PndMvdAdvancedPidAlgo.cxx

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#include "TMath.h"
#include "TRandom3.h"
#include "PndMvdAdvancedPidAlgo.h"
#include "PndMvdPidCand.h"

//test

ClassImp(PndMvdAdvancedPidAlgo)

//public

void PndMvdAdvancedPidAlgo::CalcLikelihood(PndMvdPidCand* cand) {
  //computes pid likelihoods for pi, k, p, mu, e and stores them in the likelihood
  //map with the map key used as pdg id. This is basically done by integrating the
  //respective energy loss distribution within the chosen selector limits

  double weight[kNPidType];
  double dE=0;
  double dx=0;
  fmomentum=0;

  for (int k=0;k<cand->GetMvdHits(); k++) {
    dE+=cand->GetMvdHitdE(k);
    dx+=cand->GetMvdHitdx(k);
    fmomentum+=cand->GetMvdHitMomentum(k);
  }

  if (dx>0) {
    fmomentum/=cand->GetMvdHits();
    fenergyloss=dE/dx;
  } else
    fmomentum=-1; // whateva

  CalcLikelihood(weight);

  cand->SetLikelihood(2212, weight[kProton]);
  cand->SetLikelihood(211, weight[kPion]);
  cand->SetLikelihood(321, weight[kKaon]);
  cand->SetLikelihood(13, weight[kMuon]);
  cand->SetLikelihood(11, weight[kElectron]);
}

void PndMvdAdvancedPidAlgo::CalcLikelihood(PidType part, double momentum, PndMvdPidCand* cand) {
  double weight[kNPidType];
  CalcLikelihood(part, momentum, weight);
  cand->SetLikelihood(2212, weight[kProton]);
  cand->SetLikelihood(211, weight[kPion]);
  cand->SetLikelihood(321, weight[kKaon]);
  cand->SetLikelihood(13, weight[kMuon]);
  cand->SetLikelihood(11, weight[kElectron]);
}

//the following is a workaround interface for fastsim
void PndMvdAdvancedPidAlgo::CalcLikelihood(PidType part, double momentum, double* lh) {
  fmomentum=momentum;
  //Initialise random generator if not already done
  if (!frand)
    frand=new TRandom3();
  //Build random energy loss
  fenergyloss = MeanEnergyLoss(part) + mpv(part) + frand->Landau(0, width1(part)) + frand->Gaus(0, width2(part));
  CalcLikelihood(lh);
}

//same as above plus a pdtid switch
void PndMvdAdvancedPidAlgo::CalcLikelihood(int lundId, double momentum, double* lh) {
  switch(lundId) {
    case 2212: CalcLikelihood(kProton,   momentum, lh); break;
    case 321:  CalcLikelihood(kKaon,     momentum, lh); break;
    case 211:  CalcLikelihood(kPion,     momentum, lh); break;
    case 13:   CalcLikelihood(kMuon,     momentum, lh); break;
    case 11:   CalcLikelihood(kElectron, momentum, lh); break;
  }
}

//private

void PndMvdAdvancedPidAlgo::CalcLikelihood(double* lh) {
  if (fmomentum>=0 && fmomentum<=2.5) {
    for (PidType part=kElectron; part<=kProton;part=(PidType)(part+1))
      lh[part]=LandauGaus(fenergyloss - MeanEnergyLoss(part) - mpv(part), width1(part), width2(part));
  } else
    for (int part=kElectron;part<=kProton;part++)
      lh[part]=1;
  double sum=0;
  for (int part=kElectron;part<=kProton;part++)
    sum+=lh[part];
  for (int part=kElectron;part<=kProton;part++)
    lh[part]/=sum;
}


double PndMvdAdvancedPidAlgo::MeanEnergyLoss(PidType part) {
  //Calculate the lower boundary of the energy loss distribution.

