2,555 research outputs found
The Rule for Kaons
We report on recent advances at understanding the rule for
kaons. We get reasonable matching between short-- and long--distances for
scales between between 0.6 and 1.0 GeV and reproduce the rule
huge enhancement in the chiral limit. A detailed analysis of the different
contributions to the relevant octet and 27-plet couplings is done. For the
parameter, we get in the chiral limit for scales GeV.Comment: 9 LaTeX pages, 2 ps figures included. Invited talk at QCD '99 High
Energy Euro Conference on Quantum Chromodynamics, July 1999, Montpellier,
France. Corrected eq. (16) and misprint
Progress in Decays
Recent work by J.~Prades and myself on is described. The first
part describes our method to connect in a systematic fashion the short-distance
evolution with long-distance matrix-element calculations taking the scheme
dependence of the short-distance evolution into account correctly. In the
second part I show the results we obtain for the rule in the
chiral limit.Comment: 4 pages, uses espcrc1.sty. Talk given at PANIC99, Uppsala 10-16 june
199
A new global fit of the at next-to-next-to-leading order in Chiral Perturbation Theory
A new fit is done to obtain numerical values for the order
low-energy-constants in Chiral Perturbation Theory. This includes both
new data and new calculated observables. We take into account masses, decay
constants, , and scattering lengths and slopes and
the slope of the pion scalar formfactor. We compare in detail where the changes
w.r.t. to the 10 year old "fit 10" come from. We discuss several scenarios for
estimating the order constants and search for possible values of
them that provide a good convergence for the ChPT series. We present two such
sets. One big change is that the fits do not have the expected behaviour in the
limit of large as well as before.Comment: 41 pages, p^4 values of the l_i added, numerical values for f_+(0) in
Kl3 added, a comparison with the LECS from Ecker et al., Phys. Lett. B692
(2010) 184 [arXiv:1004.3422 [hep-ph]] adde
A Parametrization for
We discuss various models and Chiral Perturbation Theory results for the
form factors and . We check in how much a simple
parametrization with a few parameters can be used to extract information from
experiment.Comment: 19 pages, 14 figure
Chiral Meson Physics at Two Loops
An overview of Chiral Perturbation Theory calculations in the mesonic sector
at the two Loop level is given. Discussed in some detail are the partially
quenched case relevant for lattice QCD, the general fitting procedures and
, scattering as well as the determination of and
decays.Comment: 7 pages, Invited plenary talk presented at the 19th European Few-Body
conference, Groningen, The Netherlands, August 23-27, 200
Comment on the Pion Pole Part of the Light-by-Light Contribution to the Muon
We comment on the recent calculations of the pion pole part of the
light-by-light contribution to the muon anomalous magnetic moment and we point
out where the analysis in our previous work was mistaken.Comment: 2 page
Chiral extrapolation and determination of low-energy constants from lattice data
We propose analytic approximations of chiral SU(3) amplitudes for the
extrapolation of lattice data to the physical meson masses. The method allows
the determination of NNLO low-energy constants in a controllable fashion. We
test the approach with recent lattice data for the ratio F_K/F_pi of meson
decay constants.Comment: 10 pages, 1 figure, matches version published in PLB: title enlarged,
comments added, results unchange
The Pseudoscalar Meson Mass to Two Loops in Three-Flavor Partially Quenched PT
This paper presents a first study of the pseudoscalar meson masses to two
loops, or NNLO, within the supersymmetric formulation of partially quenched
chiral perturbation theory (PQPT). The expression for the pseudoscalar
meson mass in the case of three valence and three sea quarks with equal masses,
but different from each other, is given to , along with a
numerical analysis.Comment: 4 pages, one reference added, small changes in discussio
Semileptonic and Decays and the Chiral Anomaly at One-loop
We calculate the corrections to the anomalous form factors appearing
in , and decays in
Chiral Perturbation Theory. The relevant dimension terms of the lagrangian
are evaluated assuming their saturation by the vector meson contribution.Comment: 10 pages of LaTeX (+3 figures available on request
Chiral logarithms to five loops
We investigate two specific Green functions in the framework of chiral
perturbation theory. We show that, using analyticity and unitarity, their
leading logarithmic singularities can be evaluated in the chiral limit to any
desired order in the chiral expansion, with a modest calculational cost. The
claim is illustrated with an evaluation of the leading logarithm for the scalar
two-point function to five-loop order.Comment: 13 pages, 5 figure
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