6 research outputs found

    Deep generative models for fast photon shower simulation in ATLAS

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    The need for large-scale production of highly accurate simulated event samples for the extensive physics programme of the ATLAS experiment at the Large Hadron Collider motivates the development of new simulation techniques. Building on the recent success of deep learning algorithms, variational autoencoders and generative adversarial networks are investigated for modelling the response of the central region of the ATLAS electromagnetic calorimeter to photons of various energies. The properties of synthesised showers are compared with showers from a full detector simulation using geant4. Both variational autoencoders and generative adversarial networks are capable of quickly simulating electromagnetic showers with correct total energies and stochasticity, though the modelling of some shower shape distributions requires more refinement. This feasibility study demonstrates the potential of using such algorithms for ATLAS fast calorimeter simulation in the future and shows a possible way to complement current simulation techniques

    Magneto-optical investigations of two-dimensional electron systems in GaAs-Al_xGa_1_-_xAs single heterojunctions

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    Optical Detection Of Charge Redistribution In A δ Modulation-doped Gaas-alxga1-xas Heterojunction

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    We have investigated magnetically-induced charge redistribution within a δ modulation-doped GaAs-AlxGa1-xAs heterojunction structure by studying the photoluminescence due to electrons from the two-dimensional (2D) electron system recombining with photoexcited holes. At well defined values of magnetic field, charge transfer occurs between this 2D electron system and the V-shaped potential well formed in the AlxGa1-xAs by Si δ modulation-doping. This redistribution of charge is observed as discontinuities in the photoluminescence energies. From these measurements we have derived the characteristic transfer time for electrons to move between these two wells. © 1998 Published by Elsevier Science Ltd. All rights reserved.1094267271Clark, R.G., High Magnetic Fields in Semiconductor Physics III (1992) Springer Series in Solid State Sciences, 101, p. 231. , edited by G. Landwehr, Springer-Verlag, Berlin and references thereinGoldberg, B.B., (1992) Surf. Sci., 263, p. 9. , and references thereinGoldys, E.M., (1992) Phys. Rev. B, 46, p. 7957. , and references thereinEllis, M.K., (1992) Phys. Rev. B, 45, p. 13765. , and reference thereinKukushkin, I.V., (1992) Phys. Rev. B, 45, p. 30. , and references thereinKukushkin, I.V., Von Klitzing, K., Ploog, K., Timofeev, V.B., (1989) Phys. Rev. B, 40, p. 7788Pulsford, N.J., Kukushkin, I.V., Hawrylak, P., Ploog, K., Haug, R.J., Von Klitzing, K., Timofeev, V.B., (1992) Phys. Stat. Sol., 173, p. 271Hayne, M., Usher, A., Plaut, A.S., Ploog, K., (1994) Phys. Rev. B, 50, p. 17208Domínguez-Adame, F., Méndez, B., Maciá, E., (1994) Semicond. Sci. Technol., 9, p. 263Dite, A.F., Kukushkin, I.V., Timofeev, V.B., Filin, A.I., Klitzing, V.K., (1991) Pis'ma Zh. Eksp. Teor. Fiz., 54, p. 393(1991) JETP Lett., 54, p. 389Aspnes, D.E., Kelso, S.M., Logan, R.A., Bhat, R., (1986) J. Appl. Phys., 60, p. 75

    Organic matter in space: from star dust to the Solar System

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    Organic compounds of high degree of complexity are now known to be widespread in the Universe, ranging from objects in our Solar System to distant galaxies. Through the techniques of millimeter-wave spectroscopy, over 140 molecules have been identified through their rotational transitions. Space infrared spectroscopy has detected the stretching and bending modes of compounds with aromatic and aliphatic structures. Analyses of samples of meteorites, comets, asteroids, and interplanetary dust also revealed a rich content of organic substances, some of which could be of extra-solar origin. We review the current state of understanding of the origin, evolution, nature, and distribution of organic matter in space. Also discussed are a number of unexplained astronomical phenomena whose origins could be traced to organic carriers. © 2008 Springer Science+Business Media B.V.link_to_subscribed_fulltex

    Mercury’s Weather-Beaten Surface: Understanding Mercury in the Context of Lunar and Asteroidal Space Weathering Studies

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