  //[GeV]
  static float eb=0.14e-6;
  //[m/s]
  static float c=2.99792458e8;
  //[GeV/c**2]
  static float Mass[kNPidType]={ 0.511e-3, 0.1058, 0.1396, 0.4937, 0.9383 };

  double sqrBeta=1/(1+pow(Mass[part]/fmomentum,2));
  return 4.9312e-05 * (log(2*Mass[kElectron]*c*c/eb*sqrBeta/(1-sqrBeta))-sqrBeta)/sqrBeta;
};

double PndMvdAdvancedPidAlgo::LandauGaus(double s_mpv, double width1, double width2) {
  // this is the adapted TF1::Integral function from
  // ROOT 5.14. GOTOs have been removed and interval
  // division has been modified to maximize performance

  if (width1<=0)
    return TMath::Gaus(s_mpv, 0, width2, true);
  else if (width2<=0)
    return TMath::Landau(s_mpv, 0, width1, true);
  else {
    static double x[12] = { 0.96028985649753623,  0.79666647741362674,
                            0.52553240991632899,  0.18343464249564980,
                            0.98940093499164993,  0.94457502307323258,
                            0.86563120238783174,  0.75540440835500303,
                            0.61787624440264375,  0.45801677765722739,
                            0.28160355077925891,  0.09501250983763744};

    static double w[12] = { 0.10122853629037626,  0.22238103445337447,
                            0.31370664587788729,  0.36268378337836198,
                            0.02715245941175409,  0.06225352393864789,
                            0.09515851168249278,  0.12462897125553387,
                            0.14959598881657673,  0.16915651939500254,
                            0.18260341504492359,  0.18945061045506850};

    double h, bb, aa, c1, c2, u, s8, s16, f1, f2;
    double xx;
    bool redo=true;
    int i;

    h = 0;
    aa = -5.0*width2;
    bb = -2.5*width2;

    do {
      c1 = 0.5*(bb+aa);
      c2 = 0.5*(bb-aa);

      s8 = 0;
      for (i=0;i<4;i++) {
        u  = c2*x[i];
        xx = c1+u;
        f1 = TMath::Landau(s_mpv+xx, 0, width1, true)*TMath::Gaus(xx, 0, width2, true);
        xx = c1-u;
        f2 = TMath::Landau(s_mpv+xx, 0, width1, true)*TMath::Gaus(xx, 0, width2, true);
        s8+= w[i]*(f1 + f2);
      }
      s16 = 0;
      for (i=4;i<12;i++) {
        u   = c2*x[i];
        xx  = c1+u;
        f1  = TMath::Landau(s_mpv+xx, 0, width1, true)*TMath::Gaus(xx, 0, width2, true);
        xx  = c1-u;
        f2  = TMath::Landau(s_mpv+xx, 0, width1, true)*TMath::Gaus(xx, 0, width2, true);
        s16+= w[i]*(f1 + f2);
      }
      s16 = c2*s16;
      if (TMath::Abs(s16-c2*s8) <= 1e-12*(s16+1) ) {
        aa =bb;
        bb+=2*c2*1.5;
        if (bb>=5*width2) {
          bb=5*width2;
          redo=false;
        }
        h += s16;
      } else
        bb = c1;
    } while (redo);
    return h;
  }
}

double PndMvdAdvancedPidAlgo::mpv(PidType part) {
  double x=fmomentum;
  double x0=0;
  double x1=0;
  double c0=0;
  double c1=0;
  double d1=0;
  double a3=0;
  double a4=0;
  double a5=0;

