951 research outputs found
Proton-proton and deuteron-gold collisions at RHIC
We try to understand recent data on proton-proton and deuteron-gold
collisions at RHIC, employing a modified parton model approach.Comment: Invited talk, given at the XXth Winter Workshop on Nuclear Dynamics,
Trelawny Beach, Jamaica, March 200
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
New Developments of EPOS 2
Since 2006, EPOS hadronic interaction model is being used for very high
energy cosmic ray analysis. Designed for minimum bias particle physics and used
for having a precise description of SPS and RHIC heavy ion collisions, EPOS
brought more detailed description of hadronic interactions in air shower
development. Thanks to this model it was possible to understand why there were
less muons in air shower simulations than observed in real data. With the start
of the LHC era, a better description of hard processes and collective effects
is needed to deeply understand the incoming data. We will describe the basic
physics in EPOS and the new developments and constraints which are taken into
account in EPOS 2.Comment: Contributed presentation to the XVI International Symposium on Very
High Energy Cosmic Ray Interactions (ISVHECRI 2010), Batavia, IL, USA (28
June 2 July 2010). 4 pages, 6 figure
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
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)
A New String Model: NEXUS 3
After discussing conceptual problems with the conventional string model, we
present a new approach, based on a theoretically consistent multiple scattering
formalism.
First results for proton-proton scattering at 158 GeV are discussed.Comment: invited talk given at the 9th Winter Workshop on Nuclear Dynamics,
Breckenridge, Colorado, February 9 - 14, 200
Models for RHIC and LHC: New Developments
We outline inconsistencies in presently used models for high energy nuclear
scattering, which make their application quite unreliable. Many "successes" are
essentially based on an artificial freedom of parameters, which does not exist
when the models are constructed properly.
The problem is the fact that any multiple scattering theory requires an
appropriate treatment of the energy sharing between the individual
interactions, which is technically very difficult to implement. Lacking a
satisfying solution to this problem, it has been simply ignored.
We introduce a fully self-consistent formulation of the multiple-scattering
scheme. Inclusion of soft and hard components - very crucial at high energies -
appears in a "natural way", providing a smooth transition from soft to hard
physics.
We can show that the effect of appropriately considering energy conservation
has a big influence on the results, and MUST therefore be included in any
serious calculation.Comment: talk given at the ``15thInternational Conference on Ultrarelativistic
Nucleus-Nucleus Collisions'', Quark Matter 2001, Stony Brook, USA, January
15-20, 200
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