Search

An extended Cu target was centrally irradiated with 22 and 44 GeV carbon ions for about 11 and 15 hours, respectively. The upper side of the target was in contact with a paraffin block for the moderation of secondary neutrons. Small holes in the moderator were filled with lanthanum salts (LaCl37H2O) where the neutrons induced the 139La(n,γ) 140La reaction. The β-decay of 140La(40h) was followed using radiochemical methods. The yields for the formation of 140La agree within large errors with other experiments on extended targets carried out at the LHE, JINR (Dubna). To a first approximation, the breeding rate of 140La doubles when the 12C energy is increased from 22 to 44 GeV. If results at 44 GeV are compared to those at 22 GeV, there cannot be excluded an excess of (20 ± 7)% in the experimentally observed 140La production over theoretical estimates. A definite conclusion in this respect must await further experimental and theoretical work. These experiments are the beginning of a research progra...

Determining the algebraic K-theory of rings of integers in number fields has been the goal of much research. In [10] D. Quillen showed that the Hurewicz map h : Q0(S ) → BGL(Z) (see 1.1 for the notation) induces an interesting map on homotopy groups from the stable homotopy groups of spheres to the algebraic K-theory of the ring Z of rational integers. Quillen observed that if ` is an odd prime and if p 6= ` is another prime generating the `-adic units, then the composite map

The application of the quantum statistical formalism to multiplicity distributions has been generalized to include corrections for nonstationarity'' in rapidity as well as the transverse-momentum dependence. The identical-particle data available so far can be explained in this formalism with a quite broad range of parameters of chaoticity and correlation lengths.

M.I. Adamovich a, M.M. Aggarwal b, Y.A. Alexandrov a, N.P. Andreeva c, Z.V. Anson c, R. Arora b, F.A. Avetyan d, S.K. Badyal e, E. Basova f, K.B. Bhalla g, A. Bhasin e, V.S. Bhatia b, V.G. Bogdanov h, V.I. Bubnov c, T.H. Burnett i, X. Cai J, I.Y. Chasnikov c, L.P. Chernova k, M.M. Chernyavski a, B. Dressel ~, G.Z. Eligbaeva c, L.E. Eremenko ~, E.M. Friedlander m, A.S. Gaitinov ~, E.R. Ganssauge ~, S. Garpman ", S.G. Gerassimov a, j. Grote i, K.G. Gulamov k, S.K. Gupta g, V. Gupta e, H.H. Heckrnan ~, H. Huang J, B. Jakobsson ", B. Judek o, S. Kachroo e, F.G. Kadyrov k, G.S. Kalyachkina c, E.K. Kanygina ~, M. Karabova P, G.L. Kaul e, M. Kaur b, S.P. Kharlamov a, T. Koss i, S.A. Krasnov P, V. Kumar g, P. Lal g, V.G. Larionova a, V.N. Lepetan ~, P.J. Lindstrom m, L.S. Liu J, S. Lokanathan g, J. Lord i, N.S. Lukicheva k, S.B. Luo q, L.K. Mangotra e, N.A. Marutyan d, N.V. Maslennikova ", I.S. Mittra b, S. Mookerjee g, C. Mueller ~, H. Nasrulaeva f, S.H. Nasyrov f, V.S. Navotny k, G.I. Orlova a, I. Otterlund n, H.S. Palsania g, N.G. Peresadko a, N.V. Petrov f, V.A. Plyushchev h, W.Y. Qian J, R. Raniwala g, S. Raniwala g, N.K. Rao ~, V.M. Rappoport a, J.T. Rhee ~, N. Saidkhanov k, N.A. Salmanova ~, L.G. Sarkisova d, V.R. Sarkisyan d, W. Schulz ~, G.S. Shabratova P, T.I. Shakhova ~, B. Singh b, D. Skelding i, K. SSderstrSm ", Z.I. Solovjeva h, E. Stenlund n, S.C. Strausz i, J.F. Sun r, L.N. Svechnikova k, K.D. Tolstov P, M.I. Tretyakova a, T.P. Trofimova r, U. Tuleeva r, S. Vokal P, H.Q. Wang J, Z.Q. Weng r, R.J. Wilkes i, G.F. Xu s, D.H. Zhang q, P.Y. Zheng s, S.I. Zhochova k, D.C. Zhou J and J.C. Zhou J

The slow, target associated particles produced in ultrarelativistic heavy-ion interactions are a quantitative probe of the cascading processes in the spectator parts of the target nucleus. These processes are directly influenced by the proper timescale for the formation of hadronic matter. In this letter we show experimental data on singly and multiply charged particles, with velocities smaller than 0.7 c , produced in ultrarelativistic heavy-ion interactions in nuclear emulsion.

