J.R. Pizzi

The production of j/

Abstract The study of oxygen-uranium reactions at 200 GeV/nucleon shows a significant transverse energy dependence of the yield of J Ψ s relative to muon pairs produced in the mass continuum. This feature, observed for the first time, is in agreement with predictions from quark-gluon plasma formation, although alternative explanations by hadronic effects cannot be ruled out at this stage.

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Abstract 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.

in 200 GeV/nucleon oxygen-uranium interactions

The γ-spectra induced by stopped K− mesons in 6Li and 7Li targets in coincidence with the accompanying charged pions and π0 mesons. The γ-line at (1.04 ± 0.04) MeV observed with charged pions was identified as a γ-transition in Λ4H, whereas the γ-line at (1.15 ± 0.04)_MeV observed with π0 mesons was ascribed to a γ-transition in Λ4He. Using these new values for the excitation energies of the 1+ levels of Λ4H and Λ4He hypernuclei, the phenomenological ΛN potential for the s-state interaction was recalculated.

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

Abstract The (3He, t) reaction has been studied at intermediate energies, 600 MeV–2.3 GeV. The reaction is a single-step direct reaction, and the angular distributions are well described by DWIA calculations. At these energies the σρ component of the interaction dominates. The ratio of the isovector strengths ¦J σρ / ρ ¦ derived from the data on 13C appears to remain roughly constant in the energy range 300–700 MeV per nucleon. The triton spectra exhibit a prominent quasi-free peak. The data at momentum transfers q ⪢ 1.7 fm−1 show a shift of the peak towards smaller energy loss than observed in (e, e) experiments at corresponding four-momentum transfers. The shift becomes progressively larger with increasing q and is about 45 MeV at q = 2.5 fm−1. The shift may be caused by particle-hole correlations in the spin-longitudinal channel.

Further investigation of the γ-transitions in Λ4H and Λ4 hypernuclei

Abstract Data are presented for the p(3He,t)Δ++ reaction at 2.0, 2.3 and 1.5 GeV. The reaction specifically excites the Δ++ with very little yield outside the resonance. The data are analysed as one pion exchange and the hadronic form factor for the 3He−1 system is extracted and compared with the magnetic form factor from electron scattering.

The (3He,t) reaction at intermediate energies: Spin-isospin transitions to states in 12N and 13N

Abstract Excitation of the Δ resonance is observed for the first time with heavy ions. It is very strong in the two mirror charge-exchange reactions ( 20 Ne , 20 F ) and ( 20 Ne , 20 Na ) at 950 MeV per nucleon. With similar incident energies per nucleon, the Δ is weakly excited with a 14 N beam and nearly absent with a 12 C beam. The role of the ejectile bound states is discussed.

The p(3He,t)Δ++ reaction

Abstract The transverse energy ET distributions of nucleus-nucleus collisions are studied in the framework of a simple geometrical model. The distributions for inclusive production of J ψ and muon pairs in the mass continuum are analyzed. The shape of the ET distribution of the continuum agreed with the model. The previously oberved decrease of the ratio ( J ψ )/continuum with increasing ET is due to the behavior of the J ψ .

First observation of the Δ resonance in relativistic heavy-ion charge-exchange reactions☆

Abstract Diffential cross sections have been measured for the ground-state groups of the (d, 3He) and (d, t) reactions on some light N = Z nuclei and for elastic scattering of 28 MeV deuterons by the same targets. The (d, 3He) and (d, t) cross sections are equal for 10B, 12C and 14N targets and different but “parallel” for 16O, 28Si, 32S and 40Ca targets. The yield of 3He is larger than the yield of tritons. The DWBA predicted ratios of (d, 3He) and (d, t) cross sections are compared with the experimental values. The influence of various terms in the DWBA calculations is studied. The Coulomb interaction is responsible for the large difference in the wave functions describing the bound states of the proton and the neutron which are to be captured. These wave functions are shown to have a predominantly influence on the absolute values of the computed cross sections.

Transverse energy distributions in nucleus-nucleus collisions at 200 GeV/nucleon

Abstract The γ spectra induced by stopped K − mesons in a 7 Li target were obtained in coincidence with the accompanying charged pions. A thorough analysis of these spectra indicates that the observed 1.09 MeV line can be ascribed to a γ transition in the 4 Λ H hypernucleus.

Comparaison des réactions (α, τ) et (α, t) sur quelques noyaux N = Z

Abstract The 6 Li(d, 2d) 4 He and 6 Li(d, dα) 2 H reactions were performed at 27 MeV. Analyses of these and the 42.8 and 55 MeV 6 Li(α, 2α) 2 H reactions were performed using distorted wave and plane wave impulse approximations. The kinematic and potential coupling approximations to final state three-body Schrodinger equation and the post and prior form approximations to off-shell scattering cross section were studied for the three reactions. It was found that only the kinematic coupling and post form approximations could be used for the consistent analyses of the three reactions. The effects of distortions and localization of the reactions were investigated. Manifestations of deuteron cluster deformation were noticed in the analyses of the three reactions.