STARLIGHT code and interface

[u/mrichter/AliRoot.git] / STARLIGHT / starlight / src / beam.cpp

diff --git a/STARLIGHT/starlight/src/beam.cpp b/STARLIGHT/starlight/src/beam.cpp
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+///////////////////////////////////////////////////////////////////////////
+//
+//    Copyright 2010
+//
+//    This file is part of starlight.
+//
+//    starlight is free software: you can redistribute it and/or modify
+//    it under the terms of the GNU General Public License as published by
+//    the Free Software Foundation, either version 3 of the License, or
+//    (at your option) any later version.
+//
+//    starlight is distributed in the hope that it will be useful,
+//    but WITHOUT ANY WARRANTY; without even the implied warranty of
+//    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+//    GNU General Public License for more details.
+//
+//    You should have received a copy of the GNU General Public License
+//    along with starlight. If not, see <http://www.gnu.org/licenses/>.
+//
+///////////////////////////////////////////////////////////////////////////
+//
+// File and Version Information:
+// $Rev:: 164                         $: revision of last commit
+// $Author:: odjuvsla                 $: author of last commit
+// $Date:: 2013-10-06 16:18:08 +0200 #$: date of last commit
+//
+// Description:
+//
+//
+//
+///////////////////////////////////////////////////////////////////////////
+
+
+#include <iostream>
+#include <fstream>
+#include <cmath>
+
+#include "starlightconstants.h"
+#include "inputParameters.h"
+#include "reportingUtils.h"
+#include "bessel.h"
+#include "beam.h"
+
+
+using namespace std;
+using namespace starlightConstants;
+
+//______________________________________________________________________________
+beam::beam(const int              Z_,
+           const int              A_,
+           const double           bdeuteron,
+           const bool             dAuCoherentProduction)
+       : nucleus(Z_,
+                 A_,
+                 bdeuteron,
+                 dAuCoherentProduction)
+       ,_beamLorentzGamma(inputParametersInstance.beamLorentzGamma())
+{
+}
+
+
+//______________________________________________________________________________
+beam::~beam()
+{ }
+
+
+//______________________________________________________________________________
+double beam::photonFlux(const double impactparameter, 
+                        const double photonEnergy) const
+{
+  // function for the calculation of the "photon density".
+  // photonFlux = number of photons / (energy * area)
+  // assume beta = 1 and gamma >> 1, i.e. neglect the (1 / gamma^2) * K_0(x) term
+  
+  const double X
+         = (impactparameter * photonEnergy) / (_beamLorentzGamma * hbarc);
+  if (X <= 0) 
+         printWarn << "X = " << X << endl;
+  
+  const double factor1 = (double(Z() * Z()) * alpha) / (pi * pi);  
+  const double factor2 = 1. / (photonEnergy * impactparameter * impactparameter);
+  const double bessel  = bessel::dbesk1(X);
+  const double factor3 = X * X * bessel * bessel;
+
+  return factor1 * factor2 * factor3;
+}