4,676 research outputs found

    On the resonance eigenstates of an open quantum baker map

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    We study the resonance eigenstates of a particular quantization of the open baker map. For any admissible value of Planck's constant, the corresponding quantum map is a subunitary matrix, and the nonzero component of its spectrum is contained inside an annulus in the complex plane, zminzzmax|z_{min}|\leq |z|\leq |z_{max}|. We consider semiclassical sequences of eigenstates, such that the moduli of their eigenvalues converge to a fixed radius rr. We prove that, if the moduli converge to r=zmaxr=|z_{max}|, then the sequence of eigenstates converges to a fixed phase space measure ρmax\rho_{max}. The same holds for sequences with eigenvalue moduli converging to zmin|z_{min}|, with a different limit measure ρmin\rho_{min}. Both these limiting measures are supported on fractal sets, which are trapped sets of the classical dynamics. For a general radius zmin<r<zmax|z_{min}|< r < |z_{max}|, we identify families of eigenstates with precise self-similar properties.Comment: 32 pages, 2 figure

    Discriminating New Physics Scenarios at NLC: The Role of Polarization

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    We explore the potential of the Next Linear Collider (NLC), operating in the eγe\gamma mode, to disentangle new physics scenarios on single WW production. We study the effects related with the exchange of composite fermion in the reaction eγWνee\gamma \to W \nu_e, and compare with those arising from trilinear gauge boson anomalous couplings. We stress the role played by the initial state polarization to increase the reach of this machine and to discriminate the possible origin of the new phenomena.Comment: 26 pages, LaTeX file using ReVTeX. 10 Figure

    Identifying the Higgs Boson in Electron--Photon Collisions

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    We analyze the production and detection of the Higgs boson in the next generation of linear e+ee^+e^- colliders operating in the eγe\gamma mode. In particular, we study the production mechanism e+γeγγe+He + \gamma \rightarrow e \gamma \gamma \rightarrow e + H, where one photon is generated via the laser backscattering mechanism, while the other is radiated via the usual bremsstrahlung process. We show that this is the most important mechanism for Higgs boson production in a 500500 GeV eγe\gamma collider for M_H\raisebox{-.4ex}{\rlap{\sim}} \raisebox{.4ex}{>}140 GeV. We also study the signals and backgrounds for detection of the Higgs in the different decay channels, bbˉb \bar b, W+WW^+W^-, and ZZZZ, and suggest kinematical cuts to improve the signature of an intermediate mass Higgs boson.Comment: (REVTEX 2.0, 12 pages and 9 figures available upon request, Preprint MAD/PH/753

    Mass spectrometry screening of Arabica coffee roasting: A non-target and non-volatile approach by EASI-MS and ESI-MS.

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    Coffee roasting needs precise control and innovative techniques that are economically viable to monitor and improve its consistency. In this study, mass spectrometry was used as a tool to screen chemical markers that appear on the surface of coffee beans (whole bean) along the roasting process. A non-target and non-volatile approach was used with an ambient technique (EASI) coupled to a single quadrupole mass analyzer to monitor roasting chemical changes in the coffee bean. Green (raw), soft, medium, dark and very dark roasted coffee beans showed a decrease in ions in the range of m/z 500–600, whereas an increase in abundance in the m/z 800–900 range was clearly observed in the most roasted coffees. A multivariate approach through PCA separated the different roasts in 70% of the variance using PC1 and PC2. The major ions in the range of m/z 500–600 were characterized by ESI-MS and also HPLC-fluorescence as the N-alkanoyltryptamides, surface constituents of coffee wax layer which are almost fully degraded in darker roasts. The ions in the range of m/z 800–900 were characterized as di-and triacylglicerols and its increase during the roasting process was systematically observed. For these classes of chemical markers of the roasting process, ESI-MS showed also the sodium and potassium adducts with good relative abundances

    GeantV: Results from the prototype of concurrent vector particle transport simulation in HEP

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    Full detector simulation was among the largest CPU consumer in all CERN experiment software stacks for the first two runs of the Large Hadron Collider (LHC). In the early 2010's, the projections were that simulation demands would scale linearly with luminosity increase, compensated only partially by an increase of computing resources. The extension of fast simulation approaches to more use cases, covering a larger fraction of the simulation budget, is only part of the solution due to intrinsic precision limitations. The remainder corresponds to speeding-up the simulation software by several factors, which is out of reach using simple optimizations on the current code base. In this context, the GeantV R&D project was launched, aiming to redesign the legacy particle transport codes in order to make them benefit from fine-grained parallelism features such as vectorization, but also from increased code and data locality. This paper presents extensively the results and achievements of this R&D, as well as the conclusions and lessons learnt from the beta prototype.Comment: 34 pages, 26 figures, 24 table
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