Index: trunk/MagicSoft/Mars/mbase/MMath.cc
===================================================================
--- trunk/MagicSoft/Mars/mbase/MMath.cc	(revision 7384)
+++ trunk/MagicSoft/Mars/mbase/MMath.cc	(revision 7386)
@@ -139,5 +139,5 @@
 {
     Double_t Ns = s - alpha*b;
-    Double_t sN = s - alpha*alpha*b;
+    Double_t sN = s + alpha*alpha*b;
 
     return Ns<0 || sN<0 ? 0 : Ns/TMath::Sqrt(sN);