共查询到20条相似文献,搜索用时 46 毫秒
1.
V. V. Dubinina N. P. Egorenkova V. I. Krotkova E. A. Pozharova V. A. Smirnitsky 《Physics of Atomic Nuclei》2005,68(3):471-473
Angular correlations between secondary particles emitted in the interaction between 56Fe nuclei of momentum 2.5 GeV/c per nucleon and photoemulsion nuclei were measured. These secondaries are partitioned into four groups: s, g, b, and f. For particles from each pair of the above groups, the average values of the collinearity factor and of the asymmetry parameter, as well as the parameter η of the function α(1+η cos ε) approximating the distribution of azimuthal-angle differences ε, were calculated. 相似文献
2.
V. V. Dubinina N. P. Egorenkova V. I. Krotkova E. A. Pozharova V. A. Smirnitsky 《Physics of Atomic Nuclei》2004,67(3):518-523
The azimuthal anisotropy of the emission of fragments and relativistic particles in collisions between 56Fe nuclei of momentum 2.5 GeV/c per nucleon and photoemulsion nuclei is measured. For semicentral collisions at impact-parameter values in the range 0.12 ≤ b/bmax ≤ 0.70, charged fragments and relativistic particles are predominantly emitted in the direction orthogonal to the nuclear-reaction plane. The azimuthal-asymmetry parameter P2 for fragments whose charge numbers are Z = 1, 2 and Z ≥ 3 takes values of, respectively, ?0.192±0.057, ?0.28±0.07, and ?0.39±0.12. Evaporated b particles have an isotropic azimuthal distribution. 相似文献
3.
4.
Kh. K. Olimov 《Physics of Atomic Nuclei》2009,72(1):77-84
The formation of cumulative nuclei of 4He in 16Op collisions at a momentum of 3.25 GeV/c per nucleon was investigated for the first time under conditions of 4π acceptance. The slope parameter of the invariant cross sections for the formation of cumulative nuclei of 4He was determined, and new data on the correlations between the yield of these cumulative nuclei and the yield of charged particles and fragments in 16Op interactions were obtained. 相似文献
5.
The algorithms and basic equations of a novel evaporation model that have been implemented in the program package EVAP15 are detailed. The level density of an excited nucleus is described by the composite Gilbert–Cameron formula with parameter values as suggested by the IAEA working group RIPL-3. Special attention is paid to the cross sections of inverse reactions and, in particular, to those for the interactions of low-energy neutrons with nuclei and for crossing of the Coulomb barrier by low-energy charged particles. The model predictions are compared with a large volume of experimental data on the spectra of particles emitted in the reactions (n, xn), (n, xp), and (n, xα) induced by neutrons with energy near 14 MeV and on the four spectra for the reaction (p, xp) induced by 62-MeV protons. 相似文献
6.
V. V. Dubinina N. P. Egorenkova V. I. Krotkova E. A. Pozharova V. A. Smirnitskii 《JETP Letters》2004,80(1):7-8
Experimental data on the emission of cumulative particles arising in the interaction of 2.5-GeV/c56Fe nuclei (FeEm) and 10–200 GeV neutrinos (νEm) with photoemulsion nuclei are analyzed. The number of cumulative particles correlates with the emission of secondary charged particles in the (FeEm) and (νEm) interactions. 相似文献
7.
A combination of the exciton and evaporation models is used to describe photonuclear reactions induced in light, medium-mass, and heavy nuclei by photons of energy in the range 7 ≤ E γ ≤ 140 MeV. Two mechanisms of the photoexcitation of nuclei are considered. These are the formation of a giant dipole resonance at energies in the range E γ ? 30 MeV and quasideuteron photoabsorption, which is dominant at energies in the region E γ ? 40 MeV. The density of particle-hole states, which appears in the exciton model, is calculated on the basis of the Fermi gas model. The emission of two preequilibrium particles is taken into account in describing the quasideuteron reaction channel. The effect of isospin conservation on giant-dipole-resonance decay accompanied by photonucleon emission is examined. The model in question is used to describe cross sections for photon-induced reactions on 26Mg, 54Fe, 112,118,119,124Sn, and 181Ta nuclei. 相似文献
8.
P. K. Raina A. Shukla P. K. Rath B. M. Dix K. Chaturverdi R. Chandra S. K. Dhiman A. J. Singh 《Physics of Atomic Nuclei》2004,67(11):2021-2026
The quality of Hartree-Fock-Bogolyubov wave functions is tested by comparing the theoretically calculated results with the available experimental data for a number of spectroscopic properties like yrast spectra, reduced B(E2) transition probabilities, quadrupole moments, and g factors for the nuclei involved in 2νββ decay. It is observed that the np interactions vis-à-vis the deformations of the intrinsic ground states of medium-mass nuclei play a crucial role in the fine tuning of the nuclear matrix elementsM2ν. 相似文献
9.
