Search

A method for determining the cross section for compound-nucleus formation, σCN, in nuclear reactions initiated by protons of energy in the range 20–100 MeV is proposed. The method is based on measuring cross sections for the yield of isotopes maximally remote from the target nucleus. The applicability of the method is illustrated by applying it to the reaction 209Bi(p, xn), which is considered by way of example. Data obtained for the cross section σCN are compared with the results of calculations performed on the basis of the intranuclear-cascade model.

Systematics is proposed for determining the isomeric ratios (and, consequently, the production cross sections) for high-spin isomeric states in nuclear reactions induced by intermediate-energy protons. It is based on experimental data obtained by bombarding tantalum targets with protons of energy 100 to 500 MeV. For reactions involving the emission of more than two nucleons, a linear dependence between the spin transfer and the logarithm of the isomeric ratio is observed; i.e., {sigma}{sub m}/{sigma}{sub g}{approx}aexp[-b|J{sub m}-J|] where {sigma}{sub g} is the cross section for the ground state (perhaps from a calculation within the intranuclear cascade-evaporation model); {sigma}{sub m} is the cross section for the isomeric state of the nucleus; J{sub m} and J{sub t} are spin values for, respectively, the product isomeric nucleus and the target nucleus; and a and b are coefficients that are determined from 16 experimental results (a {approx} 1.05, b {approx} 0.47). The systematics is assumed to be valid over a wide range of nuclei, proton energies, and isomeric ratio. An explanation for the observed regularities is given.

We have calculated the fission probabilities for 237-Np, 233,235,238-U, 232-Th, and nat-Pb following the absorption of photons with energies from 68 MeV to 3.77 GeV using the RELDIS Monte-Carlo code. This code implements the cascade-evaporation-fission model of intermediate-energy photonuclear reactions. It includes multiparticle production in photoreactions on intranuclear nucleons, pre-equilibrium emission, and the statistical decay of excited residual nuclei via competition of evaporation, fission, and multifragmentation processes. The calculations show that in the GeV energy region the fission process is not solely responsible for the entire total photoabsorption cross section, even for the actinides: ~55-70% for 232-Th, \~70-80% for 238-U, and ~80-95% for 233-U, 235-U, and 237-Np. This is because certain residual nuclei that are created by deep photospallation at GeV photon energies have relatively low fission probabilities. Using the recent experimental data on photofission cross sections for 237-Np and 233,235,238-U from the Saskatchewan and Jefferson Laboratories and our calculated fission probabilities, we infer the total photoabsorption cross sections for these four nuclei. The resulting cross sections per nucleon agree in shape and in magnitude with each other. However, disagreement in magnitude with total-photoabsorption cross-section data from previous measurements for nuclei from C to Pb calls into question the concept of a ``Universal Curve'' for the photoabsorption cross section per nucleon for all nuclei.

For the nuclear-fission process induced by photons of energy in the range 150 < E γ < 600 MeV and accompanied by pion emission, the total cross section; the angular and differential distributions of pions; the excitation-energy, mass, and charge distributions of compound nuclei; and the mass distribution of the fission fragments are predicted on the basis of the cascade-evaporation-fission model. These features are compared for the cases of nuclear fission induced by photons and protons of initial energy in the same range.

Basic features of the nuclear-fission process induced by protons of incident energy in the range 150

The production of Λ hyperons in π+A interactions is studied on the basis of the intranuclear-cascade model, and the excitation-energy, momentum, angular-momentum, charge, and mass distributions of the ensemble of product hypernuclei are determined. The decay of excited hypernuclei via particle emission and fission is considered. It is shown that, for the production of heavy Λ hypernuclei, the optimal momentum of the incident π+ meson is about 1 GeV/c. The cross section of the channel in which heavy-nucleus decay induced by a π+ meson is accompanied by the emission of a K+ meson is estimated, and it is proposed to use the reaction (π+, K+f) in measurements of the fission barrier in hypernuclei and of their level density.

Energetic antiproton-nucleus interactions allow to build up thermal excitation energies exceeding 800 MeV in nuclei of masses close to 200. We found that for these high excitation energies the fission process still remains a very significant exit channel. At excitation energies close to 800 MeV the fission process approaches 20–50% of the cross section for Ho, Au and U-like nuclei depending on the fission events selection criteria. The average intermediate mass fragment multiplicity at such high excitation energies is equal to about 1 and alpha particle multiplicity is equal to about 5 for all three reactions independently of the exit channel, including fission. A transition towards the multifragmentation is not observed.

