488 research outputs found
Gluon contribution to open heavy-meson production in heavy-ion collisions
A sizable contribution to heavy quark production in high-energy hadronic and
nuclear collisions comes from heavy quark-antiquark pair production from gluon
splitting during the parton shower evolution. We investigate the effect of
gluon-medium interaction on open heavy flavor spectra in ultra-relativistic
heavy-ion collisions. The interaction of hard gluons and heavy quarks with the
hot QCD medium is simulated by utilizing a Langevin transport model that
simultaneously incorporates contributions from collisional and radiative
processes. It is found that while the gluon splitting channel has quite an
important contribution to the single meson production cross section, its
influence on the final heavy meson nuclear modification turns out to be quite
modest because the average lifetime of hard gluons is short before splitting
into heavy quark-antiquark pairs during the evolution and propagation of the
parton shower.Comment: 5 pages, 6 figure
Heavy and light flavor jet quenching at RHIC and LHC energies
The Linear Boltzmann Transport (LBT) model coupled to hydrodynamical
background is extended to include transport of both light partons and heavy
quarks through the quark-gluon plasma (QGP) in high-energy heavy-ion
collisions. The LBT model includes both elastic and inelastic
medium-interaction of both primary jet shower partons and thermal recoil
partons within perturbative QCD (pQCD). It is shown to simultaneously describe
the experimental data on heavy and light flavor hadron suppression in
high-energy heavy-ion collisions for different centralities at RHIC and LHC
energies. More detailed investigations within the LBT model illustrate the
importance of both initial parton spectra and the shapes of fragmentation
functions on the difference between the nuclear modifications of light and
heavy flavor hadrons. The dependence of the jet quenching parameter
on medium temperature and jet flavor is quantitatively extracted.Comment: 6 pages, 6 figure
Mining Object Parts from CNNs via Active Question-Answering
Given a convolutional neural network (CNN) that is pre-trained for object
classification, this paper proposes to use active question-answering to
semanticize neural patterns in conv-layers of the CNN and mine part concepts.
For each part concept, we mine neural patterns in the pre-trained CNN, which
are related to the target part, and use these patterns to construct an And-Or
graph (AOG) to represent a four-layer semantic hierarchy of the part. As an
interpretable model, the AOG associates different CNN units with different
explicit object parts. We use an active human-computer communication to
incrementally grow such an AOG on the pre-trained CNN as follows. We allow the
computer to actively identify objects, whose neural patterns cannot be
explained by the current AOG. Then, the computer asks human about the
unexplained objects, and uses the answers to automatically discover certain CNN
patterns corresponding to the missing knowledge. We incrementally grow the AOG
to encode new knowledge discovered during the active-learning process. In
experiments, our method exhibits high learning efficiency. Our method uses
about 1/6-1/3 of the part annotations for training, but achieves similar or
better part-localization performance than fast-RCNN methods.Comment: Published in CVPR 201
Effects of jet-induced medium excitation in -hadron correlation in A+A collisions
Coupled Linear Boltzmann Transport and hydrodynamics (CoLBT-hydro) is
developed for co-current and event-by-event simulations of jet transport and
jet-induced medium excitation (j.i.m.e.) in high-energy heavy-ion collisions.
This is made possible by a GPU parallelized (3+1)D hydrodynamics that has a
source term from the energy-momentum deposition by propagating jet shower
partons and provides real time update of the bulk medium evolution for
subsequent jet transport. Hadron spectra in -jet events of A+A
collisions at RHIC and LHC are calculated for the first time that include
hadrons from both the modified jet and j.i.m.e.. CoLBT-hydro describes well
experimental data at RHIC on the suppression of leading hadrons due to parton
energy loss. It also predicts the enhancement of soft hadrons from j.i.m.e. The
onset of soft hadron enhancement occurs at a constant transverse momentum due
to the thermal nature of soft hadrons from j.i.m.e. which also have a
significantly broadened azimuthal distribution relative to the jet direction.
Soft hadrons in the direction are, on the other hand, depleted due to
a diffusion wake behind the jet.Comment: 4 pages, 4 figures in LaTeX, final version published in PL
Constraints and Soliton Solutions for the KdV Hierarchy and AKNS Hierarchy
It is well-known that the finite-gap solutions of the KdV equation can be
generated by its recursion operator.We generalize the result to a special form
of Lax pair, from which a method to constrain the integrable system to a
lower-dimensional or fewer variable integrable system is proposed. A direct
result is that the -soliton solutions of the KdV hierarchy can be completely
depicted by a series of ordinary differential equations (ODEs), which may be
gotten by a simple but unfamiliar Lax pair. Furthermore the AKNS hierarchy is
constrained to a series of univariate integrable hierarchies. The key is a
special form of Lax pair for the AKNS hierarchy. It is proved that under the
constraints all equations of the AKNS hierarchy are linearizable.Comment: 12 pages, 0 figur
Multiple jets and -jet correlation in high-energy heavy-ion collisions
-jet production is considered one of the best probes of the hot
quark-gluon plasma in high-energy heavy-ion collisions since the direct
can be used to gauge the initial energy and momentum of the associated
jet. This is investigated within the Linear Boltzmann Transport (LBT) model for
jet propagation and jet-induced medium excitation. With both parton energy loss
and medium response from jet-medium interaction included, LBT can describe
experimental data well on -jet correlation in Pb+Pb collisions at the
Large Hadron Collider. Multiple jets associated with direct production
are found to contribute significantly to -jet correlation at small
and large azimuthal angle relative to the opposite
direction of . Jet medium interaction not only suppresses the leading
jet at large but also sub-leading jets at large azimuthal
angle. This effectively leads to the narrowing of -jet correlation in
azimuthal angle instead of broadening due to jet-medium interaction. The
-jet profile on the other hand will be broadened due to jet-medium
interaction and jet-induced medium response. Energy flow measurements relative
to the direct photon is illustrated to reflect well the broadening and
jet-induced medium response.Comment: 11 pages with 12 figures, revised version includes discussions on the
background subtraction and different definitions of jet profil
- …