TangentApproachInRPhi Class Reference

#include <TangentApproachInRPhi.h>

Inheritance diagram for TangentApproachInRPhi:

Public Member Functions
virtual bool	calculate (const TrajectoryStateOnSurface &sta, const TrajectoryStateOnSurface &stb)
virtual bool	calculate (const FreeTrajectoryState &sta, const FreeTrajectoryState &stb)
virtual TangentApproachInRPhi *	clone () const
virtual GlobalPoint	crossingPoint () const
virtual float	distance () const
float	perpdist () const
virtual std::pair< GlobalPoint, GlobalPoint >	points () const
virtual bool	status () const
	TangentApproachInRPhi ()
std::pair< GlobalTrajectoryParameters, GlobalTrajectoryParameters >	trajectoryParameters () const
Public Member Functions inherited from ClosestApproachOnHelices
	ClosestApproachOnHelices ()
virtual	~ClosestApproachOnHelices ()

Private Member Functions
bool	calculate (const TrackCharge &chargeA, const GlobalVector &momentumA, const GlobalPoint &positionA, const TrackCharge &chargeB, const GlobalVector &momentumB, const GlobalPoint &positionB, const MagneticField &magField)
void	circleParameters (const TrackCharge &charge, const GlobalVector &momemtum, const GlobalPoint &position, double &xc, double &yc, double &r, const MagneticField &magField) const
GlobalTrajectoryParameters	trajectoryParameters (const GlobalPoint &newpt, const GlobalTrajectoryParameters &oldpar) const
int	transverseCoord (double cxa, double cya, double ra, double cxb, double cyb, double rb, double &xg1, double &yg1, double &xg2, double &yg2) const
double	zCoord (const GlobalVector &mom, const GlobalPoint &pos, double r, double xc, double yc, double xg, double yg) const

Private Attributes
bool	intersection_
GlobalTrajectoryParameters	paramA
GlobalTrajectoryParameters	paramB
GlobalPoint	posA
GlobalPoint	posB
bool	status_

Detailed Description

Given two trajectory states, computes the two points of tangent approach in the transverse plane for the helices extrapolated from these states. 1) computes the tangent points of the circles in transverse plane. Two cases: - Whether or not the circles intersect the points used are the points of tangent approach of the two circles. 2) computes the corresponding z-coordinates.

Definition at line 15 of file TangentApproachInRPhi.h.

Constructor & Destructor Documentation

TangentApproachInRPhi::TangentApproachInRPhi ( )

inline

Definition at line 19 of file TangentApproachInRPhi.h.

References calculate(), intersection_, and status_.

Referenced by clone().

{status_ = false; intersection_ = false;}

Member Function Documentation

bool TangentApproachInRPhi::calculate ( const TrajectoryStateOnSurface &  sta, const TrajectoryStateOnSurface &  stb  )

virtual

Implements ClosestApproachOnHelices.

Definition at line 7 of file TangentApproachInRPhi.cc.

References TrajectoryStateOnSurface::charge(), TrajectoryStateOnSurface::freeState(), TrajectoryStateOnSurface::globalMomentum(), TrajectoryStateOnSurface::globalParameters(), TrajectoryStateOnSurface::globalPosition(), GlobalTrajectoryParameters::magneticField(), and FreeTrajectoryState::parameters().

Referenced by clone(), ConversionProducer::preselectTrackPair(), and TangentApproachInRPhi().

{
  TrackCharge chargeA = sta.charge(); TrackCharge chargeB = stb.charge();
  GlobalVector momentumA = sta.globalMomentum();
  GlobalVector momentumB = stb.globalMomentum();
  GlobalPoint positionA = sta.globalPosition();
  GlobalPoint positionB = stb.globalPosition();
  paramA = sta.globalParameters();
  paramB = stb.globalParameters();

  return calculate(chargeA, momentumA, positionA, chargeB, momentumB, positionB, 
    sta.freeState()->parameters().magneticField());
}

bool TangentApproachInRPhi::calculate ( const FreeTrajectoryState &  sta, const FreeTrajectoryState &  stb  )

virtual

Implements ClosestApproachOnHelices.

