Positron annihilation lifetime spectroscopy at a superconducting electron accelerator

The Helmholtz-Zentrum Dresden-Rossendorf operates a superconducting linear accelerator for electrons with energies up to 35 MeV and average beam currents up to 1.6 mA. The electron beam is employed for production of several secondary beams including X-rays from bremsstrahlung production, neutrons, and positrons. The secondary positron beam after moderation feeds the Monoenergetic Positron Source (MePS) where positron annihilation lifetime (PALS) and positron annihilation Doppler-broadening experiments in materials science are performed in parallel. The adjustable repetition rate of the continuous-wave electron beams allows matching of the pulse separation to the positron lifetime in the sample under study. The energy of the positron beam can be set between 0.5 keV and 20 keV to perform depth resolved defect spectroscopy and porosity studies especially for thin films

Charged and Pseudoscalar Higgs production at a Muon Collider

We consider single charged Higgs ($H^{\pm}$) and pseudoscalar Higgs ($A^0$) production in association with a gauge boson at $\mu^+\mu^-$ colliders. We find that the tree-level t-channel and s-channel contributions to $\mu^+\mu^-\to H^{\pm}W^{\mp}, A^0Z$ are enhanced for large values of $\tan\beta$, allowing sizeable cross-sections whose analogies at $e^+e^-$ colliders would be very small. These processes provide attractive new ways of producing such particles at $\mu^+\mu^-$ colliders and are superior to the conventional methods in regions of parameter space.Comment: 11 pages Latex, 5 figures, formulae added in sections 2.2 and 2.3, extra discussion in section 2.3, references adde

Single Charged Higgs production as a probe of CP violation at a Muon Collider

We consider single charged Higgs ($H^{\pm}$) production in association with a $W^{\pm}$ boson at $\mu^+\mu^-$ colliders, in the context of the general CP violating Two Higgs Doublet Model (2HDM). We find that large cross-sections for the processes $\mu^+\mu^-\to H^+W^-,H^-W^+$ are possible, and offer an attractive way of producing $H^{\pm}$ at $\mu^+\mu^-$ colliders. The difference in the cross-sections for $H^+W^-$ and $H^-W^+$ may exceed 1000 fb, and this represents a novel way of probing CP violation in the Higgs sector.Comment: 15 pages, LaTex, 6 figure

AVALIAÇÃO DOS EFEITOS DE DIFERENTES CONCENTRAÇÕES DE CLORO NA DESCAPSULAÇÃO E ECLOSÃO DE LARVAS DE ARTEMIA (Artemia sp.)

This paper was prepared in the Aquaculture Laboratory of the Federal University of the State of Parana, Brazil, with the purpose of determining the best sodium hypochloride (NaClO with 6% active ingredient) dosage to be employed in the artemia oocysts hatching process.The artemia oocysts were hydrated for 1 hour, filtered and submitted to a 10-minute chlorine treatment. The chlorine dosages tested were the following (NaClO - 6% sodium hypochloride): 0.38g, 0.75g, 1.50g, 3.00g and 6.00g of active ingredient per liter of water. Soon after chlorine application the oocysts were rinsed to eliminate the chlorine and immediately the oocysts were put into transparent plastic vials with water in the constant aeration and luminosity, where they remained for 53 hours. For the nauplii count one mililiter of the vial was put into a test tube with an interconnected aeration. Three counts were made for all repetitions and the threshold analysed was the number of hatched larvae per mililiter of hatching solution. The results were submitted to a normality test and it was determined that the hatching results did not show a normal pattern, therefore, it was not possible to use those averages as a comparison basis between treatments. Subsequently non-parametric tests were performed using the overall average as a comparison basis between treatments.Techically one can see the superiority of treatment with 1.50g of active chlorine, which resulted in the highest hatching-out counts, with 50% of the observed data presented 140 larvae hatched per milimiter.O presente trabalho foi realizado no Laboratório de Aqüicultura da Universidade Federal do Paraná (UFPR), com o objetivo de determinar a melhor dose de hipoclorito de sódio (NaClO com 6% de ingrediente ativo) a ser empregada na descapsulação de oocistos de artemia. Os oocistos de artemia foram hidratados durante 1 hora, filtrados e submetidos aos tratamentos com cloro durante 10 minutos. As dosagens de cloro testadas foram as seguintes (NaClO - hipoclorito de sódio 6%): 0,38g, 0,75g, 1,50g, 3,00g e 6,00g de ingrediente ativo por litro de água. Depois da aplicação do cloro fez-se a lavagem dos oocistos para eliminar o cloro aplicado e logo após os oocistos foram colocados na água em frascos plásticos transparentes com aeração e luminosidade constante onde ficaram durante 53 horas. Para contagem dos náuplios foi pipetado um mililitro do frasco com aeração ligada. Para todas as repetições foram feitas três contagens e o parâmetro analisado foi o número de larvas eclodidas por mililitro da solução de eclosão. Os resultados foram submetidos a um teste de normalidade e foi verificado que os resultados de eclosão não tinham distribuição normal, portanto as médias não puderam ser usadas como termo de comparação entre os tratamentos. Então foram realizados testes não-paramétricos que usam a mediana como parâmetro de comparação entre os tratamentos. Tecnicamente observa-se a superioridade do tratamento de 1,50g de cloro ativo que apresentou o ponto máximo de eclosão, tendo 50% dos dados de eclosão ao redor de 140 larvas eclodidas por mililitro

