140 research outputs found
Long range rapidity correlations and the ridge in A+A collisions
We discuss results for n-gluon correlations that form the basis of the Glasma
flux tube picture of early times in heavy ion collisions. Our formalism is
valid to all orders in perturbation theory at leading logarithmic accuracy in x
and includes both QCD bremsstrahlung and the many body screening and
recombination effects that are important at large parton densities. Long range
rapidity correlations, as seen in the near-side ridge in heavy ion collisions,
are a chronometer of these early time strong color field dynamics. They also
contain information on how radial flow develops in heavy ion collisions.Comment: 4 pages, 2 figures, Talk by R.V. at Quark Matter 2009, March 30-April
4 2009, Knoxville, TN, US
Color Glass Condensate and Glasma
In this talk, I review the Color Glass Condensate theory of gluon saturation,
and its application to the early stages of heavy ion collisions.Comment: 11 pages, 14 figures, to appear in the proceedings of the RIKEN BNL
Research Center Workshop on "Saturation, the Color Glass Condensate and
Glasma: What Have we Learned from RHIC?", May 10-12, 201
Instability induced pressure isotropization in a longitudinally expanding system
In two previous works [arXiv:1009.4363,arXiv:1107.0668], we studied the time
evolution of a system of real scalar fields with quartic coupling which shares
important features with the Color Glass Condensate description of heavy ion
collisions. Our primary objective was to understand how such a system, when
initialized with a non-perturbatively large classical field configuration,
reaches thermal equilibrium. An essential goal of these works was to highlight
the role played by the quantum fluctuations. However, these studies considered
only a system confined within a box of fixed volume. In the present paper, we
extend this work to a system that expands in the longitudinal direction thereby
more closely mimicking a heavy ion collision. We conclude that the microscopic
processes that drive the system towards equilibrium are able to keep up with
the expansion of the system; the pressure tensor becomes isotropic despite the
anisotropic expansion.Comment: revised version to appear in PRD, new section on comparison with
hydrodynamics, 32 pages, 21 figure
Gluon propagation inside a high-energy nucleus
We show that, in the light-cone gauge, it is possible to derive in a very
simple way the solution of the classical Yang-Mills equations for the collision
between a nucleus and a proton. One important step of the calculation is the
derivation of a formula that describes the propagation of a gluon in the
background color field of the nucleus. This allows us to calculate observables
in pA collisions in a more straightforward fashion than already proposed. We
discuss also the comparison between light-cone gauge and covariant gauge in
view of further investigations involving higher order corrections.Comment: 12 pages, 2 figure
Long range two-particle rapidity correlations in A+A collisions from high energy QCD evolution
Long range rapidity correlations in A+A collisions are sensitive to strong
color field dynamics at early times after the collision. These can be computed
in a factorization formalism \cite{GelisLV5} which expresses the -gluon
inclusive spectrum at arbitrary rapidity separations in terms of the
multi-parton correlations in the nuclear wavefunctions. This formalism includes
all radiative and rescattering contributions, to leading accuracy in
, where is the rapidity separation between either
one of the measured gluons and a projectile, or between the measured gluons
themselves. In this paper, we use a mean field approximation for the evolution
of the nuclear wavefunctions to obtain a compact result for inclusive two gluon
correlations in terms of the unintegrated gluon distributions in the nuclear
projectiles. The unintegrated gluon distributions satisfy the
Balitsky-Kovchegov equation, which we solve with running coupling and with
initial conditions constrained by existing data on electron-nucleus collisions.
Our results are valid for arbitrary rapidity separations between measured
gluons having transverse momenta p_\perp,q_\perp\gtrsim \qs, where \qs is
the saturation scale in the nuclear wavefunctions. We compare our results to
data on long range rapidity correlations observed in the near-side ridge at
RHIC and make predictions for similar long range rapidity correlations at the
LHC.Comment: 26 pages, 9 figure
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