De los Perissodactyla europeos a los Notoungulata argentinos

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Quebrada Fiera (Mendoza), un importante centro paleobiogeográfico en el Oligoceno tardío de América del Sur

This contribution focuses on the main results and present researches on the Oligocene fauna from Quebrada Fiera (Mendoza, Argentina). This vertebrate assemblage is providing new data on the distribution and evolution of South American Deseadan (late Oligocene) mammals. Descriptions of notoungulate Notohippidae and Archaeohyracidae have been recently published. A new genus of notohippid was identified, while most archaeohyracid material was recognized as the same species present in Salla (Bolivia). Studies in progress on other native ungulates (Hegetotheriidae, Interatheriidae, Leontinidae, Homalodotheriidae, Toxodontidae, ?Proterotheriidae, and Pyrotheriidae), metatheria, xenarthra, and rodents from Quebrada Fiera will increase the knowledge of this fauna. Preliminarily, the faunal association appears as a mix of taxa. On the one hand, with Patagonian affinities, on the other hand, related to species known from lower latitudes (Bolivia), together with exclusive taxa such as Mendozahippus (Notohippidae). The ongoing research will allow a better understanding of the role of Mendoza area in the paleobiogeographic and biostratigraphic context of the South American Oligocene mammals.Esta contribución se centra en los principales resultados obtenidos en los últimos años sobre la fauna oligocena de Quebrada Fiera (Mendoza, Argentina) y las investigaciones en curso. La asociación faunística de Quebrada Fiera está aportando datos nuevos sobre la distribución y la evolución de los mamíferos sudamericanos de la Edad mamífero Deseadense. Recientemente, se han dado a conocer los restos de dos familias de notoungulados, Notohippidae y Archaeohyracidae. En el primer caso, se reconoció un género nuevo, mientras que los arqueohirácidos se identifican en su gran mayoría como la especie presente en Salla (Bolivia). Los estudios en curso sobre otras familias de ungulados nativos (Hegetotheriidae, Interatheriidae, Leontinidae, Homalodotheriidae, Toxodontidae, ?Proterotheriidae y Pyrotheriidae), así como de los restos de metaterios, xenartros y roedores recuperados en Quebrada Fiera, ampliarán el conocimiento detallado de esta fauna. De forma preliminar, el conjunto faunístico aparece como una mezcla de taxones; por un lado, con afinidades patagónicas y, por otro, relacionados con especies conocidas en latitudes bajas (Bolivia), al mismo tiempo que cuenta con representantes exclusivos como Mendozahippus (Notohippidae). El avance de las investigaciones permitirá comprender mejor el papel del área de Mendoza en las distribuciones paleobiogeográfica y bioestratigráfica de los mamíferos sudamericanos del Oligoceno tardío

Relic Neutralino Density in Scenarios with Intermediate Unification Scale

We analyse the relic neutralino density in supersymmetric models with an intermediate unification scale. In particular, we present concrete cosmological scenarios where the reheating temperature is as small as $\cal{O}$ $1 - 1000$ MeV). When this temperature is associated to the decay of moduli fields producing neutralinos, we show that the relic abundance increases considerably with respect to the standard thermal production. Thus the neutralino becomes a good dark matter candidate with 0.1\lsim \Omega h^2 \lsim 0.3, even for regions of the parameter space where large neutralino-nucleon cross sections, compatible with current dark matter experiments, are present. This is obtained for intermediate scales $M_I\sim 10^{11}-10^{14}$ GeV, and moduli masses $m_\phi\sim 100-1000$ GeV. On the other hand, when the above temperature is associated to the decay of an inflaton field, the relic abundance is too small.Comment: Latex, 11 pages, 2 figure

Direct detection of neutralino dark matter in supergravity

The direct detection of neutralino dark matter is analysed in general supergravity scenarios, where non-universal soft scalar and gaugino masses can be present. In particular, the theoretical predictions for the neutralino-nucleon cross section are studied and compared with the sensitivity of dark matter detectors. We take into account the most recent astrophysical and experimental constraints on the parameter space, including the current limit on B(Bs-> mu+ mu-). The latter puts severe limitations on the dark matter scattering cross section, ruling out most of the regions that would be within the reach of present experiments. We show how this constraint can be softened with the help of appropriate choices of non-universal parameters which increase the Higgsino composition of the lightest neutralino and minimise the chargino contribution to the b->s transition.Comment: 27 pages, 22 figure

Surrogate models for direct dark matter detection

In this work we introduce RAPIDD, a surrogate model that speeds up the computation of the expected spectrum of dark matter particles in direct detection experiments. RAPIDD replaces the exact calculation of the dark matter differential rate (which in general involves up to three nested integrals) with a much faster parametrization in terms of ordinary polynomials of the dark matter mass and couplings, obtained in an initial training phase. In this article, we validate our surrogate model on the multi-dimensional parameter space resulting from the effective field theory description of dark matter interactions with nuclei, including also astrophysical uncertainties in the description of the dark matter halo. As a concrete example, we use this tool to study the complementarity of different targets to discriminate simplified dark matter models. We demonstrate that RAPIDD is fast and accurate, and particularly well-suited to explore a multi-dimensional parameter space, such as the one in effective field theory approach, and scans with a large number of evaluations

SuperCDMS: Recent results on low-mass WIMPs

We present the rst search for weakly interacting massive particles (WIMPs) using the back- ground rejection capabilities of SuperCDMS 1. A blind analysis of data from an exposure of 577 kg-days leads to an upper limit on the spin-independent WIMP-nucleon cross section of 1:2 10????42 cm2 at 8 GeV. This result probes new parameter space for WIMP-nucleon scat- tering cross section for light WIMPs with masses < 6 GeV/c2 and is in tension with WIMP interpretations of recent experiments