TLegend header's font size

How can I change the size of the font of the TLegend’s header? Thanks in advance.

{
   TFile f("hsimple.root");
   hpx->SetFillColor(48);
   hpx->SetMarkerStyle(20);
   hpx->SetMarkerSize(1);
   hpx->Draw("HP");
   TLegend *leg=new TLegend(0.2,0.2,0.4,0.4);
   leg->SetFillColor(0);
   leg->AddEntry(hpx,"hpx e^{-} #alpha #times","fp");
   leg->SetTextFont(132);
   leg->SetHeader("Legend");
   leg->SetTextFont(42);
   leg->Draw();
   TLegendEntry *header = (TLegendEntry*)leg->GetListOfPrimitives()->First();
   header->SetTextAlign(22);
   header->SetTextColor(2);
   header->SetTextSize(.09);
}