25 research outputs found
Flow Fluctuations from Early-Time Correlations in Nuclear Collisions
We propose that flow fluctuations have the same origin as transverse momentum
fluctuations. The common source of these fluctuations is the spatially
inhomogeneous initial state that drives hydrodynamic flow. Longitudinal
correlations from an early Glasma stage followed by hydrodynamic flow
quantitatively account for many features of multiplicity and fluctuation
data. We develop a framework for studying flow and its fluctuations in this
picture. We then compute elliptic and triangular flow fluctuations, and study
their connections to the ridge
The Glasma and the Hard Ridge
Correlation measurements indicate that excess two particle correlations
extend over causally disconnected rapidity ranges. Although, this enhancement
is broad in relative rapidity , it is focused in a narrow
region in relative azimuthal angle . The resulting
structure looks like a ridge centered at . Similar ridge
structures are observed in correlations of particles associated with a jet
trigger (the hard ridge) and in correlations without a trigger (the soft
ridge). The long range rapidity behavior requires that the correlation
originates in the earliest stage of the collision, and probes properties of the
production mechanism. Glasma initial conditions as predicted by the theory of
Color Glass Condensate and provide a and early stage correlation that naturally
extends far in rapidity. We have previously shown that the soft ridge is a
consequence of particles forming from an initial Glasma phase that experience a
later stage transverse flow. We extend this work to study the ridge dependence
on the of the correlated pairs. We then determine the soft contribution
to the hard ridge.Comment: Proceeding of the APS meeting of the Division of Particles and Fields
2009, Detroit, Mi. Also see arXiv:0910.359
Long Range Correlations and the Soft Ridge in Relativistic Nuclear Collisions
Relativistic Heavy Ion Collider experiments exhibit correlations peaked in
relative azimuthal angle and extended in rapidity. Called the ridge, this peak
occurs both with and without a jet trigger. We argue that the untriggered ridge
arises when particles formed by flux tubes in an early glasma stage later
manifest transverse flow. Combining a blast wave model of flow fixed by
single-particle spectra with a simple description of the glasma, we find
excellent agreement with current data.Comment: revised text, results unchange
Two Particle Correlations And The Ridge In Relativistic Heavy Ion Collisions
Measurements at the Relativistic Heavy Ion Collider (RHIC) find an enhancement of two particle correlations in relativistic heavy ion collisions, not present in proton-proton collisions. Because the correlation structure is wide in relative pseudorapidity and narrow in relative azimuthal angle, it is known as the ridge. The most striking feature of the ridge is that it seems to extend to a long range in relative pseudorapidity where causality limits interaction. Similar ridge structures are observed in correlations of particles associated with and without a jet trigger. We argue that the untriggered ridge arises when particles formed in an early Glasma stage later manifest transverse flow. We extend this study to address the triggered ridge in the same context. Finally we address the effects of shear viscosity on our correlation formalism
Viscosity and the Soft Ridge at RHIC
Correlation studies exhibit a ridge-like feature in rapidity and azimuthal
angle, with and without a jet trigger. We ask whether the feature in
untriggered correlations can be a consequence of transverse flow and viscous
diffusion.Comment: Proc. Quark Matter 2008, Jaipur, Indi
Temporal evolution of tubular initial conditions and their influence on two-particle correlations in relativistic nuclear collisions
Relativistic nuclear collisions data on two-particle correlations exhibit
structures as function of relative azimuthal angle and rapidity. A unified
description of these near-side and away-side structures is proposed for low to
moderate transverse momentum. It is based on the combined effect of tubular
initial conditions and hydrodynamical expansion. Contrary to expectations, the
hydrodynamics solution shows that the high energy density tubes (leftover from
the initial particle interactions) give rise to particle emission in two
directions and this is what leads to the various structures. This description
is sensitive to some of the initial tube parameters and may provide a probe of
the strong interaction. This explanation is compared with an alternative one
where some triangularity in the initial conditions is assumed. A possible
experimental test is suggested.Comment: 6 pages, 6 figure
Hydrodynamics: Fluctuating Initial Conditions and Two-particle Correlations
Event-by-event hydrodynamics (or hydrodynamics with fluctuating initial
conditions) has been developed in the past few years. Here we discuss how it
may help to understand the various structures observed in two-particle
correlations.Comment: 7 pages, 9 figures, presented at the Workshop on Saturation, the
Color Glass Condensate and Glasma: What Have we Learned from RHIC
Soft Contribution to the Hard Ridge in Relativistic Nuclear Collisions
Nuclear collisions exhibit long-range rapidity correlations not present in
proton-proton collisions. Because the correlation structure is wide in relative
pseudorapidity and narrow in relative azimuthal angle, it is known as the
ridge. Similar ridge structures are observed in correlations of particles
associated with a jet trigger (the hard ridge) as well as correlations without
a trigger (the soft ridge). Earlier we argued that the soft ridge arises when
particles formed in an early Glasma stage later manifest transverse flow. We
extend this study to address new soft ridge measurements. We then determine the
contribution of flow to the hard ridge.Comment: 16 pages, 9 figures, includes comparison to dat
Exploring Early Parton Momentum Distribution with the Ridge from the Near-Side Jet
In a central nucleus-nucleus collision at high-energies, medium partons
kicked by a near-side jet acquire a momentum along the jet direction and
subsequently materialize as the observed ridge particles. They carry direct
information on the early parton momentum distribution which can be extracted by
using the ridge data for central AuAu collisions at \sqrt{s_{NN}}=200 GeV. The
extracted parton momentum distribution has a thermal-like transverse momentum
distribution but a non-Gaussian, relatively flat rapidity distribution at
mid-rapidity with sharp kinematic boundaries at large rapidities that depend on
the transverse momentum.Comment: In Proceedings of 20th International Conference on Ultra-Relativistic
Nucleus Nucleus Collisions, Jaipur, India, Feb. 4-10, 200