D. Horn

The mass dependence of CsI(Tl) scintillation response to heavy ions

Abstract The response of CsI(Tl) scintillators to heavy ions is investigated as a function of E , A , and Z . In addition to the expected dependence of light output on Z and E , we observe a significant dependence on mass number. A simple parameterization of the quenching in terms of a few physical variables permits characterization of the light output for a variety of nuclear species with a single quenching constant.

Statistical Multifragmentation in Central Au+Au Collisions at 35 MeV/u

Abstract Multifragment disintegrations, measured for central Au + Au collisions at E A = 35 MeV , are analyzed with the Statistical Multifragmentation Model. Charge distributions, mean fragment energies, and two-fragment correlation functions are well reproduced by the statistical breakup of a large, diluted and thermalized system slightly above the multifragmentation threshold.

Neck formation and decay in Pb + Au collisions at 29 MeV/u☆

Abstract Three fragment production has been studied in peripheral 208 Pb + 197 Au collisions at 29 MeV/u. The data suggests the formation and subsequent decay of necklike structures producing a small fragment emitted at mid-rapidity in between the two partners of a deep inelastic scattering. Data and trajectory calculations suggest also the existence of a competing process in which the neck is absorbed by one of the reactants, this latter decaying further by binary fission.

Evidence for fast and simultaneous multi-fragment emission in central Kr + Au collisions at 60 MeV/u

Abstract Decay products emitted in Kr+Au collisions at 60 MeV/u have been detected with a large experimental array. Events with fragment multiplicities up to 5 have been recorded. After a careful selection of central collisions leading to equilibrited events, the data are compared to two fragmentation models in which fragments are emitted either sequentially or simultaneously. It is shown that the data can be explained very well by the second model, thus suggesting a prompt multifragmentation mechanism. Possible expansion effects in the disassembly process are also investigated.

Circumstantial evidence for critical behavior in peripheral {ital A}{ital u}{bold +}{ital A}{ital u} collisions at 35 MeV/nucleon

The fragmentation resulting from peripheral Au + Au collisions at an incident energy of {ital E}=35 MeV/nucleon is investigated. A power-law charge distribution, {ital A}{sup {minus}{tau}} with {tau}{approx_equal}2.2, and an intermittency signal are observed for events selected in the region of the Campi scatter plot where {open_quote}{open_quote}critical{close_quote}{close_quote} behavior is expected. {copyright} {ital 1996 The American Physical Society.}

Nuclear disassembly time scales using space-time correlations

Abstract The lifetime, τ, with respect to multifragmentation of highly excited nuclei is deduced from the analysis of strongly damped Pb + Au collisions at 29 MeV/u. The method is based on the study of space-time correlations induced by “proximity” effects between fragments emitted by the two primary products of the reaction and gives the time between the reseparation of the two primary products and the subsequent multifragment decay of one partner. A lifetime significantly longer than the interaction time is found. It is compared with time scales corresponding to different types of dynamical instabilities which may be responsible for nuclear disassembly.

Origins of intermediate velocity particle production in heavy ion reactions

In this paper, we report for the first time clear distinctions between these prompt processes and an alternative phenomenon of delayed aligned asymmetric breakup that populates the intermediate-velocity zone by a deformation rupture of mainly the heavier of the colliding partners in mass asymmetric collisions. These distinctions were observed experimentally with intermediate-velocity particle correlation analysis of Ni+C and Ni+Au reac

Calibration of Plastic Phoswich Detectors for Charged Particle Detection

The response of an array of plastic phoswich detectors to ions of 1 ≤ Z ≤ 18 has been measured from EA = 12 to 72 MeV. The detector response has been parameterized by a three parameter fit which includes both quenching and high energy delta-ray effects. The fits have a mean variation of ≤4% with respect to the data.

Projectile excitation energy evolution in peripheral collisions for 16O + 197Au at 32.5, 50 and 70 MeV/N

Abstract A comparison of the multiple breakup of 16 O projectiles scattered by a Au target at three different energies (32.5, 50 and 70 MeV/N) is presented. The excitation energy spectra of the primary projectile-like nuclei decaying into specific output channels were reconstructed. The excitation energy of the target is found to increase faster with beam energy than the one for the quasi-projectile.

Pionic Fusion of Heavy Ions

The previously unobserved phenomenon of heavy-ion pionic fusion is the ideal tool for investigation of coherent mechanisms of pion production, since it since it is the only pionic channel open very near absolute threshold, where the contribution from on-shell nucleon-nucleon mechanisms is the smallest. We begin this paper with a discussion of the existing data on heavy-ion pion production at low energies and review the models intended to provide the requisite coherent pion production mechanisms. We then present our measurement of the 12C(12C, 24Mg)π 0 and 12C(12C, 24Na)π + cross sections at E cm = 137 MeV, which is an order of magnitude closer to threshold than the energy of earlier, inclusive heavy-ion measurements. This constitutes the first experimental observation of the pionic fusion of heavy ions and places severe constraints on the pion production mechanisms. We discuss the impact of this finding on the proposed models, which must now incorporate the kinetic energy of the entire 24-nucleon system as well as the binding energy gained in fusion.