9,459 research outputs found

    Effective gluon mass and infrared fixed point in QCD

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    We report on a special type of solutions for the gluon propagator of pure QCD, obtained from the corresponding non-linear Schwinger-Dyson equation formulated in the Feynman gauge of the background field method. These solutions reach a finite value in the deep infrared and may be fitted using a massive propagator, with the crucial characteristic that the effective ``mass'' employed depends on the momentum transfer. Specifically, the gluon mass falls off as the inverse square of the momentum, as expected from the operator-product expansion. In addition, one may define a dimensionless quantity, which constitutes the generalization in a non-Abelian context of the universal QED effective charge. This strong effective charge displays asymptotic freedom in the ultraviolet whereas in the low-energy regime it freezes at a finite value, giving rise to an infrared fixed point for QCD.Comment: 6 pages, 2 figures, Talk given at QCD@work 2007, Martina Franca, Italy, 16-20 June 200

    Secondary Baryon Asymmetry in pi(+-)p Collisions

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    The process of secondary baryon production in pi(+-)p collisions at high energies in the central and forward fragmentation regions is considered in the framework of the Quark-Gluon String Model. The contribution of the string-junction mechanism to the baryon production is analysed. The results of numerical calculations are in reasonable agreement with the experimental data on the Lambda/bar(Lambda) and p/bar(p)$ asymmetries.Comment: Contribution to the Proceedings of QCD@Work 2007, International Workshop on Quantum Chromodynamics, Theory and Experiment, Martina Franca-Valle d'Itria, Italy, June 16-20, 2007 (6 pages and 4 figures

    Efficacy and toxicity of bevacizumab in recurrent ovarian disease: an update meta-analysis on phase III trials

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    Background: To analyze the efficacy and toxicity of bevacizumab on survival outcomes in recurrent ovarian cancer. Results: Bevacizumab was associated with significant improvement of PFS and OS compared with standard treatment with HRs of 0.53 (95% CI 0.44 - 0.63; p < 0.00001) and 0.87 (95% CI, 0.77 to 0.99; p = 0.03), respectively. Bevacizumab increased the incidence of G3/G4 hypertension (RR 19.01, 95% CI 7.77 - 46.55; p < 0.00001), proteinuria (RR 17.31, 95% CI 5.42 - 55.25; p < 0.00001), arterial thromboembolic events (ATE) (RR 4.99, 95% CI 1.29 - 19.27; p = 0.02) and bleeding (RR 3.14, 95% CI 1.35 - 7.32; p = 0.008). Materials and Methods: Three randomized phase III trials representing 1502 patients were identified. Pooled hazard ratio (HR), odd ratio (OR), risk ratio (RR) with 95% confidence interval (CI) were calculated using fixed or random effects model. Conclusions: Adding bevacizumab to standard chemotherapy improved ORR, PFS and OS, and it had a higher, but manageable, incidence of toxicities graded 3 to 4

    The Missing Matter Problem: From the Dark Matter Search to Alternative Hypotheses

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    Dark matter is among the most important open problems in both astrophysics and particle physics. We review the status of art of dark matter search at theoretical and experimental level discussing also alternative hypotheses

    Spin precession in the Schwarzschild spacetime: circular orbits

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    We study the behavior of nonzero rest mass spinning test particles moving along circular orbits in the Schwarzschild spacetime in the case in which the components of the spin tensor are allowed to vary along the orbit, generalizing some previous work.Comment: To appear on Classical and Quantum Gravity, 200
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