331 research outputs found
Bose-Einstein Correlations in a Fluid Dynamical Scenario for Proton-Proton Scattering at 7 TeV
Using a fluid dynamical scenario for scattering at 7 TeV, we compute
correlation functions for pairs. Femtoscopic radii are extracted
based on three-dimensional parametrizations of the correlation functions. We
study the radii as a function of the transverse momenta of the pairs, for
different multiplicity classes, corresponding to recent experimental results
from ALICE. We find the same decrease of the radii with , more and more
pronounced with increasing multiplicity, but absent for the lowest
multiplicities. In the model we understand this as transition from string
expansion (low multiplicity) towards a three-dimensional hydrodynamical
expansion (high multiplicity)
The "Ridge" in Proton-Proton Scattering at 7 TeV
One of the most important experimental results for proton-proton scattering
at the LHC is the observation of a so-called "ridge" structure in the two
particle correlation function versus the pseudorapidity difference
and the azimuthal angle difference . One finds a strong correlation
around , extended over many units in . We show that a
hydrodynamical expansion based on flux tube initial conditions leads in a
natural way to the observed structure. To get this result, we have to perform
an event-by-event calculation, because the effect is due to statistical
fluctuations of the initial conditions, together with a subsequent collective
expansion. This is a strong point in favour of a fluid-like behavior even in
scattering, where we have to deal with length scales of the order of 0.1
fm.Comment: 5 pages, 4 figure
Anisotropic emission of thermal dielectrons from Au+Au collisions at ~GeV with EPOS3
Dileptons, as an electromagnetic probe, are crucial to study the properties
of a Quark-Gluon Plasma (QGP) created in heavy ion collisions. We calculated
the invariant mass spectra and the anisotropic emission of thermal dielectrons
from Au+Au collisions at the Relativistic Heavy Ion Collider (RHIC) energy
~GeV based on EPOS3. This approach provides a realistic
(3+1)-dimensional event-by-event viscous hydrodynamic description of the
expanding hot and dense matter with a very particular initial condition, and a
large set of hadron data and direct photons (besides and !) can
be successfully reproduced. Thermal dilepton emission from both the QGP phase
and the hadronic gas are considered, with the emission rates based on Lattice
QCD and a vector meson model, respectively. We find that the computed invariant
mass spectra (thermal contribution + STAR cocktail) can reproduce the measured
ones from STAR at different centralities. Different compared to other model
predictions, the obtained elliptic flow of thermal dileptons is larger than the
STAR measurement referring to all dileptons. We observe a clear centrality
dependence of thermal dilepton not only for elliptic flow but also for
higher orders. At a given centrality, of thermal dileptons decreases
monotonically with for .Comment: 10pages, 12fig
Multi-strange baryon measurements at LHC energies, with the ALICE experiment
The status of the charged multi-strange baryon analysis (Xi-, anti-Xi+,
Omega-, anti-Omega+) at LHC energies is presented. This report is based on the
results obtained with ALICE (A Large Ion Collider Experiment), profiting from
the characteristic cascade-decay topology. A special attention is drawn to the
early pp data-taking period (2009-2010) and subsequently, on the uncorrected
pT-spectra extracted at mid-rapidity for centre of mass energies of 0.9 TeV and
7 TeV.Comment: 4 pages, 5 figures, Hot Quarks 2010 proceedings, La Londe Les Maures,
France, June 2010 (to be published in Journal of Physics: Conference Series
Ridges and Soft Jet Components in Untriggered Di-hadron Correlations in Pb+Pb Collisions at 2.76 TeV
We study untriggered di-hadron correlations in Pb+Pb at 2.76 TeV, based on an
event-by-event simulation of a hydrodynamic expansion starting from flux tube
initial conditions. The correlation function shows interesting structures as a
function of the pseudorapidity difference and the azimuthal angle
difference , in particular comparing different centralities. We can
clearly identify a peak-like nearside structure associated with very low
momentum components of jets for peripheral collisions, which disappears towards
central collisions. On the other hand, a very broad ridge structure from
asymmetric flow seen at central collisions, gets smaller and finally disappears
towards peripheral collisions
CORSIKA 8 - Towards a modern framework for the simulation of extensive air showers
Current and future challenges in astroparticle physics require novel
simulation tools to achieve higher precision and more flexibility. For three
decades the FORTRAN version of CORSIKA served the community in an excellent
way. However, the effort to maintain and further develop this complex package
is getting increasingly difficult. To overcome existing limitations, and
designed as a very open platform for all particle cascade simulations in
astroparticle physics, we are developing CORSIKA 8 based on modern C++ and
Python concepts. Here, we give a brief status report of the project.Comment: 4 pages, 3 figures; Proceedings of Ultra High Energy Cosmic Rays 201
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