MuonFInteraction.cpp

Go to the documentation of this file.

// Mantid Repository : https://github.com/mantidproject/mantid
//
// Copyright © 2018 ISIS Rutherford Appleton Laboratory UKRI,
//   NScD Oak Ridge National Laboratory, European Spallation Source,
//   Institut Laue - Langevin & CSNS, Institute of High Energy Physics, CAS
// SPDX - License - Identifier: GPL - 3.0 +
//----------------------------------------------------------------------
// Includes
//----------------------------------------------------------------------
#include "MantidCurveFitting/Functions/MuonFInteraction.h"
#include "MantidAPI/FunctionFactory.h"
#include <cmath>
 
namespace Mantid::CurveFitting::Functions {
 
using namespace CurveFitting;
 
using namespace Kernel;
 
using namespace API;
 
DECLARE_FUNCTION(MuonFInteraction)
 
void MuonFInteraction::init() {
  declareParameter("Lambda", 0.2, "decay rate");
  declareParameter("Omega", 0.5, "angular frequency");
  declareParameter("Beta", 1, "exponent");
  declareParameter("A", 1, "Amplitude at 0");
}
 
void MuonFInteraction::function1D(double *out, const double *xValues, const size_t nData) const {
  const double lambda = getParameter("Lambda");
  const double omega = getParameter("Omega");
  const double beta = getParameter("Beta");
  const double A = getParameter("A");
  const double sqrt3 = sqrt(3.0);
 
  for (size_t i = 0; i < nData; i++) {
    double A1 = exp(-pow(lambda * xValues[i], beta)) * A / 6;
    double A2 = cos(sqrt3 * omega * xValues[i]);
    double A3 = (1.0 - 1.0 / sqrt3) * cos(((3.0 - sqrt3) / 2.0) * omega * xValues[i]);
    double A4 = (1.0 + 1.0 / sqrt3) * cos(((3.0 + sqrt3) / 2.0) * omega * xValues[i]);
 
    out[i] = A1 * (3 + A2 + A3 + A4);
  }
}
 
} // namespace Mantid::CurveFitting::Functions