FA1RCHL.f

      COMPLEX FUNCTION fa1rchl(QQ)
      IMPLICIT NONE
      REAL                     qq
      DOUBLE PRECISION m1,m2,m3
      REAL ggma1
      REAL wid_a1_fit 
c.......................................................................
c.
c.    fa1chl - rcht version of  the a1 propagator
c.
c.    inputs    : qq - invariant masses**2  [gev**2]
c.    outputs   : fa1rchl formfactor value at qq
c.
c.    COMMON    : rcht_3pi content is defined in this routine
c.
c.    calls     : functions from file ./wid_a1_fit.f
c.    called    : from file f3pi_rcht.f, fkkpi.f, fkk0pi0.f
c************************************************************************
       include '../parameter.inc'
       include '../funct_declar.inc'
c******************************************
c    initilisation of the mass of the particles
c*****************************************
        call rchl_parameters(5)

c$$$c we impose isospin symmetry requesting that charged and neutral pion mass
c$$$c are equal. this may need to be changed
c$$$        mmpi_av = (2.*mpic+mpiz)/3.

        m1 = mmpi_av      
        m2 = mmpi_av     
        m3 = mmpi_av  
c
c   Function wid_a1_fit.f calculates the energy dependence of 
c   the a1 meson width
c   
      IF(qq.GE.(m1+m2+m3)**2) THEN
        ggma1 = wid_a1_fit(qq)
      ELSE 
        ggma1 = 0.
      ENDIF


      fa1rchl = 1./(qq-mma1*mma1+i*mma1*ggma1)

      RETURN
      END

c to switch on/off remotely option for scalar contr. 
c to form1 form2 of 3 pi mode.     
      subroutine getff3piscal(INUM)
      INTEGER inum
      include '../parameter.inc'
      inum=ff3piscal
      return
      end

      subroutine setff3piscal(INUM)
      INTEGER inum
      include '../parameter.inc'
      ff3piscal=inum
      return
      end