Definition at line 23 of file TangentApproachInRPhi.cc.

References FreeTrajectoryState::charge(), GlobalTrajectoryParameters::magneticField(), FreeTrajectoryState::momentum(), FreeTrajectoryState::parameters(), and FreeTrajectoryState::position().

{
  TrackCharge chargeA = sta.charge(); TrackCharge chargeB = stb.charge();
  GlobalVector momentumA = sta.momentum();
  GlobalVector momentumB = stb.momentum();
  GlobalPoint positionA = sta.position();
  GlobalPoint positionB = stb.position();
  paramA = sta.parameters();
  paramB = stb.parameters();

  return calculate(chargeA, momentumA, positionA, chargeB, momentumB, positionB,
    sta.parameters().magneticField());
}

bool TangentApproachInRPhi::calculate ( const TrackCharge &  chargeA, const GlobalVector &  momentumA, const GlobalPoint &  positionA, const TrackCharge &  chargeB, const GlobalVector &  momentumB, const GlobalPoint &  positionB, const MagneticField &  magField  )

private

Definition at line 80 of file TangentApproachInRPhi.cc.

References RemoveAddSevLevel::flag.

{

  // centres and radii of track circles
  double xca, yca, ra;
  circleParameters(chargeA, momentumA, positionA, xca, yca, ra, magField);
  double xcb, ycb, rb;
  circleParameters(chargeB, momentumB, positionB, xcb, ycb, rb, magField);

  // points of closest approach in transverse plane
  double xg1, yg1, xg2, yg2;
  int flag = transverseCoord(xca, yca, ra, xcb, ycb, rb, xg1, yg1, xg2, yg2);
  if (flag == 0) {
    status_ = false;
    return false;
  }

  double xga, yga, zga, xgb, ygb, zgb;

  if (flag == 1) {
    intersection_ = true;
  }
  else {
    intersection_ = false;
  }

  // one point of closest approach on each track in transverse plane
  xga = xg1; yga = yg1;
  zga = zCoord(momentumA, positionA, ra, xca, yca, xga, yga);
  xgb = xg2; ygb = yg2;
  zgb = zCoord(momentumB, positionB, rb, xcb, ycb, xgb, ygb);


  posA = GlobalPoint(xga, yga, zga);
  posB = GlobalPoint(xgb, ygb, zgb);
  status_ = true;
  return true;
}

void TangentApproachInRPhi::circleParameters ( const TrackCharge &  charge, const GlobalVector &  momemtum, const GlobalPoint &  position, double &  xc, double &  yc, double &  r, const MagneticField &  magField  ) const

private

temporary code, to be replaced by call to curvature() when bug is fixed.

end of temporary code

Definition at line 165 of file TangentApproachInRPhi.cc.

References funct::abs(), funct::cos(), MagneticField::inTesla(), PV3DBase< T, PVType, FrameType >::phi(), funct::sin(), PV3DBase< T, PVType, FrameType >::transverse(), PV3DBase< T, PVType, FrameType >::x(), PV3DBase< T, PVType, FrameType >::y(), and PV3DBase< T, PVType, FrameType >::z().

Referenced by clone().

{

  // compute radius of circle
//   double bz = MagneticField::inInverseGeV(position).z();
  double bz = magField.inTesla(position).z() * 2.99792458e-3;

  // signed_r directed towards circle center, along F_Lorentz = q*v X B
  double signed_r = charge*momentum.transverse() / bz;
  r = abs(signed_r);
  // compute centre of circle
  double phi = momentum.phi();
  xc = signed_r*sin(phi) + position.x();
  yc = -signed_r*cos(phi) + position.y();

}

virtual TangentApproachInRPhi* TangentApproachInRPhi::clone ( void  ) const

inlinevirtual

Clone method

Implements ClosestApproachOnHelices.