Some shortcomings of the approaches that are used to describe T-odd ROT and TRI asymmetries in true ternary fission via reactions involving the emission of prescission alpha particles and which are based on employing the classical method of trajectory calculations are analyzed. These shortcomings are caused by the disregard of the interference between the fission widths of different sJs neutron resonance states formed in the first well of the deformation potential of fissile compound nuclei. It is shown that the method used in some studies to determine T-odd TRI-asymmetries for prescission alpha particles is at odds with basic concepts of the generalizedmodel of the nucleus and approaches to constructing collective (for example, bending) vibrations of a fissile compound nucleus. Quantum-mechanical fission theory is generalized via employing a unified mechanism of formation of T-odd TRI and ROT asymmetries for prescission alpha particles and evaporated photons (neutrons). The proposed mechanism takes correctly into account the effect of quantum rotation of a fissile compound nucleus on the angular distributions of fission fragments and alpha particles for true ternary fission, as well as on the angular distribution of prompt photons (neutrons) emitted by fragments originating from the delayed fission of the aforementioned nuclei. 相似文献
10.
Kh. K. Olimov 《Physics of Atomic Nuclei》2009,72(4):601-606
The production of cumulative three-nucleon nuclei (3H and 3He) in 16Op collisions at a momentum of 3.25 GeV/c per nucleon were studied for the first time under conditions of 4π geometry. The slope parameter of the cross section for the production of cumulative three-nucleon nuclei was determined, and new data on correlations of the yields of A = 3 cumulative nuclei, charged particles, and fragments in 16Op interactions are reported. The properties of cumulative and noncumulative events were found to be substantially different, and evidence for the presence of a common universal feature in the mechanisms for the cumulative production of hadrons and light nuclear fragments was obtained. 相似文献
11.
B. S. Dolbilkin 《Physics of Atomic Nuclei》2008,71(7):1182-1192
In recent years, the physics of electromagnetic interactions has made considerable advances in studying giant multipole resonances, which are highly excited collective states of nuclei. After the advent of new-generation continuous-beam accelerators, (e, e′x) coincidence experiments were performed, and new precision data on giant multipole resonances were obtained from these experiments. A number of examples of cross sections for decay accompanied by proton and alpha-particle emission in p-, sd-, and pf-shell nuclei of mass number in the range 16 ? A ? 64 are given. The relative contributions of these reactions are compared, their general and special features are revealed, and evaluations for semidirect and statistical decays are presented. 相似文献
12.
Proton-neutron correlations in 4Hep interactions are studied in an exclusive experiment by using a 2-m bubble chamber exposed to a 5-GeV/c beam of α particles (the kinetic energy of the protons in the nucleus rest frame is T p = 620 MeV). Data on the production of pn pairs in 4π geometry for three channels, where it is possible to reconstruct the neutron momentum unambiguously, are used to determine the pn correlation function in 4Hep interactions. The experimental results are compared with the predictions of a modified Lednicky-Lyuboshitz model. The value obtained for the root-mean-square radius of the pn-emission region is R pn = 2.1 ± 0.3 fm. The dependence of the correlation function on the modulus of the total momentum of the emitted nucleon pair and on the direction of the momentum transfer is studied. An indication that the emission of a pn pair proceeds predominantly through the production of a virtual deuteron is obtained. 相似文献
13.
Kh. K. Olimov 《Physics of Atomic Nuclei》2009,72(3):452-458
The production of cumulative nuclei of 2H in 16O p collisions at a momentum of 3.25 GeV/c per nucleon was studied for the first time under conditions of a 4π acceptance. The parameter T 0 characterizing the slope of the spectrum of invariant cross sections for cumulative-deuteron production in 16Op interactions was determined. The contribution to cumulative-deuteron production from the decay of the alpha-particle clusters in nuclei upon slow-pion absorption by these clusters was found on the basis of an analysis of the momentum distribution of these cumulative nuclei. The estimates obtained for the contribution of these processes from a comparison of the mean multiplicities of particles and fragments in cumulative and noncumulative events agree well with the respective result extracted from the momentum distribution of cumulative deuterons. 相似文献
14.
V. A. Ditlov V. V. Dubinina N. P. Egorenkova V. I. Krotkova E. A. Pozharova V. A. Smirnitsky 《Physics of Atomic Nuclei》2005,68(11):1787-1789
The mean number ?Nb〉 of particles evaporated in the interaction of 22Ne, 32S, and 56Fe nuclei with photoemulsion nuclei was measured as a function of the number of alpha particles emitted within the fragmentation cone. It is found that ?Nb〉 decreases with increasing number of the alpha particles and increases with increasing number of projectile nucleons involved in the interaction with a target nucleus and that ? Nb〉 is a linear function of the excitation energy Eex of the target-nucleus residue. The maximum experimental value of the mean number of evaporated particles is ?Nbmax〉 ? 12–13, which corresponds to Eexc ? 540 ± 60 MeV. 相似文献
15.
