3,053 research outputs found
The Bose-Einstein effect in Monte-Carlo generators: weight methods
We present a method which incorporates the Bose-Einstein effect into Monte
Carlo generators for multiple production by weighting the events. Various
aspects of weight calculations are discussed in detail. We show that our method
allows to describe reasonably well a sample of data and we outline the future
tests and applications.Comment: Latex, 10 pages including 4 .eps figure
Automated track recognition and event reconstruction in nuclear emulsion
The major advantages of nuclear emulsion for detecting charged particles are its submicron position resolution and sensitivity to minimum ionizing particles. These must be balanced, however, against the difficult manual microscope measurement by skilled observers required for the analysis. We have developed an automated system to acquire and analyze the microscope images from emulsion chambers. Each emulsion plate is analyzed independently, allowing coincidence techniques to be used in order to reject background and estimate error rates. The system has been used to analyze a sample of high-multiplicity Pb-Pb interactions (charged particle multiplicities ∼1100) produced by the 158 GeV/c per nucleon 208Pb beam at CERN. Automatically measured events agree with our best manual measurements on 97% of all the tracks. We describe the image analysis and track reconstruction techniques, and discuss the measurement and reconstruction uncertainties
Charged particle production in the Pb+Pb system at 158 GeV/c per nucleon
Charged particle multiplicities from high multiplicity central interactions
of 158 GeV/nucleon Pb ions with Pb target nuclei have been measured in the
central and far forward projectile spectator regions using emulsion chambers.
Multiplicities are significantly lower than predicted by Monte Carlo
simulations. We examine the shape of the pseudorapidity distribution and its
dependence on centrality in detail.Comment: 17 pages text plus 12 figures in postscript 12/23/99 -- Add TeX
version of sourc
Criticality, Fractality and Intermittency in Strong Interactions
Assuming a second-order phase transition for the hadronization process, we
attempt to associate intermittency patterns in high-energy hadronic collisions
to fractal structures in configuration space and corresponding intermittency
indices to the isothermal critical exponent at the transition temperature. In
this approach, the most general multidimensional intermittency pattern,
associated to a second-order phase transition of the strongly interacting
system, is determined, and its relevance to present and future experiments is
discussed.Comment: 15 pages + 2 figures (available on request), CERN-TH.6990/93,
UA/NPPS-5-9
The Importance of Correlations and Fluctuations on the Initial Source Eccentricity in High-Energy Nucleus-Nucleus Collisions
In this paper, we investigate various ways of defining the initial source
eccentricity using the Monte Carlo Glauber (MCG) approach. In particular, we
examine the participant eccentricity, which quantifies the eccentricity of the
initial source shape by the major axes of the ellipse formed by the interaction
points of the participating nucleons. We show that reasonable variation of the
density parameters in the Glauber calculation, as well as variations in how
matter production is modeled, do not significantly modify the already
established behavior of the participant eccentricity as a function of collision
centrality. Focusing on event-by-event fluctuations and correlations of the
distributions of participating nucleons we demonstrate that, depending on the
achieved event-plane resolution, fluctuations in the elliptic flow magnitude
lead to most measurements being sensitive to the root-mean-square, rather
than the mean of the distribution. Neglecting correlations among
participants, we derive analytical expressions for the participant eccentricity
cumulants as a function of the number of participating nucleons,
\Npart,keeping non-negligible contributions up to \ordof{1/\Npart^3}. We
find that the derived expressions yield the same results as obtained from
mixed-event MCG calculations which remove the correlations stemming from the
nuclear collision process. Most importantly, we conclude from the comparison
with MCG calculations that the fourth order participant eccentricity cumulant
does not approach the spatial anisotropy obtained assuming a smooth nuclear
matter distribution. In particular, for the Cu+Cu system, these quantities
deviate from each other by almost a factor of two over a wide range in
centrality.Comment: 18 pages, 10 figures, submitted to PR
Identified particles in Au+Au collisions at sqrt{s_NN} = 200 GeV
The yields of identified particles have been measured at RHIC for Au+Au
collisions at sqrt{s_NN} = 200 GeV using the PHOBOS spectrometer. The ratios of
antiparticle to particle yields near mid-rapidity are presented. The first
measurements of the invariant yields of charged pions, kaons and protons at
very low transverse momenta are also shown.Comment: 4 pages, 4 figures, Contribution to Quark Matter 2002, Nantes,
France, July 200
Predictions and recent results in susy on the lattice
In this brief review, I summarize the current theoretical knowledge in
supersymmetry on the lattice, with special emphasis on recent results in the
framework of N=1 supersymmetric Yang Mills theory, Wess-Zumino model and
Yang-Mills theory with extended supersymmetries.Comment: 15 pages. Invited brief review for Modern Physics Letters A. Minor
change
Elliptic Flow in Au+Au Collisions at RHIC
Elliptic flow is an interesting probe of the dynamical evolution of the dense
system formed in the ultrarelativistic heavy ion collisions at the Relativistic
Heavy Ion Collider (RHIC). The elliptic flow dependences on transverse
momentum, centrality, and pseudorapidity were measured using data collected by
the PHOBOS detector, which offers a unique opportunity to study the azimuthal
anisotropies of charged particles over a wide range of pseudorapidity. These
measurements are presented, together with an overview of the analysis methods
and a discussion of the results.Comment: Presented at Hot Quarks 2004; 7 pages, 6 figure
System size and centrality dependence of charged hadron transverse momentum spectra in Au+Au and Cu+Cu collisions at sqrt(s) = 62.4 and 200 GeV
We present transverse momentum distributions of charged hadrons produced in
Cu+Cu collisions at sqrt(s) = 62.4 and 200 GeV. The spectra are measured for
transverse momenta of 0.25 < p_T < 5.0 GeV/c at sqrt(s) = 62.4 GeV and 0.25 <
p_T < 7.0 GeV/c at sqrt(s) = 200 GeV, in a pseudo-rapidity range of 0.2 < eta <
1.4. The nuclear modification factor R_AA is calculated relative to p+p data at
both collision energies as a function of collision centrality. At a given
collision energy and fractional cross-section, R_AA is observed to be
systematically larger in Cu+Cu collisions compared to Au+Au. However, for the
same number of participating nucleons, R_AA is essentially the same in both
systems over the measured range of p_T, in spite of the significantly different
geometries of the Cu+Cu and Au+Au systems.Comment: 4 pages, 5 figures, submitted to Phys. Rev. Let
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