Measurements of the SUSY Higgs self-couplings and the reconstruction of the Higgs potential

We address the issue of the reconstruction of the scalar potential of a two-Higgs doublet model having in mind that of the MSSM. We first consider the general CP conserving dim-4 effective potential. To fully reconstruct this potential, we show that even if all the Higgs masses and their couplings to the standard model particles are measured one needs not only to measure certain trilinear Higgs self-couplings but some of the quartic couplings as well. We also advocate expressing the Higgs self couplings in the mass basis. We show explicitly, that in the so-called decoupling limit, the most easily accessible Higgs self-couplings are given in terms of the Higgs mass while all other dependencies on the parameters of the general effective potential are screened. This helps also easily explain how, in the MSSM, the largest radiative corrections which affect these self couplings are reabsorbed by using the corrected Higgs mass. We also extend our analysis to higher order operators in the effective Higgs potential. While the above screening properties do not hold, we argue that these effects must be small and may not be measured considering the foreseen poor experimental precision in the extraction of the SUSY Higgs self-couplings.Comment: 25 pages, 3 figure

Simulations of galactic dynamos

We review our current understanding of galactic dynamo theory, paying particular attention to numerical simulations both of the mean-field equations and the original three-dimensional equations relevant to describing the magnetic field evolution for a turbulent flow. We emphasize the theoretical difficulties in explaining non-axisymmetric magnetic fields in galaxies and discuss the observational basis for such results in terms of rotation measure analysis. Next, we discuss nonlinear theory, the role of magnetic helicity conservation and magnetic helicity fluxes. This leads to the possibility that galactic magnetic fields may be bi-helical, with opposite signs of helicity and large and small length scales. We discuss their observational signatures and close by discussing the possibilities of explaining the origin of primordial magnetic fields.Comment: 28 pages, 15 figure, to appear in Lecture Notes in Physics "Magnetic fields in diffuse media", Eds. E. de Gouveia Dal Pino and A. Lazaria

Evidence for a mixed mass composition at the `ankle' in the cosmic-ray spectrum

We report a first measurement for ultra-high energy cosmic rays of the correlation between the depth of shower maximum and the signal in the water Cherenkov stations of air-showers registered simultaneously by the fluorescence and the surface detectors of the Pierre Auger Observatory. Such a correlation measurement is a unique feature of a hybrid air-shower observatory with sensitivity to both the electromagnetic and muonic components. It allows an accurate determination of the spread of primary masses in the cosmic-ray flux. Up till now, constraints on the spread of primary masses have been dominated by systematic uncertainties. The present correlation measurement is not affected by systematics in the measurement of the depth of shower maximum or the signal in the water Cherenkov stations. The analysis relies on general characteristics of air showers and is thus robust also with respect to uncertainties in hadronic event generators. The observed correlation in the energy range around the `ankle' at $\lg(E/{\rm eV})=18.5-19.0$ differs significantly from expectations for pure primary cosmic-ray compositions. A light composition made up of proton and helium only is equally inconsistent with observations. The data are explained well by a mixed composition including nuclei with mass $A > 4$. Scenarios such as the proton dip model, with almost pure compositions, are thus disfavoured as the sole explanation of the ultrahigh-energy cosmic-ray flux at Earth.Comment: Published version. Added journal reference and DOI. Added Report Numbe

Cichlid biogeography: comment and review

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72313/1/j.1467-2979.2004.00148.x.pd

DES15E2mlf: a spectroscopically confirmed superluminous supernova that exploded 3.5 Gyr after the big bang

We present the Dark Energy Survey (DES) discovery of DES15E2mlf, the most distant superluminous supernova (SLSN) spectroscopically confirmed to date. The light curves and Gemini spectroscopy of DES15E2mlf indicate that it is a Type I superluminous supernova (SLSN-I) at z = 1.861 (a lookback time of ∼10 Gyr) and peaking at MAB = −22.3 ± 0.1 mag. Given the high redshift, our data probe the rest-frame ultraviolet (1400–3500 Å) properties of the SN, finding velocity of the C III feature changes by ∼5600 km s−1 over 14 d around maximum light. We find the host galaxy of DES15E2mlf has a stellar mass of 3.5+3.6 −2.4 × 109 M, which is more massive than the typical SLSN-I host galaxy

Dark Energy Survey Year 1 Results: A Precise H0 Measurement from DES Y1, BAO, and D/H Data

We combine Dark Energy Survey Year 1 clustering and weak lensing data with baryon acoustic oscillations and Big Bang nucleosynthesis experiments to constrain the Hubble constant. Assuming a flat ΛCDM model with minimal neutrino mass (Σm υ = 0.06 eV), we find H 0 = 67.4 -1.2+1.1 km s -1 Mpc -1 (68 per cent CL). This result is completely independent of Hubble constant measurements based on the distance ladder, cosmic microwave background anisotropies (both temperature and polarization), and strong lensing constraints. There are now five data sets that: (a) have no shared observational systematics; and (b) each constrains the Hubble constant with fractional uncertainty at the few percent level. We compare these five independent estimates, and find that, as a set, the differences between them are significant at the 2.5σ level (χ 2 /dof = 24/11, probability to exceed = 1.1 per cent). Having set the threshold for consistency at 3σ, we combine all five data sets to arrive at H 0 = 69.3 -0.6+0.4 km s -1 Mpc -