The 2H(p, 2p)n reaction at Einc = 45 MeV and its sensitivity to various separable S-wave N-N potentials

This paper presents and analyses the data for the ²H(p, pp)n reaction at E_inc = 44.9 MeV. Kinematic conditions including the quasi-free scattering region and the regions far from quasi-two-body processes are considered. The experimental results are compared with the predictions of several separable S-wave models of the N-N interaction. Potential models that differ only off-shell, as well as models that predict different N-N scattering results are included to help to isolate aspects of the break-up reaction sensitive to off-shell and on-shell differences. The regions far from quasi-free scattering are generally much more sensitive to the off-shell features of the interaction than are quasi-free scattering results. On-shell differences in the potential affect predictions in all regions of phase space with the potentials best representing the free N-N data giving the best overall fit to the data over most regions of phase space.     

A “4π-type” study of the reaction p(d,pp)n at Ed = 26.5 MeV

Experimental data on the three-nucleon reaction p(d, pp)n at E_d = 26.5 MeV obtained with the multidetector system BOL, covering most of the phase space, are presented. The data are compared with Faddeev calculations using a local S-wave potential for the nucleon-nucleon interaction. The calculated cross sections, which are in general not sensitive to the precise choice of the nucleon-nucleon potential, agree well with the data over the major part of phase space. We have, though, discovered a region in phase space with a strong discrepancy. In the same region, around a neutron c.m. angle of 140°, the calculations are sensitive to the N-N potential. Theoretical and experimental angular distributions in the p-n recoil c.m. subsystem for proton- neutron energies below 0.5 MeV agree in absolute magnitude, both being isotropic. For larger relative energies, a discrepancy develops, part of which might be related to missing higher par- tial wave components in the N-N interaction, rather than to Coulomb or S-wave scattering effects. The total breakup cross section has been deduced from the data as 169 ± 36 mb.     

Final-state interaction effects in semi-exclusive DIS off the deuteron

The effects of the final-state interaction (FSI) in semi-exclusive deep inelastic scattering of electrons off the deuteron are analyzed paying particular attention to two extreme kinematical regions: i) the one where FSI effects are minimized, so that the quark distribution of bound nucleons could be investigated, and ii) the one where the re-interaction of the produced hadrons with the spectator nucleon is maximized, which would allow one to study the mechanism of hadronization of highly virtual quarks. It is demonstrated that when the recoiling spectator nucleon is detected in the backward hemisphere with low momentum, the effects from the FSI are negligible, whereas at large transverse momenta of the spectator, FSI effects are rather large. Numerical estimates show that the FSI corrections are sensitive to the theoretical models of the hadronization mechanism.Received: 14 July 2003, Published online: 18 December 2003PACS: 24.85. + p Quarks, gluons, and QCD in nuclei and nuclear processes - 25.10. + s Nuclear reactions involving few-nucleon systems - 25.30.Fj Inelastic electron scattering to continuumL.P. Kaptari: On leave from the Bogoliubov Laboratory of Theoretical Physics, 141980, JINR, Dubna, Russia.B.Z. Kopeliovich: Also at Dzhelepov Laboratory of Nuclear Problems, 141980, JINR, Dubna, Russia.     

On the migdal-watson approach to FSI effects in meson production in NN collisions

The influence of the nucleon-nucleon final-state interaction (FSI) on properties of the meson-production amplitude near threshold is discussed. For nucleon-nucleon interaction, a simple Yamaguchi potential and realistic potential models are considered. It is shown that FSI effects cannot be factorized from the production amplitude. The absolute magnitude of FSI effects depends on the momentum transfer (or on the mass of the produced meson) and hence is not universal. Only in the case of the production of rather heavy mesons like η′ or φ FSI do effects become universal. The Jost function approach to FSI effects is critically examined.     

