989 research outputs found
Event by Event Net Charge Fluctuations
We present analyses of event-by-event dynamical net charge fluctuations
measured in 130 and 200 GeV Au Au collisions with the STAR detector. The
dynamical net charge fluctuations are evaluated using the
observable. Dynamical fluctuations measured in Au Au collisions at 130 and 200
GeV are finite, and exceed charge conservation limits. They deviate from a
perfect 1/N scaling and provide an indication that the collision dynamics
varies with collision centrality.Comment: 6 pages, 3 figures, Proc of 19th Nuclear Dynamics Conf at
Breckenridge, Colorado, Feb 8-15, 200
Search for Conical Emission with Three-Particle Correlations
We present preliminary STAR results on 3-particle azimuthal angle correlation
studies in Au+Au collisions at = 200 GeV. The studies are
carried out at mid-rapidity between a trigger particle with 3 4 GeV/c and two associated particles in 1 2 GeV/c. A
cumulant analysis reveals finite 3-particle azimuthal correlations, dominated
by near and away side particle correlations consistent with jet production, and
jet-flow correlations. We use a two-component model to remove underlying
background correlations. This analysis indicates the presence of the conical
emission signals in central Au+Au collisions within the model assumptions about
background composition and normalization.Comment: Proceedings for STAR talk presented at Quark Matter 2006, 4 pages 2
figures, Version 2: typos corrected, references adde
Methods for the Study of Transverse Momentum Differential Correlations
We introduce and compare three differential correlation functions for the
study of transverse momentum correlation in and collisions. These
consist of {\it inclusive}, {\it event-wise} and a differential version of the
correlation measure introduced by Gavin \cite{Gavin} for
experimental study of the viscosity per unit entropy of the matter produced in
collisions. We study the quantitative difference between the three
observables on the basis of PYTHIA simulations of collisions and
collisions consisting of an arbitrary superposition of collision events
at 200 GeV. We observe that {\it inclusive} and {\it event-wise}
correlation functions are remarkably identical to each other where as the
observable differs from the two. We study the robustness and
efficiency dependencies of these observables based on truncated Taylor
expansions in efficiency in collisions and on the basis of Monte Carlo
simulation using an adhoc detector efficiency parameterization. We find that
all the three observables are essentially independent of detector efficiency.
We additionally study the scaling of the correlation measures and find all the
observables exhibit an approximate dependence of the number of
participants ({\it N}) in collisions. Finally, we study the impact of
flow-like anisotropy on the {\it inclusive} correlation function and find flow
imparts azimuthal modulations similar to those observed with two-particle
densities.Comment: 19 pages, 8 figure
Simulation studies of and correlation functions in pp collisions with the PYTHIA and HERWIG models
We report studies of charge-independent (CI) and charge-dependent (CD)
two-particle differential-number correlation functions, , and transverse momentum () correlation functions,
, of charged particles in
= 2.76 TeV pp collisions with the PYTHIA and HERWIG models.
Model predictions are presented for inclusive charged hadrons (), as
well as pions (), kaons (K), and (anti-)protons (/p) in the ranges , , and , with full azimuthal coverage in the range . We compare the model predictions for the strength and shape of the
and correlators as these pertain to recent
measurements by the ALICE collaboration. The and
correlation functions estimated with PYTHIA and HERWIG exhibit qualitatively
similar near-side and away-side correlation structures but feature important
differences. Our analysis indicates that comparative studies of
and correlation functions would provide valuable insight towards
the understanding of particle production in pp collisions, and by extension,
should also be useful in studies of heavy-ion collisions. Comparison of the
dependence of and could contribute, in
particular, to a better understanding and modeling of the angular ordering of
particles produced by hadronization in jets, as well as a better description of
jet fragmentation functions of identified species at low momentum fraction
.Comment: 22 pages, 24 captioned figure
Three-particle cumulant Study of Conical Emission
We discuss the sensitivity of the three-particle azimuthal cumulant method
for a search and study of conical emission in central relativistic
collisions. Our study is based on a multi-component Monte Carlo model which
include flow background, Gaussian mono-jets, jet-flow, and Gaussian conical
signals. We find the observation of conical emission is hindered by the
presence of flow harmonics of fourth order () but remains feasible even
in the presence of a substantial background. We consider the use of probability
cumulants for the suppression of 2 order flow harmonics. We find that
while probability cumulant significantly reduce contributions, they
also complicate the cumulant of jets, and conical emission. The use of
probability cumulants is therefore not particularly advantageous in searches
for conical emission. We find the sensitivity of the (density) cumulant method
depends inextricably on strengths of
, , background and non-Poisson character of particle production.
It thus cannot be expressed in a simple form, and without specific assumptions
about the values of these parameters.Comment: 12 figures, accepted for publication in PR
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