Vector boson and charmonia measurements in pp+Pb collisions with ATLAS

The production of electroweak bosons ($Z,\gamma$ and $W$) 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 $p$+Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV. Production yields of $Z$ and $W$ bosons are presented as a function of (pseudo-)rapidity in different centrality bins. The forward-backward ratio of J/$\psi$ 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 $\sqrt{s} = 7$ 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 {$\sqrt{s_{NN}}=2.76$} 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 $0<m_{ee}<3$ GeV/$c^{2}$ are compared to the expected yields from hadronic sources for pp collisions at $\sqrt{s}=7$ TeV, and for p-Pb collisions at $\sqrt{s_{\rm NN}}=5.02$ 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 $\sqrt{s_{\rm NN}}=2.76$ 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-$N^2$ 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