Eur. Phys. J. C 18, 731-746
DOI: 10.1007/s100520100583
Charge asymmetry of pions in the process
I.F. Ginzburg1, 2, A. Schiller3 and V.G. Serbo2
1 Sobolev Institute of Mathematics, 630090 Novosibirsk, Russia
2 Novosibirsk State University, 630090 Novosibirsk, Russia
3 Institut für Theoretische Physik and NTZ, Universität Leipzig, 04109 Leipzig, Germany
ginzburg@math.nsc.ru
Arwed.Schiller@itp.uni-leipzig.de
serbo@math.nsc.ru
(Received: 6 December 2000 / Published online: 5 February 2001 -© Springer-Verlag 2001)
Abstract
The study of the charge asymmetry of produced particles allows
one to investigate
the interference of different production mechanisms and to determine
new
features of the corresponding amplitudes. In the process
the two-pion system is produced
via two
mechanisms: two-photon (C-even state) and bremsstrahlung (C-odd
state)
production. We study the charge asymmetry of pions differentially
in the
pion momenta cross section originating from interference between
these
two mechanisms. At low effective mass of the dipions this asymmetry
is directly
related to the s- and p-phases of elastic 
scattering.
At
higher energies it can give new information about the f0 meson
family, the
f2(1270) meson, etc. The asymmetry is expressed via the pion
form factor
and the helicity amplitudes Mab for the subprocess
as
,
where we have analytically calculated the coefficients Gab
for the
region giving the main contribution to the effect. Several distributions
of
the pions are presented performing a numerical analysis in a
model
with
point-like pions. In the region near the dipion threshold the
asymmetry is
of the order of 
. We show that with suitable cuts the signal
to
background ratio can be increased up to about 10% .
© Società Italiana di Fisica, Springer-Verlag 2001
