Azimuthal correlations of projectile and target fragments in collisions between gold nuclei of energy 10.6 GeV per nucleon and emulsion nuclei

Intra-and intergroup azimuthal correlations of projectile and target fragments are found in collisions between gold and emulsion nuclei. The statistical significance of these correlations is high. The methodological distortions associated with the measurement errors are investigated in detail and are taken into account.     

Single source emission of proton projectile fragments in nucleus-emulsion interactions

The projected angular distribution and transverse momentum distribution of proton projectile fragments produced in 3.7A GeV 16O,500A MeV 56Fe,and 1.7A GeV 84Kr induced by different kinds of emulsion target(H,CNO,and AgBr) interactions are investigated.It is found that the projected angular distribution and transverse momentum distribution can be well represented by a single Gaussian distribution.Comparison of transverse momentum distribution with the Maxwell-Boltzmann distribution reveals that proton projectile fragments are emitted from a single-temperature emission source.The temperature is different for different colliding systems,and linearly depends on the target size.     

Two source emission behavior of projectile fragments alpha in 84Kr interactions at around 1 GeV per nucleon

The emission of projectile fragments alpha has been studied in ⁸⁴Kr interactions with nuclei of the nuclear emulsion detector composition at relativistic energy below 2 GeV per nucleon. The angular distribution of projectile fragments alpha in terms of transverse momentum could not be explained by a straight and clean-cut collision geometry hypothesis of Participant — Spectator (PS) Model. Therefore, it is assumed that projectile fragments alpha were produced from two separate sources that belong to the projectile spectator region differing drastically in their temperatures. It has been clearly observed that the emission of projectile fragments alpha are from two different sources. The contribution of projectile fragments alpha from contact layer or hot source is a few percent of the total emission of projectile fragments alphas. Most of the projectile fragments alphas are emitted from the cold source.     

Angular anisotropy of the alpha emission from241Am nuclei oriented by magnetic hyperfine interaction

Angular anisotropy of the alpha emission from²⁴¹Am nuclei oriented by magnetic hyperfine interaction at low temperatures in ZrFe₂-host have been observed. The sign of the anisotropy indicates unambiguously the enhanced alpha emission from the poles of²⁴¹Am nucleus. The value of magnetic hyperfine field on²⁴¹Am nuclei have been estimated from the temperature dependence of the anisotropy.     

Phenomenological analysis of intermediate mass fragments emission in alpha induced reactions

Intermediate mass fragment emission in induced reactions on Al and Ti at 60 and 104 MeV, respectively has been analysed using phenomenological moving source model. Fragment emission at backward angles is found to be well explained by a single fusion-like source, whereas for forward angles an additional intermediate velocity source is required to explain the data. The relative contribution of the intermediate velocity source decreases sharply with angle for lower energies and it extends significantly to larger angles in the higher energy reaction. The fractional momentum transfer for the fusion-like source is in agreement with the corresponding Viola systematics value in the case of +Al reaction, whereas for +Ti reaction, it is larger than that obtained from the Viola systematics. The degree of incompleteness (in momentum transfer) is found to be fragment dependent; incompleteness being more for lighter fragments and vice-versa.     

NMR of short-lived nuclei implanted in crystals and a new isol for projectile fragments in relativistic heavy-ion reaction

Hyperfine interactions of substitutional and interstitial impurities in crystals were studied by use of the asymmetric β decay and NMR detection, following recoil implantation. A new ISOL for the projectile fragments produced in relativistic heavy-ion reaction separated radioactive isotopes. Their high kinetic energies obtained in the reaction enabled us to created spin polarization artificially in the isotopes and to implant them deep in any material.     

Peripheral interactions of relativistic 14N nuclei with emulsion nuclei

The results of investigation of the dissociation of the 2.86-A-GeV/c ¹⁴N nucleus in an emulsion are presented. The cross sections for various fragmentation channels are given. The invariant approach to analysis of fragmentation is used. The momentum and correlation characteristics of the α particles for the ¹⁴N → 3α + X channel in the laboratory system and c.m.s. of three α particles are examined. The results obtained for the ¹⁴N nucleus are compared with similar data for the ¹²C and ¹⁶O nuclei.     

Extraction of thermalized projectile fragments from gas

The NSCL gas cell and quadrupole ion-guide system has been used to study the thermalization of fast nuclear reaction products in a buffer gas. The fraction of radioactive ions that can be extracted from the gas cell is dramatically suppressed by space charge created by the stopping ions. The results of a review of the ion yields from the NSCL and from other gas cells from the literature with different sizes and different incident particle energies shows an overall consistency with a dramatic decline in extraction efficiency at high ionization rates.     

