349 research outputs found
Interference Phenomena in Medium Induced Radiation
We consider the interference pattern for the medium-induced gluon radiation
produced by a color singlet quark-antiquark antenna embedded in a QCD medium
with size and `jet quenching' parameter . Within the BDMPS-Z
regime, we demonstrate that, for a dipole opening angle , the interference between the
medium--induced gluon emissions by the quark and the antiquark is suppressed
with respect to the direct emissions. This is so since direct emissions are
delocalized throughout the medium and thus yield contributions proportional to
while interference occurs only between emissions at early times, when both
sources remain coherent. Thus, for \tqq \gg\theta_c, the medium-induced
radiation is the sum of the two spectra individually produced by the quark and
the antiquark, without coherence effects like angular ordering. For \tqq
\ll\theta_c, the medium--induced radiation vanishes.Comment: 4 pages, 2 figures; Proceedings of the "Quark Matter 2011" conferenc
A New Mechanism of Quark Energy Loss
We show that a heavy quark moving sufficiently fast through a quark-gluon
plasma may lose energy by Cherenkov-radiating mesons. We demonstrate that this
takes place in all strongly coupled, large-Nc plasmas with a gravity dual. The
energy loss is exactly calculable in these models despite being an
O(1/Nc)-effect. We discuss phenomenological implications for heavy-ion
collision experiments.Comment: 4 pages, 4 figures; v2: plot modified, conclusions unchange
Fourier Harmonics of High-pT Particles Probing the Fluctuating Intitial Condition Geometries in Heavy-Ion Collisions
Second Fourier harmonics of jet quenching have been thoroughly explored in
the literature and shown to be sensitive to the underlying jet path-length
dependence of energy loss and the differences between the mean eccentricity
predicted by Glauber and CGC/KLN models of initial conditions. We compute the
jet path-length dependence of energy-loss for higher azimuthal harmonics of
jet-fragments in a generalized model of energy-loss for RHIC energies and find,
however, that even the high- second moment is most sensitive to the poorly
known early-time evolution during the first fm/c. Moreover, we demonstrate that
higher-jet harmonics are remarkably insensitive to the initial conditions,
while the different vs. correlations
between the moments of monojet and dijet nuclear modifications factors remain a
most sensitive probe to differentiate between Glauber and CGC/KLN initial state
sQGP geometries.Comment: 6 pages, 7 figures, updated figures, version accepted for publication
in Phys. Rev.
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
Jet quenching via jet collimation
The strong modifications of dijet properties in heavy ion collisions measured
by ATLAS and CMS provide important constraints on the dynamical mechanisms
underlying jet quenching. In this work, we show that the transport of soft
gluons away from the jet cone - jet collimation - can account for the observed
dijet asymmetry with values of that lie in the expected order of
magnitude. Further, we show that the energy loss attained through this
mechanism results in a very mild distortion of the azimuthal angle dijet
distribution.Comment: 4 pages, 2 figures; Proceedings of the "Quark Matter 2011" conferenc
Correlations of Electrons from Heavy Flavor Decay with Hadrons in Au+Au and p+p Collisions
Measurements of electrons from the decay of open-heavy flavor mesons have
shown that the yields are suppressed in Au+Au collisions compared to
expectations from binary-scaled p+p collisions. These measurements indicate
that charm and bottom quarks interact with the hot-dense matter produced in
heavy-ion collisions much more than expected. Here we extend these studies to
two-particle correlations where one particle is an electron from the decay of a
heavy-flavor meson and the other is a charged hadron from either the decay of
the heavy meson or from jet fragmentation. These measurements provide more
detailed information about the interactions between heavy quarks and the
matter, such as whether the modifcation of the away-side-jet shape seen in
hadron-hadron correlations is present when the trigger particle is from
heavy-meson decay and whether the overall level of away-side-jet suppression is
consistent. We statistically subtract correlations of electrons arising from
background sources from the inclusive electron-hadron correlations and obtain
two-particle azimuthal correlations at =200 GeV between
electrons from heavy-flavor decay with charged hadrons in p+p and also first
results in Au+Au collisions. We find the away-side-jet shape and yield to be
modified in Au+Au collisions compared to p+p collisions.Comment: talk given at Winter Workshop in Nuclear Dynamics 201
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
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