The distributions of thermal energy generated in different target nuclei by means of the annihilation of antiprotons onto their surfaces have been investigated. The results confirm that fairly hot nuclei are produced in this approach, as predicted by Intra-Nuclear Cascade calculations. Although the transition towards multifragmentation as the primary decay channel is not observed, these data should allow to pin down the decay patterns of hot nuclei with little excitation of their collective degrees of freedom. In turn this may shed new light on the mechanisms responsible for some events associated with high fragment multiplicities as observed in heavy-ion collisions.

Neutron multiplicities after antiproton-induced fission have been determined as a function of the total mass of the fission fragments. Pre- and postscission neutron multiplicities of the reaction {bar p}+{sup 238}U have been deduced using the moving-source parametrization of the neutron energy spectra by Maxwellian distributions. A postscission multiplicity of 6.3(6) neutrons out of 20.0(10) in total emitted neutrons in fission indicates that fission is a rather slow process. The increase of the evaporative prescission neutron multiplicity is about 80{percent} of the total increase of evaporative neutrons as a measure of excitation energy. The postscission multiplicity gets only 20{percent} of the total increase, thus indicating that the nucleus has only a moderate excitation energy at the moment of scission. The results are compared with standard cascade-evaporation calculations predicting a much lower number of evaporated prescission neutrons as the experiment shows. This is a strong indication of the importance of dissipative effects in the fission process. Application of dissipative effects like a saddle-to-scission delay time and nuclear viscosity in the model calculation describes the experimental results much better. {copyright} {ital 1997} {ital The American Physical Society}

Antiproton-induced fission has been investigated with a novel double-arm fission fragment spectrometer. The correlations in mass, energy, and velocity between two fragments were measured. The dependence of total kinetic energy, velocity, momentum of the fissioning nucleus, and momentum of the fission fragments on the mass loss was deduced and analyzed in the framework of the dynamical statistical model. This model takes into account all stages before, during and after {ital {bar p}}-induced fission (atomic cascade, intranuclear cascade, evaporation cascade, fission of the compound nucleus, evaporation from the fission fragments). The mass loss was used as a measure of the excitation energy to classify the fission events according to the corresponding excitation energies. Some discrepancies between the model calculation and the experiment show the important role of dissipative effects in the {ital {bar p}}-induced fission process. {copyright} {ital 1996 The American Physical Society.}

Information on the neutron distribution in the nuclear periphery was obtained by the annihilation of stopped antiprotons and the yield of residual nuclei. The last atomic transitions of the antiproton before annihilation gives complementary results. Properties of very hot nuclei (up to 1 GeV) after annihilation of stopped antiprotons were studied by neutron emission and fission. Absolute prob­ abilities of fission induced by stopped and fast antiprotons were determined. The experimental data are compared with elaborate calculations taking into account the annihilation process, the fast cascade and pre-equilibrium emission, thermalisation, particle evaporation and fission.

The ratio of inclusive spectra of neutrons and protons in antiproton-, pion-, and proton-nucleus interactions at intermediate energies has been considered in the framework of the intranuclear cascade (INC) model. The ratio predicted by the standard INC model is consistent with the experimental data for pion- and proton-induced reactions, but contradicts the ratio obtained in antiproton-nucleus annihilation measurements. It has been shown that for pion-nucleus interactions the {ital n}/{ital p} ratio is much affected by isotopic effects in pion absorption and mainly depends on pion charge. Nevertheless, due to the presence of positive, negative, and neutral pions in antiproton-nucleon annihilation the calculated {ital n}/{ital p} ratio becomes close to the {ital N}/{ital Z} ratio of the target nucleus. The coalescence of nucleons, preequilibrium emission of particles, interaction of annihilation pions with the nuclear Coulomb field, neutron halo effects, and many body annihilation have been considered as possible candidates which would affect the {ital n}/{ital p} ratio in antiproton-nucleus annihilation. A simple quark counting estimation for the {ital n}/{ital p} ratio in many body annihilation has been made.

