arXiv subjects
Publications and source records attributed to Miklos Gyulassy.
The dilepton spectra from open charm decay in $p+A$ reactions at $\sqrt s=200$ AGeV are proposed to constrain gluon shadowing in nuclei. We show that the required measurements are feasible at RHIC.
The width $ΔT$ of the deconfinement transition region is shown to influence strongly the flow structure in the (Landau-) hydrodynamical expansion of a quark-gluon plasma. For a sharp first order transition ($ΔT=0$) the mixed phase is rather long-lived, with a lifetime that has a maximum when the initial energy density is at the phase boundary between mixed and pure quark-gluon matter. For increasing $ΔT$, however, the lifetime decreases rapidly. Hadronic matter, however, remains long-lived as a consequence of the rapid change in the degrees of freedom in the transition region and the corresponding ``softening'' of the equation of state.
Based on QCD-inspired models for multiple jets production, we developed a Monte Carlo program to study jet and the associated particle production in high energy $pp$, $pA$ and $AA$ collisions. The physics behind the program which includes multiple minijet production, soft excitation, nuclear shadowing of parton distribution functions and jet interaction in dense matter is briefly discussed. A detailed description of the program and instructions on how to use it are given.
A $χ^2$ analysis is performed to test the resolving power of two-dimensional pion interferometry using for illustration the preliminary E802 data on $Si+Au$ at 14.6 AGeV/c. We find that the resolving power to distinguish two decoupling geometries of different dynamical models is enhanced by studying the variation of the mean $χ^2$ per degrees of freedom with respect to the range of the analysis in the $q_T,q_L$ plane. The preliminary data seem to rule out dynamical models with significant $ω,η$ resonance formation yields.
The pre-equilibrium contribution to open charm production in nuclear collisions at $\sqrt{s}=200$ AGeV is calculated using three different models for the correlations between momentum and space-time coordinates. Ideal (Bjorken) correlation between the rapidity $y$ and space-time rapidity $η$ of mini-jet gluons suppresses greatly the pre-equilibrium yield and even allowing for the minimal uncertainty correlations leads, in contrast to previous estimates, only to a small pre-equilibrium charm yield as compared to initial yield due to gluon fusion. The ``intrinsic'' charm process is negligible in the mid-rapidity domain.
Correlators of magnetic and electric field energy density are investigated for SU($N_c$) gauge theory at high temperatures $T$. At separations $z\leq 2/T$ the correlators are shown to be dominated by a power--law behavior even for finite gluon screening masses. This continuum behavior is well approximated on current $4\times 16^3$--lattices in the perturbative limit and leads to a considerable overestimate of screening masses deduced from fitting the lattice correlators with conventional exponential forms. The use of extended sources and sinks to enhance the signal improves the situation for screening masses $m\gg T$ but leads to a largely uncontrolled error for masses less than $T$. In fact, we show that recent lattice QCD data of Grossmann et al., from which a magnetic screening mass $m_M \approx 2.9 \, T$ was deduced, may even be consistent with a vanishing actual magnetic screening mass.
The non-abelian analog of the Landau-Pomeranchuk-Migdal effect is investigated in perturbative QCD. Extending our previous studies, the suppression of induced soft bremsstrahlung due to multiple scatterings of quarks in the spinor representation is considered. The effective formation time of gluon radiation due to the color interference is shown to depend on the color representation of the emitting parton, and an improved formula for the radiative energy loss is derived that interpolates between the factorization and Bethe-Heitler limits.
Color diffusion is shown to be an important dissipative property of quark-gluon plasmas that rapidly damps collective color modes. We derive the characteristic color relaxation time scale, $t_c\approx (3α_s T \log(m_E/m_M ))^{-1}$, showing its sensitivity to the ratio of the static color electric and magnetic screening masses. This leads to a surprisingly small color conductivity, $σ_c\approx 2 T/\log(m_E/m_M)$, which in fact vanishes in the semi-classical (1-loop) limit.
We study the efficiency of a neural-net filter and deconvolution method for estimating jet energies and spectra in high-background reactions such as nuclear collisions at the relativistic heavy-ion collider and the large hadron collider. The optimal network is shown to be surprisingly close but not identical to a linear high-pass filter. A suitably constrained deconvolution method is shown to uncover accurately the underlying jet distribution in spite of the broad network response. Finally, we show that possible changes of the jet spectrum in nuclear collisions can be analyzed quantitatively, in terms of an effective energy loss with the proposed method. {} {Dong D W and Gyulassy M 1993}{Neural filters for jet analysis} {(LBL-31560) Physical Review E Vol~47(4) pp~2913-2922}