Characteristics of alpha projectile fragments emission in interaction of nuclei with emulsion

The properties of the relativistic alpha fragments produced in interactions of ⁸⁴Kr at around 1 A GeV in nuclear emulsion are investigated. The experimental results are compared with the similar results obtained from various projectiles with emulsion interactions at different energies. The total, partial nuclear cross-sections and production rates of alpha fragmentation channels in relativistic nucleus-nucleus collisions and their dependence on the mass number and initial energy of the incident projectile nucleus are investigated. The yields of multiple alpha fragments emitted from the interactions of projectile nuclei with the nuclei of light, medium and heavy target groups of emulsion-detector are discussed and they indicate that the projectile-breakup mechanism seems to be free from the target mass number. It is found that the multiplicity distributions of alpha fragments are well described by the Koba-Nielsen-Olesen (KNO) scaling presentation. The mean multiplicities of the freshly produced or newly created charged secondary particles, normally known as shower and secondary particles associated with target in the events where the emission of alpha fragments were accompanied by heavy projectile fragments having Z ≥ 3 seem to be constant as the alpha fragments multiplicity increases, and exhibit a behavior independent of the alpha fragments multiplicity.     

Evidence for a nuclear phase transition in target nuclei after relativistic nuclear interactions

The degree of excitation of the emulsion target nuclei due to nuclear interactions of oxygen and sulfur projectiles at 200 GeV/nucleon incident energy has been investigated. Using the plausible assumption that the numberN _b of slow particles emitted from the struck target nucleus can be interpreted as a measure of the temperatureT of the residual nucleus, we have found that there exists a critical temperatureT _c of the excited target nucleus. For Ag and Br target nuclei this temperature corresponds to <N _b>≌12 and it is attained when the impact parameters are less than about 4 fm.     

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 and particle production in interactions of 10.6 GeV/N gold nuclei with hydrogen, light and heavy targets

We have investigated the interactions of 10.6 GeV/n Au in nuclear emulsion. Two methods of separating interactions into those with hydrogen, light (C,N,O) and heavy (Ag,Br) target nuclei were used, giving almost identical results, which strengthened our confidence in the correctness of these methods. We also measured the angular distributions of singly and multiply charged relativistic particles emitted from the interaction vertices and the charges of the multiply charged projectile fragments. The fragmentation of the projectile Au nuclei and of the target nuclei were analyzed. The multiparticle production was studied as a function of the mass of the target nucleus. The multiplicity and the pseudorapidity distributions of relativistic singly charged particles were compared with the predictions of the RQMD Model. Received: 22 April 1998 / Published online: 8 September 1998     

Interactions of 10.6 GeV/n gold nuclei with light and heavy target nuclei in nuclear emulsion

Zeitschrift für Physik C Particles and Fields - We have investigated the particle production and fragmentation of nuclei participating in the interactions of 10.6 GeV/n gold nuclei in nuclear...     

Fast helium production in interactions of 3.7 A GeV <Superscript>24</Superscript>Mg with emulsion nuclei

We have studied the properties of the relativistic helium fragments emitted from the projectile in the interactions of ²⁴Mg ions accelerated at an energy of 3.7 A GeV with emulsion nuclei. The total, partial nuclear cross-sections and production rates of helium fragmentation channels in relativistic nucleus-nucleus collisions and their dependence on the mass and energy of the incident projectile nucleus are investigated. The yields of multiple helium projectile fragments disrupted from the interactions of ²⁴Mg projectile nuclei with hydrogen H, light CNO and heavy AgBr groups of target emulsion nuclei are discussed and they indicate that the breakup mechanism of the projectile seems to be independent of the target mass. Limiting fragmentation behavior of fast-moving helium fragments is observed in both the projectile and target nuclei. The multiplicity distributions of helium projectile fragments emitted in the interactions of ²⁴Mg projectile nuclei with the different target nuclei of the emulsion are well described by the KNO scaling presentation. The mean multiplicities of the different charged secondary particles, normally defined shower, grey and black ( n_s, n_g and n_b) emitted in the interactions of 3.7 A GeV ²⁴Mg with the different groups of emulsion nuclei at different ranges of projectile fragments are decreasing when the number of He fragments stripped from projectile increases. These values of n_i ( i = s, g, b and h particles) in the events where the emission of fast helium fragments were accompanied by heavy fragments having Z 3 seem to be constant as the He multiplicity increases, and exhibit a behavior independent of the He multiplicity.     

