c--- The variables R and P provide the Regular and Plus pieces associated
c--- with radiation from leg 1 (B1(a,b,c,is) and leg 2 (B2(a,b,c,is)
c--- In each case the parton labelling is Using the normal QM notation of putting 
c--- everything backward
c---       emitted line after emission =   a
c---       emitter before emission     =    b
c---       spectator                   =    c
c--- There is no label for he or she who is emitted.
c--- Note that in general each piece will be composed of many different
c--- dipole contributions

c--- NOTE: this is just an extension to PR_new which includes the
c---  possibility of distinguishing a heavy quark from a light quark
c---  (b=2, rather than the usual q=1)

      double precision 
     . B1(-1:2,-1:2,-1:2,3),B2(-1:2,-1:2,-1:2,3)
      common/RP_stop/B1,B2