[en] The role of dynamics in fission has attracted much interest since the discovery of this process over fifty years ago. However, the study of the dynamical aspects of fission was for many years hampered by the lack of suitable experimental observables against which theoretical calculations could be tested. For example, it was found that the total kinetic energy release in fission can be described equally well by very different dissipation mechanisms, namely the wall formula, that is based on the collisions of the nucleons with the moving wall of the system, as well as a bulk viscosity of the nuclear matter. Although early theoretical work suggested that the fission process may be described as a diffusion process over the fission barrier, this was largely forgotten because of the success of a purely statistical model which instead of enumerating the ultimate final states of the process argues that the fission rate is determined at the open-quote transition state close-quote as the system traverses the fission saddle point. It was therefore significant when Gavron showed that the transition state model was unable to describe the number of neutrons emitted prior to scission at high excitation energy in reactions of ¹⁶O+¹⁴²Nd. Subsequent experimental work using different methods to measure the fission dissipation/viscosity has confirmed these initial observations. It was therefore very surprising when Moretto in recent publications concluded that their analysis of fission excitation functions obtained with a and α and ³He induced projectiles was perfectly in accord with the transition state model and left no room for fission viscosity. In this paper we'll show that Moretto's analysis is flawed by assuming first chance fission only (in direct contradiction to the experimental observation of pre-scission neutron emission in heavy-ion induced fission), and reveal why the systematics presented by Moretto looked so convincing despite these flaws

[en] We have obtained α-particle angular-correlation data for the α-unbound 3^- level at E_x=9.64 MeV in ¹²C, populated in ¹²C+¹²C inelastic scattering at five energies from E_c.m.=26 to 38.0 MeV. This energy region corresponds to that where previous excitation function measurements have revealed a strong resonance in several reaction channels in the ¹²C+¹²C system. An array of four Double-Sided silicon Strip Detectors (DSSDs) was used to detect the three alpha particle from the decaying ¹²C nucleus. The angular distributions of the α particles in the ¹²C(3^-)→α +⁸Be_g.s. decay are fitted to yield the 12¹²C(3-) magnetic-substate population as a function of ¹²C scattering angle. This magnetic-substate decompostition of the inelastic scattering cross section provides information about the resonance decay l values, and the resonance spin. The data will be discussed in the context of some recent reaction-model calculation, for ¹²C+¹²C inelastic scattering

[en] The study of heavy ion collisions at the Large Hadron Collider (LHC) represents an opportunity to study partonic matter at center-of-mass energies a factor of ∼ 27 times higher than currently possible. This dramatic increase in energy will allow the creation of strongly interacting matter at the highest energy density ever produced in the laboratory. The Compact Muon Solenoid (CMS) detector is ideally suited to study the rich physics of Quantum Chromodynamics and the strong interaction in this new energy region. A brief overview of the heavy ion physics capabilities of the CMS detector is presented. (author)

[en] A Comment on the Letter by L.G. Moretto et al., Phys.Rev.Lett.75, 4186 (1995). The authors of the Letter offer a Reply. copyright 1997 The American Physical Society

[en] Strangeness production in Au+Au collisions has been measured via the yields of K⁺ , K^- at 6, 8 AGeV and of bar Λ at 10.8 AGeV beam kinetic energy in experiment E917. By varying the collision centrally and beam energy, a systematic search for indications of new phenomena and in-medium effects under high baryon density is undertaken

[en] A rapid increase with energy has been observed in the emission of prescission giant dipole resonance (GDR) γ rays in excited Th and Cf nuclei formed in the ¹⁶O+²⁰⁸Pb and ³²S+^natW,²⁰⁸Pb reactions, which is not explained by the normal reaction dynamics near the barrier. This increase occurs over a narrow excitation energy range of E_exc=40--60 MeV for the ¹⁶O+²⁰⁸Pb reaction and E_exc=70--90 MeV for the ³²S-induced reactions. Below the transition energy the γ-ray spectra can be described by the standard statistical model, whereas inclusion of an increasingly strong nuclear dissipation is required to account for the data at higher excitation energies. For the ¹⁶O+²⁰⁸Pb reaction a fit to the GDR γ-ray spectra and evaporation residue cross sections is used to extact the temperature dependence of the linear dissipation parameter

[en] The GDR in ¹⁶⁴Er at 62 MeV excitation energy has been studied in coincidence with the evaporation residues, selected using the Argonne fragment mass analyzer (FMA). The statistical model fit to the data indicate that ¹⁶⁴Er^* has a prolate shape with deformation similar to the ground state

[en] A rapid increase in the emission of prescission giant dipole resonance (GDR) γ-rays with bombarding energy is observed in excited Th and Cf nuclei formed in the reactions ¹⁶O+^20BPb and ³²S+^natW,²⁰⁸Pb. This increase begins around E_exc = 40 MeV for the ¹⁶O+²⁰⁸Pb reaction and E_exc = 70 MeV for the ³²S-induced reactions. The excess γ-ray yield above these thresholds cannot be described within the standard statistical model. Statistical model calculations which include a temperature dependent nuclear dissipation are able to reproduce simultaneously the observed GDR γ-ray spectra and recently measured evaporation residue across sections

[en] Angular correlation techniques have been used to determine the spin of a strong resonance observed in the ¹²C +¹²C(3^-;9.64 MeV) inelastic scattering channel, at a bombarding energy of 33.5 MeV in the center-of-mass system. The alpha particles produced in the sequential decay ¹²C(3^-)→⁸Be(g.s.) + α₀ were detected using four double-sided silicon strip detectors. The data are consistent with a spin assignment of J^π=18⁺ for this resonance. The current results are compared to calculations of resonance behavior in this system from the band crossing model. copyright 1996 The American Physical Society

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