7,784 research outputs found

    Coupled-cluster single-double calculations of the relativistic energy shifts in C IV, Na I, Mg II, Al III, Si IV, Ca II and Zn II

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    The relativistic coupled-cluster single-double method is used to calculate the dependence of frequencies of strong E1E1-transitions in many monovalent atoms and ions on the fine-structure constant α\alpha. These transitions are used in the search for manifestations of the variation of the fine-structure constant in quasar absorption spectra. Results of the present calculations are in good agreement with previous calculations but are more accurate.Comment: 6 pages, 4 tables, no figures; submitted to Phys. Rev.

    Evolution strategies applied to the problem of line profile decomposition in QSO spectra

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    We describe the decomposition of QSO absorption line ensembles applying an evolutionary forward modelling technique. The modelling is optimized using an evolution strategy (ES) based on a novel concept of completely derandomized self-adaption. The algorithm is described in detail. Its global optimization performance in decomposing a series of simulated test spectra is compared to that of classical deterministic algorithms. Our comparison demonstrates that the ES is a highly competitive algorithm capable to calculate the optimal decomposition without requiring any particular initialization.Comment: 9 pages, 5 figures, accepted for publication in Astron. Astrophys., corrected figure misplacements, full resolution manuscript can be obtained at http://www.hs.uni-hamburg.de/EN/Ins/Per/Quast

    Combining real and virtual Higgs boson mass constraints

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    Within the framework of the standard model we observe that there is a significant discrepancy between the most precise ZZ boson decay asymmetry measurement and the limit from direct searches for Higgs boson production. Using methods inspired by the Particle Data Group we explore the possible effect on fits of the Higgs boson mass. In each case the central value and the 95% confidence level upper limit increase significantly relative to the conventional fit. The results suggest caution in drawing conclusions about the Higgs boson mass from the existing data.Comment: 11 pages, Latex. Citations are added and paper is otherwise reconciled with version to be published in Physical Review Letter

    HE 0515-4414 - an unusual sub-damped Ly alpha system revisited

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    Using STIS and VLT UVES observations we have examined the ionization, abundances, and differential dust depletion of metals, the kinematic structure, and the physical conditions in the molecular hydrogen-bearing sub-damped Ly alpha system toward HE 0515-4414 at z = 1.15. The velocity interval of associated metal lines extends for 700 km/s. In addition, saturated H I absorption is detected in the blue damping wing of the main component. The column density ratios of associated Al II, Al III, and Fe II lines indicate that the absorbing material is ionized. 19 of in total 31 detected metal line components are formed within peripheral H II regions, while only 12 components are associated with the predominantly neutral main absorber. For the main absorber the observed abundance ratios of refractory elements to Zn range from Galactic warm disk [Si/Zn] = - 0.40, [Fe/Zn] = -1.10 to halo-like and essentially undepleted patterns. The dust-corrected metal abundances indicate a nucleosynthetic odd-even effect and might imply an anomalous depletion of Si relative to Fe for two components, but otherwise do correspond to solar ratios. The intrinsic average metallicity is almost solar [Fe/H] = -0.08, whereas the uncorrected average is [Zn/H] = -0.38. The ion abundances in the periphery conform with solar element composition. The detection of H II as well as the large variation in dust depletion for this sight line raises the question whether in future studies of damped Ly alpha systems ionization and depletion effects have to be considered in further detail. Ionization effects, for instance, may pretend an enrichment of alpha elements. An empirical recipe for detecting H II regions is provided.Comment: 26 pages, 12 figures, accepted for publication in Astronomy & Astrophysic
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