9,874 research outputs found
Revisit of directed flow in relativistic heavy-ion collisions from a multiphase transport model
We have revisited several interesting questions on how the rapidity-odd
directed flow is developed in relativistic Au+Au collisions at
= 200 and 39 GeV based on a multiphase transport model. As the
partonic phase evolves with time, the slope of the parton directed flow at
midrapidity region changes from negative to positive as a result of the later
dynamics at 200 GeV, while it remains negative at 39 GeV due to the shorter
life time of the partonic phase. The directed flow splitting for various quark
species due to their different initial eccentricities is observed at 39 GeV,
while the splitting is very small at 200 GeV. From a dynamical coalescence
algorithm with Wigner functions, we found that the directed flow of hadrons is
a result of competition between the coalescence in momentum and coordinate
space as well as further modifications by the hadronic rescatterings.Comment: 8 pages, 8 figures, version after major revisio
Target Directed Event Sequence Generation for Android Applications
Testing is a commonly used approach to ensure the quality of software, of
which model-based testing is a hot topic to test GUI programs such as Android
applications (apps). Existing approaches mainly either dynamically construct a
model that only contains the GUI information, or build a model in the view of
code that may fail to describe the changes of GUI widgets during runtime.
Besides, most of these models do not support back stack that is a particular
mechanism of Android. Therefore, this paper proposes a model LATTE that is
constructed dynamically with consideration of the view information in the
widgets as well as the back stack, to describe the transition between GUI
widgets. We also propose a label set to link the elements of the LATTE model to
program snippets. The user can define a subset of the label set as a target for
the testing requirements that need to cover some specific parts of the code. To
avoid the state explosion problem during model construction, we introduce a
definition "state similarity" to balance the model accuracy and analysis cost.
Based on this model, a target directed test generation method is presented to
generate event sequences to effectively cover the target. The experiments on
several real-world apps indicate that the generated test cases based on LATTE
can reach a high coverage, and with the model we can generate the event
sequences to cover a given target with short event sequences
Spin Correlations in top quark pair production near threshold at the Linear Collider
We investigate the spin correlations in top quark pair production near
threshold at the linear collider. Comparing with the results above
the threshold region, we find that near the threshold region the off-diagonal
basis, the optimized decomposition of the top quark spins above the threshold
region, does not exist, and the beamline basis is the optimal basis, in which
there are the dominant spin components: the up-down (UD) component for scattering and the down-up (DU) component for scattering can
make up more than 50% of the total cross section, respectively.Comment: 12 pages, 3 figures, minor modification
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