In this letter we show that most of the fluctuations in particle densities observed in relativistic heavy-ion collisions are consistent with stochastic emission, i.e., most of the correlations between produced particles are washed out due to the vast number of particles in the environment. We further explore the general trends by investigating different systems, energies and centrality cuts. Comparisons with the Fritiof model show that string fragmentation gives results similar to the data.

The use of a multiplicity cut introduces a bias distorting the Bose-Einstein correlations. An extensive Monte Carlo simulation based on a quantum statistical formalism, reveals that this bias has a substantial effect on the estimate of the true correlation length and chaoticity. It also reveals a strong antibunching effect at a fixed event multiplicity n , as has been observed experimentally.

In the present letter we discuss the general features of the multiplicity distributions in relativistic heavy ion collisions. It is shown that from simple statistical considerations it is possible to predict the dependence of the dispersions of multiplicity distributions on the average multiplicities in any given rapidty wwindow. The applicability of the negative binomial distribution to multiplicity distributions from collisions with heavy ions is discussed.

The average multiplicities of singly charged relativistic particles in oxygen-induced interactions with a nuclear emulsion target are studied over the energy range 2.1–200 A GeV. A similar energy dependence as for proton-induced interactions is observed. Both the number of participating nucleons and the number of binary collisions are shown to be of importance for the particle production.

The multiplicity distributions of low-energetic target-associated particles from 200 A GeV oxygen-induced interactions with emulsion nuclei are presented. The experimental distributions are compared with distributions obtained using the Ranft and Fritiof simulation codes. It is found that the intra-nuclear cascade plays an important role in ion-induced interactions, similar to what is the case for hadron-induced interactions.

We report on recent results obtained by the EMUO1 collaboration from studies of 16O + emulsion, at 14.6, 60 and 200 A GeV, and 32S + emulsion and 32S + Au interactions at 200 A GeV. Shower-particle production in oxygen-induced interactions are studied over the energy range 2.1-200 A GeV. Scaling and limiting fragmentation are observed. Multiplicity and angular distributions of low energy target-associated particles are presented and compared with distributions obtained using the Ranft and the Fritiof simulation codes.

Multiplicity distributions in high-energy hadronic reactions are broader in the central rapidity region than in the fragmentation region. An explanation of this phenomenon in terms of a stochastic branching equation is given supporting the picture of two sources, one mainly chaotic and one essentially coherent.

S+Au interactions at 200{ital A} GeV were observed using emulsion chambers, permitting measurement of pseudorapidities in the central region with precision {similar to}0.01 unit. Scaled-factorial-moment analyses are extended to bin sizes smaller than those accessible to other fixed-target experimental techniques. For a sample of 151 central collisions, moments are calculated using both horizontal'' and vertical'' analysis techniques. While the moments are found to rise (in a log-log plot) with decreasing pseudorapidity bin size {delta}{eta}, their slopes roll off to approximately zero for {delta}{eta}{lt}0.1.

In the quantum statistical approach to the study of multiplicity distributions the most relevant variables are the amount of chaoticity of the source, the coherence length of the fields and the mean multiplicity. The authors investigate the energy dependence of these quantities as it appears from the available data in the range 24 GeV

A recent article interpreted the experiment by Dersch et al. on the formation of 24Na in 40Ar + Cu interactions in a very simple manner. The results from emulsion experiments performed with 3.6 AGeV 22Ne were adapted for the interpretation of the experiments with 1.8 AGeV 40Ar. The model used the same mean value for the energy of minimum ionizing protons and pions at all angles. It is argued that a more complex approach is needed for a satisfactory interpretation.

