Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A combined study of the pion's static properties and form factors   We study consistently the pion's static observables and the elastic and
\gamma*\gamma -> \pi^0 transition form factors within a light-front model.
Consistency requires that all calculations are performed within a given model
with the same and single adjusted length or mass-scale parameter of the
associated pion bound-state wave function. Our results agree well with all
extent data including recent Belle data on the \gamma*\gamma -> \pi^0 form
factor at large q^2, yet the BaBar data on this transition form factor resists
a sensible comparison. We relax the initial constraint on the bound-state wave
function and show the BaBar data can partially be accommodated. This, however,
comes at the cost of a hard elastic form factor not in agreement with
experiment. Moreover, the pion charge radius is about 40% smaller than its
experimentally determined value. It is argued that a decreasing charge radius
produces an ever harder form factor with a bound-state amplitude difficultly
reconcilable with soft QCD. We also discuss why vector dominance type models
for the photon-quark vertex, based on analyticity and crossing symmetry, are
unlikely to reproduce the litigious transition form factor data.

17
The categories of this paper are: q-fin
29
The categories of this paper are: funct-an
3
The categories of this paper are: physics
27
The categories of this paper are: comp-gas
4
The categories of this paper are: cond-mat
32
The categories of this paper are: atom-ph
7
The categories of this paper are: hep-th
25
The categories of this paper are: patt-sol
9
The categories of this paper are: nlin
20
The categories of this paper are: acc-phys
11
The categories of this paper are: hep-lat
2
The categories of this paper are: math
1
The categories of this paper are: cs
24
The categories of this paper are: dg-ga
10
The categories of this paper are: q-bio
6
The categories of this paper are: astro-ph