Emulsion Nuclei Research Articles

Clustering in light nuclei in fragmentation above 1 A GeV

The relativistic invariant approach is applied to analyzing the 3.3 A GeV $^{22}$Ne fragmentation in a nuclear track emulsion. New results on few-body dissociations have been obtained from the emulsion exposures to 2.1 A GeV $^{14}$N and 1.2 A GeV $^{9}$Be nuclei. It can be asserted that the use of the invariant approach is an effective means of obtaining conclusions about the behavior of systems involving a few He nuclei at a relative energy close to 1 MeV per nucleon. The first observations of fragmentation of 1.2 A GeV $^{8}$B and $^{9}$C nuclei in emulsion are described. The presented results allow one to justify the development of few-body aspects of nuclear astrophysics.

Fragmentation in 16 O-emulsion interactions at 3.7 A GeV

The topology of 16O fragmentation at 3.7 A GeV in reactions with emulsion nuclei is presented. The multiplicity distributions of projectile fragments, charged secondaries and their dependences on the projectile residues are discussed.

Erratum to: “Study of backward, forward shower and grey particles production from the interactions of 16O with emulsion nuclei at 4.5 A GeV/c” [Chaos, Solitons and Fractals 18 (2003) 155–124

Erratum to: “Study of backward, forward shower and grey particles production from the interactions of 16O with emulsion nuclei at 4.5 A GeV/c” [Chaos, Solitons and Fractals 18 (2003) 155–124

Fast helium production in interactions of 3.7 A GeV 24Mg 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 ( 〈ns〉, 〈ng〉 and 〈nb〉) 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 〈ni〉 ( 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.

Nuclear fragmentation in interactions of3.7AGeVMg24projectiles with emulsion targets

The process of nuclear fragmentation in interactions of $3.7A\phantom{\rule{0.3em}{0ex}}\mathrm{GeV}$ $^{24}\mathrm{Mg}$ nuclei with the different target nuclei in a nuclear emulsion have been investigated. The total charge distributions of nuclear fragments are well described by the predictions of the extended Glauber model. The multiplicity and charge distributions of fragments with $Z\ensuremath{\geqslant}5$ in quasinucleon target events are found to agree satisfactorily with the calculations of the bond percolation model. The fragmentation of the projectile nucleus depends strongly on the target mass. The probability of interactions without any projectile fragments with charges $Zg2$ is zero for a hydrogen target, but increases by increasing the mass of the target. The disruption of a projectile nucleus is more severe in interactions with the heavy target nuclei than with the light ones. The topology for the nuclear fragmentation channels in interactions of the different projectiles with the different components of emulsion nuclei in the energy range $3.7--200A\phantom{\rule{0.3em}{0ex}}\mathrm{GeV}$ was analyzed. The average multiplicities and the relative rates of nuclear fragmentation channels from the incident nuclei are almost the same for all projectiles at different energies, revealing that the modes of nuclear fragmentation are energy independent. The stripped processes with relativistic hydrogen and∕or helium fragments are the dominant in all projectiles. Helium fragments are the most frequent among the multiple charged fragments and the fractional yield of nuclear fragmentation channels without projectile fragments heavier than helium fragments is about $27%$ of the total sample. The interactions in which the projectile nuclei break up into single charged particles only represent $\ensuremath{\approx}14%$ of the total sample and are mostly due to central collisions in which the majority of projectile nucleons have participated in the first stage of the collisions.

SOME CHARACTERISTICS OF6LiAND7LiISOTOPES INTERACTIONS WITH EMULSION NUCLEI AT 3.7–4.5AGeV/c

Experimental data are presented on the multiplicities of the charged secondaries of the various types in the interactions of6Li and7Li projectile isotopes with the target nuclei in nuclear emulsion at 4.5 A GeV / c and 3.7 A GeV / c , respectively. A systematic comparison using the corresponding values of4He – Em interactions is made. The results are discussed in the frameworks of the cascade evaporation, "wounded" nucleons, and generalized Andersson–Otterlund–Stenlund (AOS) models.

Nuclear clustering in processes of relativistic multifragmentation

Unique capabilities of emulsion technique are considered as applied to the study of multifragmentation of light stable and radioactive nuclei in peripheral interactions at beam energy of few GeV per nucleon. The importance of this research for the physics of few body nuclear systems and the related problems of nucleosynthesis is noted. New results on dissociation of 7Be and 22Ne in very peripheral interactions with emulsion nuclei are presented as an illustration.

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

A comparative study of results obtained from the interactions of 14.6 A 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 14.6 A 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 14.6 A GeV.