The pseudo-rapidity density distributions of shower particles (n s ) are measured in central inelastic S + Au and S + Ag,Br inter-actions. The extracted maximum energy densities, while being higher for Au than for Ag.Br interactions, were found to be similar to those obtained for oxygen emulsion interactions. The correlation between rapidity density and shower particle multiplicity shows a small deviation from the Lund Model Fritiof for the highest energy densities in S + Au interactions, whereas the bulk of the data yields satisfactory agreement.

The lengths of etched tracks in meteoritic olivine crystals have previously been used to investigate the charge spectra of heavy galactic cosmic ray nuclei. Etchable track lengths up to 350 μm (after annealing the crystals for 32 hours at 430°C) were observed in olivines and the longest tracks have been interpreted to be possibly due to superheavy elements (SHE). For the purpose of calibration, artificial olivines were irradiated with a large variety of heavy ions including high energy (∼ 1 AGeV) uranium ions from the BEVALAC (Berkeley). The crystals were annealed under several different conditions and etched using standard procedures. After applying the above-mentioned annealing procedure, we measured in a very preliminary experiment uranium track lengths. Further results will be presented. At present, the question whether long tracks in meteoritic olivines are due to SHE or not remains open.

We report from an experiment where 400 GeV protons interact with tungsten nuclei in thin wires laminated into nuclear emulsion. The mean multiplicities of black, grey and shower track producing particles are found to be 11.5±0.4, 5.2±0.2 and 20.0±0.6, respectively. The correlations between different particle categories are studied and we find that the correlation between black and grey prongs is dependent on the target mass, while the correlation between the grey prongs and the shower particles are similar to the one found when lighter elements are used as targets. This provides evidence that the grey prong particles (recoiling protons) are a measure of the number of collisions inside the nucleus.

The scattering constant of AgCl monocrystals was estimated by comparing the multiple Coulomb scattering of stopping 16 O ions as a function of residual range in an AgCl monocrystal and in Ilford G5 nuclear emulsion. The ratio of scattering constants for the two media was found to be 1.255±0.038, as compared to the theoretical prediction of 1.273. Absence of sizeable distortion in the monocrystal was checked by measurements on fast 16 O ion tracks. The reading noise level on the AgCl tracks was found to be at most equal to that in nuclear emulsion. From the observed dispersions it is estimated that a track length of 8 mm in the monocrystal should be sufficient to estimate the ion charge within one unit.

The multiplicity distributions of shower particles (ns) are measured in inclusive inelastic oxygen emulsion interactions. Scaling is observed in the normalized variable ns/〈ns〉 for 14.6, 60 and 200 AGeV. The dependence of 〈ns〉 on the charge flow in the forward direction (QZD) and the distribution of the number of participating projectile protons is examined. The normalized multiplicities as a function of QZD seem also to be independent of incident energies. A comparison with the Lund model Fritiof yields satisfactory agreement.

We report on an experiment in which emulsion chambers were exposed to a beam of 200 A GeV 16 O at the CERN SPS. Pseudo-rapidity distributions are measured with high precision. Pseudo-rapidity densities of 140 particles per unit rapidity corresponding to an energy density of about 3 GeV/fm3 are observed. Pseudo-rapidity density distributions and fluctuations are found to satisfactorily agree with the Lund Monte Carlo model Fritiof, although new and unknown sources for fluctuations might still be present.

An interpretation of Centauro events in terms of a “precocious” superfluorescent-like decay of a coherently excited fireball is proposed. Implications for p -p CERN collider experiments are discussed.

The methods of quantum statistics (QS) including a finite coherence length are applied to multiply distributions P(n) in e+-e- and mu -p reactions. The rapidity dependence of P(n) gets a simple explanation as a consequence of a scaling regularity derived from QS.

Two independent emulsion experiments using Bevalac beams of {sup 16}O and {sup 56}Fe at {approx}2 GeV/nucleon find with > 99.7% confidence that the reaction mean-free paths of projectile fragments, 3 {approx}< Z {approx}< 26, are shorter for a few centimeters after their emission than at larger distances, or than predicted from experiments on beam nuclei. This effect, which is enhanced in later generations of fragments, can be interpreted by the relatively rare occurrence of fragments that interact with an unexpectedly large cross section.

