Disease, development, and defining indigenous identity : the emergence of machupo virus in post-revolutionary Bolivia

One of the four Latin American Hemorrhagic Fevers, Machupo virus, emerged in 1959 as a hemorrhagic disease in the lowlands of eastern Bolivia. The primary factor in the emergence of Machupo virus into the human population was the development of the eastern lowlands, brought about by Bolivia’s National Revolution in 1952. The Movimiento Nacionalista Revolucionario (MNR) government encouraged mass migration to eastern Bolivia in the form of resettlement programs in an attempt to stimulate the development of agriculture. By 1959 when Machupo virus first emerged, the MNR had distributed over 400,000 parcels of uncultivated land under the Agrarian Reform Act. The resultant clearing of uncultivated lands by the indigenous population was the primary factor in the emergence of Machupo virus. The United States government, in response to the burgeoning communist threat in the middle of the twentieth century, provided direction, technological assistance, and economic aid in the colonization and development of Eastern Bolivia, the region endemic to Machupo virus. Focus shifted from indigenous resettlement to immigration in order to provide a population the West perceived as capable of successful agricultural development. This shift was in response to the image of Indians provided for the West in the accounts of nineteenth-century travel writers who explored the economic advantages of the eastern lowlands. Travel writers ascribed an identity to the indigenous population resulting in a status of less than second-class citizenship in the eyes of the West, limiting them to subsistence agriculture, which contributed to the emergence of Machupo virus

Combined Forward-Backward Asymmetry Measurements in Top-Antitop Quark Production at the Tevatron

International audienceThe CDF and D0 experiments at the Fermilab Tevatron have measured the asymmetry between yields of forward- and backward-produced top and antitop quarks based on their rapidity difference and the asymmetry between their decay leptons. These measurements use the full data sets collected in proton-antiproton collisions at a center-of-mass energy of s=1.96  TeV. We report the results of combinations of the inclusive asymmetries and their differential dependencies on relevant kinematic quantities. The combined inclusive asymmetry is AFBtt¯=0.128±0.025. The combined inclusive and differential asymmetries are consistent with recent standard model predictions

Tevatron Run II combination of the effective leptonic electroweak mixing angle

International audienceDrell-Yan lepton pairs produced in the process pp¯→ℓ+ℓ-+X through an intermediate γ*/Z boson have an asymmetry in their angular distribution related to the spontaneous symmetry breaking of the electroweak force and the associated mixing of its neutral gauge bosons. The CDF and D0 experiments have measured the effective-leptonic electroweak mixing parameter sin2θefflept using electron and muon pairs selected from the full Tevatron proton-antiproton data sets collected in 2001-2011, corresponding to 9–10  fb-1 of integrated luminosity. The combination of these measurements yields the most precise result from hadron colliders, sin2θefflept=0.23148±0.00033. This result is consistent with, and approaches in precision, the best measurements from electron-positron colliders. The standard model inference of the on-shell electroweak mixing parameter sin2θW, or equivalently the W-boson mass MW, using the zfitter software package yields sin2θW=0.22324±0.00033 or equivalently, MW=80.367±0.017  GeV/c2

Tevatron Combination of Single-Top-Quark Cross Sections and Determination of the Magnitude of the Cabibbo-Kobayashi-Maskawa Matrix Element Vtb\bf V_{tb}

We present the final combination of CDF and D0 measurements of cross sections for single-top-quark production in proton-antiproton collisions at a center-of-mass energy of 1.96 TeV. The data correspond to total integrated luminosities of up to 9.7 fb$^{−1}$ per experiment. The t-channel cross section is measured to be σ$_t$=2.25$_{-0.31}^{+0.29}$ pb. We also present the combinations of the two-dimensional measurements of the s- vs t-channel cross section. In addition, we give the combination of the s+t channel cross section measurement resulting in σ$_{s+t}$=3.30$_{-0.40}^{+0.52}$ pb, without assuming the standard model value for the ratio σ$_s$/σ$_t$. The resulting value of the magnitude of the top-to-bottom quark coupling is |V$_{tb}$|=1.02$_{-0.05}^{+0.06}$, corresponding to |V$_{tb}$|>0.92 at the 95% C.L