https://doi.org/10.1140/epja/i2009-10864-8
Regular Article - Theoretical Physics
RQM description of the charge form factor of the pion and its asymptotic behavior
Laboratoire de Physique Subatomique et de Cosmologie, Université Joseph Fourier Grenoble 1, CNRS/IN2P3, INPG, F-38026, Grenoble Cedex, France
* e-mail: desplanq@lpsc.in2p3.fr
Received:
18
June
2009
Revised:
13
August
2009
Accepted:
27
August
2009
Published online:
9
October
2009
The pion charge and scalar form factors, F 1(Q 2) and F 0(Q 2) , are first calculated in different forms of relativistic quantum mechanics. This is done using the solution of a mass operator that contains both confinement and one-gluon exchange interactions. Results of calculations, based on a one-body current, are compared to experiment for the first one. As could be expected, those point form, and instant and front-form ones in a parallel momentum configuration fail to reproduce experiment. The other results corresponding to a perpendicular momentum configuration (instant form in the Breit frame and front form with q + = 0 do much better. The comparison of charge and scalar form factors shows that the spin-1/2 nature of the constituents plays an important role. Taking into account that only the last set of results represents a reasonable basis for improving the description of the charge form factor, this one is then discussed with regard to the asymptotic QCD power law behavior Q-2. The contribution of two-body currents in achieving the right power law is considered while the scalar form factor, F 0(Q 2) , is shown to have the right power law behavior in any case. The low-Q2 behavior of the charge form factor and the pion decay constant are also discussed.
PACS: 12.39.Ki Relativistic quark model – / 13.40.Gp Electromagnetic form factors – / 14.40.Aq , K , and
mesons –
© SIF, Springer-Verlag Berlin Heidelberg, 2009