83 research outputs found
Reduction of Vector and Axial--Vector Fields in a Bosonized Nambu--Jona--Lasinio Model
We derive the effective action for pseudoscalar mesons by integrating out
vector and axial--vector collective fields in the generating functional of the
bosonized NJL--model. The corresponding modifications of the nonlinear
effective Lagrangian and the bosonized currents, arising at , are
discussed.Comment: 30p. 1 fig. on reques
On the Origin of the Enhancementof CP-violating Charge Asymmetries in Decays Predicted from Chiral Theory
We present an analysis of the enhancement of CP-violating charge asymmetries
in decays. Calculations of decay amplitudes are performed
on the basis of bosonized strong and weak Lagrangians derived from
QCD-motivated quark Lagrangians. We show that the interplay of fourth-order
contributions of chiral Lagrangians for strong interactions and penguin
operators in weak interactions significantly enhances the charge asymmetries.Comment: DESY 92-106, 15
Radiative Kaon Decays and Violation
The amplitudes of and decays have been calculated within chiral
Lagrangian approach including higher-order derivative terms and meson loops.
The selfconsistency of the simultaneous description of the experimental data on
the nonleptonic and radiative kaon decays have been demonstrated. We estimate
the effects of ``indirect'' and ``direct'' -violation in decays and discuss -violating charge asymmetries in decays.Comment: 25 p., DESY 93-06
On the --corrections to decay amplitudes in nonlinear and linear chiral models
The calculations of isotopic amplitudes and their results for the direct
--violating charge asymmetry in decays within the
nonlinear and linear (--model) chiral Lagrangian approach are compared
with each other. It is shown, that the latter, taking into account intermediate
scalar resonances, does not reproduce the --corrections of the nonlinear
approach introduced by Gasser and Leutwyler, being saturated mainly by vector
resonance exchange. The resulting differences concerning the violation
effect are traced in some detail.Comment: 14 page
Calculation of Heat-Kernel Coefficients and Usage of Computer Algebra
The calculation of heat-kernel coefficients with the classical DeWitt
algorithm has been discussed. We present the explicit form of the coefficients
up to in the general case and up to for the minimal parts.
The results are compared with the expressions in other papers. A method to
optimize the usage of memory for working with large expressions on universal
computer algebra systems has been proposed.Comment: 12 pages, LaTeX, no figures. Extended version of contribution to
AIHENP'95, Pisa, April 3-8, 199
Heat-Kernel Calculation of Quark Determinant and Computer Algebra
In this paper there we describe the calculational background of deriving a
strong meson Lagrangian from the Nambu--Jona-Lasinio quark model using the
computer algebra systems FORM and REDUCE in recursive algorithms, based on the
heat-kernel method for the calculation of the quark determinant.Comment: LATEX, 11 p., DESY 92-15
The pi N -> pi pi N reaction around the N(1440) energy
We study the pi N -> pi pi N reaction around the N(1440) mass-shell energy.
Considering the total cross sections and invariant mass distributions, we
discuss the role of N(1440) and its decay processes. The calculation is
performed by extending our previous approach [Phys. Rev. C 69, 025206 (2004)]
to this reaction, in which only the nucleon and Delta(1232) were considered as
intermediate baryon states. The characteristics observed in the recent data for
the pi- p -> pi0 pi0 n reaction obtained by Crystal Ball Collaboration (CBC),
can be understood as a strong interference between the two decay processes:
N(1440) -> pi Delta(1232) and N(1440) -> N(pi pi)_S. It is also found that the
scalar-isoscalar pi pi rescattering effect in the NN*(pi pi)_S vertex, which
corresponds to the propagation of sigma meson, seems to be necessary for
explain ing the several observables of the pi N -> pi pi N reaction: the large
asymmetric shape in the pi0-pi0 invariant mass distributions of the pi- p ->
pi0 pi0 n reaction and the pi+ p -> pi+ pi+ n total cross section.Comment: 28 pages, 13 figures. Version to appear in Phys. Rev.
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