The yield for the multistrange Xi(-) hyperon has been measured in 6A GeV Au+Au collisions via reconstruction of its decay products pi(-) and Lambda, the latter also being reconstructed from its ...daughter tracks of pi(-) and p. The measurement is rather close to the threshold for Xi(-) production and therefore provides an important test of model predictions. The measured yield for Xi(-) and Lambda are compared for several centralities. In central collisions the Xi(-) yield is found to be in excellent agreement with statistical and transport model predictions, suggesting that multistrange hadron production approaches chemical equilibrium in high baryon density nuclear matter.
We present Experiment 864's measurement of invariant antideuteron yields in 11.5A GeV/c Au+Pt collisions. The analysis includes 250x10(6) triggers representing 14x10(9) 10% central interactions ...sampled for events with high mass candidates. We find (1/2pip(t))d(2)N/dydp(t) = 3.5+/-1.5(stat)+0.9-0.5(syst)x10(-8) GeV-2 c(2) for 1.8<y<2.2, < p(t)> = 0.35 GeV/c ( y(c.m.) = 1.6) and 3.7+/-2.7(stat)+1.4-1.5(syst)x10(-8) GeV-2 c(2) for 1.4<y<1.8, < p(t)> = 0.26 GeV/c, and a coalescence parameter B2; of 4.1+/-2. 9(stat)+2.3-2.4(syst)x10(-3) GeV2 c(-3). Implications for coalescence and antimatter annihilation are discussed.
We present the first excitation function of pi(-) intensity interferometry at Alternating Gradient Synchrotron (AGS) energies (2-8 A GeV). The sensitivity of the multidimensional correlation ...functions to the geometry and dynamics of the pion-emitting system provides a stringent test of transport models of heavy ion collisions. Detailed comparisons with a realistic transport model, both with and without an explicit nuclear mean field, suggest that the beam energy evolution in the reaction dynamics is different in the model than in the data. A significantly increased pi(-) emission time scale, which has been suggested as a signal of the onset of the transition to quark-gluon plasma, is not observed.
Using reverse kinematics, we have studied the breakup of 1.0ital A GeV gold nuclei incident on a carbon target. The detector system permitted exclusive event reconstruction of nearly all charged ...reaction products. The moments of the resulting charged fragment distribution provide strong evidence that nuclear matter possesses a critical point observable in finite nuclei. We have determined values for the critical exponents gamma, beta, and tau. These values are close to those for liquid-gas systems and clearly different than those for 3D percolation and the liquid-gas mean field limit.
Directed flow measurements for Lambda hyperons are presented and compared to those for protons produced in the same Au+Au collisions (2A, 4A, and 6A GeV; b<5-6 fm). The measurements indicate that ...Lambda hyperons flow consistently in the same direction but with smaller magnitudes. A strong positive flow for Lambdas has been predicted in calculations which include the influence of the Lambda-nucleon potential. The experimental flow ratio Lambda/p is in qualitative agreement with expectations (approximately 2/3) from the quark counting rule at 2A GeV but is found to decrease with increasing beam energy.
Light nuclei can be produced in the central reaction zone via coalescence in relativistic heavy-ion collisions. Experiment 864 at BNL has measured the production of ten light nuclei with nuclear ...number A=1 to A=7 at rapidity y{approx_equal}1.9 and p{sub T}/A{<=}300 MeV/ c . Data were taken with a Au beam of momentum of 11.5A GeV/c on a Pb or Pt target with different experimental settings. The invariant yields show a striking exponential dependence on nuclear number with a penalty factor of about 50 per additional nucleon. Detailed analysis reveals that the production may depend on the spin factor of the nucleus and the nuclear binding energy as well. (c) 1999 The American Physical Society.
It is shown that the Fisher droplet model, percolation, and nuclear multifragmentation share the common features of reducibility (stochasticity in multiplicity distributions) and thermal scaling ...(one-fragment production probabilities are Boltzmann factors). Barriers obtained, for cluster production on percolation lattices, from the Boltzmann factors show a power-law dependence on cluster size with an exponent of 0.42+/-0.02. The EOS Collaboration Au multifragmentation data yield barriers with a power-law exponent of 0.68+/-0.03. Values of the surface energy coefficient of a low density nuclear system are also extracted.
PDF
