Estimate of large fragment yield forZ>56 nuclei

Summary Large fragment yields are calculated forZ>56 nuclei in the frame-work of abrasion/ablation model which includes a third-order correction for surface energy term. The results for 1.049 GeV/n¹⁹⁷Au₇₉ nuclei, 1.128 GeV/n¹⁶⁵Ho₆₇ nuclei, 1.88 GeV/n⁵⁶Fe₂₆ nuclei, 1.239 GeV¹³²Xe₅₄ nuclei and 1.489 GeV⁸⁴Kr₃₆ nuclei are compared with experimental data for different target combinations. The comparison shows that the theory provides a reasonable representation of elemental cross-section for all projectiles.     

Production of baryon resonances in collisions of 4He nuclei with carbon nuclei at a momentum of 4.2 GeV/c per nucleon

Under conditions of 4π geometry, Δ⁰-and Δ⁺⁺-resonance production in collisions of ⁴He nuclei with carbon nuclei at a momentum of 4.2 GeV/c per nucleon was investigated for the first time. The resonance masses and widths are estimated by analyzing the experimental and background invariant-mass distributions of (pπ ^±) pairs. Contributions to pion production from Δ-resonance decays, as well as from direct pion production, are determined. The results are compared with corresponding data obtained for CC collisions at the same primary momentum of 4.2 GeV/c per nucleon. By and large, the results obtained here comply with the existence of a collective mechanism of delta-isobar excitation in nuclei.     

Fragmentation of ^16O nuclei in nuclear emulsion

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

Target fragmentation at ultrarelativistic energies

We have used 200 GeV/u and 60 GeV/u oxygen beams accelerated at CERN to bombard a 1.5 mg/cm² Au target. Light nuclei have been detected at 25° and 55° using silicon telescopes. Their inclusive mass distribution follows an exponential behaviour at 200 GeV/u but is different at 60 GeV/u. In this latter case the situation is similar to what has been observed at lower bombarding energies with heavy ions, and for high energy proton-induced reactions. The results at 200 GeV/u are, however, different from those observed in proton-induced reactions in the same energy domain.     

π−-meson and nucleon yields from light targets irradiated by deuterium and tritium nuclei beams at energies of 1 GeV/nucleon

In this paper, we present a model of calculation with respect to the interactions of high-energy nuclei with matter. Based on this model, we obtain results on energy and angular spectra of the n- and π⁻-particles produced in collisions of deuterium and tritium nuclei at energiesT _d=1 GeV/nucleon with light targets such as Li, Be. We have also estimated the production yields of neutrons and π⁻-mesons in targets of various radii, as well as mean energies of these these particles. Summarizing, we find that the lithium target of radiusR=10−12 cm for which the energy cost ε_π to produce one π⁻-meson is estimated as 6.7 GeV/π for a d-beam and 5.3 GeV/π for a t-beam is the most preferred pion-production target.     

Review of brookhaven nuclear transparency measurements (p,2p) reactions at largeQ 2

In this contribution we summarize the results of two experiments to measure the transparency of nuclei in the (p,2p) quasi-elastic scattering process near 90‡ in thepp center-of-mass. The incident momenta went from 6 to 14.4 GeV/c, corresponding to 4.8 <Q ² < 127 (GeV/c)². First, we describe the measurements with the newer experiment, E850, which has more complete kinematic definition of quasi-elastic events. E850 covers a larger range of incident momenta, and thus provides more information regarding the nature of the unexpected fall in the transparency above 9 GeV/c. Second, we review the techniques used in an earlier experiment, E834, and show that the two experiments are consistent for the carbon data. We use the transparencies measured in the five nuclei from Li to Pb to set limits on the rate of expansion for protons involved in quasi-elastic scattering at large momentum transfer.     

Investigation of clustering in light nuclei by means of relativistic-multifragmentation processes

New results concerning the topology of the fragmentation of relativistic nuclei ⁷Li and ¹⁰B are presented. A program is proposed for studying the cluster structure of stable and radioactive nuclei. The use of emulsions in the investigation of nuclear clustering in the fragmentation of light nuclei at energies are in excess of 1 GeV per nucleon is discussed.     

