ConeDefinition.h

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#ifndef ConeDefinition_h
#define ConeDefinition_h

#include "DataFormats/GeometryVector/interface/GlobalPoint.h"
#include "DataFormats/GeometryVector/interface/GlobalVector.h"

#include "CommonTools/UtilAlgos/interface/DeltaR.h"

inline double getDistInPlaneSimple(const GlobalPoint caloPoint, const GlobalPoint rechitPoint) {
  // Simplified version of getDistInPlane
  // Assume track direction is origin -> point of hcal intersection

  const GlobalVector caloIntersectVector(caloPoint.x(), caloPoint.y(), caloPoint.z());

  const GlobalVector caloIntersectUnitVector = caloIntersectVector.unit();

  const GlobalVector rechitVector(rechitPoint.x(), rechitPoint.y(), rechitPoint.z());

  const GlobalVector rechitUnitVector = rechitVector.unit();
  double dotprod = caloIntersectUnitVector.dot(rechitUnitVector);
  double rechitdist = caloIntersectVector.mag() / dotprod;

  const GlobalVector effectiveRechitVector = rechitdist * rechitUnitVector;
  const GlobalPoint effectiveRechitPoint(
      effectiveRechitVector.x(), effectiveRechitVector.y(), effectiveRechitVector.z());

  GlobalVector distance_vector = effectiveRechitPoint - caloPoint;

  if (dotprod > 0.) {
    return distance_vector.mag();
  } else {
    return 999999.;
  }
}

inline double getDistInPlaneTrackDir(const GlobalPoint caloPoint,
                                     const GlobalVector caloVector,
                                     const GlobalPoint rechitPoint) {
  // Simplified version of getDistInPlane : no cone "within" Hcal, but
  // don't assume track direction is origin -> point of hcal
  // intersection.
  const GlobalVector caloIntersectVector(caloPoint.x(), caloPoint.y(),
                                         caloPoint.z());  //p

  const GlobalVector caloUnitVector = caloVector.unit();
  const GlobalVector rechitVector(rechitPoint.x(), rechitPoint.y(), rechitPoint.z());
  const GlobalVector rechitUnitVector = rechitVector.unit();
  double dotprod_denominator = caloUnitVector.dot(rechitUnitVector);
  double dotprod_numerator = caloUnitVector.dot(caloIntersectVector);
  double rechitdist = dotprod_numerator / dotprod_denominator;
  //  double rechitdist=caloIntersectVector.dot(rechitUnitVector);
  const GlobalVector effectiveRechitVector = rechitdist * rechitUnitVector;
  const GlobalPoint effectiveRechitPoint(
      effectiveRechitVector.x(), effectiveRechitVector.y(), effectiveRechitVector.z());
  GlobalVector distance_vector = effectiveRechitPoint - caloPoint;
  if (dotprod_denominator > 0. && dotprod_numerator > 0.) {
    return distance_vector.mag();
  } else {
    return 999999.;
  }
}

inline double getDistInPlane(const GlobalVector trackDirection,
                             const GlobalPoint caloPoint,
                             const GlobalPoint rechitPoint,
                             double coneHeight) {
  // The iso track candidate hits the Calo (Ecal or Hcal) at "caloPoint"
  // with direction "trackDirection".

  // "rechitPoint" is the position of the rechit.  We only care about
  // the direction of the rechit.

  // Consider the rechitPoint as characterized by angles theta and phi
  // wrt the origin which points at the calo cell of the rechit.  In
  // some sense the distance along the line theta/phi is arbitrary. A
  // simplified choice might be to put the rechit at the surface of
  // the Hcal.  Our approach is to see whether/where this line
  // intersects a cone of height "coneHeight" with vertex at caloPoint
  // aligned with trackDirection.
  // To that end, this function returns the distance between the
  // center of the base of the cone and the intersection of the rechit
  // line and the plane that contains the base of the cone.  This
  // distance is compared with the radius of the cone outside this
  // function.

  // Make vector of length cone height along track direction
  const GlobalVector heightVector = trackDirection * coneHeight;

  // Make vector from origin to point where iso track intersects the
  // calorimeter.
  const GlobalVector caloIntersectVector(caloPoint.x(), caloPoint.y(), caloPoint.z());

  // Make vector from origin to point in center of base of cone
  const GlobalVector coneBaseVector = heightVector + caloIntersectVector;

  // Make point in center of base of cone
  const GlobalPoint coneBasePoint(coneBaseVector.x(), coneBaseVector.y(), coneBaseVector.z());

  // Make unit vector pointing at rechit.
  const GlobalVector rechitVector(rechitPoint.x(), rechitPoint.y(), rechitPoint.z());
  const GlobalVector rechitDirection = rechitVector.unit();

  // Find distance "r" along "rechit line" (with angles theta2 and
  // phi2) where line intersects plane defined by base of cone.

  // Definition plane of that contains base of cone:
  // trackDirection.x() (x - coneBaseVector.x()) +
  // trackDirection.y() (y - coneBaseVector.y()) +
  // trackDirection.z() (z - coneBaseVector.z()) = 0

  // Point P_{rh} where rechit line intersects plane:
  // (rechitdist sin(theta2) cos(phi2),
  //  rechitdist sin(theta2) cos(phi2),
  //  rechitdist cos(theta2))

  // Substitute P_{rh} into equation for plane and solve for rechitdist.
  // rechitDist turns out to be the ratio of dot products:

  double rechitdist = trackDirection.dot(coneBaseVector) / trackDirection.dot(rechitDirection);

  // Now find distance between point at center of cone base and point
  // where the "rechit line" intersects the plane defined by the base
  // of the cone; i.e. the effectiveRecHitPoint.
  const GlobalVector effectiveRechitVector = rechitdist * rechitDirection;
  const GlobalPoint effectiveRechitPoint(
      effectiveRechitVector.x(), effectiveRechitVector.y(), effectiveRechitVector.z());

  GlobalVector distance_vector = effectiveRechitPoint - coneBasePoint;
  return distance_vector.mag();
}

#endif