Searches for Gauge-Mediated SUSY Breaking Topologies with the L3 Detector at LEP

Searches for topologies predicted by gauge-mediated SUSY breaking models were performed using data collected with the L3 detector at LEP. All possible lifetimes of the next-to-lightest SUSY particle (NLSP), neutralino or scalar tau, were considered. No evidence for these new phenomena was found and limits on the production cross sections and sparticle masses were derived. A scan over the parameters of the minimal GMSB model was performed, leading to lower limits of 62.2 GeV, 11 TeV, and 0.07 eV on the NLSP mass, the mass scale parameter Lambda, and the gravitino mass, respectively. The status of the LEP combined searches is also discussed.Comment: 4 pages, 2 figures, 1 table; to appear in Proceedings of SUSY06, the 14th International Conference on Supersymmetry and the Unification of Fundamental Interactions, UC Irvine, California, 12-17 June 200

Improved sensitivity of H.E.S.S.-II through the fifth telescope focus system

The Imaging Atmospheric Cherenkov Telescope (IACT) works by imaging the very short flash of Cherenkov radiation generated by the cascade of relativistic charged particles produced when a TeV gamma ray strikes the atmosphere. This energetic air shower is initiated at an altitude of 10-30 km depending on the energy and the arrival direction of the primary gamma ray. Whether the best image of the shower is obtained by focusing the telescope at infinity and measuring the Cherenkov photon angles or focusing on the central region of the shower is a not obvious question. This is particularly true for large size IACT for which the depth of the field is much smaller. We address this issue in particular with the fifth telescope (CT5) of the High Energy Stereoscopic System (H.E.S.S.); a 28 m dish large size telescope recently entered in operation and sensitive to an energy threshold of tens of GeVs. CT5 is equipped with a focus system, its working principle and the expected effect of focusing depth on the telescope sensitivity at low energies (50-200 GeV) is discussed.Comment: In Proceedings of the 33rd International Cosmic Ray Conference (ICRC2013), Rio de Janeiro (Brazil

Continuous Uniform Finite Time Stabilization of Planar Controllable Systems

Continuous homogeneous controllers are utilized in a full state feedback setting for the uniform finite time stabilization of a perturbed double integrator in the presence of uniformly decaying piecewise continuous disturbances. Semiglobal strong $\mathcal{C}^1$ Lyapunov functions are identified to establish uniform asymptotic stability of the closed-loop planar system. Uniform finite time stability is then proved by extending the homogeneity principle of discontinuous systems to the continuous case with uniformly decaying piecewise continuous nonhomogeneous disturbances. A finite upper bound on the settling time is also computed. The results extend the existing literature on homogeneity and finite time stability by both presenting uniform finite time stabilization and dealing with a broader class of nonhomogeneous disturbances for planar controllable systems while also proposing a new class of homogeneous continuous controllers

Sensitivity to the KARMEN Timing Anomaly at MiniBooNE

We present sensitivities for the MiniBooNE experiment to a rare exotic pion decay producing a massive particle, Q^0. This type of decay represents one possible explanation for the timing anomaly reported by the KARMEN collaboration. MiniBooNE will be able to explore an area of the KARMEN signal that has not yet been investigated

A new look at the cosmic ray positron fraction

The positron fraction in cosmic rays was found to be a steadily increasing in function of energy, above $\sim$ 10 GeV. This behaviour contradicts standard astrophysical mechanisms, in which positrons are secondary particles, produced in the interactions of primary cosmic rays during the propagation in the interstellar medium. The observed anomaly in the positron fraction triggered a lot of excitement, as it could be interpreted as an indirect signature of the presence of dark matter species in the Galaxy. Alternatively, it could be produced by nearby astrophysical sources, such as pulsars. Both hypotheses are probed in this work in light of the latest AMS-02 positron fraction measurements. The transport of the primary and secondary positrons in the Galaxy is described using a semi-analytic two-zone model. MicrOMEGAs is used to model the positron flux generated by dark matter species. The description of the positron fraction from astrophysical sources is based on the pulsar observations included in the ATNF catalogue. We find that the mass of the favoured dark matter candidates is always larger than 500 GeV. The only dark matter species that fulfils the numerous gamma ray and cosmic microwave background bounds is a particle annihilating into four leptons through a light scalar or vector mediator, with a mixture of tau (75%) and electron (25%) channels, and a mass between 0.5 and 1 TeV. The positron anomaly can also be explained by a single astrophysical source and a list of five pulsars from the ATNF catalogue is given. Those results are obtained with the cosmic ray transport parameters that best fit the B/C ratio. Uncertainties in the propagation parameters turn out to be very significant. In the WIMP annihilation cross section to mass plane for instance, they overshadow the error contours derived from the positron data.Comment: 20 pages, 16 figures, accepted for publication in A&A, corresponds to published versio