Study of the Δ isobar excitation in nuclei with the (3He,t) reaction

Data for the Δ excitation by the (³He,t) reaction at 2.0 GeV on various nuclei are presented together with results on ¹²C at 1.5 and 2.3 GeV. The Δ peak position and width are found to be target mass independent. Comparison with the p(³He,t) Δ⁺⁺ reaction, however, shows a shift of the position in energy of the Δ peak. Implications of these results are discussed.     

Multiparticle emission in the interactions of hadrons with complex nuclei at incident momenta from 2 to 4 GeV/c

The charged secondary particles emitted in inelastic reactions of 4 GeV/cπ⁺ and π^? with the nuclei Be, Cu and Ta are thoroughly studied in their multiplicities, particle correlations and the distributions of kinematical variables, with the 1 m hydrogen bubble chamber into which the three nuclear target plates were installed. The numbers of charged secondaries emitted in the π^?(2.3 GeV/c), π⁺(2 GeV/c) and p(4 GeV/c) reactions are also investigated. From these data, characteristic features of the multiplication process of secondaries in nuclear matter are clarified. The experimental results are compared with the calculation of an intra-nuclear cascade model which takes into account the process of pion absorption by two-nucleon clusters in the nucleus. It is found that the experimental results on the properties of charged secondaries are consistently explained by the model. The model can also give an account of the experimental finding that fairly high momentum protons are emitted from the heavier nuclei into the backward hemisphere in the lab system.     

Cross-sections of large-angle hadron production in proton– and pion–nucleus interactions VII: tin nuclei and beam momenta from ±3 GeV/c to ±15 GeV/c

We report on double-differential inclusive cross-sections of the production of secondary protons, charged pions, and deuterons, in the interactions with a 5% λ _int thick stationary tin target, of proton and pion beams with momentum from ±3 GeV/c to ±15 GeV/c. Results are given for secondary particles with production angles 20^○<θ<125^○. Cross-sections on tin nuclei are compared with cross-sections on beryllium, carbon, copper, tantalum and lead nuclei.     

Photonuclear reactions in medium weight nuclei 51V, 55Mn and Cu

New results on the photospallation of the medium weight nuclei ⁵¹V, ⁵⁵Mn and Cu at maximum bremsstrahlung energy between 2 and 5 GeV are presented. The yields of residual nuclei were measured by the activation method using a Ge(Li) detector. The results are analyzed with the empirical Rudstam formula and compared with data obtained in lower energy photon and proton induced reactions.     

Evidence for the production of a new particle in neutrino interactions

We present here evidence, based on 5 events recorded in cosmic ray experiments deep underground, for the production of new, massive (? 2 GeV) and long lived (τ ～^?9 sec) particles in neutrino with rock nuclei.     

Taking into Account the Centre-of-Mass Correlations in the Cross Sections for Elastic Scattering of Intermediate Energy Protons on the Exotic Nuclei <Superscript>6</Superscript>He and <Superscript>8</Superscript>He

We calculate the differential cross sections for proton elastic scattering on the exotic halo nuclei ⁶He and ⁸He at energies around ~0.7 GeV at the momentum transfers squared up to 0.30 (GeV/c)² and investigate the influence of the nucleon centre-of-mass correlations on the calculated cross sections. In particular, we show that the approximate account of the centre-of-mass correlations used previously considerably overestimates the cross sections at high values of the momentum transfer.     

A study of fast neutron production in p20Ne and pp interactions at 300 GeV/c

Data on the multiplicity, momentum and angular spectra of fastp _n1 GeV/c) neutrons produced in inelastic interactions of protons with neon nuclei and protons at 300 GeV/c are presented. The experimental results obtained for p²⁰Ne interactions are compared with predictions of the additive quark model in which the intranuclear cascading of slow particles is taken into account.We thank V. G. Grishin and R. J. Loveless for valuable discussions.     

