计算结果和实验数据符合较差;而随着入射电子能量的增加,符合程度逐渐改善.     

共面双对称几何条件下Ne原子(e,2e)反应的三重微分截面

利用标准一阶扭曲波玻恩近似方法（DWBA）计算了共面双对称几何条件下不同能量电子碰撞电离Ne原子的三重微分截面(TDCS),与Nixon和Murray 最新的实验测量数据进行比较.当入射电子能量较低时,理论计算结果和实验数据符合较差;随着入射电子能量的增加,而符合程度逐渐改善.