The A dependence of nuclear fission induced by stopped antiprotons has been measured. An unambiguous identification of the binary fission decay mode was provided by a coordinate measurement of complementary fission fragments in coincidence using a large-acceptance fission detector based on low pressure multiwire proportional chambers. A deep fissility minimum was observed nearA=100, in agreement with the general behaviour predicted by the liquid-drop model. An unexpectedly low and high fission probability was found for the Ag and Cu nuclei, respectively.

We present preliminary results of calculations by the phenomenological model of the estimated yield of some heavy actinide isotopes. It is assumed that these isotopes are produced as a result of multinucleon transfers followed by neutrons and charged particle emission A.S. Iljinov and E.A. Cherepanov (Proc. Int. Symp. on Synthesis and Properties of New Elements, Dubna, 1980, Joint Institute for Nuclear Research, Dubna, 1980, D7-80-556, p. 29). The yield P Z N (E∗) of primary excited actinides is found using the model of N.V. Antonenko and R.V. Jolos (Z. Phys. A, 338 (1991) 423). Absolute cross-sections for different binary reaction channels are obtained by summing the cross-sections for all subchannels with an appreciable yield according to J. Wilczynski et al. (Phys. Rev. Lett., 45 (1980) 606).

Absolute probabilities for the fission induced by stopped antiprotons have been determined for U, Th, Au, Ho by measuring the fission fragments in coincidence. The numbers of antiprotons stopped in the targets were obtained from an activation analysis. The fission probabilities are 77(4)%, 70(4)% and 3.1(3)% for 238 U, 232 Th and 197 Au. For 165 Ho an upper limit of 1.1% was determined. The results are compared with intranuclear cascade calculations.

Experimental data on multiplicities of secondary charged particles in interactions of oxygen nuclei in a hydrogen bubble chamber at the incident momentum of 3.1 A GeV/c are presented and discussed. Multiplicity correlations are studied in details and it is shown that the character of these correlations is strongly influenced by the electric charge and baryon number conservation. Topologies and probabilities of different channels of fragmentation are determined for projectile oxygen nuclei. It is established that channels with production of helium nuclei play an important role in the processes of multifragment break-up of oxygen nuclei. Comparison of the experimental data with predictions of the cascadefragmentation-evaporation model has shown that the model provide the qualitative description of the considerable amount of experimental observations.

The photofission cross section of [sup 232]Th was measured in the energy range 250--1200 MeV using a monochromatic tagged photon beam and a parallel-plate avalanche detector. The [sup 232]Th nuclear photofissility was obtained by measuring simultaneously and in the same energy range the photofission cross section of [sup 238]U and assuming a photofissility equal to one for [sup 238]U. It was found that, contrary to the case for heavier actinides, the [sup 232]Th photofissility value does not saturate up to 1200 MeV. Rather, it lies between 0.6 and 0.8, and shows a weak energy dependence: it increases by about 15% over an interval of 1 GeV. A comparison of these experimental findings with the predictions of an intranuclear-cascade Monte Carlo calculation is given.

An intranuclear cascade model, which takes into account η- and ω-production in πN and NN collisions, their scattering on intranuclear nucleons and absorption in nuclear medium, has been developed. Sensitivity of the cross section of meson production and the η energy spectra to assumptions of the model has been investigated. The model described satisfactorily the results of the first experiments on η-production on nuclei. Predictions for the ω-production cross section on nuclei by pions have been done in the framework of the model.

Cooled antiprotons from the LEAR storage ring facility have been stopped in targets from A = 6 to 238 to investigate the processes following annihilation at the nuclear surface. Among the recent results are the following: The measured spectra can be fitted to N(p2) = N0 exp (–p2/p02), where p is the momentum of the ejectiles and p0 ≈ 360MeV/c for all ejected particles from protons to alpha particles and for all 16 targets except 6Li. The proton spectra show an additional low-momentum component attributed to evaporation. The measured residual nucleus distribution from stopped p annihilation in Cu, when compared with INC calculations and with residual mass distributions from energetic π+, π- and proton interactions with Cu, indicate that the energy set free in the annihilation process is used only in part as excitation energy. The residual nucleus distribution from a 238U target shows that both symmetric and asymmetric fission take place. Detection and analysis of coincident fission products from 209Vi, 232Th and 238U enabled us to determine the individual and total mass and energy distributions of the fragments, their opening angle, the average excitation energy and momentum of the nucleus at scission, and the number of nucleons emitted before and after scission. We also found that the process is asymmetric for low excitation energies and symmetric for higher ones. INC calculations have reproduced the experimental results.

