Mateo, D., Barranco, M., & Navarro, J. (2010). Elementary excitations in superfluid He-3-He-4 mixtures. Phys. Rev. B, 82(13), 134529–13pp.
Abstract: We have studied the dynamic structure function of superfluid He-3-He-4 mixtures at zero temperature as a function of pressure and He-3 concentration. Results obtained in the full random-phase approximation (RPA) plus density-functional theory and in a generalized Landau-Pomeranchuk approach are presented and compared with experiment. Analytic expressions for several sum rules of the dynamic structure functions have been determined, and have been used to obtain average energies of the collective excitations. In the RPA approach, the dispersion relation of the collective modes shows typical features of level repulsion between zero-soundlike and phonon-rotonlike excitations. The structure of the coupled RPA equations for the mixture leads in a natural way to the hybridization of the collective modes. The mixed He-3-He-4 dynamic structure function quenches the zero-soundlike mode before it crosses the phonon-roton branch, causing that the former mode only appears with enough strength after the crossing.
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CDF Collaboration(Aaltonen, T. et al), & Cabrera, S. (2010). Search for New Physics with a Dijet Plus Missing E-T Signature in p(p)over-bar Collisions at root s=1.96 TeV. Phys. Rev. Lett., 105(13), 131801–8pp.
Abstract: We present results of a signature-based search for new physics using a dijet plus missing transverse energy (E-T) data sample collected in 2 fb(-1) of p (p) over bar collisions at root s = 1.96 TeV with the CDF II detector at the Fermilab Tevatron. We observe no significant event excess with respect to the standard model prediction and extract a 95% C. L. upper limit on the cross section times acceptance for a potential contribution from a nonstandard model process. The search is made by using novel, data-driven techniques for estimating backgrounds that are applicable to first searches at the LHC.
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CDF Collaboration(Aaltonen, T. et al), Cabrera, S., & Cuenca Almenar, C. (2010). First Measurement of the b-Jet Cross Section in Events with a W Boson in p(p)over-bar Collisions at root s=1.96 TeV. Phys. Rev. Lett., 104(13), 131801–8pp.
Abstract: The cross section for jets from b quarks produced with a W boson has been measured in p (p) over bar collision data from 1: 9 fb(-1) of integrated luminosity recorded by the CDF II detector at the Tevatron. The W + b-jets process poses a significant background in measurements of top quark production and prominent searches for the Higgs boson. We measure a b-jet cross section of 2.74 + 0.27(stat) +/- 0.42(syst) pb in association with a single flavor of leptonic W boson decay over a limited kinematic phase space. This measured result cannot be accommodated in several available theoretical predictions.
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Aguilar, A. C., Binosi, D., & Papavassiliou, J. (2010). Nonperturbative gluon and ghost propagators for d=3 Yang-Mills theory. Phys. Rev. D, 81(12), 125025–13pp.
Abstract: We study a manifestly gauge-invariant set of Schwinger-Dyson equations to determine the non-perturbative dynamics of the gluon and ghost propagators in d = 3 Yang-Mills theory. The use of the well-known Schwinger mechanism, in the Landau gauge leads to the dynamical generation of a mass for the gauge boson (gluon in d = 3), which, in turn, gives rise to an infrared finite gluon propagator and ghost dressing function. The propagators obtained from the numerical solution of these nonperturbative equations are in very good agreement with the results of SU(2) lattice simulations.
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Carlson, E. D., Anderson, P. R., Fabbri, A., Fagnocchi, S., Hirsch, W. H., & Klyap, S. A. (2010). Semiclassical gravity in the far field limit of stars, black holes, and wormholes. Phys. Rev. D, 82(12), 124070–24pp.
Abstract: Semiclassical gravity is investigated in a large class of asymptotically flat, static, spherically symmetric spacetimes including those containing static stars, black holes, and wormholes. Specifically the stress-energy tensors of massless free spin 0 and spin 1/2 fields are computed to leading order in the asymptotic regions of these spacetimes. This is done for spin 0 fields in Schwarzschild spacetime using a WKB approximation. It is done numerically for the spin 1/2 field in Schwarzschild, extreme Reissner-Nordstrom, and various wormhole spacetimes. And it is done by finding analytic solutions to the leading order mode equations in a large class of asymptotically flat static spherically symmetric spacetimes. Agreement is shown between these various computational methods. It is found that, for all of the spacetimes considered, the energy density and pressure in the asymptotic region are proportional to r(-5) to leading order. Furthermore, for the spin 1/2 field and the conformally coupled scalar field, the stress-energy tensor depends only on the leading order geometry in the far field limit. This is also true for the minimally coupled scalar field for spacetimes containing either a static star or a black hole, but not for spacetimes containing a wormhole.
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