Avaliação do potencial de cinco cultivares de videiras americanas para sucos de uva no sul de Minas Gerais.

Objetivou-se, no presente trabalho realizar uma caracterização dos sucos de uva de cinco cultivares de videira americana Vitis labrusca (Folha de Figo, Alwood, Concord, BRS-Rúbea e Isabel) segundo suas características visuais, olfativas e gustativas, utilizando um método descritivo por um painel de degustadores da Embrapa Uva e Vinho (EMBRAPA/CNPUV) de Bento Gonçalves e da Associação Brasileira de Enologia (ABE), constituído por doze degustadores. De acordo com os resultados, os sucos das cultivares Isabel e Folha de Figo foram superiores aos demais, segundo a análise de componentes principais (ACP), principalmente pelas variáveis limpidez, equilíbrio olfativo, intensidade e corpo gustativo, persistência olfato-gustativa e julgamento geral (notas). O suco Folha de Figo foi superior ao Isabel quanto à tonalidade, sendo o primeiro caracterizado como vermelho-violáceo. A cultivar Folha de Figo é a mais utilizada na região para a produção de suco, podendo os produtores utilizarem também a cultivar Isabel, que mostrou potencial nas condições edafo-climáticas do sul de Minas Gerais.Disponível também on-line

The electromagnetic calorimeter of the AMS-02 experiment

The electromagnetic calorimeter (ECAL) of the AMS-02 experiment is a 3-dimensional sampling calorimeter, made of lead and scintillating fibers. The detector allows for a high granularity, with 18 samplings in the longitudinal direction, and 72 sampling in the lateral direction. The ECAL primary goal is to measure the energy of cosmic rays up to few TeV, however, thanks to the fine grained structure, it can also provide the separation of positrons from protons, in the GeV to TeV region. A direct measurement of high energy photons with accurate energy and direction determination can also be provided.Comment: Proceedings of SF2A conference 201

The HADES Tracking System

The tracking system of the dielectron spectrometer HADES at GSI Darmstadt is formed out of 24 low-mass, trapezoidal multi-layer drift chambers providing in total about 30 square meter of active area. Low multiple scattering in the in total four planes of drift chambers before and after the magnetic field is ensured by using helium-based gas mixtures and aluminum cathode and field wires. First in-beam performance results are contrasted with expectations from simulations. Emphasis is placed on the energy loss information, exploring its relevance regarding track recognition.Comment: 6 pages, 4 figures, presented at the 10th Vienna Conference on Instrumentation, Vienna, February 2004, to be published in NIM A (special issue

The Minimal Supersymmetric Standard Model: Group Summary Report

CONTENTS: 1. Synopsis, 2. The MSSM Spectrum, 3. The Physical Parameters, 4. Higgs Boson Production and Decays, 5. SUSY Particle Production and Decays, 6. Experimental Bounds on SUSY Particle Masses, 7. References.Comment: 121 pages, latex + epsfig, graphicx, axodraw, Report of the MSSM working group for the Workshop "GDR-Supersym\'etrie",France. Rep. PM/98-4

Thermodynamics and collapse of self-gravitating Brownian particles in D dimensions

We address the thermodynamics (equilibrium density profiles, phase diagram, instability analysis...) and the collapse of a self-gravitating gas of Brownian particles in D dimensions, in both canonical and microcanonical ensembles. In the canonical ensemble, we derive the analytic form of the density scaling profile which decays as f(x)=x^{-\alpha}, with alpha=2. In the microcanonical ensemble, we show that f decays as f(x)=x^{-\alpha_{max}}, where \alpha_{max} is a non-trivial exponent. We derive exact expansions for alpha_{max} and f in the limit of large D. Finally, we solve the problem in D=2, which displays rather rich and peculiar features