30 research outputs found
Forward particle productions at RHIC and the LHC from CGC within local rcBK evolution
In order to describe forward hadron productions in high-energy nuclear
collisions, we propose a Monte-Carlo implementation of
Dumitru-Hayashigaki-Jalilian-Marian formula with the unintegrated gluon
distribution obtained numerically from the running-coupling BK equation. We
discuss influence of initial conditions for the BK equation by comparing a
model constrained by global fit of small-x HERA data and a newly proposed one
from the running coupling MV model.Comment: Talk given at conference Quark Matter 2011, 4 page
CGC initial conditions at RHIC and LHC
Monte-Carlo implementations of kT -factorization formula with both KLN and
running-coupling BK unintegrated gluon distributions for nucleus-nucleus
collisions are used to analyze recent experimental data on the particle
multiplicities from RHIC(Au+Au@200GeV) and LHC([email protected]). We also compare
the predicted transverse energy at midrapidity to new data from ALICE.Comment: 6 pages and 7 figures. Contribution to the proceedings of the 27th
Winter Workshop on Nuclear Dynamics held in Winter Park, Colorado, 6-13
February 201
Initial State: Theory Status
I present a brief discussion of the different approaches to the study initial
state effects in heavy ion collisions in view of the recent results from Pb+Pb
and p+p collisions at the LHC.Comment: 8 pages, 6 figures. Contribution to the proceedings of the XXII
International Conference on Ultrarelativistic Nucleus-Nucleus Collisions,
QM2011. Annecy, France, 22-28 May 201
Long-Range Rapidity Correlations in Heavy Ion Collisions at Strong Coupling from AdS/CFT
We use AdS/CFT correspondence to study two-particle correlations in heavy ion
collisions at strong coupling. Modeling the colliding heavy ions by shock waves
on the gravity side, we observe that at early times after the collision there
are long-range rapidity correlations present in the two-point functions for the
glueball and the energy-momentum tensor operators. We estimate rapidity
correlations at later times by assuming that the evolution of the system is
governed by ideal Bjorken hydrodynamics, and find that glueball correlations in
this state are suppressed at large rapidity intervals, suggesting that
late-time medium dynamics can not "wash out" the long-range rapidity
correlations that were formed at early times. These results may provide an
insight on the nature of the "ridge" correlations observed in heavy ion
collision experiments at RHIC and LHC, and in proton-proton collisions at LHC.Comment: 32 pages, 2 figures; v2: typos corrected, references adde
Quark-Gluon Plasma at RHIC and the LHC: Perfect Fluid too Perfect?
Relativistic heavy ion collisions have reached energies that enable the
creation of a novel state of matter termed the quark-gluon plasma. Many
observables point to a picture of the medium as rapidly equilibrating and
expanding as a nearly inviscid fluid. In this article, we explore the evolution
of experimental flow observables as a function of collision energy and attempt
to reconcile the observed similarities across a broad energy regime in terms of
the initial conditions and viscous hydrodynamics. If the initial spatial
anisotropies are very similar for all collision energies from 39 GeV to 2.76
TeV, we find that viscous hydrodynamics might be consistent with the level of
agreement for v2 of unidentified hadrons as a function of pT . However, we
predict a strong collision energy dependence for the proton v2(pT). The results
presented in this paper highlight the need for more systematic studies and a
re-evaluation of previously stated sensitivities to the early time dynamics and
properties of the medium.Comment: 11 pages, 9 figures, submitted to the New Journal of Physics focus
issue "Strongly Correlated Quantum Fluids: From Ultracold Quantum Gases to
QCD Plasmas
JIMWLK evolution in the Gaussian approximation
We demonstrate that the Balitsky-JIMWLK equations describing the high-energy
evolution of the n-point functions of the Wilson lines (the QCD scattering
amplitudes in the eikonal approximation) admit a controlled mean field
approximation of the Gaussian type, for any value of the number of colors Nc.
This approximation is strictly correct in the weak scattering regime at
relatively large transverse momenta, where it reproduces the BFKL dynamics, and
in the strong scattering regime deeply at saturation, where it properly
describes the evolution of the scattering amplitudes towards the respective
black disk limits. The approximation scheme is fully specified by giving the
2-point function (the S-matrix for a color dipole), which in turn can be
related to the solution to the Balitsky-Kovchegov equation, including at finite
Nc. Any higher n-point function with n greater than or equal to 4 can be
computed in terms of the dipole S-matrix by solving a closed system of
evolution equations (a simplified version of the respective Balitsky-JIMWLK
equations) which are local in the transverse coordinates. For simple
configurations of the projectile in the transverse plane, our new results for
the 4-point and the 6-point functions coincide with the high-energy
extrapolations of the respective results in the McLerran-Venugopalan model. One
cornerstone of our construction is a symmetry property of the JIMWLK evolution,
that we notice here for the first time: the fact that, with increasing energy,
a hadron is expanding its longitudinal support symmetrically around the
light-cone. This corresponds to invariance under time reversal for the
scattering amplitudes.Comment: v2: 45 pages, 4 figures, various corrections, section 4.4 updated, to
appear in JHE
Predictions for Pb Collisions at TeV: Comparison with Data
Predictions made in Albacete {\it et al} prior to the LHC Pb run at
TeV are compared to currently available data. Some
predictions shown here have been updated by including the same experimental
cuts as the data. Some additional predictions are also presented, especially
for quarkonia, that were provided to the experiments before the data were made
public but were too late for the original publication are also shown here.Comment: 55 pages 35 figure
Nonlinear equation for coherent gluon emission
Motivated by the regime of QCD explored nowadays at LHC, where both the total
energy of collision and momenta transfers are high, we investigate evolution
equations of high energy factorization. In order to study such effects like
parton saturation in final states one is inevitably led to investigate how to
combine physics of the BK and CCFM evolution equations. In this paper we obtain
a new exclusive form of the BK equation which suggests a possible form of the
nonlinear extension of the CCFM equation
Thermal Dileptons at LHC
We predict dilepton invariant-mass spectra for central 5.5 ATeV Pb-Pb
collisions at LHC. Hadronic emission in the low-mass region is calculated using
in-medium spectral functions of light vector mesons within hadronic many-body
theory. In the intermediate-mass region thermal radiation from the Quark-Gluon
Plasma, evaluated perturbatively with hard-thermal loop corrections, takes
over. An important source over the entire mass range are decays of correlated
open-charm hadrons, rendering the nuclear modification of charm and bottom
spectra a critical ingredient.Comment: 2 pages, 2 figures, contributed to Workshop on Heavy Ion Collisions
at the LHC: Last Call for Predictions, Geneva, Switzerland, 14 May - 8 Jun
2007 v2: acknowledgment include