A simple expression for the inclusive cross section of η production on light nuclei by protons has been obtained in the first collision approximation in the framework of the intranuclear cascade approach. An intranuclear cascade model which takes into account η production by primary proton and secondary pion, elastic scattering of η on intranuclear nucleons and absorption of η in nuclear matter has been developed. The calculated cross sections are found to be in satisfactory agreement with the experimental data.

Antiproton induced fission has been investigated with a novel double-arm fission fragment spectrometer and with a special arrangement to determine absolute fission yields in various targets. The spectrometer measures five parameters per fission event: two masses, two energies and the folding angle. Asymmetric, symmetric and pre-equilibrium fission was observed. The number of nucleons emitted before and after scission was deduced indicating fast fission of hot nuclei.

The double strangeness production has been observed in two final states of annihilation of antiprotons at momentum less than 0.9 GeV/c on Xe nuclei: K+K+X (8 events) and K+K0ΛX (6 events). The probabilities of the reaction pXe → K+K+X vary from 2 · 10−5 (at rest) up to 7 · 10−5 (in flight). The reaction pXe → K+K0ΛX is observed only in flight with probability 3 · 10−4. The properties of the observed reactions are similar to those resulting from the cascade process with production of Ξ hyperon: pN → K∗−K∗, K∗ → Kπ, −K∗N → ΞK, ΞN → ΛΛ. The new upper limit on the production probability of the stable H(S = −2) dibaryon in the reaction Xe → K+K+H(H → Σ− p)X was obtained to be < 2 · 10− (90%C.L.).

Energy spectra of protons, deuterons and tritons from stopped-antiproton annihilation in Li, Si, Ca, Ni, Ge, Mo, Ho, Yb, Pb and Th have been measured with a Ge detector telescope. The shapes of these and of previously obtained spectra and the corresponding yields were analysed and compared with statistical calculations including intranuclear cascade, coalescence, pre-equilibrium processes, evaporation, multifragmentation and Fermi break-up. The relative importance and the A -dependence of the various processes are elucidated.

All existing data on the level densities, decay widths and lifetimes of excited nuclei have been analyzed in the framework of the statistical model in order to better determine the parameters of the phenomenological systematics of the nuclear level density. Data on level densities of several hundred nuclides obtained in the excitation energy range from 2 up to 20 MeV were used. The level densities of nuclei with large deformation (at the saddle point) have been studied by analyzing the data on the nuetron emission and fission partial width ratio Γn/Γf, and the values of the fission barrier heights Bf, the level density parameters ratio af/an and the saddle point shell corrections δWs.p. have been extracted. The influence of shell and collective effects on the level density and the decay widths of nuclei which have different excitation energies and deformations has been studied.

The effects of production of mesonic resonances and their subsequent interaction with the nuclear medium are considered in the framework of the “optical+cascade” model that describes the absorption of stopped antiprotons by nuclei. Basing on the statistical model with SU(3) symmetry, we analyze the data on heavy meson production in p N annihilation and develop a scheme for calculating the exclusive characteristics of this process. We estimate the cross sections of the interaction of η- and ω-mesons with nucleons. We develop the model of the intranuclear cascade with account of the η- and ω-mesons. We find those characteristics of p N annihilation at rest that are sensitive to the effect of heavy meson production.

Antiprotons have been stopped in a target of Ba(NO3)2. The induced radioactivity from antiproton annihilation in Ba was used to determine the distribution of residual nuclei. The results are compared with intranuclear cascade calculations. The agreement between theory and experiment is very good.

Experimental data have been obtained on the multiplicities of pions and protons in the interaction of antineutrons and antideuterons with tantalum nuclei. A target 3 mm thick was placed in the active volume of a two-metre hydrogen-filled chamber «LYUDMILA» of the High-Energy Laboratory of JINR, which was exposed to a beam of antideuterons with a momentum of 12.2 GeV/c in the accelerator of the Institute for High-Energy Physics at Serpukhov. Antineutrons were produced in the stripping of anti-deuterons on hydrogen in the chamber. The results obtained are compared with the data on proton-nucleus interactions and with the calculations using the model of intranuclear cascades. The possibility of formation of a cluster of hot hadronic matter in the process of annihilation within the nucleus is discussed.

