1,407 research outputs found
Event-by-event study of DCC-like fluctuation in ultra-relativistic nuclear collisions
A method based on sliding window scheme is developed to search for patches in
the pseudorapidity-azimuth plane, on an event-by-event basis, having unusual
fluctuation in the neutral pion fraction which may arise due to the formation
of Disoriented Chrial Condensates (DCC) in high energy nuclear collisions. The
efficiency of the method to extract the patches and the purity of the extracted
sample are studied for possible experimental situations.Comment: 10 pages, 5 figure
Effect of Finite Granularity of Detectors on Anisotropy Coefficients
The coefficients that describe the anisotropy in the azimuthal distribution
of particles are lower when the particles are recorded in a detector with
finite granularity and measures only hits. This arises due to loss of
information because of multiple hits in any channel. The magnitude of this loss
of signal depends both on the occupancy and on the value of the coefficient.
These correction factors are obtained for analysis methods differing in detail,
and are found to be different.Comment: 11 pages including 2 figure
Evolution of Fluctuation in relativistic heavy-ion collisions
We have studied the time evolution of the fluctuations in the net baryon
number for different initial conditions and space time evolution scenarios. We
observe that the fluctuations at the freeze-out depend crucially on the
equation of state (EOS) of the system and for realistic EOS the initial
fluctuation is substantially dissipated at the freeze-out stage. At SPS
energies the fluctuations in net baryon number at the freeze-out stage for
quark gluon plasma and hadronic initial state is close to the Poissonian noise
for ideal as well as for EOS obtained by including heavier hadronic degrees of
freedom. For EOS obtained from the parametrization of lattice QCD results the
fluctuation is larger than Poissonian noise. It is also observed that at RHIC
energies the fluctuations at the freeze-out point deviates from the Poissonian
noise for ideal as well as realistic equation of state, indicating presence of
dynamical fluctuations.Comment: 9 pages and 6 figures (Major modifications done
A Honeycomb Proportional Counter for Photon Multiplicity Measurement in the ALICE Experiment
A honeycomb detector consisting of a matrix of 96 closely packed hexagonal
cells, each working as a proportional counter with a wire readout, was
fabricated and tested at the CERN PS. The cell depth and the radial dimensions
of the cell were small, in the range of 5-10 mm. The appropriate cell design
was arrived at using GARFIELD simulations. Two geometries are described
illustrating the effect of field shaping. The charged particle detection
efficiency and the preshower characteristics have been studied using pion and
electron beams. Average charged particle detection efficiency was found to be
98%, which is almost uniform within the cell volume and also within the array.
The preshower data show that the transverse size of the shower is in close
agreement with the results of simulations for a range of energies and converter
thicknesses.Comment: To be published in NIM
Measurements of Heavy Flavor and Di-electron Production at STAR
Heavy quarks are produced early in the relativistic heavy ion collisions, and
provide an excellent probe into the hot and dense nuclear matter created at
RHIC. In these proceedings, we will discuss recent STAR measurements of heavy
flavor production, to investigate the heavy quark interaction with the medium.
Electromagnetic probes, such as electrons, provide information on the various
stages of the medium evolution without modification by final stage
interactions. Di-electron production measurements by STAR will also be
discussed.Comment: 5 pages, 6 figures, proceedings for CPOD201
Beam-Energy-Dependent Two-Pion Interferometry and the Freeze-Out Eccentricity of Pions Measured in Heavy Ion Collisions at the Star Detector
We present results of analyses of two-pion interferometry in Au + Au collisions at root s(NN) = 7.7, 11.5, 19.6, 27, 39, 62.4, and 200 GeV measured in the STAR detector as part of the BNL Relativistic Heavy Ion Collider Beam Energy Scan program. The extracted correlation lengths (Hanbury-Brown-Twiss radii) are studied as a function of beam energy, azimuthal angle relative to the reaction plane, centrality, and transverse mass (m(T)) of the particles. The azimuthal analysis allows extraction of the eccentricity of the entire fireball at kinetic freeze-out. The energy dependence of this observable is expected to be sensitive to changes in the equation of state. A new global fit method is studied as an alternate method to directly measure the parameters in the azimuthal analysis. The eccentricity shows a monotonic decrease with beam energy that is qualitatively consistent with the trend from all model predictions and quantitatively consistent with a hadronic transport model
The STAR Photon Multiplicity Detector
Details concerning the design, fabrication and performance of STAR Photon
Multiplicity Detector (PMD) are presented. The PMD will cover the forward
region, within the pseudorapidity range 2.3--3.5, behind the forward time
projection chamber. It will measure the spatial distribution of photons in
order to study collective flow, fluctuation and chiral symmetry restoration.Comment: 15 pages, including 11 figures; to appear in a special NIM volume
dedicated to the accelerator and detectors at RHI
New results from fluctuation analysis in NA49 at the CERN SPS
The exploration of the phase diagram of strongly interacting matter,
particularly the study of the phase transition from hadronic to partonic matter
and the search for a hypothetical critical endpoint of the first order
transition line, is one of the most challenging tasks in present heavy ion
physics.
In this talk new results on chemical (particle ratio), transverse momentum,
multiplicity and azimuthal angle fluctuations will be presented. We also
discuss their connection to the onset of deconfinement and to the critical
endpoint.Comment: The Proceedings of the International Conference "Critical Point and
Onset of Deconfinement - CPOD 2011", Wuhan, November 7-11, 201
Search and study of Quark Gluon Plasma at the CERN-LHC
The major aim of nucleus-nucleus collisions at the LHC is to study the
physics of strongly interacting matter and the quark gluon plasma (QGP), formed
in extreme conditions of temperature and energy density. We give a brief
overview of the experimental program and discuss the signatures and observables
for a detailed study of QGP matter.Comment: 15 pages, Invited article for the volume on LHC physics to celebrate
the Platinum Jubilee of the Indian National Science Academy, Edited by
Amitava Datta, Biswarup Mukhopadhyaya and Amitava Raychaudhuri (Jan 2009
Photon interferometry and size of the hot zone in relativistic heavy ion collisions
The parameters obtained from the theoretical analysis of the single photon
spectra observed by the WA98 collaboration at SPS energies have been used to
evaluate the two photon correlation functions. The single photon spectra and
the two photon correlations at RHIC energies have also been evaluated, taking
into account the effects of the possible spectral change of hadrons in a
thermal bath. We find that the ratio for SPS and
for RHIC energy.Comment: text changed, figures adde
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