Universality of multifragmentation of residual nuclei produced in high-energies nucleus-nucleus interactions

Experimental data on the multifragmentation of residual nuclei produced in the krypton interactions with photoemulsion nuclei at 0.9 GeV per projectile nucleon are presented and compared with similar data on fragmentation from experiments where gold nuclei of energy 10.7 GeV per nucleon appear as projectiles. It is shown for the first time that there exist two modes of nuclear multifragmentation, those where less (first mode) or more (second mode) than half of nucleons are knocked out of the incident nucleus. Residual nuclei that have close masses and which are produced in various reactions accompanied by the knock-on of more than half of nucleons of the initial nucleus fragment in nearly the same way. In addition, evidence for a radial flux of spectator fragments is obtained for the first time in the decay of residual nuclei of krypton projectiles.     

Justification of Landau Hydrodynamic-Tube model in central relativistic heavy-ion collisions

The statistical event-by-event analysis of inelastic interactions of ¹⁶O and ³²S nuclei in emulsion at 60 A?GeV/c and 200 A?GeV/c reveals the existence of groups of high multiplicity events belonging to very central nuclear interactions with Gaussian pseudorapidity distributions for produced particles as suggested by the original hydrodynamic-tube model. Characteristics of these events are presented. The experimental observations are interpreted as a result of quark-gluon plasma formation in the course of central nuclear interactions.     

Fragmentation and multifragmentation of 10.6A GeV gold nuclei

The experimental data on the interactions of 10.6A GeV gold nuclei in nuclear emulsions are analyzed with particular emphasis of target separation interactions and study of critical exponents. Charged fragment moments, conditional moments as well as two and three – body asymmetries of the fast moving projectile particles are determined in terms of the total charge remaining bound in the multiply charged projectile fragments. Some differences in the average yields of helium nuclei and heavier fragments are observed, which may be attributed to a target effect. However, two and three-body asymmetries and conditional moments indicate that the breakup mechanism of the projectile seems to be independent of target mass. We looked for evidence of critical point observable in finite nuclei by study the resulting charged fragments distributions. We have obtained the values for the critical exponents γ, β and τ and compare our results with those at lower energy experiment (1.0A GeV data). The values suggest that a phase transition like behavior, is observed. Received: 2 July 1998 / Revised version: 26 March 1999     

Azimuthal structures of produced particles in heavy-ion interactions

The angular structures of particles produced in ²⁰⁸Pb at 158 A GeV/c and ¹⁹⁷Au at 11.6 A GeV/c induced interactions with Ag(Br) nuclei in emulsion detector have been investigated. Nonstatistical well-ordered ring-like structures of produced particles in azimuthal plane of a collision have been found, and their parameters have been determined. The text was submitted by the authors in English.     

Multifractal critical thermodynamics in nucleus-nucleus collisions

Critical points approach in the frames of multifractal thermodynamics is suggested to interpret the experimental data on nuclear multifragmentation which come from interactions in nuclear emulsion (in which ¹⁹⁷ ₇₉Au₁₁₈ nuclei of energy ∼1 GeV/nucleon break up into fragments) and from the charge distributions of projectile fragments in sulphur (³²S) fragmentation at 200 GeV/nucleon. It is also shown that multifragmentation after macro-solids collisions exhibits properties analogous to those observed in the nuclear multifragmentation experiments. Received: 19 October 1999     

Detailed study of relativistic 9Be → 2α fragmentation in peripheral collisions in a nuclear track emulsion

Recent studies of clustering in light nuclei with an initial energy above 1 A GeV in a nuclear track emulsion are overviewed. The results of investigations of the relativistic ₉Be nuclei fragmentation in emulsion, which entails the production of α particles, are presented. It is shown that most precise angular measurements provided by this technique play a crucial role in the restoration of the excitation spectrum of the α particle system. In peripheral interactions ₉Be → 2α nuclei are dissociated practically totally through the 0⁺ and 2⁺ states of the ⁸Be nucleus.     

