53 research outputs found
Anisotropic flow and jet quenching in ultra-relativistic U+U collisions
Full-overlap U+U collisions provide significantly larger initial energy
densities at comparable spatial deformation, and significantly larger
deformation and volume at comparable energy density, than semicentral Au+Au
collisions. We show quantitatively that this provides a long lever arm for
studying the hydrodynamic behavior of elliptic flow in much larger and denser
collision systems and the predicted non-linear path-length dependence of
radiative parton energy loss.Comment: 4 pages, incl. 5 figures. First figure of v1 removed due to space
limitations. Title changed by journal request. Minor other changes and a few
references added or updated. This version accepted by Physical Review Letter
Energy loss in high energy heavy ion collisions from the Hydro+Jet model
We investigate the effect of energy loss of jets in high energy heavy ion
collisions by using a full three-dimensional space-time evolution of a fluid
combined with (mini-)jets that are explicitly evolved in space-time. In order
to fit the pi^0 data for the Au+Au collisions at sqrt(s_{NN}) = 130 GeV, the
space-time averaged energy loss dE/dx(tau <= 3 fm/c) = 0.36 GeV/fm is extracted
within the model. It is found that most energy loss occurs at the very early
time less than 2 fm/c in the QGP phase and that energy loss in the mixed phase
is negligible within our parameterization for jet energy loss. This is a
consequence of strong expansion of the system.Comment: 4 pages, 5 figures; one figure adde
The eccentricity in heavy-ion collisions from Color Glass Condensate initial conditions
The eccentricity in coordinate-space at midrapidity of the overlap zone in
high-energy heavy-ion collisions predicted by the -factorization
formalism is generically larger than expected from scaling with the number of
participants. We provide a simple qualitative explanation of the effect which
shows that it is not caused predominantly by edge effects. We also show that it
is quite insensitive to ``details'' of the unintegrated gluon distribution
functions such as the presence of leading-twist shadowing and of an extended
geometric scaling window. The larger eccentricity increases the azimuthal
asymmetry of high transverse momentum particles. Finally, we point out that the
longitudinal structure of the Color Glass Condensate initial condition for
hydrodynamics away from midrapidity is non-trivial but requires understanding
of large- effects.Comment: 8 pages, 7 figures; v3: added note regarding Qs2~n_part versus
Qs2~T_A, final version to appear in PR
BRAHMS Overview
A brief review of BRAHMS measurements of bulk particle production in RHIC
Au+Au collisions at is presented, together with some
discussion of baryon number transport. Intermediate measurements in
different collision systems (Au+Au, d+Au and p+p) are also discussed in the
context of jet quenching and saturation of the gluon density in Au ions at RHIC
energies. This report also includes preliminary results for identified
particles at forward rapidities in d+Au and Au+Au collisions.Comment: 8 pages 6 figures, Invited plenary talk at 5th International
Conference on Physics and Astrophysics of Quark Gluon Plasma (ICPAQGP 2005),
Salt Lake City, Kolkata, India, 8-12 Feb 200
suppression in the threshold model at RHIC and LHC energy
In the QGP based threshold model \cite{Blaizot:2000ev,Blaizot:1996nq}, in
addition to the normal nuclear absorption, 's are subjected to an
'anomalous' suppression such that above a threshold density , all
the 's are melted. In the threshold model we have analysed the recent
PHENIX data on the centrality dependence of suppression in Au+Au
collisions at RHIC. Feedback from decay of the state is accounted for.
's are anomalously suppressed above a threshold density,
. Threshold density for anomalous
suppression of the state is uncertain to a large extent, . The fraction of the state can not be determined
unambiguously, depending on the nuclear absorption, it can vary from 20% to
40%. We have also predicted for the suppression in Pb+Pb collisions at LHC
energy. In central Pb+Pb collisions, 's are suppressed by a factor of
3-4. Suppression pattern is rather similar to that in Au+Au collisions, if not
slighty less in central collisions. Using the PHENIX data on the participant
number dependence of the Bjorken energy density, we have also estimated the QGP
formation time. For critical temperature =192 MeV, estimated QGP formation
time ranges between 0.07-0.09 fm/c.Comment: 9 pages, 9 figure
CGC, Hydrodynamics, and the Parton Energy Loss
Hadron spectra in Au+Au collisions at RHIC are calculated by hydrodynamics
with initial conditions from the Color Glass Condensate (CGC). Minijet
components with parton energy loss in medium are also taken into account by
using parton density obtained from hydrodynamical simulations. We found that
CGC provides a good initial condition for hydrodynamics in Au+Au collisions at
RHIC.Comment: Quark Matter 2004 contribution, 4 pages, 2 figure
HBT: A (mostly) experimental overview
I will present a review of the field of Hanbury Brown-Twiss interferometry in
relativistic heavy-ion collisions. The "HBT puzzle" is explored in detail,
emphasizing recent theoretical attempts to understand the persisting puzzle. I
also present recent experimental results on azimuthally sensitive HBT, HBT of
direct photons, and some surprises in the comparison of HBT results from p+p
and Au+Au collisions at RHIC.Comment: 8 pages, 3 figures. Proceedings of the Quark Matter 2004 conference
(Oalkland, CA, USA, January 2004
Jet tomography
I summarize the recent advances in jet tomographic studies of cold and hot
nuclear matter based on perturbative QCD calculations of medium-induced gluon
bremsstrahlung. Quantitative applications to ultrarelativistic heavy ion
reactions at RHIC indicate the creation of a deconfined state of QCD with
initial energy density on the order of 100 times cold nuclear matter density.Comment: Plenary talk given at the seventeenth international conference on
Ultra-Relativistic Nucleus-Nucleus Collisions (Quark Matter 2004). 8 pages,
12 figures. Updated references, updated Table
Hydrodynamics and Flow
In this lecture note, we present several topics on relativistic hydrodynamics
and its application to relativistic heavy ion collisions. In the first part we
give a brief introduction to relativistic hydrodynamics in the context of heavy
ion collisions. In the second part we present the formalism and some
fundamental aspects of relativistic ideal and viscous hydrodynamics. In the
third part, we start with some basic checks of the fundamental observables
followed by discussion of collective flow, in particular elliptic flow, which
is one of the most exciting phenomenon in heavy ion collisions at relativistic
energies. Next we discuss how to formulate the hydrodynamic model to describe
dynamics of heavy ion collisions. Finally, we conclude the third part of the
lecture note by showing some results from ideal hydrodynamic calculations and
by comparing them with the experimental data.Comment: 40 pages, 35 figures; lecture given at the QGP Winter School, Jaipur,
India, Feb.1-3, 2008; to appear in Springer Lecture Notes in Physic
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