Definition at line 51 of file TangentApproachInRPhi.h.

References calculate(), ALCARECOTkAlJpsiMuMu_cff::charge, circleParameters(), position, alignCSCRings::r, TangentApproachInRPhi(), trajectoryParameters(), transverseCoord(), and zCoord().

                                                {
    return new TangentApproachInRPhi(* this);
  }

GlobalPoint TangentApproachInRPhi::crossingPoint ( ) const

virtual

arithmetic mean of the two points of closest approach

Implements ClosestApproachOnHelices.

Definition at line 47 of file TangentApproachInRPhi.cc.

References Exception.

Referenced by ConversionProducer::preselectTrackPair(), and status().

{
  if (!status_)
    throw cms::Exception("TrackingTools/PatternTools","TangentApproachInRPhi::could not compute track crossing. Check status before calling this method!");
  return GlobalPoint((posA.x() + posB.x())/2., 
             (posA.y() + posB.y())/2., 
             (posA.z() + posB.z())/2.);
}

float TangentApproachInRPhi::distance ( ) const

virtual

distance between the two points of closest approach in 3D

Implements ClosestApproachOnHelices.

Definition at line 57 of file TangentApproachInRPhi.cc.

References Exception.

Referenced by status().

{
  if (!status_)
    throw cms::Exception("TrackingTools/PatternTools","TangentApproachInRPhi::could not compute track crossing. Check status before calling this method!");
  return (posB - posA).mag();
}

float TangentApproachInRPhi::perpdist

(

)

const

signed distance between two points of closest approach in r-phi plane (-ive if circles intersect)

Definition at line 64 of file TangentApproachInRPhi.cc.

References Exception, and perp().

Referenced by ConversionProducer::preselectTrackPair(), and status().

{
  if (!status_)
    throw cms::Exception("TrackingTools/PatternTools","TangentApproachInRPhi::could not compute track crossing. Check status before calling this method!");
  
  float perpdist = (posB - posA).perp();
  
  if (intersection_) {
    perpdist = -perpdist;
  }
  
  return perpdist;
  
}

pair< GlobalPoint, GlobalPoint > TangentApproachInRPhi::points ( ) const

virtual

Returns the two PCA on the trajectories.

Implements ClosestApproachOnHelices.

Definition at line 38 of file TangentApproachInRPhi.cc.

References Exception.

Referenced by status().

{
  if (!status_)
    throw cms::Exception("TrackingTools/PatternTools","TangentApproachInRPhi::could not compute track crossing. Check status before calling this method!");
  return  pair<GlobalPoint, GlobalPoint> (posA, posB);
}

virtual bool TangentApproachInRPhi::status ( void  ) const

inlinevirtual

Implements ClosestApproachOnHelices.

Definition at line 27 of file TangentApproachInRPhi.h.

References crossingPoint(), distance(), perpdist(), points(), status_, and trajectoryParameters().

Referenced by ConversionProducer::preselectTrackPair().

{return status_;}

pair< GlobalTrajectoryParameters, GlobalTrajectoryParameters > TangentApproachInRPhi::trajectoryParameters

(

)

const

Returns not only the points, but the full GlobalTrajectoryParemeters at the points of closest approach

Definition at line 126 of file TangentApproachInRPhi.cc.

References Exception.

Referenced by clone(), ConversionProducer::preselectTrackPair(), and status().

{
  if (!status_)
    throw cms::Exception("TrackingTools/PatternTools","TangentApproachInRPhi::could not compute track crossing. Check status before calling this method!");
  pair <GlobalTrajectoryParameters, GlobalTrajectoryParameters> 
    ret ( trajectoryParameters ( posA, paramA ),
          trajectoryParameters ( posB, paramB ) );
  return ret;
}

GlobalTrajectoryParameters TangentApproachInRPhi::trajectoryParameters ( const GlobalPoint &  newpt, const GlobalTrajectoryParameters &  oldpar  ) const

private

Definition at line 136 of file TangentApproachInRPhi.cc.

