7 research outputs found
Model analysis of the world data on the pion transition form factor
We discuss the impact of recent Belle data on our description of the pion
transition form factor based on the assumption that a perturbative formalism
and a nonperturbative one can be matched in a physically acceptable manner at a
certain hadronic scale . We discuss the implications of the different
parameters of the model in comparing with world data and conclude that within
experimental errors our description remains valid. Thus we can assert that the
low nonperturbative description together with an additional term
at the matching scale have a strong influence on the behavior up to very
high values of .Comment: 6 pages and 3 figures. Contains a comparison with other models and
additional reference
Vacuum condensates and the pion wave functions in the nonlocal chiral model
We use the simple instanton motivated Nambu Jona-Lasinio - type model to
calculate a twist 3 pseudoscalar pion light cone wave function. Using
normalisation condition for this wave function we calculate the quark
condensate and also the gluon condensate, which agree with the phenomenological
values for these quantities. Since we can compute also the k_T^2 dependence of
the light cone wave functions, we calculate k_T^2 moments of the pseudo-scalar
and axial-vector wave functions which are related to the mixed vacuum
condensates. This allows us to extract the condensates and compare them with
existing estimates.Comment: 12 pages, 7 figures; three new paragraphs added: one (in sec. IV)
discusses the relation between quark and gluon condensates, the other two (in
secs. I and VI) clarify the difference between the normalisation scale Q_0,
at which the condensates are evaluated, and the model parameter Lambda; new
references added; to be published in Phys. Rev.