The inelasticity distribution is shown to affect in a decisive manner many particle production processes determining the correlation between transverse momenta and multiplicities. The effects on the energy dependence of 〈 p T 〉 and the multiplicity distribution are also studied.

Proton-nucleus interactions have been studied in nuclear emulsion exposed to the NAL 200 GeV proton beam. The inelastic mean free path is found to be 35.5 ± 0.8 cm and the average shower particle multiplicity is 12.9 ± 0.2. The angular distribution reveals some characteristics features of proton-nucleus interactions.

In relativistic heavy ion interactions some very interesting and possibly new phenomena have been reported. After a short review, the main emphasis of this paper is placed on the unusual behavior of projectile fragments formed in the interaction of 72 GeV Ar-40 and 44 GeV C-12 with thick Cu-targets. The effect has been investigated with nuclear chemistry techniques and CR-39 SSNTD. It could be an “anomalous” phenomenon. The importance of a combination of various techniques is stressed in order to investigate wide-angle emission of energetic secondary fragments , producing Na-24 in copper. Some emphasis will be placed on the contribution of CR-39 SSNTD studies towards this problem.

We present the results of 1179 precise charge measurements carried out on 1 ⩽ Z ⩽ 3 projectile fragment nuclei from relativistic nucleus-nucleus collisions in nuclear emulsion. We find no evidence for the existence of third-integral fractionally charged projectile fragments, particularly for those with charges 5 3 and 7 3 .

An exclusive-type study of the transverse momentum distribution of alpha particles emerging as relativistic projectile fragments from collisions of a 1.9 GeV/nucleon 56Fe beam in nuclear emulsion reveals that the events fall into either one or the other of two distinct classes with sharply differing characteristics. Each of these classes is characterised by a Maxwellian distribution in the projectile rest frame, but the associated temperatures differ by a factor of about four (namely approximately=10 MeV and approximately=40 MeV; the same 40 MeV temperature is observed among target-related alpha particles emitted from 12C collisions in nuclear emulsion at 0.87 GeV/nucleon and 2.1 GeV/nucleon). The authors show that the 'hot' (T approximately=40 MeV) events are not simulated by 'projectile bounce' effects, and that they occur among events of high multiplicity as well as among those of low multiplicity. They are regarded as direct evidence for a highly collective mechanism.

Two consequences of coherence of mesonic fields have been tested in proton-nucleus collisions. Multiplicity fluctuations measured in finite rapidity intervals are found to obey a Poisson distribution at large rapidities where nuclear transparency occurs. In close analogy to quantum optics we present a quark-parton model in which this link between coherence and transparency is realized via the phenomenon of self-induced transparency.

The ratio of the production of very slow antiprotons to that of pions in the same momentum interval was measured at the ISR by means of nuclear emulsions. Averaged over the interval 0.12 GeV/c ⩽ p⊥ ⩽ 0.34 GeV/c and 0 ⩽ p∥ ⩽ 0.2 GeV/c, N(p)/N(π−) = 0.063 ± 0.012.

Angular and multiplicity correlations in proton–nucleus interactions in emulsion are interpreted within the framework of the Energy Flux Cascade model. The average mass of the 'slow bodies' or novae emitted in the backward hemisphere is ~3.5 GeV/c2 at both energies. This result is in reasonable agreement with previous work on two-particle correlations.

ICAMS (Interactive Computer Assisted Measurement System) is designed to permit the acquisition and analysis of emulsion scan and measurement data at a rate much faster than any existing manual techniques. It accomplishes this by taking the burden of stage motion control and data recording away from the scanner and putting it onto the computer. It is a modern distributed network system, where a central PDP-11 computer running under RSX-11M V4 communicates with two-ported UNIBUS memory; each two-ported memory resides on the local intelligence of each independent ODS (Optical Data Station). The intelligence of each ODS is a 6512 microcomputer running under FORTH and enhanced with a floating point processor card. Each ODS is supported on ICAMS using the virtual memory features of FORTH, permitting full access to the disk storage facilities of the PDP system. To the scanner, each ODS is conversational and menu driven. To the physicist, utilities have been written that permit FORTRAN-77 programs to easily acquire and thus analyze the data base on the PDP-11.

