#<pre>
#include <stdio.h>
#include <math.h>
main(){
float mh,mh2,rs,s,wgt,sum,Gluons_measure,Gx,Gxp,x,xp;
float factor,xsect,Gf,pi;
int i,np;
/*  Find the  rate for gg->H (m_H=100 GeV) at Tevatron rs=2000 GeV
*/
         np=2000;           /* number of integration points */
         Gf=1.166e-5;
         pi=3.1415926;
         mh=100;
         mh2=mh*mh;
         rs=2000.;
         s=rs*rs;
	 factor=sqrt(2.)*pow(0.1,2.)*Gf/(64.*pi)*(1./9.)
               *mh2/s
               *389379662.; 
/*       1 GeV^{-2} = 389379662 pb 
         1 barn     = 10^{-24} cm^2
	 1 microbarn= 10^{-30} cm^2
	 1 nb       = 10^{-33} cm^2
	 1 pb       = 10^{-36} cm^2
The TEVATRON has accuminated about 
100 pb^{-1} integrated Luminosity before 1997.
*/
         wgt=1./2; 
      for (i=1; i<=np+1; i++) {
         x  =mh2/s+(1.-mh2/s)*(i-1)/((float) np)  ;
         xp =mh2/(x*s);             
         Gx =3* pow((1.-x),5.)/x;
         Gxp=3* pow((1.-xp),5.)/xp;
         Gluons_measure=Gx*Gxp/x/((float)np)*(1.-mh2/s) ; 
         sum=sum+Gluons_measure*wgt;
         wgt=1.;
                                 }
         sum=sum-Gluons_measure/2.;
         xsect=sum*factor;
 printf (" The cross section for m_H = %f  is %f  (pb) \n",mh,xsect);
        }
 /* 

After running the above C-program, we have found this simple
numerical caluclation gives a cross section for 
m_H = 100 GeV to be 0.53 (pb) 

*/