Density effect added (Yu.Belikov)

diff --git a/TPC/AliTPCpidESD.cxx b/TPC/AliTPCpidESD.cxx
index 32a21190560223088b5bd2ec582b303f3b887978..29f447e44dc992f28dde842b3cc96a1d90888736 100644 (file)
--- a/TPC/AliTPCpidESD.cxx
+++ b/TPC/AliTPCpidESD.cxx
@@ -41,7 +41,11 @@ Double_t AliTPCpidESD::Bethe(Double_t bg) {
   // This is the Bethe-Bloch function normalised to 1 at the minimum
   //
   Double_t bg2=bg*bg;
-  Double_t bethe=(1.+ bg2)/bg2*(log(5940*bg2) - bg2/(1.+ bg2));
+  Double_t bethe;
+  if (bg<3.5e1) 
+      bethe=(1.+ bg2)/bg2*(log(5940*bg2) - bg2/(1.+ bg2));
+  else // Density effect ( approximately :) 
+      bethe=1.15*(1.+ bg2)/bg2*(log(3.5*5940*bg) - bg2/(1.+ bg2));
   return bethe/11.091;
 }