1,982 research outputs found
A Cone Jet-Finding Algorithm for Heavy-Ion Collisions at LHC Energies
Standard jet finding techniques used in elementary particle collisions have
not been successful in the high track density of heavy-ion collisions. This
paper describes a modified cone-type jet finding algorithm developed for the
complex environment of heavy-ion collisions. The primary modification to the
algorithm is the evaluation and subtraction of the large background energy,
arising from uncorrelated soft hadrons, in each collision. A detailed analysis
of the background energy and its event-by-event fluctuations has been performed
on simulated data, and a method developed to estimate the background energy
inside the jet cone from the measured energy outside the cone on an
event-by-event basis. The algorithm has been tested using Monte-Carlo
simulations of Pb+Pb collisions at TeV for the ALICE detector at
the LHC. The algorithm can reconstruct jets with a transverse energy of 50 GeV
and above with an energy resolution of .Comment: 13 pages, 7 figure
Hydrodynamic modeling of deconfinement phase transition in nuclear collisions
The (3+1)-dimensional ideal hydrodynamics is used to simulate collisions of
gold nuclei with bombarding energies from 1 to 160 GeV per nucleon. The initial
state is represented by two cold Lorentz-boosted nuclei. Two equations of
state: with and without the deconfinement phase transition are used. We have
investigated dynamical trajectories of compressed baryon-rich matter as
functions of various thermodynamical variables. The parameters of collective
flow and hadronic spectra are calculated. It is shown that presence of the
deconfinement phase transition leads to increase of the elliptic flow and to
flattening of proton rapidity distributions.Comment: 11 pages, 6 figure
Decoherence and energy loss in QCD cascades in nuclear collisions
The medium modifications in the properties of QCD cascades are considered. In
particular, the changes in the intrajet rapidity distributions due to
medium-induced decoherence, collisional losses of cascade gluons and those of
final prehadrons are analyzed
Strangeness dynamics in relativistic nucleus-nucleus collision
We investigate hadron production as well as transverse hadron spectra in
nucleus-nucleus collisions from 2 GeV to 21.3 TeV within two
independent transport approaches (UrQMD and HSD) that are based on quark,
diquark, string and hadronic degrees of freedom. The comparison to experimental
data demonstrates that both approaches agree quite well with each other and
with the experimental data on hadron production. The enhancement of pion
production in central Au+Au (Pb+Pb) collisions relative to scaled
collisions (the 'kink') is well described by both approaches without involving
any phase transition. However, the maximum in the ratio at 20 to 30
AGeV (the 'horn') is missed by 40%. A comparison to the
transverse mass spectra from and C+C (or Si+Si) reactions shows the
reliability of the transport models for light systems. For central Au+Au
(Pb+Pb) collisions at bombarding energies above 5 AGeV, however,
the measured -spectra have a larger inverse slope parameter
than expected from the calculations. The approximately constant slope of
spectra at SPS (the 'step') is not reproduced either. Thus the pressure
generated by hadronic interactions in the transport models above 5
AGeV is lower than observed in the experimental data. This finding
suggests that the additional pressure - as expected from lattice QCD
calculations at finite quark chemical potential and temperature - might be
generated by strong interactions in the early pre-hadronic/partonic phase of
central Au+Au (Pb+Pb) collisions.Comment: 10 pages, 5 figures, Invited talk presented by H. Stocker at
ERICE-2003 (Sep. 2003, Erice, Italy), to be published in Prog. Part. Nucl.
Phys. 52 (2004
- …