1,181 research outputs found

    Focusing of laser-generated ion beams by a plasma cylinder: similarity theory and the thick lens formula

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    It is shown that plasma-based optics can be used to guide and focus highly divergent laser-generated ion beams. A hollow cylinder is considered, which initially contains a hot electron population. Plasma streaming toward the cylinder axis maintains a focusing electrostatic field due to the positive radial pressure gradient. The cylinder works as thick lens, whose parameters are obtained from similarity theory for freely expanding plasma in cylindrical geometry. Because the lens parameters are energy dependent, the lens focuses a selected energy range of ions and works as a monochromator. Because the focusing is due to the quasineutral part of the expanding plasma, the lens parameters depend on the hot electron temperature TeT_e only, and not their density

    micrOMEGAs: recent developments

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    The program micrOMEGAs that calculates the relic density of the lightest supersymmetric particle (LSP) in the MSSM is presented. The impact of coannihilation channels and of higher order corrections to Higgs widths is stressed. The dependence on the RGE code used to calculate the soft parameters is also discussed.Comment: 5 pages, 2 figures, Talk presented at IDM2002, York, England; Reference adde

    micrOMEGAs : a tool for dark matter studies

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    micrOMEGAs is a tool for cold dark matter (DM) studies in generic extensions of the standard model with a R-parity like discrete symmetry that guarantees the stability of the lightest odd particle. The code computes the DM relic density, the elastic scattering cross sections of DM on nuclei relevant for direct detection, and the spectra of positrons, anti-protons and photons originating from DM annihilation including porpagation of charged cosmic rays. The cross sections and decay properties of new particles relevant for collider studies are included as well as constraints from the flavour sector on the parameter space of supersymmetric models.Comment: 10 pages, Proceedings of LC09, e+e- Physics at the TeV scale and the Dark Matter connection, Perugia, Italy, 21-24 sept. 200

    micrOMEGAs4.1: two dark matter candidates

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    micrOMEGAs is a code to compute dark matter observables in generic extensions of the standard model. This version of micrOMEGAs includes a generalization of the Boltzmann equations to take into account the possibility of two dark matter candidates. The modification of the relic density calculation to include interactions between the two DM sectors as well as semi-annihilation is presented. Both DM signals in direct and indirect detection are computed as well. An extension of the standard model with two scalar doublets and a singlet is used as an example.Comment: 13 pages, 1 figur

    micrOMEGAs: Version 1.3

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    We present the latest version of micromegas, a code that calculates the relic density of the lightest supersymmetric particle in the MSSM. All tree-level processes for the annihilation of the LSP are included as well as all possible coannihilation processes with neutralinos, charginos, sleptons, squarks and gluinos. The cross-sections extracted from CalcHEP are calculated exactly using loop-corrected masses and mixings as specified in the SUSY Les Houches Accord. Relativistic formulae for the thermal average are used and care is taken to handle poles and thresholds by adopting specific integration routines. The input parameters can be either the soft SUSY parameters in a general MSSM or the parameters of a SUGRA model specified at some high scale (GUT). In the latter case, a link with Suspect, Softsusy, Spheno and Isajet allows to calculate the supersymmetric spectrum, Higgs masses, as well as mixing matrices. Higher-order corrections to Higgs couplings to quark pairs including QCD as well as some SUSY corrections (deltaMb) are implemented. Routines calculating (g-2), bsgamma and bsmumu are also included. In particular the bsgamma routine includes an improved NLO for the SM and the charged Higgs while the SUSY large tan(beta) effects beyond leading-order are included. This new version also provides cross-sections for any 2->2 process as well as partial decay widths for two-body final states in the MSSM allowing for easy simulation at colliders.Comment: 45 page

    W+2jets production at Tevatron -- VECBOS and CompHEP comparison

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    Results of calculation of all subprocesses in proton-antiproton collisions which contribute to the W+2jets final state are presented at Tevatron energy. The calculation has been carried out by means of the CompHEP software package. A detail comparison with VECBOS generator results for cross sections and various distributions shows an agreement at the level of Monte-Carlo accuracy. Therefore the additional independent check of VECBOS generator has been done. In complement to the VECBOS generator a new generator based on CompHEP allows to study individual subprocesses like WbbňČWb\bar{b} or WccňČWc\bar{c}. The last point is important, for instance, for study WbbňČWb\bar{b} part of the background for single top or Standard Model Higgs signal at Tevatron.Comment: 8 pages including 4 figures as a gzipped postscript fil

    Precision measurements, dark matter direct detection and LHC Higgs searches in a constrained NMSSM

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    We reexamine the constrained version of the Next-to-Minimal Supersymmetric Standard Model with semi universal parameters at the GUT scale (CNMSSM). We include constraints from collider searches for Higgs and SUSY particles, upper bound on the relic density of dark matter, measurements of the muon anomalous magnetic moment and of B-physics observables as well as direct searches for dark matter. We then study the prospects for direct detection of dark matter in large scale detectors and comment on the prospects for discovery of heavy Higgs states at the LHC.Comment: 22 pages, 8 figures. Note added and references adde

    Voronoi Particle Merging Algorithm for PIC Codes

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    We present a new particle-merging algorithm for the particle-in-cell method. Based on the concept of the Voronoi diagram, the algorithm partitions the phase space into smaller subsets, which consist of only particles that are in close proximity in the phase space to each other. We show the performance of our algorithm in the case of the two-stream instability and the magnetic shower.Comment: 11 figure

    Isospin-violating dark matter from a double portal

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    We study a simple model that can give rise to isospin-violating interactions of Dirac fermion asymmetric dark matter to protons and neutrons through the interference of a scalar and U(1)′' gauge boson contribution. The model can yield a large suppression of the elastic scattering cross section off Xenon relative to Silicon thus reconciling CDMS-Si and LUX results while being compatible with LHC findings on the 126 GeV Higgs, electroweak precision tests and flavour constraints.Comment: 25 pages, 7 figure
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