Search

We calculate the dimuon production rate from a thermalized quark-gluon plasma in heavy-ion collisions at RHIC energies. Higher-order QCD corrections are included by using an analytical correction factor K(i), which gives very good agreement with experimental Drell-Yan data, and predicts a large enhancement of the thermal dimuon emission over the lowest order rates. We compare the thermal dimuon yields with the expected production from open-charm decays and Drell-Yan background and assess the prospects of observing thermal dimuons from the quark-gluon-plasma at invariant masses of a few GeV.

The enhancement of k+/π+ ratio in A+B collisions comparing to p+A and/or p+p collisions at similar incident energy is predicted as a possible signal of the quark-gluon plasma formation in ultra-relativistic nucleus- nucleus collisions. Several hadronic models have been developed to see whether the enhancement can also be explained in hadronic scheme. Most of the hadronic thermal models1−4 give positive answer. However,the answers of two hadronic transport models5−6 were really opposite.

The experimental data of proton and pion rapidity distributions and proton transverse mass distribution in reaction of (14.6 AGeV/c)Si + Au are compared with a simple relativistic hadronic cascade simulation. The theoretical results seem to prefer the statement of strong but incomplete nuclear stopping at AGS energy.

A simple Monte Carlo simulation and even a partition method can be used to reproduce quite well the power law behavior between the factorial moment and the charge interval of fragment charge distributions from the multifragmentation of nucleus bombarding emulsion at nucleon. This indicates that the above power law seems not to be a unique precursor of the intermittent behavior in nuclear multifragmentations.

We present simulation results of net charge fluctuation in $Au+Au$ collisions at $\sqrt{s_{nn}}$=130 GeV from a dynamic model, JPCIAE. The calculations are done for the quark-gluon phase before hadronization, the pion gas, the resonance pion gas from $\rho$ and $\omega$ decays and so on. The simulations of the charge fluctuation show that the discrepancy exists between the dynamic model and the thermal model for a pion gas and a resonance pion gas from $\rho$ and $\omega$ decays while the simulated charge fluctuation of the quark-gluon phase is close to the thermal model prediction. JPCIAE results of net charge fluctuation in the hardonic phase are nearly 4-5 times larger than one for the quark-gluon phase, which implies that the charge fluctuation in the quark-gluon phase may not survive the hadronization (string fragmentation) as implemented in JPCIAE., Comment: 9 pages, 3 figures

It has been observed recently that while continuum dilepton production and open charm production in high-energy $pA$ collisions can be described in terms of the superposition of $pp$ collisions, dilepton yields in S+U collisions are in excess of similar extrapolations. This feature can be explained as arising from the interaction of gluons produced in different soft baryon-baryon collisions, leading to additional open-charm pairs in nucleus-nucleus collisions but not in $pA$ collisions., 11 pages (REVTeX), includes 2 uuencoded compressed postscript figures