59 research outputs found
Bilocal expansion of the Borel amplitude and the hadronic tau decay width
The singular part of Borel transform of a QCD amplitude near the infrared
renormalon can be expanded in terms of higher order Wilson coefficients of the
operators associated with the renormalon. In this paper we observe that this
expansion gives nontrivial constraints on the Borel amplitude that can be used
to improve the accuracy of the ordinary perturbative expansion of the Borel
amplitude. In particular, we consider the Borel transform of the Adler function
and its expansion around the first infrared renormalon due to the gluon
condensate. Using the next-to-leading order Wilson coefficient of the gluon
condensate operator, we obtain an exact constraint on the Borel amplitude at
the first IR renormalon. We then extrapolate, using judiciously chosen
conformal transformations and Pade approximants, the ordinary perturbative
expansion of the Borel amplitude in such a way that this constraint is
satisfied. This procedure allows us to predict the coefficient
of the Adler function, which gives a result consistent with the estimate by
Kataev and Starshenko using a completely different method. We then apply this
improved Borel amplitude to the tau decay width, and obtain the strong coupling
constant . We then compare this result with those of
other resummation methods.Comment: 30 pages, 4 eps-figures, revtex; version as appears in PRD; no major
changes; more careful rounding of some number
Sex and the Single Cell. II. There Is a Time and Place for Sex
In both male and female Drosophila, only a subset of cells have the potential to sexually differentiate, making both males and females mosaics of sexually differentiated and sexually undifferentiated cells
A compact and cost-effective hard X-ray free-electron laser driven by a high-brightness and low-energy electron beam
We present the first lasing results of SwissFEL, a hard X-ray free-electron laser (FEL) that recently came into operation at the Paul Scherrer Institute in Switzerland. SwissFEL is a very stable, compact and cost-effective X-ray FEL facility driven by a low-energy and ultra-low-emittance electron beam travelling through short-period undulators. It delivers stable hard X-ray FEL radiation at 1-Ă
wavelength with pulse energies of more than 500 ÎŒJ, pulse durations of ~30 fs (root mean square) and spectral bandwidth below the per-mil level. Using special configurations, we have produced pulses shorter than 1 fs and, in a different set-up, broadband radiation with an unprecedented bandwidth of ~2%. The extremely small emittance demonstrated at SwissFEL paves the way for even more compact and affordable hard X-ray FELs, potentially boosting the number of facilities worldwide and thereby expanding the population of the scientific community that has access to X-ray FEL radiation
Unmet needs and current and future approaches for osteoporotic patients at high risk of hip fracture
Wirtschaftlichkeit des Einsatzes von nachwachsenden Rohstoffen als Co-Substrate zur Erzeugung von Biogas Abschlussbericht
Economic, ecological and process data of agricultural biogas plants were compiled and analysed, aiming at an economic validation of the applications of renewable fuels as energy sources for co-processing in agricultural biogas plants.Im Rahmen dieser Studie werden die zur oekonomischen, oekologischen und verfahrenstechnischen Bewertung der Energiegewinnung in landwirtschaftlichen Biogasanlagen derzeit vorhandenen Erkenntnisse erarbeitet und zusammengestellt. Ziel ist die oekonomische Validierung der Einsatzmoeglichkeiten unterschiedlicher nachwachsender Rohstoffe als Energietraeger zur Mitverarbeitung in landwirtschaftlichen Biogasanlagen. (orig.)SIGLEAvailable from TIB Hannover: F02B1741 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekFachagentur Nachwachsende Rohstoffe e.V., Guelzow (Germany)DEGerman
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