Initial-state distortion and final-state interactions in the 2H(3He, 3He p)n and 2H(3He, 3H p)p reactions

The predictions of two fully antisymmetrized reaction theories (DWBA and PWBA-FSI) are compared with absolute coincidence cross sections for the ²H(³He, ³He p)n and ²H(³He, ³H p)p reactions exhibiting final-state interactions (FSI) and quasi-elastic scattering (QES) both with and without charge exchange. The DWBA theory takes into account both the initial ³He-d and the final N-N interactions, while the PWBA-FSI theory includes only the latter. New QES data at E_He = 35.9 MeV, as well as previously reported 26.8 and 35.9 MeV data, are fitted. The DWBA theory gives good fits, both in shape and magnitude, to spectra showing N-N final-state interactions but gives somewhat poorer fits to QES spectra whose predicted magnitudes are two to ten times too large. The PWBA-FSI theory always predicts cross sections that are too large; however the predicted shapes are about as good as those from the DWBA. The initial-state interaction is shown to affect both the width and position of QES peaks from these reactions.     

Measurements of the spin-correlation coefficients Cxx, Cyy and S for d-p scattering at Ed = 17.4, 19.5, 23.8 and 26.1 MeV

The spin-correlation coefficients C_xx, C_yy and S have been measured by scattering the vector and tensor polarized deuteron beam of the Grenoble cyclotron from a polarized proton target. Comparison is made with Faddeev equation calculations using a separable N-N interaction. The results are in good agreement only when P-waves and the tensor force are taken into account in the N-N interaction.     

Threshold electrodisintegration of the deuteron caused by backward scattering of electrons

Using a new relativistic integral representation for the matrix element of electromagnetic current in terms of experimental phase shifts alone (representation of Shirokov RS) the cross section of the threshold electrodisintegration of the deuteron caused by backward scattered electrons is calculated for the S-wave deuteron in the interval of the four-momentum transfers squared 0.16 ? q² ? 5 fm^?2. Nucleon-nucleon interaction in the deuteron and the final state interaction (FSI) are taken into account in a unified manner and exactly. The effects of the meson exchange currents (MEC) and the inelastic n-p channels are neglected. The calculated cross section coincides with the experimental one.     

Effects of exchange and final-state interactions in the reactions 2H(3He, 3H p)p and 2H(3He, 3He p)n

Absolute coincidence cross sections for the ²H(³He, ³He p)n and ²H(³He,³H p)p reactions were measured at E_He = 35.9 MeV. Spectra dominated by the nucleon-nucleon final-state interaction (FSI) are fitted by a fully antisymmetrized PWBA theory which includes the effects of FSI in all its matrix elements. Previously reported 26.8 MeV data showing both FSI and quasi-elastic scattering (both with and without charge exchange) are also fitted by the theory, which qualitatively describes the shapes of all these spectra and the ratios of the cross sections for the various processes. Predictions of Watson-Migdal theory are fitted to the FSI spectra and differences between the two theories are analyzed.     

利用受激布里渊散射能量反射率测量液体介质运动黏度方法的研究

本文提出了一种利用受激布里渊散射(SBS)能量反射率的变化测定不同温度时的液体介质运动黏度的方法.液体介质的运动黏度随温度而变化,这导致了介质增益系数和SBS能量反射率的变化,因此通过SBS能量反射率的变化可测定不同温度时的液体介质的运动黏度.在Countinuum Nd: YAG种子注入激光系统中测定了不同温度时的水的运动黏度并与运动黏度计测定的结果进行了比较.用本方法获得的不同温度时的水的运动黏度测量值与运动黏度计测量值很接近,相对误差小于5%. 关键词： 受激布里渊散射 SBS能量反射率 温度 运动黏度     

Velocity-dependent potentials in the shell model of O and F

The low-lying energy levels of ¹⁸O and ¹⁸F are calculated in the harmonic oscillator shell model taking Green's velocity-dependent N-N potential as the residual interaction. It is found that the shell-model matrix elements agree substantially with those calculated by Kuo and Brown from the unrenormalized Hamada-Johnston hard-core N-N potential. It is found furthermore that Green's parameters give rather unsatisfactory agreement with the experimental spectra. It is shown that somewhat improved agreements with experiment are possible by making appropriate parameter adjustments.     

