void drawAlpha()
{

const int pts   = 100; 

double XX[pts] ={405.6,403.888136,398.554567,389.419165,376.503576,360.148341,340.902528,319.393152,296.187242,271.825048,246.776893,221.444914,196.203534,171.404929,147.356267,124.355775,102.686798,82.620676,64.4157,48.313907,34.541801,23.285574,14.635972,8.503451,4.55634,2.264232};
double Ymin[pts]={0.5838548039,0.5823328985,0.5784296792,0.573755237,0.566361358,0.5562849205,0.5438159064,0.5307395425,0.5155712765,0.4992876162,0.4819052656,0.464754584,0.4484843723,0.4320740899,0.4168631973,0.4046426261,0.3946776118,0.392880336,0.4000790117,0.4187968999,0.456868543,0.5164912751,0.5965511941,0.6875978227,0.7734610535,0.8360784304};
double Ymax[pts] = {1.140604882,1.137458027,1.129485914,1.119705516,1.104252305,1.083101733,1.056783455,1.028787348,0.9961379798,0.9606359884,0.9222212044,0.8833176314,0.8450120249,0.8048740727,0.7651232776,0.7285312597,0.6926235642,0.6676196831,0.6526729944,0.6503062385,0.6708934735,0.7149591196,0.7778321354,0.8467180483,0.9054888772,0.941200881};

   TGraph *gr = new TGraph(2*pts);
   for (int i=0;i<pts;i++) {
      gr->SetPoint(i,XX[i],Ymax[i]);
      gr->SetPoint(pts+i,XX[pts-i-1],Ymin[pts-i-1]);
      }
   gr->SetFillColorAlpha(2,0.00001);

// ================

   TCanvas *cn = new TCanvas("cn","cn",933,771);
   cn->SetTopMargin(0.068);
   cn->SetBottomMargin(0.183);
   cn->SetLeftMargin(0.13);
   cn->SetRightMargin(0.04);
   cn->SetTickx(1);
   cn->SetTicky(1);


   gr->Draw("AF");

}