We present a new type of flow analysis, based on a particle-pair correlation function, in which there is no need for an event-by-event determination of the reaction plane. Consequently, the need to correct for dispersion in an estimated reaction plane does not arise. Our method also offers the option to avoid any influence from particle misidentification. Using this method, streamer chamber data for collisions of Ar+ KCl and Ari-BaI, at 1.2 GeV/nucleon are compared with predictions of a nuclear transport model.Many intermediate-energy heavy ion experiments have been directed toward the goal of inferring properties of the nuclear equation of state (EOS) [I]. In parallel with this effort, theoretical work in the area of nuclear transport models has focused on the task of identifying the most appropriate experimental observables for probing the EOS and on the related task of establishing a quantitative connection between such observables and the EOS [2]. Many factors, both theoretical and experimental, have contributed to the current lack of a Consensus on Data [3,4] from the Diogene and Plastic Ball detectors Support this assumption for rapidities other than the midrapidity region where the "squeeze-out" [5] effect can result in a more complex distribution. In the present study, we restrict our analysis to forward rapidities (see below). The maximum azimuthal anisotropy, as defined by Welke et al. [ 6 ] , is even a relatively coarse characterization of the compresl + h R=-sional potential energy at maximum density (in other 1-h ' words, a characterization of the EOS as relatively "hard" or "soft"). One such factor, for example, arises from the fact that detector inefficiencies and distortions can be difficult to simulate and quantify (particularly in the case of a 4n-detector), and this leads to systematic uncertainties in measurements of collective flow. This paper presents a new form of collective flow analysis for two data sets from the Bevalac streamer chamber. The most noteworthy feature of this new method is that it is designed to minimize the type of systematic uncertainty mentioned above; more specifically, the influences of particle misidentification and dispersion of the reaction plane can be removed.For a nonzero impact parameter, the beam direction ( z ) and the line joining the Centers of the nuclei determine the reaction plane, i.e., the X -2 plane. The azimuthal angle of a fragment in this coordinate system is We assume that the distribution function of 4 in an interval of rapidity centered on y , can be described by an expression of the form The method proposed by Welke et al. [6] for determining R in an experiment involves estimating 4 in Eqs. (1) and (2) using the relation 4=+obs-+R, where +obs is the observed azimuth of a fragment, and +R is the estimated azimuth of the reaction plane as deter.mined from the observed fragments in the final state. This method requires that the resulting R be corrected upward, to allow for the fact that 4R is distributed about + = O with a finite dispersion. Eac...

A systematic study of energy spectra for light particles emitted at midrapidity from Au+Au collisions at E=0.25-1.15 A GeV reveals a significant non-thermal component consistent with a collective radial flow. This component is evaluated as a function of bombarding energy and event centrality. Comparisons to Quantum Molecular Dynamics (QMD) and Boltzmann-Uehling-Uhlenbeck (BUU) models are made for different equations of state.PACS numbers: 25.75.+r, 25.70.GhCollective motion plays an important role in the decay of excited nuclear matter and has been studied over a wide range of bombarding energies in heavy ion collisions

The cluster distributions of different systems are examined to search for signatures of a continuous phase transition. In a system known to possess such a phase transition, both sensitive and insensitive signatures are present; while in systems known not to possess such a phase transition, only insensitive signatures are present. It is shown that nuclear multifragmentation results in cluster distributions belonging to the former category, suggesting that the fragments are the result of a continuous phase transition.Comment: 31 pages, two columns with 30 figure

Multifragmentation MF results from 1A GeV Au on C have been compared with the Copenhagen statistical multifragmentation model ͑SMM͒. The complete charge, mass, and momentum reconstruction of the Au projectile was used to identify high momentum ejectiles leaving an excited remnant of mass A, charge Z, and excitation energy E* which subsequently multifragments. Measurement of the magnitude and multiplicity ͑energy͒ dependence of the initial free volume and the breakup volume determines the variable volume parametrization of SMM. Very good agreement is obtained using SMM with the standard values of the SMM parameters. A large number of observables, including the fragment charge yield distributions, fragment multiplicity distributions, caloric curve, critical exponents, and the critical scaling function are explored in this comparison. The two stage structure of SMM is used to determine the effect of cooling of the primary hot fragments. Average fragment yields with Zу3 are essentially unaffected when the excitation energy is р7 MeV/nucleon. SMM studies suggest that the experimental critical exponents are largely unaffected by cooling and event mixing. The nature of the phase transition in SMM is studied as a function of the remnant mass and charge using the microcanonical equation of state. For light remnants Aр100, backbending is observed indicating negative specific heat, while for Aу170 the effective latent heat approaches zero. Thus for heavier systems this transition can be identified as a continuous thermal phase transition where a large nucleus breaks up into a number of smaller nuclei with only a minimal release of constituent nucleons. Zр2 particles are primarily emitted in the initial collision and after MF in the fragment deexcitation process.

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