4,678 research outputs found
Jets and produced particles in pp collisions from SPS to RHIC energies for nuclear applications
Higher-order pQCD corrections play an important role in the reproduction of
data at high transverse momenta in the energy range 20 GeV GeV. Recent calculations of photon and pion production in collisions
yield detailed information on the next-to-leading order contributions. However,
the application of these results in proton-nucleus and nucleus-nucleus
collisions is not straightforward. The study of nuclear effects requires a
simplified understanding of the output of these computations. Here we summarize
our analysis of recent calculations, aimed at handling the NLO results by
introducing process and energy-dependent factors.Comment: 4 pages with 5 eps figures include
Pion production in d+Au collisions at RHIC energy
We present our results on neutral pion pi0 production in pp and dAu
collisions at RHIC energy. Pion spectra are calculated in a next-to-leading
order (NLO) perturbative QCD-based model. The model includes the transverse
component of the initial parton distribution (``intrinsic kT''). We compare our
results to the available experimental data from RHIC, and fit the data with
high precision. The calculation tuned this way is repeated for the dAu
collision, and used to investigate the interplay of shadowing and multiple
scattering at RHIC. The centrality dependence of the nuclear modification
factor shows a measurable difference between different shadowing
parameterizations.Comment: Final version published in the Eur. Phys. J. ST in the Proceedings of
the Zimanyi Memorial Workshop, 2-4 July, 2007, Budapest, Hungary; 12 pages in
Latex, 6 EPS figure
Multifragmentation calculated with relativistic force
A saturating hamiltonian is presented in a relativistically covariant
formalism. The interaction is described by scalar and vector mesons, with
coupling strengths adjusted to the nuclear matter. No explicit density depe
ndence is assumed. The hamiltonian is applied in a QMD calculation to determine
the fragment distribution in O + Br collision at different energies (50 -- 200
MeV/u) to test the applicability of the model at low energies. The results are
compared with experiment and with previous non-relativistic calculations.
PACS: 25.70Mn, 25.75.+rComment: 23 pages, latex, with 10 PS figures, available at
http://www.gsi.de/~papp
K+/pi+ probes of jet quenching in AA collisions
Non-abelian energy loss in quark gluon plasma is shown to lead to novel
hadron ratio suppression patterns in ultrarelativistic nuclear collisions. We
apply recent (GLV) estimates for the gluon radiative energy loss, which
increases linearly with the jet energy up to E<20 GeV and depends quadratically
on the nuclear radius, R. The K+/\pi+ ratio is found to be most sensitive to
the initial density of the plasma.Comment: Presented at 6th International Conference on Strange Quarks in
Matter: 2001: A Flavourspace Odyssey (SQM2001), Frankfurt, Germany, 25-29 Sep
200
Continued fraction representation of the Coulomb Green's operator and unified description of bound, resonant and scattering states
If a quantum mechanical Hamiltonian has an infinite symmetric tridiagonal
(Jacobi) matrix form in some discrete Hilbert-space basis representation, then
its Green's operator can be constructed in terms of a continued fraction. As an
illustrative example we discuss the Coulomb Green's operator in
Coulomb-Sturmian basis representation. Based on this representation, a quantum
mechanical approximation method for solving Lippmann-Schwinger integral
equations can be established, which is equally applicable for bound-, resonant-
and scattering-state problems with free and Coulombic asymptotics as well. The
performance of this technique is illustrated with a detailed investigation of a
nuclear potential describing the interaction of two particles.Comment: 7 pages, 4 ps figures, revised versio
Stability and instability of a hot and dilute nuclear droplet
The diabatic approach to collective nuclear motion is reformulated in the
local-density approximation in order to treat the normal modes of a spherical
nuclear droplet analytically. In a first application the adiabatic isoscalar
modes are studied and results for the eigenvalues of compressional (bulk) and
pure surface modes are presented as function of density and temperature inside
the droplet, as well as for different mass numbers and for soft and stiff
equations of state. We find that the region of bulk instabilities (spinodal
regime) is substantially smaller for nuclear droplets than for infinite nuclear
matter. For small densities below 30% of normal nuclear matter density and for
temperatures below 5 MeV all relevant bulk modes become unstable with the same
growth rates. The surface modes have a larger spinodal region, reaching out to
densities and temperatures way beyond the spinodal line for bulk instabilities.
Essential experimental features of multifragmentation, like fragmentation
temperatures and fragment-mass distributions (in particular the power-law
behavior) are consistent with the instability properties of an expanding
nuclear droplet, and hence with a dynamical fragmentation process within the
spinodal regime of bulk and surface modes (spinodal decomposition).Comment: 17 pages, 11 figures, LaTeX2e, EPJA style (included
Instabilities of a hot expanded nuclear droplet
The stability of hot expanded nuclear droplets against small bulk and surface
oscillations is examined and possible consequences for multifragmentation are
discussed.Comment: LaTeX (uses epsfig.sty), 6 pages with 6 eps figures inside text. Talk
given at XXVII International Workshop on Gross Properties of Nuclei and
Nuclear Excitations, "MULTIFRAGMENTATION", Hirschegg, January 17--23, 199
Kaon and Pion Ratio Probes of Jet Quenching in Nuclear Collisions
Non-abelian energy loss in quark gluon plasmas is shown to lead to novel
hadron ratio suppression patterns in ultrarelativistic nuclear collisions. We
apply GLV estimates for the gluon radiative energy loss. The K^-/K^+ and
K^+/\pi^+ ratios are found to be most sensitive to the initial density of the
plasma.Comment: 10 pages in Latex, 6 EPS figure
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