V. G. Riabov 《Physics of Atomic Nuclei》2009,72(3):509-516
An overview of the latest physics results obtained in the PHENIX experiment by studying pp, dAu, and AuAu interactions at √sNN = 200 GeV is given. Results of measurements of nuclear-modification factors, direct-photon production, and properties of light vector mesons and particles containing heavy c and b quarks are presented. These results are used to deduce information about the properties of dense parton matter produced in collisions of relativistic heavy nuclei at the Relativistic Heavy Ion Collider (RHIC). 相似文献
16.
V. V. Dubinina N. P. Egorenkova V. I. Krotkova E. A. Pozharova V. A. Smirnitskii 《JETP Letters》2005,82(1):14-16
The azimuthal anisotropy of the emission of α particles in collisions of the 22Ne, 24Mg, 56Fe, and 197Au nuclei with photoemulsion nuclei has been measured at projectile energies Epr = 1.88–10.6 GeV/nucleon. The results are compared with similar measurements for protons. It has been found that the ratio of the azimuthal anisotropy coefficients v2 for α particles and protons is equal to 6 ± 2 at low energies Epr ≈ 2 GeV/nucleon, whereas these coefficients coincide with each other for energies Epr ≥ 4 GeV/nucleon. This difference may indicate that, at low projectile energies, α particles are formed predominantly at the early stage of a collective flow. Formation of α particles for Epr ≥ 4 GeV/nucleon likely occurs at the stage of nuclear matter scattering. 相似文献
17.
Yu.?B.?Gurov V.?S.?Karpukhin L.?Yu.?Korotkova S.?V.?Lapushkin T.?I.?Leonova R.?V.?Pritula B.?A.?Chernyshev
The spectra of p, d, and t charged particles produced in stopped-pion absorption by nuclei are analyzed. Respective measurements were performed for 17 nuclei by means of a semiconductor spectrometer. A phenomenological model developed previously for medium-heavy and heavy nuclei was applied to describing the spectra and yields of charged particles originating from light nuclei (6,7Li, 9Be, 10,11B, and 12C). The contribution of intranuclear clusters (such as pp and 3,4He) to pion absorption was estimated. 相似文献
18.
M. Portesi F. Holik P. W. Lamberti G. M. Bosyk G. Bellomo S. Zozor 《The European physical journal. Special topics》2018,227(3-4):335-344
We study a version of the generalized (h, ?)-entropies, introduced by Salicrú et al. [M. Salicrú et al., Commun. Stat. Theory Method. 22, 2015 (1993)], for a wide family of probabilistic models that includes quantum and classical statistical theories as particular cases. We extend previous works by exploring how to define (h, ?)-entropies in infinite dimensional models. 相似文献
19.
S. G. Kadmensky A. O. Bulychev 《Bulletin of the Russian Academy of Sciences: Physics》2016,80(8):921-926
Systems of kinetic equations for decay chains of genetically related nuclei, the R-matrix theory of nuclear reactions with formation of unstable particles, and a diagram technique with Green’s function are used to study the general form for the widths of n-step statistical decays of parent nuclei that are in quasi-stationary resonance states. Conditions under which sequential and virtual decays occur are analyzed. Cases where interactions between particles emitted at different stages of processes must be allowed for are considered. Processes related to fissile nuclei that simultaneously emit three or more particles are discussed. 相似文献
20.
The anisotropy of angular distributions of fission fragments and the average multiplicity of prescission neutrons were calculated within a stochastic approach to fission dynamics on the basis of three-dimensional Langevin equations. This approach was combined with a Monte Carlo algorithm for the degree of freedom K (projection of the total angular momentum I onto the fission axis). The relaxation time τ K in the coordinate K was considered as a free parameter of the model; it was estimated on the basis of a fit to experimental data on the anisotropy of angular distributions. Specifically, the relaxation time τ K was estimated at 2 × 10?21 s for the compound nuclei 224Th and 225Pa and at 4 × 10?21 s for the heavier nuclei 248Cf, 254Fm, and 264Rf. The potential energy was calculated on the basis of the liquid-drop model with allowance for finiteness of the range of nuclear forces and for the diffuseness of the nuclear surface. A modified one-body viscosity mechanism featuring a coefficient k s that takes into account the reduction of the contribution from the wall formula was used to describe collective-energy dissipation. The coefficient k s was also treated as a free parameter and was estimated at 0.5 on the basis of a fit to experimental data on the average prescission multiplicity of neutrons. 相似文献