12,101 research outputs found

### Effects of jet quenching on the hydrodynamical evolution of quark-gluon plasma

We study the effects of jet quenching on the hydrodynamical evolution of the
quark-gluon plasma (QGP) fluid created in a heavy-ion collision. In jet
quenching, a hard QCD parton, before fragmenting into a jet of hadrons,
deposits a fraction of its energy in the medium, leading to suppressed
production of high-pT hadrons. Assuming that the deposited energy quickly
thermalizes, we simulate the subsequent hydrodynamic evolution of the QGP
fluid. For partons moving at supersonic speed, v_p > c_s, and sufficiently
large energy loss, a shock wave forms leading to conical flow [1]. The PHENIX
Collaboration recently suggested that observed structures in the azimuthal
angle distribution [2] might be caused by conical flow. We show here that
conical flow produces different angular structures than predicted in [1] and
that, for phenomenologically acceptable values of parton energy loss, conical
flow effects are too weak to explain the structures seen by PHENIX [2].Comment: 4 pages, 3 figures. Last figure changed, now showing angular
distribution of pions instead of photons. Added comments on "lost jets" and
pT-dependence of angular correlation

### Equation of State and Collective Dynamics

This talk summarizes the present status of a program to quantitatively relate
data from the Relativistic Heavy Ion Collider (RHIC) on collective expansion
flow to the Equation of State (EOS) of hot and dense strongly interacting
matter, including the quark-gluon plasma and the quark-hadron phase transition.
The limits reached with the present state of the art and the next steps
required to make further progress will both be discussed.Comment: 8 pages, 6 two-part figures. Invited talk given at the 5th
International Conference on the Physics and Astrophysics of Quark-Gluon
Plasma (ICPAQGP 2005), Kolkata (India), Feb 8-12, 2005. Proceedings to be
published in Journal of Physics: Conference Series (Jan-E Alam et al., eds.

### Jet trails and Mach cones: The interaction of microquasars with the ISM

A sub-set of microquasars exhibit high peculiar velocity with respect to the
local standard of rest due to the kicks they receive when being born in
supernovae. The interaction between the radio plasma released by microquasar
jets from such high-velocity binaries with the ISM must lead to the production
of trails and bow shocks similar to what is observed in narrow-angle tailed
radio galaxies and pulsar wind nebulae. We present a set of numerical
simulations of this interaction that illuminate the long term dynamical
evolution and the observational properties of these microquasar bow shock
nebulae and trails. We find that this interaction always produces a structure
that consists of a bow shock, a trailing neck, and an expanding bubble. Using
our simulations to model emission, we predict that the shock surrounding the
bubble and the neck should be visible in H{\alpha} emission, the interior of
the bubble should be visible in synchrotron radio emission, and only the bow
shock is likely to be detectable in X-ray emission. We construct an analytic
model for the evolution of the neck and bubble shape and compare this model
with observations of X-ray binary SAX J1712.6-3739.Comment: 33 pages, 13 figures, 1 table; Accepted to Ap

### Optimal entanglement criterion for mixed quantum states

We develop a strong and computationally simple entanglement criterion. The
criterion is based on an elementary positive map Phi which operates on state
spaces with even dimension N >= 4. It is shown that Phi detects many entangled
states with positive partial transposition (PPT) and that it leads to a class
of optimal entanglement witnesses. This implies that there are no other
witnesses which can detect more entangled PPT states. The map Phi yields a
systematic method for the explicit construction of high-dimensional manifolds
of bound entangled states.Comment: 4 pages, no figures, replaced by published version (minor changes),
Journal-reference adde

### Formation Time of QGP from Thermal Photon Elliptic Flow

We show that the transverse momentum dependent elliptic flow $v_2(p_T)$ of
thermal photons is quite sensitive to the initial formation time ($\tau_0$) of
Quark Gluon Plasma (QGP) for semi-central collision of gold nuclei at RHIC
\cite{tau}. A smaller value of the formation time or a larger initial
temperature leads to a significant increase in the thermal photon radiation
from QGP phase, which has a smaller $v_2$. The elliptic flow of thermal photon
is dominated by the contribution from the quark matter at intermediate and high
$p_T$ range and as a result sum $v_2$ decreases with smaller $\tau_0$ for $p_T
\ge 1.5$ GeV. On the other hand we find that the elliptic flow parameter for
hadrons depends only marginally on the value of $\tau_0$.Comment: 4 pages, 3 figures - To appear in the conference proceedings for
Quark Matter 2009, March 30 - April 4, Knoxville, Tennessee, v2: minor
correction

### Bose-Einstein Final State Symmetrization for Event Generators of Heavy Ion Collisions

We discuss algorithms which allow to calculate identical two-particle
correlations from numerical simulations of relativistic heavy ion collisions. A
toy model is used to illustrate their properties.Comment: Talk given at CRIS'98 (Catania, June 8-12, 1998), to appear in
"CRIS'98: Measuring the size of things in the Universe: HBT interferometry
and heavy ion physics", (S. Costa et al., eds.), World Scientific, Singapore,
1998. (10 pages Latex, 1 eps-figure, extended version of conference
proceedings, Fig1 a,b added and corresponding discussion enlarged

### Bose-Einstein Correlations in a Space-Time Approach to e+ e- Annihilation into Hadrons

A new treatment of Bose-Einstein correlations is incorporated in a space-time
parton-shower model for e+ e- annihilation into hadrons. Two alternative
afterburners are discussed, and we use a simple calculable model to demonstrate
that they reproduce successfully the size of the hadron emission region. One of
the afterburners is used to calculate two-pion correlations in e+ e- -> Z^0 ->
hadrons and e+ e- -> W+ W- -> hadrons. Results are shown with and without
resonance decays, for correlations along and transverse to the thrust jet axis
in these two classes of events.Comment: 30 pages, Latex, 8 figure

### Elliptic flow of thermal dileptons in relativistic nuclear collisions

We calculate the transverse momentum and invariant mass dependence of
elliptic flow of thermal dileptons for Au+Au collisions at the Relativistic
Heavy Ion Collider. The system is described using hydrodynamics, with the
assumption of formation of a thermalized quark-gluon plasma at some early time,
followed by cooling through expansion, hadronization and decoupling. Dileptons
are emitted throughout the expansion history: by annihilation of quarks and
anti-quarks inthe early quark-gluon plasma stage and through a set of hadronic
reactions during the late hadronic stage. The resulting differential elliptic
flow exhibits a rich structure, with different dilepton mass windows providing
access to different stages of the expansion history. Elliptic flow measurements
for dileptons,combined with those of hadrons and direct photons, are a powerful
tool for mapping the time-evolution of heavy-ion collisions.Comment: Latex 8 pages including a total of 13 postscript figures. Added 2
figures, additional references, and expanded discussions. Figures modified
for better viewing. To appear in Phys. Rev.

- â€¦