CbmLitMath.cxx

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/* Copyright (C) 2008-2017 GSI/JINR-LIT, Darmstadt/Dubna
   SPDX-License-Identifier: GPL-3.0-only
   Authors: Andrey Lebedev [committer], Timur Ablyazimov */
 
#include "utils/CbmLitMath.h"
 
#include "data/CbmLitHit.h"
#include "data/CbmLitPixelHit.h"
#include "data/CbmLitStripHit.h"
#include "data/CbmLitTrack.h"
#include "data/CbmLitTrackParam.h"
 
#include <cmath>
#include <iostream>
 
namespace lit
{
 
  litfloat ChiSq(const CbmLitTrackParam* par, const CbmLitHit* hit)
  {
    litfloat chisq = 0.;
    if (hit->GetType() == kLITSTRIPHIT) {
      chisq = ChiSq(par, static_cast<const CbmLitStripHit*>(hit));
    }
    else if (hit->GetType() == kLITPIXELHIT) {
      chisq = ChiSq(par, static_cast<const CbmLitPixelHit*>(hit));
    }
    return chisq;
  }
 
  litfloat ChiSq(const CbmLitTrackParam* par, const CbmLitStripHit* hit)
  {
    litfloat duu        = hit->GetDu() * hit->GetDu();
    litfloat phiCos     = hit->GetCosPhi();
    litfloat phiSin     = hit->GetSinPhi();
    litfloat phiCosSq   = phiCos * phiCos;
    litfloat phiSinSq   = phiSin * phiSin;
    litfloat phi2SinCos = 2 * phiCos * phiSin;
    litfloat C0         = par->GetCovariance(0);
    litfloat C1         = par->GetCovariance(1);
    litfloat C5         = par->GetCovariance(5);
 
    litfloat ru = hit->GetU() - par->GetX() * phiCos - par->GetY() * phiSin;
 
    return (ru * ru) / (duu - phiCosSq * C0 - phi2SinCos * C1 - phiSinSq * C5);
  }
 
  litfloat ChiSq(const CbmLitTrackParam* par, const CbmLitPixelHit* hit)
  {
    litfloat dxx = hit->GetDx() * hit->GetDx();
    litfloat dxy = hit->GetDxy();
    litfloat dyy = hit->GetDy() * hit->GetDy();
    litfloat dtt = hit->GetDt() * hit->GetDt();
    litfloat xmx = hit->GetX() - par->GetX();
    litfloat ymy = hit->GetY() - par->GetY();
    litfloat tmt = hit->GetT() - par->GetTime();
    litfloat C0  = par->GetCovariance(0);
    litfloat C1  = par->GetCovariance(1);
    litfloat C5  = par->GetCovariance(5);
    litfloat C6  = par->GetCovariance(6);
    litfloat C10 = par->GetCovariance(10);
    litfloat C20 = par->GetCovariance(20);
 
    /*litfloat norm = dxx * dyy - dxx * C5 - dyy * C0 + C0 * C5
              - dxy * dxy + 2 * dxy * C1 - C1 * C1;
   if (norm == 0.) { norm = 1e-10; }
   return ((xmx * (dyy - C5) - ymy * (dxy - C1)) * xmx
           +(-xmx * (dxy - C1) + ymy * (dxx - C0)) * ymy) / norm;*/
    litfloat norm = (dxx - C0) * ((dyy - C6) * (dtt - C20) - C10 * C10)
                    + (dxy - C1) * (C5 * C10 - (dxy - C1) * (dtt - C20)) + C5 * ((dxy - C1) * C10 - (dyy - C6) * C5);
 
    if (norm == 0.) {
      norm = 1e-10;
    }
 
    // Mij is the (symmetric) inverse of the residual matrix
    litfloat M00 = ((dyy - C6) * (dtt - C20) - C10 * C10) / norm;
    litfloat M01 = ((dxy - C1) * (dtt - C20) - C5 * C10) / norm;
    litfloat M02 = ((dxy - C1) * C10 - (dyy - C6) * C5) / norm;
    litfloat M11 = ((dxx - C0) * (dtt - C20) - C5 * C5) / norm;
    litfloat M12 = ((dxx - C0) * C10 - (dxy - C1) * C5) / norm;
    litfloat M22 = ((dxx - C0) * (dyy - C6) - (dxy - C1) * (dxy - C1)) / norm;
 
    return xmx * (xmx * M00 + ymy * M01 + tmt * M02) + ymy * (xmx * M01 + ymy * M11 + tmt * M12)
           + tmt * (xmx * M02 + ymy * M12 + tmt * M22);
  }
 
  Int_t NDF(const CbmLitTrack* track)
  {
    Int_t ndf = 0;
    for (Int_t i = 0; i < track->GetNofHits(); i++) {
      if (track->GetHit(i)->GetType() == kLITPIXELHIT) {
        ndf += 2;
      }
      else if (track->GetHit(i)->GetType() == kLITSTRIPHIT) {
        ndf++;
      }
    }
    ndf -= 5;
    if (ndf > 0) {
      return ndf;
    }
    else {
      return 1;
    }
  }
 
}  // namespace lit