Index: trunk/Mars/msim/MPhotonData.cc
===================================================================
--- trunk/Mars/msim/MPhotonData.cc	(revision 18447)
+++ trunk/Mars/msim/MPhotonData.cc	(revision 18449)
@@ -63,5 +63,5 @@
     : fPosX(0), fPosY(0), fCosU(0), fCosV(0), fTime(0), fWavelength(0),
     /*fNumPhotons(1),*/ fProductionHeight(0), fPrimary(MMcEvtBasic::kUNDEFINED),
-    fTag(-1), fWeight(1)
+      fTag(-1), fWeight(1), fMirrorTag(-1)
 {
    // fName  = name  ? name  : "MPhotonData";
Index: trunk/Mars/msim/MPhotonData.h
===================================================================
--- trunk/Mars/msim/MPhotonData.h	(revision 18447)
+++ trunk/Mars/msim/MPhotonData.h	(revision 18449)
@@ -43,4 +43,5 @@
 
     Int_t   fTag;    //! A tag for external use
+    Int_t   fMirrorTag;    // Tag for the mirror ID of the mirror which was hit by this photon
     Float_t fWeight; //! A weight for external use
 
@@ -108,4 +109,7 @@
     Int_t GetTag() const { return fTag; }
 
+    void SetMirrorTag(Int_t mirrorTag) { fMirrorTag=mirrorTag; }
+    Int_t GetMirrorTag() const { return fMirrorTag; }
+
     // TObject
     //void Clear(Option_t * = NULL);