  switch(part) {
  case kProton:
    x0 = 0.45;
    x1 = 1.3;
    c0 = 0.383451e-03;
    c1 = -0.126986e-03;
    d1 = -5.21351e-06;
    a3 = -3.05821;
    a4 = 24.6356;
    a5 = -68.632;
    break;
  case kKaon:
    x0 = 0.25;
    x1 = 1.05;
    c0 = 0.326259e-03;
    c1 = -7.68052e-05;
    d1 = 1.51033e-05;
    a3 = -19.6615;
    a4 = 264.382;
    a5 = -1238.09;
    break;
  case kPion:
    x0 = 0.1;
    x1 = 1.0;
    c0 = 0.274692e-03;
    c1 = 3.2571e-05;
    d1 = 9.16527e-06;
    a5 = -6624.05;
    break;
  case kMuon:
    x0 = 0.15;
    x1 = 1.15;
    a3 = 4.33244;
    a4 = -107.686;
    a5 = 699.522;
    c0 = 0.248749e-03;
    c1 = 6.57118e-05;
    d1 = -4.09447e-06;
    break;
  case kElectron:
    x1 = 1.20;
    c0 = 2.93999e-03;
    c1 = 1.76792e-05;
    break;
  }
  if (x>=x1)
    return c0+c1*(x1-x0)+d1*(x-x1);
  if (x>=x0)
    return c0+c1*(x-x0);
  else
    return c0+c1*(x-x0)+pow(x0-x,3)*(a3+(x0-x)*(a4+(x0-x)*a5));
}

double PndMvdAdvancedPidAlgo::width1(PidType part) {
  double x=fmomentum;
  switch(part) {
  case kProton:
    if (x>=1.10)
      return +3.81174e-04+x*(-2.25108e-04+x*+5.45154e-05);
    else
      return -5.28145e-05+x*(+8.29883e-04+x*-5.35972e-04);
    break;
  case kKaon:
    if (x>=1.05)
      return +2.61134e-04+x*(-1.30818e-04+x*+3.44165e-05);
    else
      return +3.41858e-04+x*(-3.21115e-04+x*+1.37459e-04);
    break;
  case kPion:
    if (x>=1.00)
      return +1.88718e-04+x*(-6.38948e-05+x*+1.78590e-05);
    else
      return +1.82872e-04+x*(-1.28373e-04+x*+8.01459e-05);
    break;
  case kMuon:
    if (x>=1.20)
      return +1.06142e-04+x*(+3.68777e-05+x*-1.00190e-05);
    else
      return +1.89374e-04+x*(-1.46441e-04+x*+9.10813e-05);
    break;
  case kElectron:
    if (x>1.2) x=1.2;
    // electrons are constant for momentum > 1.2GeV
    return +1.27955e-04+x*(-3.15732e-06+x*+9.64736e-06);
    break;
  }
  //TODO: what to return?
  return -999.;
}

double PndMvdAdvancedPidAlgo::width2(PidType part) {
  double x=fmomentum;
  switch(part) {
  case kProton:
    if (x>=1.10)
      return +6.41067e-04+x*(-3.82507e-04+x*+9.03732e-05);
    else
      return +6.40328e-04-3.21725e-04*x+3.17708e-05*pow(x,-3);
    break;
  case kKaon:
    if (x>=1.05)
      return +2.22504e-04+x*(-6.40051e-06+x*+2.14434e-06);
    else
      return +3.86684e-04-1.61873e-04*x+7.76586e-06*pow(x,-3);
    break;
  case kPion:
    if (x>=1.00)
      return +1.32999e-04+x*(+1.19714e-04+x*-3.53302e-05);
    else
      return +2.21603e-04-3.21357e-06*x+4.64793e-06*pow(x,-2);
    break;
  case kMuon:
   if (x>=1.20)
      return +7.84582e-05+x*(+1.88988e-04+x*-5.49637e-05);
    else
      return +1.67388e-04+5.67991e-05*x+3.42702e-06*pow(x,-2);
    break;
  case kElectron:
    if (x>1.2) x=1.2;
    // electrons are constant for momentum > 1.2GeV
    return +4.08849e-04-3.56548e-05*x+1.84825e-08*pow(x,-3);
    break;
  }
  //TODO: what to return?
  return -999.;
}

double PndMvdAdvancedPidAlgo::fmomentum;
double PndMvdAdvancedPidAlgo::fenergyloss;
TRandom3* PndMvdAdvancedPidAlgo::frand=0;