23 research outputs found
Jet quenching in thin plasmas
We investigate the energy loss of quarks and gluons produced in hard
processes resulting from final state rescatterings in a finite quark-gluon
plasma. The angular distribution of the soft gluon bremsstrahlung induced by
n_s=1 rescatterings in the plasma is computed in the Gyulassy-Wang model.
Special focus is on how the interference between the initial hard radiation
amplitude, the multiple induced Gunion-Bertsch radiation amplitudes, and gluon
rescattering amplitudes modifies the classical parton cascade results.Comment: 4 pages in Latex and 3 EPS figures, Proceedings of the Quark
Matter'99 Conference, 10-15 May, 1999, Torin
Probe Initial Parton Density and Formation Time via Jet Quenching
Medium modification of jet fragmentation function due to multiple scattering
and induced gluon radiation leads directly to jet quenching or suppression of
leading particle distribution from jet fragmentation. One can extract an
effective total parton energy loss which can be related to the total transverse
momentum broadening. For an expanding medium, both are shown to be sensitive to
the initial parton density and formation time. Therefore, one can extract the
initial parton density and formation time from simultaneous measurements of
parton energy loss and transverse momentum broadening. Implication of the
recent experimental data on effects of detailed balance in parton energy loss
is also discussed.Comment: 4 pages, 2 figures, talk at Quark Matter 2002, 16th International
Conference on Ultrarelativistic Nucleus-nucleus Collisions, Nantes, July
18-24, 200
Multiple Parton Scattering in Nuclei: Parton Energy Loss
Multiple parton scattering and induced parton energy loss is studied in
deeply inelastic scattering (DIS) off nuclei. The effect of multiple scattering
of a highly off-shell quark and the induced parton energy loss is expressed in
terms of the modification to the quark fragmentation functions. We derive such
modified quark fragmentation functions and their QCD evolution equations in DIS
using generalized factorization of higher twist parton distributions. We
consider double-hard, hard-soft parton scattering as well as their
interferences in the same framework. The final result, which depends on both
the diagonal and off-diagonal twist-four parton distributions in nuclei,
demonstrates clearly the Landau-Pomeranchuk-Migdal interference features and
predicts a unique nuclear modification of the quark fragmentation functions.Comment: Final version published in Nucl. Phys. A. 40 pages in RevTex with 15
postscript figure
Non-Abelian Energy Loss at Finite Opacity
A systematic expansion in opacity, , is used to clarify the
non-linear behavior of induced gluon radiation in quark-gluon plasmas. The
inclusive differential gluon distribution is calculated up to second order in
opacity and compared to the zeroth order (factorization) limit. The opacity
expansion makes it possible to take finite kinematic constraints into account
that suppress jet quenching in nuclear collisions below RHIC (
AGeV) energies.Comment: 4 pages (revtex) with 3 eps figures, submitted to PR
Metastable Quantum Phase Transitions in a Periodic One-dimensional Bose Gas: Mean-Field and Bogoliubov Analyses
We generalize the concept of quantum phase transitions, which is
conventionally defined for a ground state and usually applied in the
thermodynamic limit, to one for \emph{metastable states} in \emph{finite size
systems}. In particular, we treat the one-dimensional Bose gas on a ring in the
presence of both interactions and rotation. To support our study, we bring to
bear mean-field theory, i.e., the nonlinear Schr\"odinger equation, and linear
perturbation or Bogoliubov-de Gennes theory. Both methods give a consistent
result in the weakly interacting regime: there exist \emph{two topologically
distinct quantum phases}. The first is the typical picture of superfluidity in
a Bose-Einstein condensate on a ring: average angular momentum is quantized and
the superflow is uniform. The second is new: one or more dark solitons appear
as stationary states, breaking the symmetry, the average angular momentum
becomes a continuous quantity, and the phase of the condensate can be
continuously wound and unwound
Parton Energy Loss at Twist-Six in Deeply Inelastic e-A Scattering
Within the framework of the generalized factorization in pQCD, we investigate
the multiple parton scattering and induced parton energy loss at twist-6 in
deeply inelastic e-A scattering with the helicity amplitude approximation. It
is shown that twist-6 processes will give rise to additional nuclear size
dependence of the parton energy loss due to LPM interference effect while its
contribution is power suppressed.Comment: 6 pages, 2 figure
Multiple Parton Scattering in Nuclei: Beyond Helicity Amplitude Approximation
Multiple parton scattering and induced parton energy loss in deeply inelastic
scattering (DIS) off heavy nuclei is studied within the framework of
generalized factorization in perturbative QCD with a complete calculation
beyond the helicity amplitude (or soft bremsstrahlung) approximation. Such a
calculation gives rise to new corrections to the modified quark fragmentation
functions. The effective parton energy loss is found to be reduced by a factor
of 5/6 from the result of helicity amplitude approximation.Comment: 20 pages, 14 figure
QGP and Modified Jet Fragmentation
Recent progresses in the study of jet modification in hot medium and their
consequences in high-energy heavy-ion collisions are reviewed. In particular, I
will discuss energy loss for propagating heavy quarks and the resulting
modified fragmentation function. Medium modification of the parton
fragmentation function due to quark recombination are formulated within finite
temperature field theory and their implication on the search for deconfined
quark-gluon plasma is also discussedComment: 8 pages, 6 figures, invited plenary talk at HP2004, Ericeira,
Portugal, Nov. 4-10, 200
Jet energy loss in heavy ion collisions from RHIC to LHC energies
The suppression of hadron production originated from the induced jet energy
loss is one of the most accepted and well understood phenomena in heavy ion
collisions, which indicates the formation of color deconfined matter consists
of quarks, antiquarks and gluons. This phenomena has been seen at RHIC energies
and now the first LHC results display a very similar effect. In fact, the
suppression is so close to each other at 200 AGeV and 2.76 ATeV, that it is
interesting to investigate if such a suppression pattern can exist at all. We
use the Gyulassy-Levai-Vitev description of induced jet energy loss combined
with different nuclear shadowing functions and describe the experimental data.
We claim that a consistent picture can be obtained for the produced hot matter
with a weak nuclear shadowing. The interplay between nuclear shadowing and jet
energy loss playes a crucial role in the understanding of the experimental
data.Comment: 8 pages, 4 figures, Proceedings of ICPAQGP'2010 Conference, Goa,
Indi
Heavy Quark Radiative Energy Loss in QCD Matter
Heavy quark medium induced radiative energy loss is derived to all orders in
opacity, . The analytic expression generalizes the GLV opacity
expansion for massless quanta to heavy quarks with mass in a QCD plasma
with a gluon dispersion characterized by an asymptotic plasmon mass,
. Remarkably, we find that the general result is obtained by
simply shifting all frequencies in the GLV series by .
Numerical evaluation of the first order in opacity energy loss shows that both
charm and bottom energy losses are much closer to the incoherent radiation
limit than light partons in nuclear collisions at both RHIC and LHC energies.
However, the radiation lengths of heavy quarks remain large compared to nuclear
dimensions and hence high heavy quark production is volume rather than
surface dominated.Comment: 32 pages, 14 figure