Use for PID in ITS the Bethe Bloch from AliExternalTrackParam

[u/mrichter/AliRoot.git] / ITS / AliITSpidESD.cxx

diff --git a/ITS/AliITSpidESD.cxx b/ITS/AliITSpidESD.cxx
index 2d4a26a1490c9635b58d825049fbcce09a4e9158..4c6c0572e34de4d8d1638f63c62b09f6c5f78030 100644 (file)
--- a/ITS/AliITSpidESD.cxx
+++ b/ITS/AliITSpidESD.cxx
@@ -13,6 +13,8 @@
  * provided "as is" without express or implied warranty.                  *
  **************************************************************************/
 
+/* $Id$ */
+
 //-----------------------------------------------------------------
 //           Implementation of the ITS PID class
 // Very naive one... Should be made better by the detector experts...
@@ -23,6 +25,7 @@
 
 #include "AliITSpidESD.h"
 #include "AliESDtrack.h"
+#include "AliExternalTrackParam.h"
 
 ClassImp(AliITSpidESD)
 
@@ -32,16 +35,14 @@ AliITSpidESD::AliITSpidESD():TObject(){
   //Default constructor
  
 }
-Double_t AliITSpidESD::Bethe(Double_t bg) {
-  //
-  // This is the Bethe-Bloch function normalised to 1 at the minimum
-  //
-  Double_t bg2=bg*bg;
-  Double_t bethe;
-  /*if (bg<3.5) 
-     bethe=(1.+ bg2)/bg2*(log(5940*bg2) - bg2/(1.+ bg2));
-  else*/  // not 100% clear why...
-  bethe=(1.+ bg2)/bg2*(TMath::Log(3.5*5940*bg) - bg2/(1.+ bg2));
-  return bethe/11.091;
-}
 
+Double_t AliITSpidESD::Bethe(Double_t p,Double_t mass) {
+  // returns AliExternalTrackParam::BetheBloch normalized to 1 at the minimum
+  Double_t density=2.33; // g/cm3
+  Double_t thickness=0.03; // cm
+  Double_t meanMIPSi=116.24; // keV in 300 microns of Si
+  Double_t conv=density*1E6*thickness/meanMIPSi;
+  Float_t betagamma=p/mass;
+  return conv*AliExternalTrackParam::BetheBlochSolid(betagamma);
+
+}