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.     

Deuteron production in collisions of 250 GeV/c π+ andK + mesons with Al and Au nuclei

Experimental data are presented on deuteron production in the target fragmentation region for 250 GeV/c π⁺ interactions with Al and Au nuclei, and compared with analogous data on proton production. Indications are observed for narrow structures in the (dπ^-) effective mass system at ～2.04 and ～2.08 GeV.     

Measurement of the azimuthal anisotropy coefficient <Emphasis Type="Italic">v</Emphasis><Subscript>2</Subscript> for the emission of α particles in nucleus-nucleus collisions at energies 1.88–10.6 GeV/nucleon

The azimuthal anisotropy of the emission of α particles in collisions of the ²²Ne, ²⁴Mg, ⁵⁶Fe, and ¹⁹⁷Au nuclei with photoemulsion nuclei has been measured at projectile energies E_pr = 1.88–10.6 GeV/nucleon. The results are compared with similar measurements for protons. It has been found that the ratio of the azimuthal anisotropy coefficients v₂ for α particles and protons is equal to 6 ± 2 at low energies E_pr ≈ 2 GeV/nucleon, whereas these coefficients coincide with each other for energies E_pr ≥ 4 GeV/nucleon. This difference may indicate that, at low projectile energies, α particles are formed predominantly at the early stage of a collective flow. Formation of α particles for E_pr ≥ 4 GeV/nucleon likely occurs at the stage of nuclear matter scattering.     

Interactions between 4He nuclei and protons at intermediate energies

Since the early 1970s, experiments have been performed to investigate the fragmentation of the lightest nuclei (d, ³H, ³He, and ⁴He) on protons at intermediate energies (～0.2–2 GeV per nucleon). These experiments were set up in ITEP and LHE JINR and realized in an exclusive approach with the help of liquid hydrogen bubble chambers. This investigation is of great interest from two points of view: first, the possibility of detailed theoretical analysis of the data obtained in 4π geometry on the basis of a good understanding of the structure of the wavefunctions of these nuclei and, second, the search for exotic interaction mechanisms. This overview presents the latest, most interesting results of the ITEP experiment on the study of ⁴Hep interactions at ⁴He momenta of 2.7 and 5 GeV/c, on cross sections, elastic scattering, pair correlations of secondary nucleons, cumulative production of nucleons and the lightest nuclei (d, ³H, and ³He), the main features of exclusive reactions, and the search for possible multiquark bag production (dibaryons and tribaryons). The essential results of the independent JINR experiment at 8.6 and 13.6 GeV/c also come under discussion.     

Measurement of the elliptic flux of Z ⩾ 2 charged particles in collisions of relativistic nuclei with photoemulsion nuclei

The azimuthal asymmetry is measured for the emission of Z ≥ 2 particles from the interaction of ²²Ne, ²⁴Mg, ³²S, ⁵⁶Fe, ¹⁹⁷Au, and ²⁰⁷Pb nuclei with photoemulsion nuclei that is induced by semicentral collisions characterized by projectile energies in the range E _pr = 1.88–200 GeV per nucleon and by impact-parameter (b) values in the range 0.12 ≤ b/b _max ≤ 0.70. The results of these measurements are compared with the results of similar measurements for protons. It is found that, at a low energy of E _pr ≈ 2 GeV per nucleon, the ratio of the azimuthal-anisotropy coefficients v ₂ for Z ≥ 2 particles and protons is 6 ± 2, but that, for energies in the region E _pr ≥ 4 GeV per nucleon, the coefficients in question agree with each other. This may suggest that, at low energies, Z ≥ 2 particles are predominantly formed at an early stage of the development of a collective flow. For E _pr ≥ 4 GeV per nucleon, these particles are presumably formed at the stage of nuclear-matter expansion. Other possible explanations for the results of the observation of an elliptic flux of Z ≥ 2 particles are discussed.     

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.