Charged particle production in interactions of 24Mg nuclei in nuclear emulsion at 3.7 A GeV

A systematic study on the multiplicity characteristics of relativistic particles in interactions of 3.7 A GeV 24Mg projectile with nuclear emulsion targets was carried out. The dependence of average multiplicities of produced charged particles on the calculated numbers of wounded nucleons and the total number of interactions is studied. In the framework of the wounded nucleon model, the average number of produced particles per participant is independent of impact parameter. The dependence of the mean produced particle multiplicities in nucleus–nucleus interactions ⟨nπ⟩ on the normalized charge flow in the forward direction ζ, which is experimentally measured and strongly correlated with the impact parameter b, is investigated via a single formula based on a simple geometrical model. A strong dependence of the average value of the produced charged particles on both size and energy of the beam nucleus is observed. The experimental values are in good agreement with the theoretical calculations based on a simple geometrical model.

Study of backward, forward shower and grey particles production from the interactions of 16O with emulsion nuclei at 4.5 A GeV/c

This paper presents the results of the study of interaction of the relativistic 16O nucleus with the momentum 4.5 A GeV/c with the photo emulsion. The average multiplicities of the different emitted hadrons (shower and grey) in the forward (FHS) and backward (BHS) hemisphere, compared with other data from the interaction of 1P, 4He, 6Li, 12C, 22Ne and 28Si at nearly the same momentum, have been studied as a function of projectile mass number, the number of interacting projectile nucleons, impact parameter and number of shower particles emitted in the backward hemisphere. The multiplicity distribution of the shower particles emitted in the forward and backward hemisphere directions using the KNO representation are represented and described by an exponential form for BHS shower particles. Another objective of this paper is to examine whether the mechanism of particle production in the BHS is significantly different from the operating in the production of particles in the FHS which can help to solve some questions connected with the role of collective phenomena in the backward emission of particles from the nuclear targets.

Fragmentation of 16 O nuclei in nuclear emulsion

We present the topology of 16O fragmentation at 60 A GeV in reactions with emulsion nuclei. We discuss the multiplicity distributions of projectile fragments, charged secondaries and their dependence on the target residues.

The characteristics of proton and induced neutron-emulsion high energy interactions

We used the technique of the separation of Coulomb and diffraction dissociation of incident heavy ion to select the events due to induced neutron from 16O leaving sub-oxygen nucleus to break-up. The characteristics of these events of neutron emulsion collisions are displayed and compared with that obtained from incident proton at the same energy. The studied interactions are classified according to the type of target nucleus (H, CNO and AgBr) by using the method of separation. Cascade-evaporation model (CEM) calculations are taken into account and compared with that obtained from the interactions of induced neutron from 16O (4.5 A GeV/ c) with emulsion nuclei and with the results of incident proton at the same target and energy. CEM can describe the distributions of proton and neutron interactions. It is conjuctured that it may be possible to develop a similar theoretical model based on the modern methods of nonlinear dynamics, neural network and complexity [Randomness and Undecidability in Physics, World Scientific, Singapore, 1993].

Multiplicities of forward–backward particles in 32S–emulsion interactions at 4.5 A GeV/c

An exclusive study of the characteristics of the interactions accompanied by the backward emission (θLab ≥ 90°) of relativistic and fast hadrons in the collisions of 4.5 A GeV/c 32S beam with emulsion nuclei is carried out. The experimental multiplicity distributions of different particles emitted in the forward (θLab < 90°) and backward hemispheres due to the interactions with the two emulsion components (CNO, AgBr) are presented and analysed. The correlations between the multiplicities of the different emitted particles are also investigated. This study reveals that there are signatures for a collective mechanism, which plays a role in the production of particles in the backward hemisphere. Hence, the backward multiplicity distribution of the emitted shower or grey particles at 4.5 A GeV/c incident momentum can be represented by a decay exponential law formula independent of the projectile size. The exponent of the power was found to increase with decreasing target size. The experimental data favour the idea that the backward particles were emitted due to the decay of the system in the latter stage of the reaction. While the mean values of the shower particles emitted in the forward hemisphere ⟨nfs⟩ are strongly dependent on the projectile size and incident energy, the mean value of the multiplicity of the shower particles flying into the backward hemisphere ⟨nbs⟩ are found to be only a function of the target size (i.e. impact parameter). Therefore, the results yield quite interesting information regarding the mechanism of the backward particle production in heavy ion interactions. The present data are believed to support the mechanism, which considers the backward particle production as a consequence of the isotropic decay of a highly excited target system, in its rest frame, after the forward particle emission.

