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GsfMultipleScatteringUpdator Class Reference

Description of multiple scattering with two Gaussian components as described in HEPHY-PUB 724-99. More...

#include <TrackingTools/GsfTracking/interface/GsfMultipleScatteringUpdator.h>

Inheritance diagram for GsfMultipleScatteringUpdator:

List of all members.

Public Member Functions
virtual GsfMultipleScatteringUpdator *	clone () const
	GsfMultipleScatteringUpdator (float mass)
	constructor with explicit mass
Protected Member Functions
virtual bool	newArguments (const TrajectoryStateOnSurface &, const PropagationDirection) const
virtual void	storeArguments (const TrajectoryStateOnSurface &, const PropagationDirection) const
Private Member Functions
virtual void	compute (const TrajectoryStateOnSurface &, const PropagationDirection) const
	Computation: generates vectors of weights, means and standard deviations.
Private Attributes
float	theLastDz
float	theLastP
PropagationDirection	theLastPropDir
float	theLastRadLength

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Detailed Description

Description of multiple scattering with two Gaussian components as described in HEPHY-PUB 724-99.

Gaussians as a function of x/X0 are parametrized as polynomials. The mixture is parametrized as a function of the thickness, velocity and Xs=X0*h(Z).

Definition at line 14 of file GsfMultipleScatteringUpdator.h.

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Constructor & Destructor Documentation

GsfMultipleScatteringUpdator::GsfMultipleScatteringUpdator

(

float

mass

)

[inline]

constructor with explicit mass

Definition at line 25 of file GsfMultipleScatteringUpdator.h.

Referenced by clone().

00025                                            :
00026     GsfMaterialEffectsUpdator(mass),
00027     theLastDz(0.),
00028     theLastP(0.),
00029     theLastPropDir(alongMomentum),
00030     theLastRadLength(0.) {}
  

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Member Function Documentation

virtual GsfMultipleScatteringUpdator* GsfMultipleScatteringUpdator::clone

(

void

)

const [inline, virtual]

Implements GsfMaterialEffectsUpdator.

Definition at line 32 of file GsfMultipleScatteringUpdator.h.

References GsfMultipleScatteringUpdator().

  {
    return new GsfMultipleScatteringUpdator(*this);
  }

void GsfMultipleScatteringUpdator::compute	(	const TrajectoryStateOnSurface &	TSoS,
		const	PropagationDirection
	)			const [private, virtual]

Computation: generates vectors of weights, means and standard deviations.

Implements GsfMaterialEffectsUpdator.

Definition at line 10 of file GsfMultipleScatteringUpdator.cc.

References h, TrajectoryStateOnSurface::localMomentum(), funct::log(), PV3DBase< T, PVType, FrameType >::mag(), GsfMaterialEffectsUpdator::mass(), Surface::mediumProperties(), p, PV3DBase< T, PVType, FrameType >::perp(), funct::pow(), MediumProperties::radLen(), sl, funct::sqrt(), storeArguments(), TrajectoryStateOnSurface::surface(), GsfMaterialEffectsUpdator::theDeltaCovs, GsfMaterialEffectsUpdator::theDeltaPs, GsfMaterialEffectsUpdator::theWeights, w1, w2, PV3DBase< T, PVType, FrameType >::x(), PV3DBase< T, PVType, FrameType >::y(), PV3DBase< T, PVType, FrameType >::z(), and z.

