1,553 research outputs found
Heavy quark induced effective action for gauge fields in the SU(N_c) x U(1) model and the low-energy structure of heavy quark current correlators
We calculate the low-energy limit of heavy quark current correlators within
an expansion in the inverse heavy quark mass. The induced low-energy currents
built from the gluon fields corresponding to the initial heavy quark currents
are obtained from an effective action for gauge fields in the one-loop
approximation at the leading order of the 1/m expansion. Explicit formulae for
the low-energy spectra of electromagnetic and tensor heavy quark current
correlators are given. Consequences of the appearance of a nonvanishing
spectral density below the two-particle threshold for high precision
phenomenology of heavy quarks are discussed quantitatively.Comment: 21 pages in LaTeX, 2 PostScript figures included in the tex
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
Analytical calculation of heavy baryon correlators in NLO of perturbative QCD
We present analytical next-to-leading order results for the correlator of
baryonic currents at the three-loop level with one finite mass quark. We obtain
the massless and the HQET limits of the correlator as particular cases from the
general formula, we also give explicit expressions for the moments of the
spectral density. Calculations have been performed with an extensive use of the
symbolic manipulation programs MATHEMATICA and REDUCE.Comment: 16 pages in LaTeX, including 7 Postscript figures, contribution to
the "VII International Workshop on Advanced Computing and Analysis Techniques
in Physics Research (ACAT2000)", Oct 16-20, 2000, Fermi National Laboratory,
Batavia, Illinois, USA, to appear in the proceeding
Perturbative relations between annihilation and decay observables including resummation effects
By exploiting the analyticity properties of the two-point current-current
correlator we obtain numerical predictions for the moments in terms of
the decay rate. We perform a partial resummation of the pertinent
perturbative series expansion by solving the renormalization group equation for
Adler's function. Our predictions are renormalization scheme independent but
depend on the order of the perturbative -function expansion. The
analysis involves the unknown five-loop coefficient for which we give
some new estimates.Comment: 10 pages, LaTeX, 2 postscript figure
Next-to-Leading Order perturbative QCD corrections to baryon correlators in matter
We compute the next-to-leading order perturbative QCD corrections to the
correlators of nucleon interpolating currents in relativistic nuclear matter.
The main new result is the calculation of the O(alpha_s) perturbative
corrections to the coefficient functions of the vector quark condensate in
matter. This condensate appears in matter due to the violation of Lorentz
invariance. The NLO perturbative QCD corrections turn out to be large which
implies that the NLO corrections must be included in a sum rule analysis of the
properties of both bound nucleons and relativistic nuclear matter.Comment: 19 pages in LaTeX, including 5 Postscript figure
Landau equations and asymptotic operation
The pinched/non-pinched classification of intersections of causal
singularities of propagators in Minkowski space is reconsidered in the context
of the theory of asymptotic operation as a first step towards extension of the
latter to non-Euclidean asymptotic regimes. A highly visual
distribution-theoretic technique of singular wave fronts is tailored to the
needs of the theory of Feynman diagrams. Besides a simple derivation of the
usual Landau equations in the case of the conventional singularities, the
technique naturally extends to other types of singularities e.g. due to linear
denominators in non-covariant gauges etc. As another application, the results
of Euclidean asymptotic operation are extended to a class of quasi-Euclidean
asymptotic regimes in Minkowski space.Comment: 15p PS (GSview), IJMP-A (accepted
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