1,560 research outputs found

    Virtual Supersymmetric Corrections in e^+e^- Annihilation

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    Depending on their masses, Supersymmetric particles can affect various measurements in Z decay. Among these are the total width (or consequent extracted value of αs\alpha_s), enhancement or suppression of various flavors, and left-right and forward-backward asymmetries. The latter depend on squark mass splittings and are, therefore, a possible test of the Supergravity related predictions. We calculate leading order corrections for these quantities considering in particular the case of light photino and gluino where the SUSY effects are enhanced. In this limit the effect on αs\alpha_s is appreciable, the effect on RbR_b is small, and the effect on the asymmetries is extremely small.Comment: 11 pages, LaTeX, 3 figures, revised, a reference adde

    Gluino Contribution to the 3-loop QCD beta function in the Minimal Supersymmetric Standard Model

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    We deduce the gluino contribution to the three-loop QCD \beta function within the minimal supersymmetric Standard Model (MSSM) from its standard QCD expression. The result is a first step in the computation of the full MSSM three-loop \beta function. In addition, in the case of a light gluino it provides the strong three-loop SUSY correction to the extrapolation of the strong coupling constant from the low energy regime to the Z region and up to the squark threshold.Comment: 11 pages, RevTex, 4 Postscript figur

    Why does the Engel method work? Food demand, economies of size and household survey methods

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    Estimates of household size economies are needed for the analysis of poverty and inequality. This paper shows that Engel estimates of size economies are large when household expenditures are obtained by respondent recall but small when expenditures are obtained by daily recording in diaries. Expenditure estimates from recall surveys appear to have measurement errors correlated with household size. As well as demonstrating the fragility of Engel estimates of size economies, these results help resolve a puzzle raised by Deaton and Paxson (1998) about differences between rich and poor countries in the effect of household size on food demand

    Silicon-based molecular electronics

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    Molecular electronics on silicon has distinct advantages over its metallic counterpart. We describe a theoretical formalism for transport through semiconductor-molecule heterostructures, combining a semi-empirical treatment of the bulk silicon bandstructure with a first-principles description of the molecular chemistry and its bonding with silicon. Using this method, we demonstrate that the presence of a semiconducting band-edge can lead to a novel molecular resonant tunneling diode (RTD) that shows negative differential resistance (NDR) when the molecular levels are driven by an STM potential into the semiconducting band-gap. The peaks appear for positive bias on a p-doped and negative for an n-doped substrate. Charging in these devices is compromised by the RTD action, allowing possible identification of several molecular highest occupied (HOMO) and lowest unoccupied (LUMO) levels. Recent experiments by Hersam et al. [1] support our theoretical predictions.Comment: Author list is reverse alphabetical. All authors contributed equally. Email: rakshit/liangg/ ghosha/[email protected]

    The Foundation Supernova Survey: Measuring Cosmological Parameters with Supernovae from a Single Telescope

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    Measurements of the dark energy equation-of-state parameter, ww, have been limited by uncertainty in the selection effects and photometric calibration of z<0.1z<0.1 Type Ia supernovae (SNe Ia). The Foundation Supernova Survey is designed to lower these uncertainties by creating a new sample of z<0.1z<0.1 SNe Ia observed on the Pan-STARRS system. Here, we combine the Foundation sample with SNe from the Pan-STARRS Medium Deep Survey and measure cosmological parameters with 1,338 SNe from a single telescope and a single, well-calibrated photometric system. For the first time, both the low-zz and high-zz data are predominantly discovered by surveys that do not target pre-selected galaxies, reducing selection bias uncertainties. The z>0.1z>0.1 data include 875 SNe without spectroscopic classifications and we show that we can robustly marginalize over CC SN contamination. We measure Foundation Hubble residuals to be fainter than the pre-existing low-zz Hubble residuals by 0.046±0.0270.046 \pm 0.027 mag (stat+sys). By combining the SN Ia data with cosmic microwave background constraints, we find w=−0.938±0.053w=-0.938 \pm 0.053, consistent with Λ\LambdaCDM. With 463 spectroscopically classified SNe Ia alone, we measure w=−0.933±0.061w=-0.933\pm0.061. Using the more homogeneous and better-characterized Foundation sample gives a 55% reduction in the systematic uncertainty attributed to SN Ia sample selection biases. Although use of just a single photometric system at low and high redshift increases the impact of photometric calibration uncertainties in this analysis, previous low-zz samples may have correlated calibration uncertainties that were neglected in past studies. The full Foundation sample will observe up to 800 SNe to anchor the LSST and WFIRST Hubble diagrams.Comment: 30 pages, 17 figures, accepted by Ap

    Inclusive Electron Scattering from Nuclei at x≃1x \simeq 1

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    The inclusive A(e,e') cross section for x≃1x \simeq 1 was measured on 2^2H, C, Fe, and Au for momentum transfers Q2Q^2 from 1-7 (GeV/c)2^2. The scaling behavior of the data was examined in the region of transition from y-scaling to x-scaling. Throughout this transitional region, the data exhibit Ο\xi-scaling, reminiscent of the Bloom-Gilman duality seen in free nucleon scattering.Comment: 4 pages, RevTeX; 4 figures (postscript in .tar.Z file
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