The deuteron breakup reaction induced by protons of 65, 85 and 100 MeV

Coplanar energy sharing spectra for p + d breakup at 65, 85 and 100 MeV proton bombarding energies were measured using the University of Maryland sectored isochronous cyclotron, by measuring the energies of either two protons or one proton and one neutron in coincidence. The detector angles were chosen to enhance either the p-p or p-n quasifree scattering, or the p-n final state interaction. The energy dependence of the peak cross section at equal symmetric quasifree scattering angle pairs was extracted for the ²H(p, 2p)n and ²H(p, pn)p reactions. Quasifree angular distributions were obtained for the reaction ²H(p, 2p)n at 65 MeV and for the reaction ²H(p, pn)p at 65, 85 and 100 MeV. The plane wave impulse approximation theory can only qualitatively reproduce the shape of the quasifree scattering peak in the energy sharing spectra and the shape of the p-p quasifree angular distribution. The discrepancies observed between the plane wave impulse approximation theory and the experimental data imply that the presence of the spectator particle (i.e., the multiple scattering effects) has a strong influence on the magnitude and the shape of the experimental results. Multiple scattering calculations were carried out in the three-body model of Aaron, Amado and Yam except that the S-wave separable two-body amplitudes were modified to fit two-nucleon elastic scattering data at higher energies. Comparisons of the results of these multiple scattering calculations to the experimental data show excellent quantitative agreement throughout the energy range and the angular region of this experiment, except for a few cases in which this model is inherently insufficient; namely, regions in which the Coulomb interaction is important, or regions for which a Hulthén wave function is inaccurate and the off-shell effects are not properly taken into account.     

Smoothed particle hydrodynamics(SPH) for modeling fluid-structure interactions

Fluid-structure interaction(FSI) is a class of mechanics-related problems with mutual dependence between the fluid and structure parts and it is observable nearly everywhere, in natural phenomena to many engineering systems. The primary challenges in developing numerical models with conventional grid-based methods are the inherent nonlinearity and timedependent nature of FSI, together with possible large deformations and moving interfaces. Smoothed particle hydrodynamics(SPH) method is a truly Lagrangian and meshfree particle method that conveniently treats large deformations and naturally captures rapidly moving interfaces and free surfaces. Since its invention, the SPH method has been widely applied to study different problems in engineering and sciences, including FSI problems. This article presents a review of the recent developments in SPH based modeling techniques for solving FSI-related problems. The basic concepts of SPH along with conventional and higher order particle approximation schemes are first introduced. Then, the implementation of FSI in a pure SPH framework and the hybrid approaches of SPH with other grid-based or particle-based methods are discussed. The SPH models of FSI problems with rigid, elastic and flexible structures, with granular materials, and with extremely intensive loadings are demonstrated. Some discussions on several key techniques in SPH including the balance of accuracy, stability and efficiency, the treatment of material interface, the coupling of SPH with other methods, and the particle regularization and adaptive particle resolution are provided as concluding marks.     

Cabibbo-Suppressed Non-leptonic Decays of Ac and Final State Interaction

With the diquark structure of Ac, we investigate the branching ratio of Ac → nr and pro. The results show that without considering the final state interaction (FSI), the branching ratio of Ac → pπ0 is only of order 10-6 whereas this ratio could reach 10-4 and is at the same order as Ac → nr if taking into account the FSI effects. Concrete values depend on phenomenological parameters adopted in the calculations. These branching ratios can be measured in the experiments to come.     

N－N关联和有限核相对论平均场方法

密度有关的核子－介子相互作用耦合常数是在相对论平均场近似下用核物质的相对论Ｂｒｕｅｃｋｎｅｒ－Ｈａｒｔｒｅｅ－Ｆｏｃｋ近似计算的自能参数化得到的．这种密度有关的相互作用考虑了介质中Ｎ－Ｎ关联效应，用这种密度有关的相互作用来研究有限核的基态性质，如单粒子能级，平均结合能，电荷均方根半径，与实验值较好地符合，同时还与其它模型的结果进行了比较。     

ONE BOSON EXCHANGE N-N,N-Δ AND Δ-Δ INTERACTION FROM QUARK POTENTIAL MODEL

The equivalent one-boson-exchange potentials of the N-N, N-Δ and Δ-Δ interaction were calculated rigorously in momentum space with the vertex functions derived from quark-pair-creation model.The results of the N-N interaction were compared with those calculated approximately in coordinate space and the conventional one-boson-exchange potentials. A11 of the results indicate that they have very similar behaviour for the medium- and Long-range parts.     

