#include <ThirdHitPredictionFromCircle.h>

Public Member Functions
	HelixRZ ()
	HelixRZ (const ThirdHitPredictionFromCircle *circle, double z1, double z2, double curvature)
double	rAtZ (double z) const
double	zAtR (double r) const
Static Public Member Functions
static double	maxCurvature (const ThirdHitPredictionFromCircle *circle, double z1, double z2, double z3)
Private Attributes
const ThirdHitPredictionFromCircle *	circle
double	curvature
double	dzdu
double	seg
double	z1

Detailed Description

Definition at line 30 of file ThirdHitPredictionFromCircle.h.

Constructor & Destructor Documentation

ThirdHitPredictionFromCircle::HelixRZ::HelixRZ ( ) [inline]

Definition at line 32 of file ThirdHitPredictionFromCircle.h.

: circle(0) {}

ThirdHitPredictionFromCircle::HelixRZ::HelixRZ	(	const ThirdHitPredictionFromCircle *	circle,
		double	z1,
		double	z2,
		double	curvature
	)

Definition at line 187 of file ThirdHitPredictionFromCircle.cc.

References abs, ThirdHitPredictionFromCircle::delta, dzdu, alignCSCRings::e, likely, M_PI_2, seg, and z1.

                                                                                 :
  circle(circle), curvature(curv), z1(z1)
{
  double absCurv = std::abs(curv);
  seg = circle->delta;

  if (likely(absCurv > 1.0e-5)) {
    seg *= absCurv;
    seg = seg < -1.0 ? -M_PI_2 : seg > 1.0 ? M_PI_2 : std::asin(seg);
    seg /= absCurv;
  }

  seg *= 2.;
  dzdu = likely(std::abs(seg) > 1.0e-5) ? ((z2 - z1) / seg) : 99999.0;
}

Member Function Documentation

double ThirdHitPredictionFromCircle::HelixRZ::maxCurvature	(	const ThirdHitPredictionFromCircle *	circle,
		double	z1,
		double	z2,
		double	z3
	)		`[static]`

Definition at line 204 of file ThirdHitPredictionFromCircle.cc.

References ThirdHitPredictionFromCircle::delta, M_PI, funct::sin(), and unlikely.

Referenced by PixelTripletLargeTipGenerator::hitTriplets().

{
  static const double maxAngle = M_PI;
  double halfAngle = (0.5 * maxAngle) * (z2 - z1) / (z3 - z1);
  if (unlikely(halfAngle <= 0.0))
    return 0.0;

  return std::sin(halfAngle) / circle->delta;
}

double ThirdHitPredictionFromCircle::HelixRZ::rAtZ ( double z ) const

Definition at line 246 of file ThirdHitPredictionFromCircle.cc.

References abs, trackerHits::c, ThirdHitPredictionFromCircle::center, funct::cos(), ThirdHitPredictionFromCircle::curvature(), alignCSCRings::e, M_PI, mag(), max(), AlCaHLTBitMon_ParallelJobs::p, ThirdHitPredictionFromCircle::phi(), CosmicsPD_Skims::radius, alignCSCRings::s, FWPFMaths::sgn(), funct::sin(), funct::sqr(), mathSSE::sqrt(), unlikely, Basic2DVector< T >::x(), and Basic2DVector< T >::y().

{
  if (unlikely(std::abs(dzdu) < 1.0e-5))
    return 99999.0;

  if (unlikely(std::abs(curvature) < 1.0e-5)) {
    double tip = circle->axis * circle->p1;
    double lip = circle->axis.y() * circle->p1.x() -
                 circle->axis.x() * circle->p1.y();
    return std::sqrt(sqr(tip) + sqr(lip + (z - z1) / dzdu));
  }

  // we won't go below that (see comment below)
  double minR = (2. * circle->center - circle->p1).mag();

  double phi = curvature * (z - z1) / dzdu;

  if (unlikely(std::abs(phi) > 2. * M_PI)) {
    // with a helix we can get problems here - this is used to get the limits
    // however, if phi gets large, we get into the regions where we loop back
    // to smaller r's.  The question is - do we care about these tracks?
    // The answer is probably no:  Too much pain, and the rest of the
    // tracking won't handle looping tracks anyway.
    // So, what we do here is to return nothing smaller than the radius
    // than any of the two hits, i.e. the second hit, which is presumably
    // outside of the 1st hit.

    return minR;
  }

  double radius = 1. / curvature;
  double orthog = sgn(curvature) * clamped_sqrt(sqr(radius) - circle->delta2);
  Point2D center = circle->center + orthog * circle->axis;
  Point2D rel = circle->p1 - center;

  double c = cos(phi);
  double s = sin(phi);

  Point2D p(center.x() + c * rel.x() - s * rel.y(),
            center.y() + s * rel.x() + c * rel.y());

  return std::max(minR, p.mag());
}

double ThirdHitPredictionFromCircle::HelixRZ::zAtR ( double r ) const

Definition at line 215 of file ThirdHitPredictionFromCircle.cc.

References abs, b, ThirdHitPredictionFromCircle::center, ThirdHitPredictionFromCircle::curvature(), alignCSCRings::e, Basic2DVector< T >::mag2(), CosmicsPD_Skims::radius, FWPFMaths::sgn(), funct::sqr(), mathSSE::sqrt(), and unlikely.

{
  if (unlikely(std::abs(curvature) < 1.0e-5)) {
     double tip = circle->axis * circle->p1;
     double lip = circle->axis.y() * circle->p1.x() -
                  circle->axis.x() * circle->p1.y();
     return z1 + (std::sqrt(sqr(r) - sqr(tip)) - lip) * dzdu;
  }

  double radius = 1.0 / curvature;
  double radius2 = sqr(radius);
  double orthog = sgn(curvature) * clamped_sqrt(radius2 - circle->delta2);
  Point2D center = circle->center + orthog * circle->axis;

  double b2 = center.mag2();
  double b = std::sqrt(b2);

  double cos1 = 0.5 * (radius2 + b2 - sqr(r)) * curvature / b;
  double cos2 = 0.5 * (radius2 + b2 - circle->p1.mag2()) * curvature / b;

  double phi1 = clamped_acos(cos1);
  double phi2 = clamped_acos(cos2);

  // more plausbility checks needed...
  // the two circles can have two possible intersections
  double u1 = std::abs((phi1 - phi2) * radius);
  double u2 = std::abs((phi1 + phi2) * radius);

  return z1 + ((u1 >= seg && u1 < u2)? u1 : u2) * dzdu;
}