18,601 research outputs found
Vector boson and charmonia measurements in +Pb collisions with ATLAS
The production of electroweak bosons ( and ) and charmonia is
sensitive to the initial-state geometry of heavy-ion collisions and to the
parton distribution function with its potential nuclear modification. Since
their leptonic decay products do not interact strongly, their kinematics are
unmodified by the strongly interacting medium, which can be created in a
heavy-ion collision. We report on the latest results of the ATLAS Collaboration
on electroweak boson and charmonia production in +Pb collisions at
TeV. Production yields of and bosons are
presented as a function of (pseudo-)rapidity in different centrality bins. The
forward-backward ratio of J/ is shown as a function of transverse
momentum and center-of-mass rapidity.Comment: 5 pages, 7 figures, Proceedings of XXIV International Workshop on
Deep-Inelastic Scattering and Related Subjects (DIS 2016), DESY Hamburg,
Germany, 11-15 April, 201
Low-mass dielectron measurement in pp and Pb--Pb collisions in ALICE
We report on the first dielectron measurement in pp collisons at TeV with the ALICE detector system. The results are compared to the expected
hadronic sources. The hadronic cocktail agrees to the measured dielectron
continuum within statistical and systematic uncertainties. The status of the
dielectron measurement in Pb--Pb collisions at {} TeV is
addressed.Comment: 4 pages, 7 figures, Proceedings for Hot Quarks 2012 workshop (October
14-20, 2012, Copamarina, Puerto Rico
Dielectron measurements in pp, p-Pb and Pb-Pb collisions with ALICE at the LHC
Electromagnetic probes are excellent messengers from the hot and dense medium
created in high-energy heavy-ion collisions. Since leptons do not interact
strongly, their spectra reflect the entire space-time evolution of the
collision. The surrounding medium can lead to modifications of the dielectron
production with respect to the vacuum rate. To quantify modifications in
heavy-ion collisions, measurements in pp collisions serve as a reference, while
the analysis of p-A collisions allows for the disentanglement of cold nuclear
matter effects from those of the hot and dense medium. In this proceedings,
dielectron measurements with the ALICE central barrel detectors are presented.
The invariant mass distributions in the range GeV/ are
compared to the expected yields from hadronic sources for pp collisions at TeV, and for p-Pb collisions at TeV.
The cross section of direct photons measured via virtual photons in pp
collisions is compared to predictions from NLO pQCD calculations as a function
of the transverse momentum. The status of the analysis of Pb-Pb collisions at TeV is presented.Comment: 4 pages, 8 figures, Proceedings of the "Quark Matter 2014
Conference", XXIV International Conference on Ultrarelativistic
Nucleus-Nucleus Collisions, Darmstadt, May 19-24 201
Learning Optimal Control of Synchronization in Networks of Coupled Oscillators using Genetic Programming-based Symbolic Regression
Networks of coupled dynamical systems provide a powerful way to model systems
with enormously complex dynamics, such as the human brain. Control of
synchronization in such networked systems has far reaching applications in many
domains, including engineering and medicine. In this paper, we formulate the
synchronization control in dynamical systems as an optimization problem and
present a multi-objective genetic programming-based approach to infer optimal
control functions that drive the system from a synchronized to a
non-synchronized state and vice-versa. The genetic programming-based controller
allows learning optimal control functions in an interpretable symbolic form.
The effectiveness of the proposed approach is demonstrated in controlling
synchronization in coupled oscillator systems linked in networks of increasing
order complexity, ranging from a simple coupled oscillator system to a
hierarchical network of coupled oscillators. The results show that the proposed
method can learn highly-effective and interpretable control functions for such
systems.Comment: Submitted to nonlinear dynamic
Local Relativistic Exact Decoupling
We present a systematic hierarchy of approximations for {\it local}
exact-decoupling of four-component quantum chemical Hamiltonians based on the
Dirac equation. Our ansatz reaches beyond the trivial local approximation that
is based on a unitary transformation of only the atomic block-diagonal part of
the Hamiltonian. Systematically, off-diagonal Hamiltonian matrix blocks can be
subjected to a unitary transformation to yield relativistically corrected
matrix elements. The full hierarchy is investigated with respect to the
accuracy reached for the electronic energy and molecular properties on a
balanced test molecule set that comprises molecules with heavy elements in
different bonding situations. Our atomic (local) assembly of the unitary
transformation needed for exact decoupling provides an excellent local
approximation for any relativistic exact-decoupling approach. Its order-
scaling can be further reduced to linear scaling by employing the
neighboring-atomic-blocks approximation. Therefore, it is an efficient
relativistic method perfectly well suited for relativistic calculations on
large molecules. If a large molecule contains many light atoms (typically
hydrogen atoms), the computational costs can be further reduced by employing a
well-defined non-relativistic approximation for these light atoms without
significant loss of accuracy
- …