Charged-particle multiplicity distributions in different rapidity windows in 800 GeV proton-nucleus interactions

Multiplicity distributions of charged particles produced in interactions of 800 GeV protons with emulsion nuclei in various rapidity windows are presented. The data is also analyzed separately for the forward and the backward hemispheres, for rapidity windows of different widths. It is found that the Negative Binomial Distribution (NBD) describes well the multiplicity distribution of secondary particles in various rapidity windows and also in both the hemispheres. We have compared the NBD parameters, in both the hemispheres, at 200 GeV and 360 GeV, with those at 800 GeV. The behaviour of NBD parameters in rapidity windows of different widths and for different targets has also been studied.

Fragmentation of nuclei as a function of centrality of collision in interactions of gold projectiles at 10.6 A GeV

We have studied the fragmentation of light (C/N/O) and heavy (Ag/Br) nuclei of emulsion in collisions with gold projectiles at 10.6 A GeV and the fragmentation of these gold nuclei in collisions with hydrogen, (C/N/O) and (Ag/Br) nuclei. The analysis was restricted to the investigation of the number of fragments and in some cases the total charge of fragments as a function of the centrality of collisions with nuclei of different masses. We observe a decrease in the number of target fragments with increasing centrality for interactions of projectiles with masses comparable or greater than the mass of the target nucleus. As the collision becomes more central a significant number of participating protons from the target nucleus get enough momentum to become relativistic due to intranuclear interactions. These results have been compared with the predictions of the RQMD model.

Rapidity correlations in 800 GeV proton-nucleus interactions

Rapidity correlations in 800 GeV proton interactions with emulsion nuclei are investigated for different targets and multiplicity regions. To study the energy dependence, the results have been compared with proton interactions at 200 GeV and 400 GeV. A common feature of all the interactions is the existence of strong, short-range correlations. However, no dependence of cluster parameters on primary energy or target mass is found. A marginal increase of correlation strength with multiplicity is observed.

Study of double-strangeness nuclei with hybrid-emulsion method (KEK-PS E373)

Abstract An experiment to search for double-strangeness nuclei in nuclear emulsion is now being carried on as KEK-PS E373. Preliminary results of the data analysis for the K + spectrometer and the scintillating fiber detectors are presented. Status of the automatic track finding method for the emulsion is reported.

Structures and angular distributions of slow and relativistic charged particles produced in 7Li-emulsion interactions at 3 GeV/c per projectile nucleon

Experimental results on the multiplicity distributions of various particles produced in the interactions of 7Li with emulsion nuclei at a momentum of 3 GeV/c per projectile nucleon are reported. A comparison with data on collisions induced by other nuclei at a nearly identical momentum per nucleon is presented in order to reveal the dependence on the projectile mass. The internal structure of 7Li is explored by studying the projectile fragment. The mean multiplicity of shower particles, 〈ns〉, induced by 7Li is found to be less than that in the case of 6Li projectiles. The angular distributions of target fragments and relativistic charged secondaries are investigated. No shock-wave phenomena are observed. Forward-to-backward ratios are calculated for each case. The probability distributions for relativistic secondaries produced per unit rapidity are studied in detail, along with the rapidity densities and their dependence on the projectile and the target mass. A comparison of the angular spectra of shower particles produced in central and peripheral collisions supports the limiting-fragmentation hypothesis. The collisions in question seem to become more central with increasing shower-particle multiplicity.

Central events in the interactions of 28Si and 32S with heavy emulsion targets

Data on the multiplicity of secondaries in central events of 28Si (14.6 AGeV) and 32S (3.7 AGeV) interactions with AgBr emulsion nuclei have been compiled and studied. The dependence of the multiplicities of the outgoing charged stripping particles on the number of interacting nucleons and therefore on the impact parameter, as indicated by the target size, and consequently, on the degree of centrality is investigated. The resultant multiplicity distribution of the produced pions for each studied case is fitted by both Negative Binomial (NB) and Poisson distributions. The NB distribution is valid for most of the considered cases. The transparency of the target for a projectile was found to become more pronounced as the incident energy increased.

Production of twin Λ-hypernuclei from Ξ− hyperon capture at rest

A hybrid emulsion experiment was carried out to study double-strangeness nuclei produced via Ξ − hyperon capture at rest with the expectation of ten times larger statistics than previous experiments. We have analyzed 5% of the total emulsion and found one “twin-hypernuclei” event involving the emission of two single- Λ hypernuclei and a nuclear fragment from a Ξ − hyperon stopping point. The event is interpreted as the decay of a Ξ −+ 14 N atomic system to 5 Λ He+ 5 Λ He+ 4 He+ neutron . The species of the Ξ −-atom and the fragmentation products are uniquely identified for the first time for twin-hypernuclei events. Combined with the results from a past hybrid-emulsion experiment, one double- Λ hypernucleus and three twin-hypernuclei events have been found from Ξ − captures on light emulsion nuclei. The ratio of the detected rate of double- Λ hypernuclei to that of twin-hypernuclei is compared with theoretical estimates.