4,120 research outputs found
Low-energy expansion of the pion-nucleon Lagrangian
The renormalized pion-nucleon Lagrangian is calculated to O(p^3) in heavy
baryon chiral perturbation theory. By suitably chosen transformations of the
nucleon field, the Lagrangian is brought to a standard form.Comment: 10 pages, Latex, 1 figure in uuencoded postscript file embedded with
epsfig.st
Four-pion production in e+ e- annihilation
We calculate the processes e+ e- -> 4 pions and tau -> nu_tau + 4 pions to
O(p^4) in the low-energy expansion of the standard model. The chiral amplitudes
of O(p^4) can be extended via resonance exchange to energies around 1 GeV.
Higher-order effects have been included in the form of omega, a_1 and double
rho exchange and by performing a resummation of the pion form factor. The
predicted cross sections and the branching ratios BR(rho -> 4 pions) are in
good agreement with available data.Comment: 24 pages, 8 figures, small changes in the text, results and
conclusions unchanged, version to appear in EPJ
Parabolic methods for the construction of spacelike slices of prescribed mean curvature in cosmological spacetimes
Spacelike hypersurfaces of prescribed mean curvature in cosmological space times are constructed as asymptotic limits of a geometric evolution equation. In particular, an alternative, constructive proof is given for the existence of maximal and constant mean curvature slices
Four-pion production
Starting from the low-energy structure derived from QCD, we extend the
amplitudes for four-pion production in e+ e- annihilation and tau decays up to
invariant four-pion masses of 1 GeV. Cross sections and branching ratios
BR(rho^0 -> 4 pi) are compared with available data.Comment: 4 pages, 3 figures, contribution to Proc. of QCD'02, Montpellier,
July 2002, misprints correcte
Renormalization of chiral perturbation theory to order p^6
The renormalization of chiral perturbation theory is carried out to
next-to-next-to-leading order in the meson sector. We calculate the divergent
part of the generating functional of Green functions of quark currents to
O(p^6) for chiral SU(n), involving one- and two-loop diagrams. The
renormalization group equations for the renormalized low-energy constants of
O(p^6) are derived. We compare our results with previous two-loop calculations
in chiral perturbation theory.Comment: 43 pages, LaTeX2e, 1 figur
Radiative Semileptonic Kaon Decays
We evaluate the matrix elements for the radiative kaon decays , and \ () to next-to-leading order in chiral perturbation theory. We calculate
total rates and rates with several kinematical cuts and confront the results
with existing data. Measurements at future kaon facilities will allow for a
more detailed comparison between theory and experiment.Comment: LaTeX, 40 pages, 5 figures (not included), CERN-TH 6625/92,
BUTP-92/3
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