1,475 research outputs found
Euclidean asymptotic expansions of Green functions of quantum fields (II) Combinatorics of the asymptotic operation
The results of part I (hep-ph/9612284) are used to obtain full asymptotic
expansions of Feynman diagrams renormalized within the MS-scheme in the regimes
when some of the masses and external momenta are large with respect to the
others. The large momenta are Euclidean, and the expanded diagrams are regarded
as distributions with respect to them. The small masses may be equal to zero.
The asymptotic operation for integrals is defined and a simple combinatorial
techniques is developed to study its exponentiation. The asymptotic operation
is used to obtain the corresponding expansions of arbitrary Green functions.
Such expansions generalize and improve upon the well-known short-distance
operator-product expansions, the decoupling theorem etc.; e.g. the low-energy
effective Lagrangians are obtained to all orders of the inverse heavy mass. The
obtained expansions possess the property of perfect factorization of large and
small parameters, which is essential for meaningful applications to
phenomenology. As an auxiliary tool, the inversion of the R-operation is
constructed. The results are valid for arbitrary QFT models.Comment: one .sty + one .tex (LaTeX 2.09) + one .ps (GSview) = 46 pp. Many
fewer misprints than the journal versio
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
An interpolation of the vacuum polarization function for the evaluation of hadronic contributions to the muon anomalous magnetic moment
We propose a simple parameterization of the two-point correlator of hadronic
electromagnetic currents for the evaluation of the hadronic contributions to
the muon anomalous magnetic moment. The parameterization is explicitly done in
the Euclidean domain. The model function contains a phenomenological parameter
which provides an infrared cutoff to guarantee the smooth behavior of the
correlator at the origin in accordance with experimental data in e+ e-
annihilation. After fixing a numerical value for this parameter from the
leading order hadronic contribution to the muon anomalous magnetic moment the
next-to-leading order results related to the vacuum polarization function are
accurately reproduced. The properties of the four-point correlator of hadronic
electromagnetic currents as for instance the so-called light-by-light
scattering amplitude relevant for the calculation of the muon anomalous
magnetic moment are briefly discussed.Comment: 23 pages in LaTeX, 11 PostScript figures included in the tex
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
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