58 research outputs found
Angular Dependence of Jet Quenching Indicates Its Strong Enhancement Near the QCD Phase Transition
We study dependence of jet quenching on matter density, using "tomography" of
the fireball provided by RHIC data on azimuthal anisotropy of high
hadron yield at different centralities. Slicing the fireball into shells with
constant (entropy) density, we derive a "layer-wise geometrical limit"
which is indeed above the data . Interestingly, the
limit is reached only if quenching is dominated by shells with the entropy
density exactly in the near- region. We show two models that
simultaneously describe the high and data and conclude
that such a description can be achieved only if the jet quenching is few times
stronger in the near- region relative to QGP at . One possible
reason for that may be recent indications that the near- region is a
magnetic plasma of relatively light color-magnetic monopoles.Comment: 4 pages, 4 figures. Final version published as PRL102,202302(2009
S-Wave Quarkonia in Potential Models
We discuss S-wave quarkonia correlators and spectral function using the
Wong-potential, and show that these do not agree with the lattice results.Comment: based on talk presented at Strangeness in Quark Matter, UCLA, March
26-31, 200
Mach Cones in Quark Gluon Plasma
The experimental azimuthal dihadron distributions at RHIC show a double peak
structure in the away side ( rad.) for intermediate
particles. A variety of models have appeared trying to describe this
modification. We will review most of them, with special emphasis in the Conical
Flow scenario in which the observed shape is a consequence of the emission of
sound by a supersonic high momentum particle propagating in the Quark Gluon
Plasma.Comment: 8 pages, 3 figures, Invited plenary talk given at the 19th
International Conference on Ultrarelativistic Nucleus-Nucleus Collisions:
Quark Matter 2006 (QM 2006), Shanghai, China, 14-20 Nov 200
Quark-Gluon Plasma - New Frontiers
As implied by organizers, this talk is not a conference summary but rather an
outline of progress/challenges/``frontiers'' of the theory. Some fundamental
questions addressed are:
Why is sQGP such a good liquid? Do we understand (de)confinement and what do
we know about ``magnetic'' objects creating it? Can we understand the AdS/CFT
predictions, from the gauge theory side? Can they be tested experimentally? Can
AdS/CFT duality help us understand rapid equilibration/entropy production? Can
we work out a complete dynamical ``gravity dual'' to heavy ion collisions?Comment: final talk at Quark Matter 2008, Jaipur, India, Feb.200
Probing Color Response - Wakes in a Color Plasma
The wake induced in a hot QCD medium by a high momentum parton (jet
precursor) is calculated in the framework of linear response theory. Two
different scenarios are discussed: a weakly coupled quark gluon plasma (pQGP)
as described by hard-thermal loop (HTL) perturbation theory and a strongly
cupled QGP (sQGP) with the properties of a quantum liquid. In the latter case
the wake could exhibit a pronounced Mach cone structure. This physical
mechanism could be important for the understanding of preliminary data from the
PHENIX and STAR experiments at RHIC on the angular distribution of low-pt
secondaries stemming from the away-side jet which indicate maxima at
.Comment: Prepared for: Workshop on Correlations and Fluctuations in
Relativistic Nuclear Collisions, MIT, Cambridge, Massachusetts, USA, 21-23
April 200
A Comment on Conical Flow Induced by Heavy-Quark Jets
The suppression of high transverse momentum particles, recently discovered at
RHIC, is commonly interpreted as due to parton energy loss. In high energy
nuclear collisions, QCD jets would deposit a large fraction of their energy and
into the produced matter. The question of how this energy is degraded and
whether we can use this phenomenon to probe the properties of the produced
matter is now under active discussion. It has been proposed that if this
matter, which is now being referred to as a {\em strongly coupled Quark-Gluon
Plasma} (sQGP), may behave as a liquid with a very small viscosity.
In this case, a very specific collective excitation should be produced,
called the ``conical flow'', similar e.g. to the sonic booms generated by the
shock waves produced by supersonic planes. The RHIC experiments seem indeed to
be obtaining some indication that the production of particles emitted opposite
to a high- jet may actually be peaked away from the quenched jet
direction, at an angle roughly consistent with the direction expected in case a
shock wave is produced (i.e. orthogonal to the Mach cone). In this note we
speculate that for tagged heavy-quark jets one may observe a shrinkage of the
Mach cone at moderate . The experimental observation of such an effect
would be a very good test for the validity of the whole picture currently
emerging from the study of partonic matter in nuclear collisions
Understanding jet quenching and medium response with di-hadron correlation
A brief review of the dependence of the dihadron correlations from RHIC
is presented. We attempt to construct a consistent picture that can describe
the data as a whole, focusing on the following important aspects, 1) the
relation between jet fragmentation of survived jet and medium response to
quenched jets, 2) the possible origin of the medium response and its relation
to intermediate physics for single hadron production, 3) the connection
between the near-side ridge and away-side cone, 4) and their relations to low
energy results.Comment: 8 pages, 8 figures, presented at the 20th International Conference on
Ultra-Relativistic Nucleus-Nucleus Collisions, "Quark Matter 2008", Jaipur,
India, February 4-10, 2008. Updated with the published versio
- …