Yields of nuclear fragments in the interactions of carbon nuclei with a beryllium target at a projectile energy of 0.6 GeV per nucleon

The yields of long-lived nuclear fragments at an angle of 3.5° that originate fromthe fragmentation of carbon ions with an energy of T₀ = 0.6 GeV per nucleon on a berylliumtarget were measured in the FRAGMexperiment at the ITEP TWA heavy-ion accelerator. The momentum spectra of these fragments cover both the fragmentation-maximum region and the cumulative region. The respective differential cross sections change by about five orders of magnitude. The momentum distributions of fragments in the laboratory frame and their kinetic-energy distributions in the rest frame of the fragmenting nucleus are used to test the predictions of four models of ion–ion interactions: BC, INCL++, LAQGSM03.03, and QMD.     

Search for projectile fragments with fractional charge in relativistic heavy ion collisions

We measured the charge of about 35 000 projectile fragments with Z5e produced by 14.5 GeV/nucleon and 200 GeV/nucleon ¹⁶O beams in a Pb target using CR39 plastic nuclear track detectors. A minimum track length of 3 mm in the detector without nuclear interaction was required. No evidence for fragments carrying a fractional charge was found.     

Polarization in projectile fragmentation andg-factor measurements for neutron-rich nuclei

A method to produce beams of polarized unstable nuclei was developed, which fully exploits the advantageous features of the projectile fragmentation reaction. The method was applied tog-factor measurements of several neutron-rich nuclei. We present experimental results so far obtained and discuss capabilities and limitations the present polarization method has.     

Yields of projectile fragments in sulphur-emulsion interactions at 3.7 A GeV

This work presents the basic characteristics of singly,doubly and heavily charged projectile fragments(PFs) emitted in inelastic interactions of ~(32)S ions with photo-emulsion nuclei at Dubna energy(3.7 A GeV).Our experimental data are compared with the corresponding data for other projectiles at the same incident energy.The study of mean multiplicities of different charged PFs against the projectile mass shows a power-law relationship.The multiplicity distributions of singly and doubly charged PFs have been fitted well with a Gaussian distribution function.The yields of PFs broken up from the interactions of ~(32)S projectile nuclei with different target nuclei are studied.The beam energy dependence in terms of the various order moments is studied as well.     

On-line isotope separation of projectile fragments produced in relativistic heavy-ion reactions

A new on-line isotope separator was constructed and used successfully for the study on short-lived isotopes at the Bevalac at Lawrence Berkeley Laboratory. The isotopes were produced through projectile fragmentation processes of high energy heavy-ion reactions. Various isotopes were rigidity-separated by use of a beam line and, finally, the desired single isotope was range analyzed to stop in a catcher. A large number of β-emitting²¹F nuclei were successfully collected and the nuclear lifetime was determined by detecting β-rays.     

Intra- and intergroup azimuthal correlations of particles in the interaction of gold nuclei with silver and bromine nuclei of track emulsions at the projectile energy of 10.6 GeV per nucleon

Inter- and intragroup azimuthal correlations of target and projectile fragments and of shower particles in the interactions between gold nuclei of energy 10.6 GeV per nucleon and silver and bromine nuclei of a track emulsion are studied at intermediate values of the impact parameter. The asymmetry index β′₁ and the collinearity index β′₂ of groups’ asymmetry vectors are used to study azimuthal correlations between two and three groups of particles. The interplay of effects of intra- and intergroup azimuthal particle correlations is investigated.     

Fragmentation of relativistic gold nuclei in nuclear emulsion

Basic data are presented on the parameters of fragmentation, multiplicities and angular spectra of low energetic targed associated particles in the interction of ¹⁹⁷Au nuclei of 10.7A GeV.     

Transverse momenta of fragments of relativistic sulfur and lead nuclei after their interaction with track-emulsion nuclei at energies of 200 and 160 GeV per nucleon

Transverse-momentum distributions of doubly charged fragments of sulfur and lead nuclei having energies of 200 and 160 GeV per nucleon and interacting with nuclei in a track emulsion were investigated. No trace of compression or heating of nuclear matter in the interaction of these nuclei with track-emulsion nuclei was revealed experimentally. Transverse momenta of fragments of relativistic nuclei were found to obey a normal distribution that corresponds to a degenerate momentum distribution of nucleons in the ground state of a nucleus before its interaction with a track-emulsion nucleus. There is no piece of evidence that fragments of relativistic nuclei originate from some excited state of an intermediate nucleus. This picture of the fragmentation of relativistic nuclei complies with the naive parton model proposed by Feynman and Gribov. In summary, the fragmentation of relativistic nuclei at energies of 160 and 200 GeV per nucleon is cold and fast.