Coverity fix.

[u/mrichter/AliRoot.git] / STEER / AliMathBase.cxx

diff --git a/STEER/AliMathBase.cxx b/STEER/AliMathBase.cxx
index 2509074b9c3c340b33fdf76b7d13a1de9f8240c3..cdae2369d06d0477342b06bbae8e26c2f9a8c7d2 100644 (file)
--- a/STEER/AliMathBase.cxx
+++ b/STEER/AliMathBase.cxx
@@ -29,6 +29,8 @@
 #include "TF1.h"
 #include "TLinearFitter.h"
 
+#include "AliExternalTrackParam.h"
+
 //
 // includes neccessary for test functions
 //
@@ -552,6 +554,19 @@ Float_t AliMathBase::GetCOG(Short_t *arr, Int_t nBins, Float_t xMin, Float_t xMa
 }
 
 
+Double_t AliMathBase::ErfcFast(Double_t x){
+  // Fast implementation of the complementary error function
+  // The error of the approximation is |eps(x)| < 5E-4
+  // See Abramowitz and Stegun, p.299, 7.1.27
+
+  Double_t z = TMath::Abs(x);
+  Double_t ans = 1+z*(0.278393+z*(0.230389+z*(0.000972+z*0.078108)));
+  ans = 1.0/ans;
+  ans *= ans;
+  ans *= ans;
+
+  return (x>=0.0 ? ans : 2.0 - ans);
+}
 
 ///////////////////////////////////////////////////////////////
 //////////////         TEST functions /////////////////////////
@@ -759,15 +774,14 @@ Double_t AliMathBase::BetheBlochAleph(Double_t bg,
          Double_t kp4,
          Double_t kp5) {
   //
-  // This is the ALEPH parameterisation of the Bethe-Bloch formula
+  // This is the empirical ALEPH parameterization of the Bethe-Bloch formula.
+  // It is normalized to 1 at the minimum.
+  //
+  // bg - beta*gamma
+  // 
+  // The default values for the kp* parameters are for ALICE TPC.
+  // The returned value is in MIP units
   //
 
-  Double_t beta = bg/TMath::Sqrt(1.+ bg*bg);
-
-  Double_t aa = TMath::Power(beta,kp4);
-  Double_t bb = TMath::Power(1./bg,kp5);
-
-  bb=TMath::Log(kp3+bb);
-  
-  return (kp2-aa-bb)*kp1/aa;
+  return AliExternalTrackParam::BetheBlochAleph(bg,kp1,kp2,kp3,kp4,kp5);
 }