trackingTools Namespace Reference

Functions
FreeTrajectoryState	ftsFromVertexToPoint (MagneticField const &magField, GlobalPoint const &xmeas, GlobalPoint const &xvert, float momentum, TrackCharge charge)

Function Documentation

ftsFromVertexToPoint()

FreeTrajectoryState trackingTools::ftsFromVertexToPoint	(	MagneticField const &	magField,
		GlobalPoint const &	xmeas,
		GlobalPoint const &	xvert,
		float	momentum,
		TrackCharge	charge
	)

Description: Utility class to create FTS from supercluster

Definition at line 17 of file ftsFromVertexToPoint.cc.

References ALCARECOTkAlJpsiMuMu_cff::charge, f, dqmMemoryStats::float, runTauDisplay::gp, MagneticField::inTesla(), eostools::move(), PV3DBase< T, PVType, FrameType >::perp(), DiDispStaMuonMonitor_cfi::pt, mathSSE::sqrt(), Vector3DBase< T, FrameTag >::unit(), and PV3DBase< T, PVType, FrameType >::z().

Referenced by HLTPMMassFilter::approxMomAtVtx(), TrackingRegionsFromSuperClustersProducer::createTrackingRegion(), TrajSeedMatcher::ftsFromVertexToPoint(), and PixelHitMatcher::operator()().

                                                                            {
  auto magFieldAtPoint = magField.inTesla(xmeas);
  auto BInTesla = magFieldAtPoint.z();
  GlobalVector xdiff = xmeas - xvert;
  auto mom = momentum * xdiff.unit();
  auto pt = mom.perp();
  auto pz = mom.z();
  auto pxOld = mom.x();
  auto pyOld = mom.y();

  auto curv = (BInTesla * 0.29979f * 0.01f) / pt;

  // stays as doc...
  // auto alpha = std::asin(0.5f*xdiff.perp()*curv);
  // auto ca = std::cos(float(charge)*alpha);
  // auto sa = std::sin(float(charge)*alpha);

  auto sa = 0.5f * xdiff.perp() * curv * float(charge);
  auto ca = sqrt(1.f - sa * sa);

  auto pxNew = ca * pxOld + sa * pyOld;
  auto pyNew = -sa * pxOld + ca * pyOld;
  GlobalVector pNew(pxNew, pyNew, pz);

  GlobalTrajectoryParameters gp(xmeas, pNew, charge, &magField, std::move(magFieldAtPoint));

  return FreeTrajectoryState(gp);
}