535 research outputs found
On the presence of nonjet "higher harmonic" components in 2D angular correlations from high energy heavy ion collisions
It is conjectured that several higher harmonic flows may result from
initial-state geometry fluctuations in \aa collisions coupled to a
radially-expanding medium. But as with "elliptic flow" measurements,
non-hydrodynamic mechanisms such as jet production may contribute to other
higher azimuth multipoles as biases. Careful distinctions should be
maintained between jet-related and nonjet (possibly hydrodynamic) contributions
to (e.g., "nonflow" and "flow"). In this study we consider several
questions: (a) To what extent do jet-like structures in two-dimensional (2D)
angular correlations contribute to azimuth multipoles inferred from various
methods? (b) If a multipole element is added to a 2D fit model is a
nonzero amplitude indicative of a corresponding flow component? and (c) Can 2D
correlations establish the necessity of nonjet contributions to some or all
higher multipoles? Model fits to 2D angular correlations are used to establish
the origins of azimuth multipoles inferred from 1D projections onto azimuth or
from nongraphical numerical methods. We find that jet-like angular
correlations, and specifically a 2D peak at the angular origin consistent with
jet production, constitute the dominant contribution to inferred higher
multipoles, and the data do not {\em require} higher multipoles in isolation
from the jet-like 2D peak. Inference of "higher harmonic flows" results from
identifying certain nominally jet-like structure as flow manifestations through
unjustified application of 1D Fourier series analysis. Although the peak
structure at the angular origin is strongly modified in more-central collisions
some properties remain compatible with relevant pQCD theory expectations for
jet production.Comment: 14 pages, 11 figure
Transverse Momentum Correlations in Relativistic Nuclear Collisions
From the correlation structure of transverse momentum in relativistic
nuclear collisions we observe for the first time temperature/velocity structure
resulting from low- partons. Our novel analysis technique does not invoke
an {\em a priori} jet hypothesis. autocorrelations derived from the scale
dependence of fluctuations reveal a complex parton dissipation process
in RHIC heavy ion collisions. We also observe structure which may result from
collective bulk-medium recoil in response to parton stopping.Comment: 10 pages, 10 figures, proceedings, MIT workshop on fluctuations and
correlations in relativistic nuclear collision
The equivalence of fluctuation scale dependence and autocorrelations
We define optimal per-particle fluctuation and correlation measures, relate
fluctuations and correlations through an integral equation and show how to
invert that equation to obtain precise autocorrelations from fluctuation scale
dependence. We test the precision of the inversion with Monte Carlo data and
compare autocorrelations to conditional distributions conventionally used to
study high- jet structure.Comment: 10 pages, 9 figures, proceedings, MIT workshop on correlations and
fluctuations in relativistic nuclear collision
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