16,467 research outputs found

    The leptonic future of the Higgs

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    Precision study of electroweak symmetry breaking strongly motivates the construction of a lepton collider with center-of-mass energy of at least 240 GeV. Besides Higgsstrahlung (e+ehZe^+e^- \to hZ), such a collider would measure weak boson pair production (e+eWWe^+e^- \to WW) with an astonishing precision. The weak-boson-fusion production process (e+eννˉhe^+e^- \to \nu \bar{\nu} h) provides an increasingly powerful handle at higher center-of-mass energies. High energies also benefit the associated top-Higgs production (e+ettˉhe^+e^-\to t\bar th) that is crucial to constrain directly the top Yukawa coupling. The impact and complementarity of differential measurements, at different center-of-mass energies and for several beam polarization configurations, are studied in a global effective-field-theory framework. We define a "global determinant parameter" (GDP) which characterizes the overall strengthening of constraints independently of the choice of operator basis. The reach of the CEPC, CLIC, FCC-ee, and ILC designs is assessed.Comment: 55 pages, lots of figures, v2: references added, minor corrections, extended discussions on quadratic EFT contributions and beam polarization effects, matches published version in JHE

    Polly's Polyhedral Scheduling in the Presence of Reductions

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    The polyhedral model provides a powerful mathematical abstraction to enable effective optimization of loop nests with respect to a given optimization goal, e.g., exploiting parallelism. Unexploited reduction properties are a frequent reason for polyhedral optimizers to assume parallelism prohibiting dependences. To our knowledge, no polyhedral loop optimizer available in any production compiler provides support for reductions. In this paper, we show that leveraging the parallelism of reductions can lead to a significant performance increase. We give a precise, dependence based, definition of reductions and discuss ways to extend polyhedral optimization to exploit the associativity and commutativity of reduction computations. We have implemented a reduction-enabled scheduling approach in the Polly polyhedral optimizer and evaluate it on the standard Polybench 3.2 benchmark suite. We were able to detect and model all 52 arithmetic reductions and achieve speedups up to 2.21×\times on a quad core machine by exploiting the multidimensional reduction in the BiCG benchmark.Comment: Presented at the IMPACT15 worksho

    Testing supersymmetry at the LHC through gluon-fusion production of a slepton pair

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    Renormalizable quartic couplings among new particles are typical of supersymmetric models. Their detection could provide a test for supersymmetry, discriminating it from other extensions of the Standard Model. Quartic couplings among squarks and sleptons, together with the SU(3) gauge couplings for squarks, allow a new realization of the gluon-fusion mechanism for pair-production of sleptons at the one-loop level. The corresponding production cross section, however, is at most of O(1){\cal O}(1) fb for slepton and squark masses of O(100){\cal O}(100) GeV. We then extend our investigation to the gluon-fusion production of sleptons through the exchange of Higgs bosons. The cross section is even smaller, of O(0.1){\cal O}(0.1) fb, if the exchanged Higgs boson is considerably below the slepton-pair threshold, but it is enhanced when it is resonant. It can reach O(10){\cal O}(10) fb for the production of sleptons of same-chirality, exceeding these values for τ~\widetilde{\tau}'s of opposite-chirality, even when chirality-mixing terms in the squark sector are vanishing. The cross section can be further enhanced if these mixing terms are nonnegligible, providing a potentially interesting probe of the Higgs sector, in particular of parameters such as AA, μ\mu, and tanβ\tan\beta.Comment: 28 pages, 11 figure

    Continuous control of ionization wave chaos by spatially derived feedback signals

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    In the positive column of a neon glow discharge, two different types of ionization waves occur simultaneously. The low-dimensional chaos arising from the nonlinear interaction between the two waves is controlled by a continuous feedback technique. The control strategy is derived from the time-delayed autosynchronization method. Two spatially displaced points of observation are used to obtain the control information, using the propagation characteristics of the chaotic wave.Comment: Elsevier-Tex-File, 8 pages, 6 figures, submitted to PL
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