15 research outputs found
First Study of the Negative Binomial Distribution Applied to Higher Moments of Net-charge and Net-proton Multiplicity Distributions
A study of the first four moments (mean, variance, skewness, and kurtosis)
and their products ( and ) of the net-charge and
net-proton distributions in Au+Au collisions at = 7.7-200
GeV from HIJING simulations has been carried out. The skewness and kurtosis and
the collision volume independent products and have
been proposed as sensitive probes for identifying the presence of a QCD
critical point. A discrete probability distribution that effectively describes
the separate positively and negatively charged particle (or proton and
anti-proton) multiplicity distributions is the negative binomial (or binomial)
distribution (NBD/BD). The NBD/BD has been used to characterize particle
production in high-energy particle and nuclear physics. Their application to
the higher moments of the net-charge and net-proton distributions is examined.
Differences between and a statistical Poisson assumption of
a factor of four (for net-charge) and 40% (for net-protons) can be accounted
for by the NBD/BD. This is the first application of the properties of the
NBD/BD to describe the behavior of the higher moments of net-charge and
net-proton distributions in nucleus-nucleus collisions.Comment: 13 pages, 4 figure
Searching for the QCD Critical Point Using Particle Ratio Fluctuations and Higher Moments of Multiplicity Distributions
Dynamical fluctuations in global conserved quantities such as baryon number,
strangeness, or charge may be observed near a QCD critical point. Results from
new measurements of dynamical , , and ratio fluctuations
are presented. The commencing of a QCD critical point search at RHIC has
extended the reach of possible measurements of dynamical , , and
ratio fluctuations from Au+Au collisions to lower energies. The STAR
experiment has performed a comprehensive study of the energy dependence of
these dynamical fluctuations in Au+Au collisions at the energies
= 7.7, 11.5, 39, 62.4, and 200 GeV. New results are compared to
previous measurements and to theoretical predictions from several models. The
measured dynamical fluctuations are found to be independent of
collision energy, while dynamical and fluctuations have a
negative value that increases toward zero at top RHIC energy. Fluctuations of
the higher moments of conserved quantities (net-proton and net-charge)
distributions, which are predicted to be sensitive to the presence of a
critical point, are also presented.Comment: 4 pages, 2 figures, Proceedings of the 21st International Conference
On Ultra-Relativistic Nucleus-Nucleus Collisions (Quark Matter 2011), Annecy,
France, May 23 - May 28, 201
Energy Dependence of Short and Long-Range Multiplicity Correlations in Au+Au Collisions from STAR
A general overview of the measurement of long-range multiplicity correlations
measured by the STAR experiment in Au+Au collisions at RHIC is presented. The
presence of long-range correlations can provide insight into the early stages,
and the type of matter produced in, these collisions. These measurements have
been made in Au+Au collisions at = 200 and 62.4 GeV. These
results indicate a relatively large long-range correlation is produced in Au+Au
collisions compared to a {\it pp} baseline at = 200 GeV. A
weaker long-range correlation is seen as a function of incident energy.
Further, comparison of the onset of the long-range correlation to the
calculated percolation density parameter at = 200 GeV is
presented.Comment: 8 pages, 6 figures, Conference Proceedings for the XI International
Workshop on Correlation and Fluctuation in Multiparticle Production,
Hangzhou, China, November 21-25, 200