{
  //
  // clear cache
  //
  theWeights.clear();
  theDeltaPs.clear();
  theDeltaCovs.clear();
  //
  // Get surface and check presence of medium properties
  //
  const Surface& surface = TSoS.surface();
  //
  // calculate components
  //
  if ( surface.mediumProperties() ) {
    LocalVector pvec = TSoS.localMomentum();
    double p = TSoS.localMomentum().mag();
    pvec *= 1./p;
    // thickness in radiation lengths
    double rl = surface.mediumProperties()->radLen()/fabs(pvec.z());
    // auxiliary variables for modified X0
    const double z = 14;                 // atomic number of silicon
    const double logz = log(z);
    const double h = (z+1)/z*log(287*sqrt(z))/log(159*pow(z,-1./3.));
    double beta2 = 1./(1.+mass()*mass()/p/p);
    // reduced thickness
    double dp1 = rl/beta2/h;
    double logdp1 = log(dp1);
    double logdp2 = 2./3.*logz + logdp1;
    // means are always 0
    theDeltaPs.push_back(0.);
    theDeltaPs.push_back(0.);
    // weights
    double w2;
    if ( logdp2<log(0.5) )  
      w2 = 0.05283+0.0077*logdp2+0.00069*logdp2*logdp2;
    else
      w2 =-0.01517+0.1151*logdp2-0.00653*logdp2*logdp2;
    double w1 = 1.-w2;
    theWeights.push_back(w1);
    theWeights.push_back(w2);
    // reduced variances
    double var1 = 0.8510+0.03314*logdp1-0.001825*logdp1*logdp1;
    double var2 = (1.-w1*var1)/w2;
    for ( int ic=0; ic<2; ic++ ) {
      // choose component and multiply with total variance
      double var = ic==0 ? var1 : var2;
      var *= 225.e-6*dp1/p/p;
      AlgebraicSymMatrix55 cov;
      // transform from orthogonal planes containing the
      // momentum vector to local parameters
      double sl = pvec.perp();
      double cl = pvec.z();
      double cf = pvec.x()/sl;
      double sf = pvec.y()/sl;
      cov(1,1) = var*(sf*sf*cl*cl + cf*cf)/(cl*cl*cl*cl);
      cov(1,2) = var*(cf*sf*sl*sl        )/(cl*cl*cl*cl);
      cov(2,2) = var*(cf*cf*cl*cl + sf*sf)/(cl*cl*cl*cl);
      theDeltaCovs.push_back(cov);
    }
  }
  else {
    theWeights.push_back(1.);
    theDeltaPs.push_back(0.);
    theDeltaCovs.push_back(AlgebraicSymMatrix55());
  }
  //
  // Save arguments to avoid duplication of computation
  //
  storeArguments(TSoS,propDir); 
}

bool GsfMultipleScatteringUpdator::newArguments	(	const TrajectoryStateOnSurface &	TSoS,
		const	PropagationDirection
	)			const [protected, virtual]

Reimplemented from GsfMaterialEffectsUpdator.

Definition at line 88 of file GsfMultipleScatteringUpdator.cc.

References TrajectoryStateOnSurface::localMomentum(), PV3DBase< T, PVType, FrameType >::mag(), Surface::mediumProperties(), MediumProperties::radLen(), TrajectoryStateOnSurface::surface(), theLastDz, theLastP, theLastPropDir, theLastRadLength, Vector3DBase< T, FrameTag >::unit(), and PV3DBase< T, PVType, FrameType >::z().

                                                                                      {
  return TSoS.localMomentum().unit().z()!=theLastDz ||
    TSoS.localMomentum().mag()!=theLastP || propDir!=theLastPropDir ||
    TSoS.surface().mediumProperties()->radLen()!=theLastRadLength;
}

void GsfMultipleScatteringUpdator::storeArguments	(	const TrajectoryStateOnSurface &	TSoS,
		const	PropagationDirection
	)			const [protected, virtual]

Reimplemented from GsfMaterialEffectsUpdator.

Definition at line 97 of file GsfMultipleScatteringUpdator.cc.

References TrajectoryStateOnSurface::localMomentum(), PV3DBase< T, PVType, FrameType >::mag(), Surface::mediumProperties(), MediumProperties::radLen(), TrajectoryStateOnSurface::surface(), theLastDz, theLastP, theLastPropDir, theLastRadLength, Vector3DBase< T, FrameTag >::unit(), and PV3DBase< T, PVType, FrameType >::z().

Referenced by compute().

                                                                                             {
  theLastDz = TSoS.localMomentum().unit().z();
  theLastP = TSoS.localMomentum().mag();
  theLastPropDir = propDir;
  theLastRadLength = TSoS.surface().mediumProperties()->radLen();
}

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Member Data Documentation

float GsfMultipleScatteringUpdator::theLastDz [mutable, private]

Definition at line 49 of file GsfMultipleScatteringUpdator.h.

Referenced by newArguments(), and storeArguments().

float GsfMultipleScatteringUpdator::theLastP [mutable, private]

Definition at line 50 of file GsfMultipleScatteringUpdator.h.

Referenced by newArguments(), and storeArguments().

PropagationDirection GsfMultipleScatteringUpdator::theLastPropDir [mutable, private]

Definition at line 51 of file GsfMultipleScatteringUpdator.h.

Referenced by newArguments(), and storeArguments().

float GsfMultipleScatteringUpdator::theLastRadLength [mutable, private]

Definition at line 52 of file GsfMultipleScatteringUpdator.h.

Referenced by newArguments(), and storeArguments().

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The documentation for this class was generated from the following files:

• TrackingTools/GsfTracking/interface/GsfMultipleScatteringUpdator.h
• TrackingTools/GsfTracking/src/GsfMultipleScatteringUpdator.cc

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