In the framework of the model of absorption of stopped antiprotons by nuclei which has been developed earlier, the experimental data on\(\tilde pA\)-fission were analysed. The results of calculations are in good agreement with the nuclear fissilities obtained experimentally and with the momentum distribution of residual nuclei before fission.

The dependence on excitation energyE* of photofissilityPf of preactinide nuclei is examined. An accurate evaluation ofE*, and of mass and charge configurations of the compound nucleus for (100÷300) MeV photons is calculated by means of an intranuclear-cascade model. It is found that, at high excitation energy, is no longer a correct variable to describe the excitation energy dependence ofPf.

A cascade-fragmentation-evaporation (CFE) model of proton-nucleus reactions at intermediate energies is developed. Within the framework of this model a systematic analysis has been performed of a broad set of data on nuclear fragmentation induced by protons with energies E p ≈ 1–100 GeV. This includes: fragment mass and charge yields, angular and energy distribution, fragment yields in correlation with fast particles, etc. A satisfactory agreement between the CFE model predictions and experimental data has been obtained. Unresolved problems and ways of improving the CFE model are discussed.

Inclusive neutron energy spectra were measuredb y time of flight using 1.22 GeV antiprotons from LEAR, CERN, as projectiles andtargets from natural Al, Cu, Ag, Ho, Ta, Au, Pb, Bi, U. The sum of two Maxwellian distributions was fitted to the spectra d2 σ/(dΩdE) obtainedat several forward andbac kwardangles yielding neutron multiplicities M i andslop e or temperature parameters T i for the low-energy (evaporative, i = 1) andhigh-energy (pre-equilibrium, i = 2) parts, respectively. M 1 increases with A, proportional to the nuclear volume, and M 2 is growing with A 1/3, proportional to the nuclear radius. The T parameters are nearly independent of A. The results are comparedwith previous multiplicity measurements with a 4π neutron detector, intranuclear cascade calculations and neutron spectra from stoppedan tiproton annihilation on nuclei. With the measuredproton spectra also the ratio of emitted neutrons to protons was determined for Au.

We study nuclear reactions induced by virtual photons associated with Lorentz-boosted Coulomb fields of ultrarelativistic heavy ions. Evaporation, fission and multifragmentation mechanisms are included in a new RELDIS code, which describes the deexcitation of residual nuclei formed after single and double photon absorption in peripheral heavy-ion collisions. Partial cross sections for different dissociation channels, including the multiple neutron emission ones, are calculated and compared with data when available. Rapidity and transverse momentum distributions of nucleons, nuclear fragments and pions, produced electromagnetically, are also calculated. These results provide important information for designing large-rapidity detectors and zero-degree calorimeters at RHIC and LHC. The electromagnetic dissociation of nuclei imposes some constrains on the investigation of exotic particle production in gamma-gamma fusion reactions., Comment: 26 LaTeX pages including 8 figures, uses epsf.sty

We study the disintegration of nuclei by strong electromagnetic fields induced by ultrarelativistic heavy ions. The proposed multi-step model includes 1) the absorption of a virtual photon by a nucleus, 2) intranuclear cascades of produced hadrons and 3) statistical decay of the excited residual nucleus. The combined model describes well existing data on projectile fragmentation at energy 200 GeV per nucleon. Electromagnetic multifragmentation of nuclei is predicted to be an important reaction mechanism at RHIC and LHC energies., Comment: 18 LaTeX pages including 4 figures, uses epsf.sty. Submitted to Phys.Rev. C

The $\omega$- and $\rho$-resonance production and their dileptonic decay in $\pi^- A$ reactions at GSI energies are calculated within the intranuclear cascade (INC) approach. The invariant mass distribution of the dilepton pair for each resonance is found to have two components which correspond to the decay of the resonances outside and inside the target nucleus. The latter components are strongly distorted by the nuclear medium due to resonance-nucleon scattering and a possible mass shift at finite baryon density. These medium modifications are compared to background sources in the dilepton spectrum from $\pi N$ bremsstrahlung and the Dalitz decays of $\Delta$'s and $\eta$ mesons produced in the reaction., Comment: 10 pages, LaTeX, plus 4 postscript figures, submitted to Phys. Lett. B