Projectile fragments formed in the interaction of 0.9A-GeV and 1.8A-GeV /sup 40/Ar ions with a Cu disk interact with a second Cu disk and the relative yields of products in the two disks are measured by radioactivation techniques as a function of the distance between them. The data at 1.8A-GeV demand either (1) decay in flight (t/sub 1/2/roughly-equal10/sup -10/ s) of some projectile fragments having large cross sections or (2) production of secondaries with unexpectedly large transverse momenta.

An investigation of the energy dependence of grey prong producing particles in 16 O+ emulsion interactions at energies from 2.1 to 200 A GeV is reported. Many of the features of these particles, known from hadron-induced interactions, are shown to be of importance also in heavy-ion interactions, i.e. multiplicity and angular distributions as well as the impact parameter dependence are energy independent. Furthermore the angular distribution seems to be independent of the projectile and target masses as well as centrality of the interactions. Both the Fritiof and Ranft models fail to reproduce this general angular shape.

Here we present results on charged hadron production in an experiment using tracking detectors with the highest possible spatial resolution: emulsion chambers. A sample of the most central collisions will be compared to the predictions of the Lund Model, which does an accurate job of representing conventional (non−quark−gluon plasma) physics in nuclear reactions. We can use the high resolution of our detectors to examine spatial correlations in several ways. In particular, the radial size of the particle formation region can be estimated using pion interferometry techniques. (AIP)

Pseudorapidity distributions of relativistic singly charged particles in oxygen-induced emulsion interactions at 14.6, 60, and 200 GeV/nucleon are studied. Limiting fragmentation behavior is observed in both the target and projectile fragmentation regions for a central as well as for a minimum-bias sample. Comparisons with the fritiof model reveal that the picture of fragmenting strings successfully describes the observed data.

The acceleration and extraction of uranium-238 nuclei by the Bevalac have been confirmed by their visual detection in nuclear research emulsion. A preliminary result for the collision mean free path for stopping uranium-238 (energy less than or equal to 115 million electron volts per nucleon) is 3.1 +- 0.6 centimeters. Qualitative characteristics of the observed uranium-nucleus collisions are also described.

Experimental studies of the interactions between nuclei at relativistic energies had their beginnings with the momentous discovery of the existence of the heavy-ion component of the primary cosmic rays in 1948 by Freier et. al. (Fr 48,48a). Because of the broad energy spectra of the cosmic rays, highly relativistic nucleus-nucleus collisions, with abundant particle production, were observed in these early experiments. Also, it was realized that complementary investigations on the elemental and isotopic abundances of the heavy-ion component would have profound astrophysical implications.

Two apparently unrelated effects, viz. the behavior of transverse momentum spectra at “large” pT in p-p collisions(1) and the “enhancement” of such spectra in p-nucleus collisions(2), are shown to follow in a natural way from a hydrodynamical model in which the space-time evolution of the system is taken into account.

Annihilation of heavy'' antinuclei, such as {ital {bar d}}, {ital {bar t}}, or {bar {alpha}} in nuclear matter could serve to probe whether the constituent antinucleons annihilate independently of each other or whether a single fireball is formed. In the latter case the total meson multiplicity distribution should have a lower mean and a larger relative width than in the trivial case. The meson spectrum would be correspondingly harder.

Fluctuations in particle densities of non-statistical origin are studied in central 16 O+Ag(Br) and 32 S+Au interactions at 200 A GeV. Non-statistical fluctuations in the 32 S-induced interactions seem to enhance the local particle densities, and suggest the presence of intermittancy. The fluctuations are found to be accompanied by a clustering tendency also in the azimuthal plane. A new method for the study of azimuthal correlations is proposed.

Quantum statistics including a finite coherence length is applied to the study of multiplicity distributions from high-energy hadronic collisions measured in finite rapidity windows. A new scaling property in rapidity (''..beta.. scaling'') is derived. It contains forward-backward correlations as a special case. Agreement with data is satisfactory. We find strong indications for an increase of chaoticity with energy. Further experimental tests are suggested.