Measurement of complex fragments and clues to the entropy production from 42-137-MeV/nucleon Ar + Au

Intermediate-rapidity fragments with A=1-14 emitted from 42-137-MeV/nucleon Ar + Au have been measured. Evidence is presented that these fragments arise from a common moving source. Entropy values are extracted from the mass distributions by use of quantum statistical and Hauser-Feshbach theories. The extracted entropy values of S/A≈2-2.4 are much smaller than the values expected from measured deuteron-to-proton ratios, but are still considerably higher than theoretically predicted values

Light particle spectra from 35 MeV/nucleon 12C-induced reactions on 197Au

Energy spectra for p, d, t, 3He, 4He, and 6He from the reaction 12C+197Au at 35 MeV/nucleon are presented. A common intermediate rapidity source is identified using a moving source fit to the spectra that yields cross sections which are compared to analogous data at other bombarding energies and to several different models. The excitation function of the composite to proton ratios is compared with quantum statistical, hydrodynamic, and thermal models

Heavy ion collisions: Correlations and Fluctuations in particle production

Correlations and fluctuations (the latter are directly related to the 2-particle correlations) is one of the important directions in analysis of heavy ion collisions. At the current stage of RHIC exploration, when the details matter, basically any physics question is addressed with help of correlation techniques. In this talk I start with a general introduction to the correlation and fluctuation formalism and discuss weak and strong sides of different type of observables. In more detail, I discuss the two-particle $p_t$ correlations/\mpt fluctuations. In spite of not observing any dramatic changes in the event-by-event fluctuations with energy, which would indicate a possible phase transition, such correlations measurements remain an interesting and important subject, bringing valuable information. Lastly, I show how radial flow can generate characteristic azimuthal, transverse momentum and rapidity correlations, which could qualitatively explain many of recently observed phenomena in nuclear collisions.Comment: 8 pages, 8 figures. Invited talk at 5th International Conference on Physics and Astrophysics of Quark Gluon Plasma, February 8-12, 2005, Salt Lake City, Kolkata, Indi

Differential flow in heavy-ion collisions at balance energies

A strong differential transverse collective flow is predicted for the first time to occur in heavy-ion collisions at balance energies. We also give a novel explanation for the disappearance of the total transverse collective flow at the balance energies. It is further shown that the differential flow especially at high transverse momenta is a useful microscope capable of resolving the balance energy's dual sensitivity to both the nuclear equation of state and in-medium nucleon-nucleon cross sections in the reaction dynamics.Comment: Phys. Rev. Lett. (1999) in pres

Neutrons from multiplicity-selected Au-Au collisions at 150, 250, 400, and 650 AMeV

We measured neutron triple-differential cross sections from multiplicity-selected Au-Au collisions at 150, 250, 400, and 650 \AMeV. The reaction plane for each collision was estimated from the summed transverse velocity vector of the charged fragments emitted in the collision. We examined the azimuthal distribution of the triple-differential cross sections as a function of the polar angle and the neutron rapidity. We extracted the average in--plane transverse momentum $\langle P_x\rangle$ and the normalized observable $\langle P_x/P_\perp\rangle$, where $P_\perp$ is the neutron transverse momentum, as a function of the neutron center-of-mass rapidity, and we examined the dependence of these observables on beam energy. These collective flow observables for neutrons, which are consistent with those of protons plus bound nucleons from the Plastic Ball Group, agree with the Boltzmann--Uehling--Uhlenbeck (BUU) calculations with a momentum--dependent interaction. Also, we calculated the polar-angle-integrated maximum azimuthal anisotropy ratio R from the value of $\langle P_x/P_\perp\rangle$.Comment: 20 LaTeX pages. 11 figures to be faxed on request, send email to sender's addres

Nucleon Flow and Fragment Flow in Heavy Ion Reactions

The collective flow of nucleons and that of fragments in the 12C + 12C reaction below 150 MeV/nucleon are calculated with the antisymmetrized version of molecular dynamics combined with the statistical decay calculation. Density dependent Gogny force is used as the effective interaction. The calculated balance energy is about 100 MeV/nucleon, which is close to the observed value. Below the balance energy, the absolute value of the fragment flow is larger than that of nucleon flow, which is also in accordance with data. The dependence of the flow on the stochastic collision cross section and its origin are discussed. All the results are naturally understood by introducing the concept of two components of flow: the flow of dynamically emitted nucleons and the flow of the nuclear matter which contributes to both the flow of fragments and the flow of nucleons due to the statistical decay.Comment: 20 pages, PostScript figures, LaTeX with REVTeX and EPSF, KUNS 121

Classes of Multiple Decision Functions Strongly Controlling FWER and FDR

This paper provides two general classes of multiple decision functions where each member of the first class strongly controls the family-wise error rate (FWER), while each member of the second class strongly controls the false discovery rate (FDR). These classes offer the possibility that an optimal multiple decision function with respect to a pre-specified criterion, such as the missed discovery rate (MDR), could be found within these classes. Such multiple decision functions can be utilized in multiple testing, specifically, but not limited to, the analysis of high-dimensional microarray data sets.Comment: 19 page

Δ\Delta-scaling and heat capacity in relativistic ion collisions

The $\Delta$-scaling method has been applied to the total multiplicity distribution of the relativistic ion collisions of p+p, C+C and Pb+Pb which were simulated by a Monte Carlo package, LUCIAE 3.0. It is found that the $\Delta$-scaling parameter decreases with the increasing of the system size. Moreover, the heat capacities of different mesons and baryons have been extracted from the event-by-event temperature fluctuation in the region of low transverse mass and they show the dropping trend with the increasing of impact parameter.Comment: version 2: major change: 4 pages, 3 figures; Proceeding of International Conference on "Strangeness in Quark Matter" (SQM2004), Cape Town, South Africa, Spet. 2004 (Submitted to J. Phys. G.

The importance of initial-final state correlations for the formation of fragments in heavy ion collisions

Using quantum molecular dynamics simulations, we investigate the formation of fragments in symmetric reactions between beam energies of E=30AMeV and 600AMeV. After a comparison with existing data we investigate some observables relevant to tackle equilibration: dsigma/dErat, the double differential cross section dsigma/pt.dpz.dpt,... Apart maybe from very energetic E>400AMeV and very central reactions, none of our simulations gives evidence that the system passes through a state of equilibrium. Later, we address the production mechanisms and find that, whatever the energy, nucleons finally entrained in a fragment exhibit strong initial-final state correlations, in coordinate as well as in momentum space. At high energy those correlations resemble the ones obtained in the participant-spectator model. At low energy the correlations are equally strong, but more complicated; they are a consequence of the Pauli blocking of the nucleon-nucleon collisions, the geometry, and the excitation energy. Studying a second set of time-dependent variables (radii, densities,...), we investigate in details how those correlations survive the reaction especially in central reactions where the nucleons have to pass through the whole system. It appears that some fragments are made of nucleons which were initially correlated, whereas others are formed by nucleons scattered during the reaction into the vicinity of a group of previously correlated nucleons.Comment: 45 pages text + 20 postscript figures Accepted for publication in Physical Review

Radial Flow in Au+Au Collisions at E=0.25-1.15 A GeV

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.Comment: 10 pages of text and 4 figures (all ps files in a uuencoded package)