1,318 research outputs found
Elliptic flow from event-by-event hydrodynamics
We present an event-by-event hydrodynamical framework which takes into
account the initial density fluctuations arising from a Monte Carlo Glauber
model. The elliptic flow is calculated with the event plane method and a
one-to-one comparison with the measured event plane is made. Both the
centrality- and -dependence of the are remarkably well reproduced.
We also find that the participant plane is a quite good approximation for the
event plane.Comment: 4 pages, 3 figures. Talk given at Quark Matter 2011, 22-28 May 2011,
Annecy, Franc
Jet Fragmentation via Recombination of Parton Showers
We study hadron production in jets by applying quark recombination to jet
shower partons. With the jet showers obtained from PYTHIA and augmented by
additional non-perturbative effects, we compute hadron spectra in e+ +
e-collisions at sqrt(s)=200 GeV. Including contributions from resonance decays,
we find that the resulting transverse momentum spectra for pions, kaons, and
protons reproduce reasonably those from the string fragmentation as implemented
in PYTHIA.Comment: 4 pages, 3 figures, contribution to Nucleus-Nucleus Collisions 201
First Direct Measurement of Jets in GeV Heavy Ion Collisions by STAR
We present the first measurement of reconstructed jets in ultra-relativistic
heavy ion collisions. Utilizing the large coverage of the STAR Time Projection
Chamber and Electromagnetic Calorimeter, we apply several modern jet
reconstruction algorithms and background subtraction techniques and explore
their systematic uncertainties in heavy ion events. The differential spectrum
for inclusive jet production in central Au+Au collisions at GeV is presented. In order to assess the jet reconstruction biases, this
spectrum is compared with the jet cross section measured in GeV
p+p collisions scaled by the number of binary N-N collisions to account for
nuclear geometric effects.Comment: Proceedings of the 3rd International Conference on Hard and Electro-
Magnetic Probes of High-Energy Nuclear Collisions 8-14 June 2008, Illa da
Toxa (Galicia-Spain
ExHuME: A Monte Carlo Event Generator for Exclusive Diffraction
We have written the Exclusive Hadronic Monte Carlo Event (ExHuME) generator.
ExHuME implements the perturbative QCD calculation of Khoze, Martin and Ryskin
of the process pp-> p+X+p, where X is a centrally produced colour singlet
system.Comment: 11 pages, 3 figure
Parton distributions of real and virtual photons
Recent progress on the parton distribution functions of the photon, both real
and virtual, is briefly reviewed and experimental possibilities at HERA are
discussed.Comment: 10 pages, LaTeX, 4 eps figures included in file using filecontents
environment
Production, elliptic flow and energy loss of heavy quarks in the quark-gluon plasma
Production, elliptic flow and the nuclear modification factor of charm and
bottom quarks are studied in central and non-central heavy-ion collisions at
RHIC and LHC using the partonic transport model Boltzmann Approach of
MultiParton Scatterings (BAMPS). Employing an initial heavy quark yield
obtained with PYTHIA the full space-time evolution of charm and bottom quarks
in the quark-gluon plasma (QGP) is carried out with BAMPS, taking also
secondary production in the QGP into account. Only elastic collisions of heavy
quarks with particles from the medium cannot describe the experimentally
observed elliptic flow and nuclear modification factor. However, using an
improved Debye screening and the running coupling yields a result which is much
closer to data.Comment: 4 pages, 1 figure, to appear in the conference proceedings of Hot
Quarks 2010, few minor modifications in 2nd versio
Wroclaw neutrino event generator
A neutrino event generator developed by the Wroclaw Neutrino Group is
described. The physical models included in the generator are discussed and
illustrated with the results of simulations. The considered processes are
quasi-elastic scattering and pion production modelled by combining the
resonance excitation and deep inelastic scattering.Comment: Talk given at 2nd Scandanavian Neutrino Workshop (SNOW 2006),
Stockholm, Sweden, 2-6 May 2006. 3 pages, 6 figure
Jet-hadron correlations in STAR
Advancements in full jet reconstruction have made it possible to use jets as
triggers in azimuthal angular correlations to study the modification of
hard-scattered partons in the medium created in ultrarelativistic heavy-ion
collisions. This increases the range of parton energies accessible in these
analyses and improves the signal-to-background ratio compared to dihadron
correlations. Results of a systematic study of jet-hadron correlations in
central Au-Au collisions at sqrt(s_NN) = 200 GeV are indicative of a broadening
and softening of jets which interact with the medium. Furthermore, jet-hadron
correlations suggest that the suppression of the associated hadron yield at
high-pT is balanced in large part by low-pT enhancement.Comment: 4 pages, 2 figures, proceedings for Quark Matter 201
Multiple Hard Parton Interactions at HERA
At HERA, the large flux of almost real photons accompanying the electron beam
leads to the copious photoproduction of jets. Regions of small momentum
fractions of the incoming particles are explored, where the density of
partons is high. As a result, the probability for more than one hard partonic
scattering occurring in a single collision could become significant.
It is well known that this effect modifies the contribution of jets (minijets)
to the total cross section. We discuss the latest HERA data on the total
cross section in this context. The possible effects of multiple hard
interactions on event shapes and jet cross sections at HERA have been studied
using Monte Carlo programs. We review some of the available results, which in
general indicate that the effects of multiple interactions should be
significant and may already be manifest in the existing HERA data.Comment: 12 pages LATEX with 4 figures in a single uuuencoded fil
Dijet Cross Section and Longitudinal Double Spin Asymmetry Measurements in Polarized Proton-proton Collisions at \sqrt{s}=200 GeV at STAR
These proceedings show the preliminary results of the dijet cross sections
and the dijet longitudinal double spin asymmetries A_LL in polarized
proton-proton collisions at \sqrt{s} = 200 GeV at the mid-rapidity |eta| < 0.8.
The integrated luminosity of 5.39 pb^{-1} collected during RHIC Run-6 was used
in the measurements. The preliminary results are presented as functions of the
dijet invariant mass M_jj. The dijet cross sections are in agreement with
next-to-leading-order pQCD predictions. The A_LL is compared with theoretical
predictions based on various parameterizations of polarized parton
distributions of the proton. Projected precision of data analyzed to date from
Run-9 are shown.Comment: 8 pages, 5 figures, Proceedings of the SPIN2010 conference (Juelich,
Germany, 2010
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