real function flxnue(e,pol,emu)

c
c gives mumu flux from muon decay at 1 km 
c in 1/GeV/m^2/muon
c
c
      real e, pol, emu
      real val
      real x 

c      pol = 1. 
c      emu = 4. 

      gam = emu/0.10566
      x = e/emu 
      
      val = (1./emu/1.e6)
      val = val*gam*gam*x*x*12./4./3.14159265 
      val = val*((1-x)+(1-x)*pol)

      flxnue = val

      return 
      end