References GlobalTrajectoryParameters::charge(), GlobalTrajectoryParameters::magneticField(), GlobalTrajectoryParameters::momentum(), GlobalTrajectoryParameters::position(), alignCSCRings::r, mathSSE::sqrt(), PV3DBase< T, PVType, FrameType >::x(), PV3DBase< T, PVType, FrameType >::y(), and PV3DBase< T, PVType, FrameType >::z().

{
  // First we need the centers of the circles.
  double xc, yc, r;
  circleParameters( oldgtp.charge(), oldgtp.momentum(),
      oldgtp.position(), xc, yc, r, oldgtp.magneticField()  );

  // now we do a translation, move the center of circle to (0,0,0).
  double dx1 = oldgtp.position().x() - xc;
  double dy1 = oldgtp.position().y() - yc;
  double dx2 = newpt.x() - xc;
  double dy2 = newpt.y() - yc;

  // now for the angles:
  double cosphi = ( dx1 * dx2 + dy1 * dy2 ) / 
    ( sqrt ( dx1 * dx1 + dy1 * dy1 ) * sqrt ( dx2 * dx2 + dy2 * dy2 ));
  double sinphi = - oldgtp.charge() * sqrt ( 1 - cosphi * cosphi );

  // Finally, the new momenta:
  double px = cosphi * oldgtp.momentum().x() - sinphi * oldgtp.momentum().y();
  double py = sinphi * oldgtp.momentum().x() + cosphi * oldgtp.momentum().y();

  GlobalVector vta ( px, py, oldgtp.momentum().z() );
  GlobalTrajectoryParameters gta( newpt , vta , oldgtp.charge(), &(oldgtp.magneticField()) );
  return gta;
}

int TangentApproachInRPhi::transverseCoord ( double  cxa, double  cya, double  ra, double  cxb, double  cyb, double  rb, double &  xg1, double &  yg1, double &  xg2, double &  yg2  ) const

private

Definition at line 195 of file TangentApproachInRPhi.cc.

References funct::abs(), RemoveAddSevLevel::flag, Validation_hcalonly_cfi::sign, mathSSE::sqrt(), and findQualityFiles::v.

Referenced by clone().

{
  int flag = 0;
  double x1, y1, x2, y2;

  // new reference frame with origin in (cxa, cya) and x-axis 
  // directed from (cxa, cya) to (cxb, cyb)

  double d_ab = sqrt((cxb - cxa)*(cxb - cxa) + (cyb - cya)*(cyb - cya));
  if (d_ab == 0) { // concentric circles
    return 0;
  }
  // elements of rotation matrix
  double u = (cxb - cxa) / d_ab;
  double v = (cyb - cya) / d_ab;

  // conditions for circle intersection
  if (d_ab <= ra + rb && d_ab >= abs(rb - ra)) {

    // circles cross each other
//     flag = 1;
// 
//     // triangle (ra, rb, d_ab)
//     double cosphi = (ra*ra - rb*rb + d_ab*d_ab) / (2*ra*d_ab);
//     double sinphi2 = 1. - cosphi*cosphi;
//     if (sinphi2 < 0.) { sinphi2 = 0.; cosphi = 1.; }
// 
//     // intersection points in new frame
//     double sinphi = sqrt(sinphi2);
//     x1 = ra*cosphi; y1 = ra*sinphi; x2 = x1; y2 = -y1;

    //circles cross each other, but take tangent points anyway
    flag = 1;

    // points of closest approach in new frame 
    // are on line between 2 centers
    x1 = ra; y1 = 0; x2 = d_ab - rb; y2 = 0;