Competition between neutron-proton rescattering and deuteron break-up in (d,np) reactions

Existing final-state interaction (FSI) theories predict observable rescattering effects in low-energy nuclear reactions with three or more particles in the final state. Obvious yields which could be attributed to this effect have only been reported in (d, np) reactions. However,n-p rescattering might be confused with the neutron-proton FSI following deuteron break-up since both contribute strongest at low relative neutron-proton energies. We have re-examined the (d, np) reactions on¹²C and⁴⁰Ca in a kinematically complete experiment making special effort to try to distinguish between rescattering and then-p FSI. Data have been taken within and outside the reaction plane at different bombarding energies. Attempts to simultaneously fit the detailed shapes of the proton spectra and the azimuthal angularn-p correlations with theoretical predictions in a consistent way were unsuccessful forboth reaction mechanisms. Improvements in the fits at particular energy and angle combinations were always at the expense of the agreement at other angles or energies. Therefore it must be concluded from our analysis that on the basis of calculations available at present the contributions fromn-p rescattering and deuteron break-up cannot be distinguished in a conclusive manner in the (d, np) experiments performed to date.     

Neutron-proton final state interaction in the 3H(3He,pα)n reaction at low bombarding energies

The ³H(³He, pα)n reaction has been studied in a kinematically complete experiment at ³He bombarding energies between 0.31 and 2.80 MeV in order to detect a possible resonant energy dependence of the spin singlet (T = 1) neutron-proton final state interaction (FSI). The data in the region of low n-p relative energies have been analyzed in terms of the Watson-Migdal formalism. Only a slight relative increase of the ¹S₀ n-p FSI is observed with increasing bombarding energy. This result is not easily related to the strong isospin violations found in the two-body reaction ³H(³He, d)⁴He at similar ³He energies.     

核介质中核子－核子散射截面的BHF微观计算

在Ｂｒｕｅｃｋｎｅｒ－Ｈａｒｔｒｅｅ－Ｆｏｃｋ（ＢＨＦ）框架下，计算了核介质中核子－核子（Ｎ－Ｎ）散射总截面．计算中，Ｎ－Ｎ相互作用势采用Ｐａｒｉｓ势的可分离表示，单粒子谱采用连续选择．计算结果表明，质子－质子散射及质子－中子散射的总截面随核密度的增加而强烈地减小，特别是对低能散射．对结果作了简单的讨论，并与已有的一些计算结果进行了比较．     

Competition between neutron-proton rescattering and deuteron break-up in (d, np) reactions

Existing final-state interaction (FSI) theories predict observable rescattering effects in low-energy nuclear reactions with three or more particles in the final state. Obvious yields which could be attributed to this effect have only been reported in (d, np) reactions. However,n-p rescattering might be confused with the neutron-proton FSI following deuteron break-up since both contribute strongest at low relative neutron-proton energies. We have re-examined the (d, np) reactions on¹²C and⁴⁰Ca in a kinematically complete experiment making special effort to try to distinguish between rescattering and then-p FSI. Data have been taken within and outside the reaction plane at different bombarding energies. Attempts to simultaneously fit the detailed shapes of the proton spectra and the azimuthal angularn-p correlations with theoretical predictions in a consistent way were unsuccessful forboth reaction mechanisms. Improvements in the fits at particular energy and angle combinations were always at the expense of the agreement at other angles or energies. Therefore it must be concluded from our analysis that on the basis of calculations available at present the contributions fromn-p rescattering and deuteron break-up cannot be distinguished in a conclusive manner in the (d, np) experiments performed to date.     

Measurement of K0S, Λ and Λ? production at HERA

The production of the neutral strange hadrons K⁰ _S, Λ and Λ̄ has been measured in ep collisions at HERA using the ZEUS detector. Cross sections, baryon-to-meson ratios, relative yields of strange and charged light hadrons, Λ (Λ̄) asymmetry and polarization have been measured in three kinematic regions: Q² > 25 GeV²; 5 < Q² < 25 GeV²; and in photoproduction (Q²≃0). In photoproduction the presence of two hadronic jets, each with at least 5 GeV transverse energy, was required. The measurements agree in general with Monte Carlo models and are consistent with measurements made at e⁺e^- colliders, except for an enhancement of baryon relative to meson production in photoproduction.