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the charge pion form factor has been considered in many frameworks , ranging from field theory to relativistic quantum mechanics ones .
the latter approaches include well known instant and front forms proposed by dirac @xcite .
it is relatively recently that the point form has been used @xcite . at first sight
, the implementation of this approach agrees well with experiment , suggesting that it is on a safe ground .
it has however been noticed that the same implementation of the point - form approach ( denoted with quotation marks in the following , see comment in ref .
@xcite ) was failing to reproduce the results expected from a theoretical model @xcite .
this one , based on scalar constituents , is perhaps the simplest one that can be imagined .
moreover , the effect of some ingredients , like form factors of the constituents that can affect the comparison of theory to experiment , factors out and can be ignored here .
the theoretical model therefore provides a stringent test of the method .
it was thus found that the form factors obtained in the `` point form '' tend to decrease too rapidly , especially in cases where a relativistic approach is required ( high momentum transfer and/or large binding ) .
the instant and front forms do relatively well for standard kinematics @xcite .    motivated by the above results , we re - examine the calculation of the pion form factor in the `` point form '' of relativistic quantum mechanics @xcite .
we pay a particular attention to a rescaling of the relation of the breit - frame pion momentum to the momentum transfer , which was made , according to the authors , to ensure the correct nonrelativistic limit @xcite .
actually , as the approach is a relativistic one , this modification is not needed .
moreover , we include the correct expression for the quark matrix element of the current , previously taken as equal to 1 .
the present study mainly relies on analytic expressions of form factors @xcite .
they have been obtained using simple phenomenological wave functions such as a gaussian one employed in an earlier work @xcite or a hulthn one which may be more realistic : @xmath0 , \hspace{1 cm } { \rm with } \;\;v^2=\frac{q^2}{4\,m^2_{\pi } + q^2}\ ; , \label{a}\ ] ] @xmath1}{\sqrt{m^2-\alpha^2 } } -\frac{\arctan[2\,v\sqrt{m^2-\alpha^2}\,/(\alpha+\beta - v^2(\beta-\alpha ) ) ] } { \sqrt{m^2-\alpha^2 } } \right .
\nonumber \\ & &   \qquad \,\left . + \ ,   \frac{\arctan [ v\,\sqrt{m^2-\beta^2}\,/\beta]}{\sqrt{m^2-\beta^2 } } - \frac{\arctan[2\,v\sqrt{m^2-\beta^2}\,/(\alpha+\beta+v^2(\beta-\alpha ) ) ] } { \sqrt{m^2-\beta^2 } }   \right ) .
\label{b}\end{aligned}\ ] ] numerical results are presented in fig .
[ fig : ffpi ] .
they include form factors calculated with reasonable parameters for the two wave functions . in both cases ,
upper limits that essentially correspond to a point pion are shown ( denoted in the figure by the subscript @xmath2 ) . as a guide , a curve which represents a good approximation to the form factor of ref .
@xcite , which includes the re - scaling made by the authors , is also given : @xmath3    in all cases involving the correct definition of the velocity , eqs .
( [ a ] , [ b ] ) , we found that the squared charge radius has an incompressible value determined by the inverse of the squared pion mass , of the order of a few @xmath4 , one order of magnitude larger than experiment .
this prevents one from making a sensible fit to the measured form factor ( assuming we would like to do it ) . on the other hand
, we can not reproduce in any way its expected asymptotic power law , @xmath5 .
the fall off is always too fast .
these results are confirmed by using a more realistic but numerical wave function .
the present results confirm those obtained in a theoretical model @xcite .
they indicate that the implementation of the point - form approach used until now requires major improvements .
these ones include the contribution of two - body currents that could remove the main drawbacks of present calculations in relation with the dependence of form factors on the ratio @xmath6 .
ultimately , the features in relation with the goldstone boson nature of the pion , which concern in particular the asymptotic behavior and the charge radius , should be accounted for .
the present re - evaluation leaves room for them .    while developping this program , it may be useful to keep in mind other results .
recently , coester and riska @xcite showed that the nucleon form factors could be successfully reproduced in the limit of a point nucleon .
as this approximation corresponds to our upper limits ( denoted with the subscript @xmath2 ) , it appears that what works in one case does not in the other .
the difference is mainly due to the mass of the system under consideration . on the other hand ,
results very similar to the present ones are obtained in other forms but for non - standard kinematics @xcite that are known as giving incomplete results ( see also field - theory motivated approaches @xcite ) . the relationship may help to solve the problems evidenced by the implementation of the point - form approach used in this work .    9 p.a.m .
dirac , rev .
( 1949 ) 392 .
allen and w.h .
klink , phys .
c58 ( 1998 ) 3670 .
a. amghar , b. desplanques and l. theul , hep - ph/0301235 .
b. desplanques and l. theul , eur .
j. a13 ( 2002 ) 461 .
a. amghar , b. desplanques and l. theul , nucl .
a714 ( 2003 ) 213 .
f. coester and d.o .
riska , nucl - th/0306002 and contribution to this conference . s. simula , phys . rev .
c66 ( 2002 ) 035201 .
bakker , h .-
choi and c .- r .
ji , phys .
d63 ( 2001 ) 074014 . j.p.b.c .
de melo et al . , nucl .
a707 ( 2002 ) 399 .
the pion form factor calculation in the `` point - form '' of relativistic quantum mechanics is re - considered . 
 particular attention is given to the relation between the momentum of the system and the momentum transfer as well as to the quark current .