The intranuclear cascade (INC) model for photonuclear reactions has been extended at energies up to 10 GeV. To this end a phenomenological method for exclusive description of the elementary γN-interaction has been developed taking into account both the resonance contribution from the two-body channels γN → πB ∗ and γN → M ∗ N ( B ∗ and M ∗ being baryon and meson resonances) and the non-resonant statistical contribution from multibody channels γN → iπN (2 ⩽ i ⩽ 8). This method well describes a wide range of γN data up to Eγ ∼ 10 GeV. The INC model takes into account rescattering and absorption in a nucleus of pions, nucleons, and η-, ϱ-, ω-mesons generated in the γN-interaction. The evaporation, fission and multifragmentation of highly excited residual nucleus have also been taken into account. As a result of the Monte Carlo simulation an event of γA-reaction is generated which contains mesons, nucleons, nuclear fragments, fission fragments and final nuclide. The model well describes the available data on meson production and proton emission obtained with quasi-monochromatic photons.

Simultaneous measurements of inclusive energy spectra and multiplicities of ${\mathrm{\ensuremath{\pi}}}^{\ifmmode\pm\else\textpm\fi{}}$, ${\mathit{K}}^{\ifmmode\pm\else\textpm\fi{}}$, n, p, d, and t following antiproton annihilation on nuclei over a wide energy range and in the case of neutrons down to the evaporative part of the spectra are reported. Thirteen targets in the mass range of A=12--238 were used in a target mass dependent investigation of the fast stage of the antiproton-nucleus interaction. The deduced transferred, preequilibrium and equilibrium excitation energies agree very well with the dynamical picture drawn by the intranuclear cascade model (INC). Ratios of directly emitted neutrons to protons have been determined to be about twice the N/Z ratio in the target nucleus nearly independently of its mass. These unexpected values for this new sensitive observable are not completely understood in the standard framework of INC. Possible effects of isospin and nucleon densities as well as further schemes beyond the INC are discussed.

Antiproton-induced fission has been investigated with a novel double-arm fission fragment spectrometer. Inclusive distributions of total mass, individual mass, and total kinetic energy of the fragments, and of the momentum of the fissioning nucleus, were measured. A dynamical model which takes into account all stages of p\ifmmode\bar\else\textasciimacron\fi{}-induced fission (atomic cascade, intranuclear cascade, evaporation cascade, fission of compound nucleus, evaporation from fission fragments) was formulated for the first time. In particular, the dynamics of the descent of fissioning nuclei from saddle point to scission point are described by the diffusion model. The data on p\ifmmode\bar\else\textasciimacron\fi{}-induced fission were analyzed in the framework of this model and good agreement between experiment and theory was obtained.

The photofission cross section o f232Th was measured in the energy range 250-1200 MeV using a monochromatic tagged photon beam and a parallel-plate avalanche detector. The 232Th nuclear photofissility was obtained by measuring simultaneously and in the same energy range the photofission cross section of 238U and assuming a photofissility equal to one for 238U. It was found that, contrary to the case for heavier actinides, the 232Th photofissility value does not saturate up to 1200 MeV. Rather, it lies between 0,6 and 0,8, and shows a weak energy dependence: it increases by about 15% over an interval of 1 GeV. A comparison of these experimental findings with the predictions of an intranuclear-cascade Monte Carlo calculation is given.

A natural Cu target was irradiated with the antiproton beam from the Low Energy Antiproton Ring facility at CERN. The 105 MeV/[ital c] [ital [bar p]] beam was completely slowed down inside a thick target producing many radioactive products. Starting shortly after the irradiation and continuing for about one year, this residual activity was counted using off-line gamma-ray spectroscopy techniques. The yields of 40 radioactive reaction products were determined. The charge dispersion and complete mass yield distribution were deduced using a well-established fitting procedure. The shape of the mass yield and, in particular, the average number of removed nucleons, the dispersion of the mass distribution, and its logarithmic slope characterize the average energy deposited during the antiproton-nucleus interaction. We compare these quantities with similar data gathered for other projectiles interacting with natural Cu targets. These comparisons indicate that the average excitation energy of the system formed after the stopped antiproton annihilation is similar to the average excitation energy following 2-GeV proton interaction with Cu nuclei. The observed mass distribution is also compared with the intranuclear cascade calculations.

Information recently obtained by the PS179 (STREAMER) collaboration at LEAR on p4He elastic scattering, strangeness production in antiproton annihilation at rest and p annihilation in nuclear photo‐emulsion is presented.