Recent results on particle production from silicon emulsion interactions at 14.6A GeV

A comparative study of results obtained from the interactions of 14.6A GeV ²⁸Si in nuclear emulsion is presented. In this work the experimental data serve as one of the decisive signature of quark–gluon plasma formation. The data for 200 and 400 proton-emulsion interactions are used to investigate the assumption which consider interaction of ²⁸Si-Em at 14.6A GeV is such that for a proton with total energy corresponding to that for effective number of interacting nucleons (12.6×14.6=175) or as a proton having the total energy of ²⁸Si (i.e., 28×14.6=409 GeV). It is also shown that the relativistic quantum molecular dynamics model nicely predicts the multiplicities and correlations of shower and grey particles in the interactions of ²⁸Si with emulsion nuclei at 14.6A GeV.     

Characteristics of He-nucleus interactions at relativistic energy

From the peripheral collisions of²⁸Si projectile at 14.5 A GeV in nuclear emulsion, emerged⁴He nuclei among the projectile fragments, are followed for their interactions. Multiplicity and pseudorapidity distributions of the produced particles emanating from 366 inelastic⁴He induced emulsion reactions are compared with those of²⁸Si at 14.5A GeV,⁴He at 140A GeV and proton at 800 GeV beams. Standard deviation of the Gaussian fittings to the pseudorapidity distributions for different values of average shower particle multiplicities represents an approximate measure of the impact parameter. Second moments of the multiplicity distributions of the shower tracks can be parameterized in terms of a universal polynomial dependence. Results agree quite well with the predictions of the multistring model VENUS.     

Multiplicity of secondary particles and fragmentation in nuclear interactions of22Ne and32S nuclei with emulsion at (4.1–4.5)A GeV/c

The interactions of 4.1AGeV/c ²²Ne and 4.5AGeV/c ³²S nuclei with emulsion have been studied and the dependence of the average multiplicities of the emitted secondary charged particles and the interacting projectile nucleons on the impact parameters have been investigated. The behavior of the Koba-Neilsen-Olesen (KNO) scaling formula of the multiplicity distributions produced due to the interactions of²²Ne and³²S at the energies mentioned above is satisfied by all target protons. The multiplicity distributions of the emitted⁴He fragments and the fragmentation cross-section relative to the inelastic cross-section have been investigated and give a⁴He-fragments yield which is always ten times greater than the yield of any other fragments. The dependence of the normalized mean multiplicity and the reduced multiplicity on the mass of the projectile and target nucleus can be described by a power law.     

Analysis of charged-particle production in nucleus-nucleus interactions near and beyond the kinematical limit for free NN collisions within the FRITIOF model

The production of charged particles (π ^± mesons and protons) in nucleus-nucleus interactions at energies in the range 3.3–3.7 GeV/nucleon is considered. It is shown that the FRITIOF model adapted to moderately high energies reproduces satisfactorily the energy spectra of mesons emitted into the backward hemisphere in the laboratory frame, as well as their dependence on the masses of colliding nuclei. The FRITIOF model supplemented with the Reggeon model of nuclear breakup allows one to describe the soft part of the spectra of backward-emitted protons. Other approaches are required for describing the hard part of the spectra.     

Inelastic interactions of 9.38 GeV/c deuteron in emulsion

Characteristics of the inelastic interactions of 9.38 GeV/c deuterons with nuclear emulsion nuclei have been studied. These have been compared with nucleon-nucleus interactions at a corresponding momentum. The probability of nucleon stripping in deuteron-nucleus interactions has been observed to be 0.5. The charged particle multiplicity in deuteron-nucleus interactions exhibitA-dependence of the typeA ^α with α=0.08. The experimental data disagree with KNO scaling.     

Search for shock-wave phenomena in central 16O-AgBr interactions at 0.2 and 2.0 GeV/nucleon

Angular distributions of high energy He nuclei, emitted from the target in central ¹⁶O-AgBr interactions, are found to be highly forward-peaked at 0.2 GeV/nucleon but almost isotropic at 2 GeV/nucleon. The angular distributions are in qualitative agreement with recent shock-wave calculations. However, we observe no narrow peaks neither in the angular nor in the energy distributions of He nuclei.     

Interaction of relativistic alpha particles in emulsion at 2.1 GeV/c/nucleon

An analysis for 2,000 events produced by 2.1 GeV/c/n alpha particles in nuclear emulsion has been carried out. Multiplicity and angular distributions of charged secondaries have been measured and correlation among them are discussed. The presented data are compared with relevant values from proton and¹⁴N interactions with nuclei. The multiplicity distribution of showers has been tested by a modified independent nucleon-nucleus multiple scattering model (INAM) of reference [8], and by the model of reference [12].