PrecisionUtil.h

/**************************************************************************
 * basf2 (Belle II Analysis Software Framework)                           *
 * Author: The Belle II Collaboration                                     *
 *                                                                        *
 * See git log for contributors and copyright holders.                    *
 * This file is licensed under LGPL-3.0, see LICENSE.md.                  *
 **************************************************************************/
#pragma once
 
#include <framework/logging/Logger.h>
#include <functional>
#include <cmath>
 
namespace Belle2 {
  namespace TrackFindingCDC {

    class PrecisionUtil {
 
    public: // Auxiliary stuff
      static constexpr int getLookupGridLevel() {return c_lookupGridLevel; };

      static constexpr const int c_lookupGridLevel = 16;

      static double convertRhoToPt(double curv) {return 1.5 * 0.00299792458 / fabs(curv); };
 
    public: // Variations of precision functions
      using PrecisionFunction = std::function<double(double)>;

      static double getBasicCurvPrecision(double __attribute__((unused)) curv)
      {
        // 0.3 is the width of the Legendre phase-space in curvatures direction.
        return 0.3 / pow(2, 16);
      }

      static double getOriginCurvPrecision(double curv)
      {
        // Convert to pt making the cut-off of that has been here before
        double pt = convertRhoToPt(curv);
        if (not(pt <= 3.0)) {
          pt = 3.0;
        }
 
        double precision = exp(-16.1987 * pt - 5.96206) + 0.000190872 - 0.0000739319 * pt;
 
        /* 10.5 - 0.24 * exp(-4.13118 * convertRhoToPt(curv) + 2.74); */
        B2DEBUG(25, "origin: precision = " << precision << "; curv = " << curv);
        return precision;
      }

      static double getNonOriginCurvPrecision(double curv)
      {
        // Convert to pt making the cut-off of that has been here before
        double pt = convertRhoToPt(curv);
        if (not(pt <= 3.0)) {
          pt = 3.0;
        }
 
        double precision{};
        if (pt < 0.36) {
          precision = exp(-0.356965 - 0.00186066 * pt) - 0.697526;
        } else {
          precision = exp(-0.357335 + 0.000438872 * pt) - 0.697786;
        }
 
        B2DEBUG(25, "non origin: precision = " << precision << "; curv = " << curv);
        return precision;
      }
    };
  }
}