added a GbG LF calculator (standalone for now)

src/tests/GbG_LF/CMakeLists.txt

@@ -0,0 +1,11 @@
+cmake_minimum_required(VERSION 2.8)
+
+project(GbG_LF)
+
+set(DependOnLibs gsl)
+set(DependOnLibs gslcblas)
+
+add_executable(GbG_LF GbG_LF.cpp)
+
+target_link_libraries(GbG_LF gslcblas gsl)
+

src/tests/GbG_LF/GbG_LF.cpp

@@ -0,0 +1,116 @@
+#include <iostream>
+#include <fstream>
+#include <vector>
+using namespace std;
+
+#include <gsl/gsl_integration.h>
+
+#define GAMMA_BAR_MUON  1.35538817e-2
+#define TWO_PI 6.28318530717958647692528676656
+
+typedef struct {
+  double wExt;
+  double s0;
+  double s1;
+} fun_params;
+
+void syntax()
+{
+  cout << endl;
+  cout << "usage: GbG_LF Bext sigma0 sigmaGbG tmax fln" << endl;
+  cout << "       Bext in (G)" << endl;
+  cout << "       sigma0 in (1/us)" << endl;
+  cout << "       sigmaGbG in (1/us)" << endl;
+  cout << "       tmax in (us)" << endl;
+  cout << "       fln : output file name" << endl;
+  cout << endl << endl;
+}
+
+double pz_GbG_2(double x, void *param)
+{
+  fun_params *par = (fun_params*) param;
+  double s02 = par->s0 * par->s0;
+  double s12 = par->s1 * par->s1;
+  double x2 = x*x;
+  double aa = 1.0+x2*s12;
+
+  return 2.0*(s02*s02+3.0*s12*s12*aa*aa+6.0*s02*s12*aa)/(pow(par->wExt, 3.0)*pow(aa, 4.5))*exp(-0.5*s02*x2/aa);
+}
+
+int main(int argc, char *argv[])
+{
+  if (argc != 6) {
+    syntax();
+    return -1;
+  }
+
+  double Bext = atof(argv[1]);
+  double sigma0 = atof(argv[2]);
+  double sigma1 = atof(argv[3]);
+  double tmax = atof(argv[4]);
+
+  // calculate needed time step size
+  double dt = 1.0 / (GAMMA_BAR_MUON*Bext) / 10.0;
+  if (10.0/dt < 500.0)
+    dt = 0.02;
+  cout << "dt = " << dt << " (us)" << endl;
+
+  double wExt = TWO_PI * GAMMA_BAR_MUON * Bext;
+  double s0   = sigma0;
+  double s1   = sigma1;
+
+  double wExt2 = wExt*wExt;
+  double s02   = s0*s0;
+  double s12   = s1*s1;
+
+  gsl_integration_workspace *w = gsl_integration_workspace_alloc(65536);
+  gsl_function fun;
+  fun.function = &pz_GbG_2;
+  fun_params param = { wExt, s0, s1 };
+  fun.params = &param;
+
+  gsl_integration_qawo_table *tab = gsl_integration_qawo_table_alloc(wExt, tmax, GSL_INTEG_SINE, 16);
+
+  double result = 0.0, err = 0.0;
+  double t = 0.0, t2 = 0.0, dval=0.0, aa=0.0;
+  vector<double> time;
+  vector<double> pol, pol1, pol2;
+  do {
+    time.push_back(t);
+    t2 = t*t;
+
+    dval = 0.0;
+
+    // P_z^LF (GbG, 1st part)
+    aa = 1.0+t2*s12;
+    dval = 1.0 - 2.0*(s02+s12)/wExt2 + 2.0*(s02+s12*aa)/(wExt2*pow(aa,2.5))*cos(wExt*t)*exp(-0.5*s02*t2/aa);
+    pol1.push_back(dval);
+
+    // P_z^LF (GbG, 2nd part)
+    gsl_integration_qawo_table_set_length(tab, t);
+    gsl_integration_qawo(&fun, 0.0, 1.0e-9, 1.0e-9, 1024, w, tab, &result, &err);
+    pol2.push_back(result);
+    dval += result;
+
+    pol.push_back(dval);
+
+    t += dt;
+  } while (t <= tmax);
+
+  gsl_integration_workspace_free(w);
+  gsl_integration_qawo_table_free(tab);
+
+  ofstream fout(argv[5], ofstream::out);
+  fout << "% Bext (G)        : " << Bext << endl;
+  fout << "% sigma0 (1/us)   : " << sigma0 << endl;
+  fout << "% sigma1 (1/us)   : " << sigma1 << endl;
+  fout << "%----" << endl;
+  fout << "% time (us), pol1, pol2, pol" << endl;
+  for (unsigned int i=0; i<time.size(); i++) {
+    fout << time[i] << ", " << pol1[i] << ", " << pol2[i] << ", " << pol[i] << endl;
+  }
+
+  fout.close();
+
+  return 0;
+}