613 research outputs found
Meson resonances, large N_c and chiral symmetry
We investigate the implications of large N_c and chiral symmetry for the mass
spectra of meson resonances. Unlike for most other mesons, the mass matrix of
the light scalars deviates strongly from its large-N_c limit. We discuss the
possible assignments for the lightest scalar nonet that survives in the
large-N_c limit.Comment: 14 page
The Inverse Amplitude Method in Scattering in Chiral Perturbation Theory to Two Loops
The inverse amplitude method is used to unitarize the two loop
scattering amplitudes of SU(2) Chiral Perturbation Theory in the ,
and channels. An error analysis in terms of the low energy
one-loop parameters and existing experimental data is
undertaken. A comparison to standard resonance saturation values for the two
loop coefficients is also carried out. Crossing
violations are quantified and the convergence of the expansion is discussed.Comment: (Latex, epsfig) 30 pages, 13 figures, 8 table
Splitting Strong and Electromagnetic Interactions in K(L4) Decays
We recently considered decays in the framework of chiral
perturbation theory based on the effective Lagrangian including mesons,
photons, and leptons. There, we published analytic one-loop-level expressions
for form factors and corresponding to the mixed process,
. We propose here a possible splitting
between strong and electromagnetic parts allowing analytic (and numerical)
evaluation of Isospin breaking corrections. The latter are sensitive to the
infrared divergence subtraction scheme and are sizeable near the
production threshold. Our results should be used for the extraction of the
-wave iso-vector phase shift from the outgoing data of the
currently running KTeV experiment at FNAL.Comment: 47 pages, LaTeX, 6 postscript figure
The electromagnetic effects in decay
The final state interaction of pions in decay allows one to obtain
the value of the isospin and angular momentum zero scattering length
.We take into account the electromagnetic interaction of pions and
isospin symmetry breaking effects caused by different masses of neutral and
charged pions and estimate the impact of these effects on the procedure of
scattering length extraction from decay.Comment: 8 pages,1 figur
Scattering in Three Flavour ChPT
We present the scattering lengths for the processes in the three
flavour Chiral Perturbation Theory (ChPT) framework at next-to-next-to-leading
order (NNLO). The calculation has been performed analytically but we only
include analytical results for the dependence on the low-energy constants
(LECs) at NNLO due to the size of the expressions. These results, together with
resonance estimates of the NNLO LECs are used to obtain constraints on the
Zweig rule suppressed LECs at NLO, and . Contrary to
expectations from NLO order calculations we find them to be compatible with
zero. We do a preliminary study of combining the results from
scattering, scattering and the scalar form-factors and find only a
marginal compatibility with all experimental/dispersive input data.Comment: 23 page
Scalar meson dynamics in Chiral Perturbation Theory
A comparison of the linear sigma model (LM) and Chiral Perturbation
Theory (ChPT) predictions for pion and kaon dynamics is presented. Lowest and
next-to-leading order terms in the ChPT amplitudes are reproduced if one
restricts to scalar resonance exchange. Some low energy constants of the order
ChPT Lagrangian are fixed in terms of scalar meson masses. Present values
of these low energy constants are compatible with the LM dynamics. We
conclude that more accurate values would be most useful either to falsify the
LM or to show its capability to shed some light on the controversial
scalar physics.Comment: 9 pages, REVTeX 4.0. Final version accepted for publicatio
Pion mass dependence of the semileptonic scalar form factor within finite volume
We calculate the scalar semileptonic kaon decay in finite volume at the
momentum transfer , using chiral perturbation
theory. At first we obtain the hadronic matrix element to be calculated in
finite volume. We then evaluate the finite size effects for two volumes with and and find that the difference between the finite
volume corrections of the two volumes are larger than the difference as quoted
in \cite{Boyle2007a}. It appears then that the pion masses used for the scalar
form factor in ChPT are large which result in large finite volume corrections.
If appropriate values for pion mass are used, we believe that the finite size
effects estimated in this paper can be useful for Lattice data to extrapolate
at large lattice size.Comment: 19 pages, 5 figures, accepted for publication in EPJ
Inclusive Decays of Heavy Quarkonium to Light Particles
We derive the imaginary part of the potential NRQCD Hamiltonian up to order
1/m^4, when the typical momentum transfer between the heavy quarks is of the
order of Lambda_{QCD} or greater, and the binding energy E much smaller than
Lambda_{QCD}. We use this result to calculate the inclusive decay widths into
light hadrons, photons and lepton pairs, up to O(mv^3 x
(Lambda_{QCD}^2/m^2,E/m)) and O(mv^5) times a short-distance coefficient, for
S- and P-wave heavy quarkonium states, respectively. We achieve a large
reduction in the number of unknown non-perturbative parameters and, therefore,
we obtain new model-independent QCD predictions. All the NRQCD matrix elements
relevant to that order are expressed in terms of the wave functions at the
origin and six universal non-perturbative parameters. The wave-function
dependence factorizes and drops out in the ratio of hadronic and
electromagnetic decay widths. The universal non-perturbative parameters are
expressed in terms of gluonic field-strength correlators, which may be fixed by
experimental data or, alternatively, by lattice simulations. Our expressions
are expected to hold for most of the charmonium and bottomonium states below
threshold. The calculations and methodology are explained in detail so that the
evaluation of higher order NRQCD matrix elements in this framework should be
straightforward. An example is provided.Comment: 61 pages, 9 figures. Minor change
Chiral Extrapolation of the Strangeness Changing K pi Form Factor
We perform a chiral extrapolation of lattice data on the scalar K pi form
factor and the ratio of the kaon and pion decay constants within Chiral
Perturbation Theory to two loops. We determine the value of the scalar form
factor at zero momentum transfer, at the Callan-Treiman point and at its soft
kaon analog as well as its slope. Results are in good agreement with their
determination from experiment using the standard couplings of quarks to the W
boson. The slope is however rather large. A study of the convergence of the
chiral expansion is also performed.Comment: few minor change
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