  } 
  else if (d_ab > ra + rb) {

    // circles are external to each other
    flag = 2;

    // points of closest approach in new frame 
    // are on line between 2 centers
    x1 = ra; y1 = 0; x2 = d_ab - rb; y2 = 0;
  }
  else if (d_ab < abs(rb - ra)) {

    // circles are inside each other
    flag = 2;

    // points of closest approach in new frame are on line between 2 centers
    // choose 2 closest points
    double sign = 1.;
    if (ra <= rb) sign = -1.;
    x1 = sign*ra; y1 = 0; x2 = d_ab + sign*rb; y2 = 0;
  }
  else {
    return 0;
  }

  // intersection points in global frame, transverse plane
  xg1 = u*x1 - v*y1 + cxa; yg1 = v*x1 + u*y1 + cya;
  xg2 = u*x2 - v*y2 + cxa; yg2 = v*x2 + u*y2 + cya;

  return flag;
}

double TangentApproachInRPhi::zCoord ( const GlobalVector &  mom, const GlobalPoint &  pos, double  r, double  xc, double  yc, double  xg, double  yg  ) const

private

Definition at line 271 of file TangentApproachInRPhi.cc.

References funct::abs(), PVValHelper::dz, alignCSCRings::r, mathSSE::sqrt(), PV3DBase< T, PVType, FrameType >::transverse(), PV3DBase< T, PVType, FrameType >::x(), x(), PV3DBase< T, PVType, FrameType >::y(), and PV3DBase< T, PVType, FrameType >::z().

Referenced by clone().

{

  // starting point
  double x = pos.x(); double y = pos.y(); double z = pos.z();

  double px = mom.x(); double py = mom.y(); double pz = mom.z();

  // rotation angle phi from starting point to crossing point (absolute value)
  // -- compute sin(phi/2) if phi smaller than pi/4, 
  // -- cos(phi) if phi larger than pi/4
  double phi = 0.;
  double sinHalfPhi = sqrt((x-xg)*(x-xg) + (y-yg)*(y-yg))/(2*r);
  if (sinHalfPhi < 0.383) { // sin(pi/8)
    phi = 2*asin(sinHalfPhi);
  }
  else {
    double cosPhi = ((x-xc)*(xg-xc) + (y-yc)*(yg-yc))/(r*r);
    if (std::abs(cosPhi) > 1) cosPhi = (cosPhi > 0 ? 1 : -1);
    phi = abs(acos(cosPhi));
  }
  // -- sign of phi
  double signPhi = ((x - xc)*(yg - yc) - (xg - xc)*(y - yc) > 0) ? 1. : -1.;

  // sign of track angular momentum
  // if rotation is along angular momentum, delta z is along pz
  double signOmega = ((x - xc)*py - (y - yc)*px > 0) ? 1. : -1.;

  // delta z
  // -- |dz| = |cos(theta) * path along helix|
  //         = |cos(theta) * arc length along circle / sin(theta)|
  double dz = signPhi*signOmega*(pz/mom.transverse())*phi*r;

  return z + dz;
}

Member Data Documentation

bool TangentApproachInRPhi::intersection_

private

Definition at line 100 of file TangentApproachInRPhi.h.

Referenced by TangentApproachInRPhi().

GlobalTrajectoryParameters TangentApproachInRPhi::paramA

private

Definition at line 99 of file TangentApproachInRPhi.h.

GlobalTrajectoryParameters TangentApproachInRPhi::paramB

private

Definition at line 99 of file TangentApproachInRPhi.h.

GlobalPoint TangentApproachInRPhi::posA

private

Definition at line 98 of file TangentApproachInRPhi.h.

GlobalPoint TangentApproachInRPhi::posB

private

Definition at line 98 of file TangentApproachInRPhi.h.

bool TangentApproachInRPhi::status_

private

Definition at line 97 of file TangentApproachInRPhi.h.

Referenced by status(), and TangentApproachInRPhi().