433 research outputs found
The Riemann Surface of a Static Dispersion Model and Regge Trajectories
The S-matrix in the static limit of a dispersion relation is a matrix of a
finite order N of meromorphic functions of energy in the plane with
cuts . In the elastic case it reduces to N functions
connected by the crossing symmetry matrix A. The scattering of
a neutral pseodoscalar meson with an arbitrary angular momentum l at a source
with spin 1/2 is considered (N=2). The Regge trajectories of this model are
explicitly found.Comment: 5 pages, LaTe
Axial anomaly and the interplay of quark loops with pseudoscalar and vector mesons in the gamma* --> pi+ pi0 pi- process
Motivated by the ongoing measurements of the Primakoff process pi- gamma* -->
pi- pi0 by COMPASS collaboration at CERN, the transition form factor for the
canonical anomalous process gamma* --> pi+ pi0 pi- is calculated in a
constituent quark loop model. The simplest contribution to this process is the
quark "box" amplitude. In the present paper we also explicitly include the
vector meson degrees of freedom, i.e., the rho and the omega, thus giving rise
to additional, resonant contributions. We find that in order to satisfy the
axial anomaly result, a further subtraction in the resonant part is needed. The
results are then compared with the vector meson dominance model as well as the
Dyson--Schwinger calculations, the chiral perturbation theory result, and the
available data.Comment: 21 pages, 8 eps figures, revtex4, a factor of 2 in resonant
contribution corrected, three figures revised and one added, discussion
enlarged and references adde
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