[en] The proceedings of the 8. International workshop on multiparticle production contains the abstracts of papers on various topics of correlations and fluctuations. Hydrodynamic models, Bose-Einstein correlations, hadron-hadron interactions, heavy ion reactions are discussed in detail. 54 items are indexed separately for the INIS database. (K.A.)

[en] The geometry of the critical fluctuations for a general system undergoing a thermal second-order phase transition is investigated. Adopting a generalized free-energy for the local description of the fluctuations of the order parameter at the critical temperature it is shown that instanton-like configurations corresponding to the minima of the free-energy functional, build up clusters with fractal geometry characterizing locally the critical fluctuations. For sufficiently small coarse-graining scales these configurations dominate the partition function and provide an exact description of the critical system. The connection between the corresponding (local) fractal dimension and the critical exponents is derived. Implications of these ideas to chiral QCD phase transition in relativistic heavy ion collisions are also discussed. (author)

[en] One of the main characteristics of the high-energy hadronic or nuclear collisions is the existence of large event-by-event fluctuations, manifested in several observed quantities. The effects of fluctuations in the initial conditions, by using the Interacting Gluon Model, modified by the inclusion also of the impact-parameter fluctuation is investigated. Some observables which follow directly from this model, such as the inelasticity and leading-particle distributions as well as the energy-dependence of the average inelasticity, exhibit a good agreement with all the existing data. The rapidity and pseudo-rapidity distributions calculated by applying the one-dimensional hydrodynamical model with fluctuating mass and momentum show a considerable deviation from those computed with the average initial conditions, using the same mechanism. To account for the semi-inclusive distributions and the forward-backward correlation, it is necessary to take into account also the multiplicity fluctuation, for fireballs of fixed masses. This has been done within the longitudinal phase-space model, with the energy and momentum distributions of the fireballs given by the IGM. (author)

[en] Starting from the past experimental results on multiplicity distributions in intervals of rapidity and of their analysis in terms of the superposition of events of soft and semi-hard type (see the talk of A. Giovannini) three possible scenarios for hh collisions in the TeV energy region are discussed. (author)

[en] Tin is determined at the low nanogram level in biological samples by neutron activation using the pure β^- emitter ¹²¹Sn (half-life 27 hours). The method is based on the selective extraction of tin into an organic phase, which, after addition of a scintillant (PPO), can be directly counted by liquid scintillation counting with near 100% efficiency. Tin is first selectively extracted as its iodide into toluene, stripped and then re-extracted selectively into a toluene solution of N-benzoyl N-phenylhydroxylamine for scintillation counting. Results are given for various biological reference materials. With neutron flux of 10¹³ n cm^-2sec^-1, sensitivities below 10^-9 g Sn are attainable. In general, L.S. counting of β^- emitters of moderate energy may be useful for some other radionuclides where the element can be selectively extracted into a suitable solvent with a non-quenching reagent. (T.G.)

[en] The carbonate and the non-carbonate fractions of marine limestones from Southern Germany have been resolved with respect to their trace element contents. The analytical steps involved (1) instrumental neutron-activation analysis on the whole rock sample, (2) plotting regression lines for the element concentration (ppm) versus corresponding predetermined insoluble residue content (wt %), and (3) reading out the regression functions. Such a regression analysis is simple to perform, less tedious and less time consuming and more reliable as compared with the separate analysis of the carbonate and the non-carbonate components of the rock. Judging from the regression functions, the elements analysed have been grouped into (a) those associated with elastic material (Sc, Cr, Hf, Zr, etc.), (b) those with pronounced diagenetic history (Sr, U), and (c) those which were partly associated with authogenic material (rare earth elements). The geochemical significance of group (c) with particular reference to their coprecipitation with CaCO₃ precipitated from sea water, is discussed. (T.G.)

[en] A new method of silicon determination in molybdenum by the ³⁰Si(n,γ)³¹Si was developed. Problems occuring during this analysis including standardization, quantitative dissolution, silicon sorption on vessels, reproducibility of β-counting etc. were carefully studied and new answers were brought to them. The chemical separation of silicon was performed with a column of anion exchange resin in HCl-Hf-H₂O₂ solution and a column of alumina at pH 9. It was shown that alkaline fusion must be used in order to dissolve silicon impurity. Fluorine ions must be present when the separation is performed in acid aqueous solutions, otherwise a fraction of silicon is lost by adsorption. Heating of a solution containing HF is prohibited, otherwise silicon is lost by distillation. The radioactivity is measured while silicon is fixed on the last exchanger; this avoids the precipitation step which formerly ended the separation procedures for the activation analysis of silicon. A detection limit of 0.005 μg was achieved. Accuracy and reproducibility were controlled on standard samples prepared by fusion of inactive molybdenum and radioactive silicon in a plasma furnace. (T. G.)

[en] By the use of isomeric activation (the reaction ⁷⁷Se(γ, γ')sup(77m)Se) a rapid method is available for the determination and control of selenium content of samples of different origin. One mg of selenium can be determined with a relative error of 10% when the weight of sample is about 20 g. This sensitivity can be achieved easily using a 5-10 kCi cobalt-60 source. The analysis is carried out by the measurement of 160 keV gamma rays of sup(77m)Se with a physical half-life of 18 sec. (T.G.)

[en] A gamma-spectrometric method independent of radon escape for determination of U and Ra in rock samples based on the 63 keV and 1001 keV as well as 185 keV lines is described and discussed. The gamma-spectra of rock samples have been measured by a coaxial Ge(Li) detector of 67 cm³ coupled to a computer based analyzer system. Samples of 0.8 g/cm² thicknesses in powder form were enclosed in a polystirene container 1 mm thick and having a radius of 16 mm. A simple experimental procedure is given for the determination of the self-absorption factor. The method has been applied for the determination of uranium and radium in rock samples from Morocco containing uranium between 17.5 wt.% and 0.026 wt.%. The limits of determination, at 95% confidence level and 10% standard deviation, for the 63 keV and 1001 keV lines were found to be 0.075 wt.% and 0.62 wt.%, respectively, using samples of 6 g and chosing 1 h measuring time. (T.G.)

[en] An analytical procedure and an automatic apparatus are described for the determination of tritium in organic compounds by gas counting. The sample is pyrolysed in hydrogen atmosphere at 1000 deg C then, with hydrogen, the decomposition products are rinsed through a column of molecular sieve-5A heated to 550 deg C. Tritium in water, hydrogen sulphide, ammonia and hydrogen cyanide is transferred into the hydrogen stream by isotope exchange completed on the column. The inactive water vapor, hydrogen sulphide, ammonia and hydrogen cyanide as well as carbon dioxide are removed from the gas stream by appropriate absorbents, and the radioactive hydrogen together with tritiated methane, carbon monoxide and nitrogen included in the pyrolytic products is led into an internal proportional counter tube for radioactivity measurement. The method provides quantitative recovery, it is free of memory effect and suitable for the rapid assay of a wide variety of organic compounds containing C, H, N, O, S in addition to tritium. (author)