2,225 research outputs found
Determination of the strange quark mass from Cabibbo-suppressed tau decays with resummed perturbation theory in an effective scheme
We present an analysis of the m_s^2-corrections to Cabibbo-suppressed tau
lepton decays employing contour improved resummation within an effective scheme
which is an essential new feature as compared to previous analyses. The whole
perturbative QCD dynamics of the tau-system is described by the beta-function
of the effective coupling constant and by two gamma-functions for the effective
mass parameters of the strange quark in different spin channels. We analyze the
stability of our results with regard to high-order terms in the perturbative
expansion of the renormalization group functions. A numerical value for the
strange quark mass in the MS scheme is extracted m_s(M_\tau)=130\pm 27_{exp}\pm
9_{th} MeV. After running to the scale 1 GeV this translates into m_s(1
GeV)=176 \pm 37_{exp}\pm 13_{th} MeV.Comment: 32 pages, latex, 4 postscript figures, revised version to appear in
European Physical Journal C, discussion of the choice of the moments added,
some errors correcte
Asymptotic structure of perturbative series for lepton decay observables: corrections
In a previous paper we performed an analysis of asymptotic structure of
perturbation theory series for semileptonic -lepton decays in massless
limit. We extend our analysis to the Cabibbo suppressed decay
modes of the lepton. In particular we address the problem of
corrections to theoretical formulas. The properties of the asymptotic behavior
of the finite order perturbation theory series for the coefficient functions of
the corrections are studied.Comment: 25 page
Asymptotic structure of perturbative series for tau lepton observables
We analyze tau lepton decay observables, namely moments of the hadronic
spectral density in the finite energy interval (0,M_\tau), within finite order
perturbation theory including \alpha_s^4 corrections. The start of asymptotic
growth of perturbation theory series is found at this order in a scheme
invariant manner. We establish the ultimate accuracy of finite order
perturbation theory predictions and discuss the construction of optimal
observables.Comment: 21 page
Quantum field theory on projective modules
We propose a general formulation of perturbative quantum field theory on
(finitely generated) projective modules over noncommutative algebras. This is
the analogue of scalar field theories with non-trivial topology in the
noncommutative realm. We treat in detail the case of Heisenberg modules over
noncommutative tori and show how these models can be understood as large
rectangular pxq matrix models, in the limit p/q->theta, where theta is a
possibly irrational number. We find out that the modele is highly sensitive to
the number-theoretical aspect of theta and suffers from an UV/IR-mixing. We
give a way to cure the entanglement and prove one-loop renormalizability.Comment: 52 pages, uses feynm
Damping Properties vs. Structure Fineness of the High-zinc Aluminum Alloys
The subject of this study is the presentation of relation between the degree of structure fineness and ultrasonic wave dampingcoefficient for the high-zinc aluminium alloys represented in this study by the sand mould cast alloy Al - 20 wt% Zn (AlZn20). Thestudied alloy was refined with a modifying (Al,Zn)-Ti3 ternary master alloy, introducing Ti in the amount of 400 pm into metal. Based on the analysis of the initial and modified alloy macrostructure images and ultrasonic testing, it was found that the addition of (Al,Zn)-Ti3 master alloy, alongside a significant fragmentation of grains, does not reduce the coefficient of ultrasonic waves with a frequency of 1 MHz
Changes in the morphology of the acinar cells of the rat pancreas in the oedematous and necrotic types of experimental acute pancreatitis
Limited experimental models of the oedematous and necrotic types of acute
pancreatitis provide some understanding of the pathophysiology of this disease.
Wistar rats were treated with cerulein at 10 mg/kg of body weight or with
L-arginine at 1.5 or 3 g/kg of body weight in order to induce the oedematous or
necrotic type of acute pancreatitis. After the induction period we examined
samples of pancreata with light and electron microscopes. Morphological
examination showed profound changes in the histology of the pancreas and its
acinar cells and subcellular structures, especially in the group of rats which
received a higher dose of L-arginine, amounting to 3 g/kg body weight. These
included parenchymal haemorrhage and widespread acinar cell necrotic changes.
4-OH-TEMPO successfully prevented morphological deterioration as well as
amylase release, suggesting that the severity of the two types of disease strongly
depends on the intensity of the oxidative stress. Our results lend support to the
assumption that reactive oxygen species play an axial role in the pathogenesis of
both types of acute pancreatitis
Quasi-quantum groups from Kalb-Ramond fields and magnetic amplitudes for strings on orbifolds
We present the general form of the operators that lift the group action on the twisted sectors of a bosonic string on an orbifold , in the presence of a Kalb-Ramond field strength . These operators turn out to generate the quasi-quantum group , introduced in the context of orbifold conformal field theory by R. Dijkgraaf, V. Pasquier and P. Roche. The 3-cocycle entering in the definition of is related to by a series of cohomological equations in a tricomplex combining de Rham, Cech and group coboundaries. We construct magnetic amplitudes for the twisted sectors and show that arises as a consistency condition for the orbifold theory. Finally, we recover discrete torsion as an ambiguity in the lift of the group action to twisted sectors, in accordance with previous results presented by E. Sharpe
Determination of Fungitoxic Value of Preservatives in Laboratory Wood-Block Tests
Laboratory-modified agar-block tests were made to determine the fungitoxic value of the wood preservative CCA against the test fungus Serpula lacrymans. The procedure applied to determine the results accounted for different standards: EN (toxic limit), ASTM (threshold retention), GOST (threshold retention and protection probability), PN (toxic dose), and JIS (value of efficiency). In order to improve the objectivity and repeatability of the toxic value results, statistical methods were used. Regression equations related sample mass loss and preservative retention
Influence of periodontal surgery on the subgingival microbiome-A systematic review and meta-analysis
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