EnergyLossUpdator Class Reference

#include <EnergyLossUpdator.h>

Inheritance diagram for EnergyLossUpdator:

Public Member Functions
virtual EnergyLossUpdator *	clone () const
	EnergyLossUpdator (double mass)
Public Member Functions inherited from MaterialEffectsUpdator
virtual const AlgebraicSymMatrix55 &	deltaLocalError (const TrajectoryStateOnSurface &TSoS, const PropagationDirection propDir) const
virtual double	deltaP (const TrajectoryStateOnSurface &TSoS, const PropagationDirection propDir) const
double	mass () const
	MaterialEffectsUpdator (double mass)
virtual TrajectoryStateOnSurface	updateState (const TrajectoryStateOnSurface &TSoS, const PropagationDirection propDir) const
virtual bool	updateStateInPlace (TrajectoryStateOnSurface &TSoS, const PropagationDirection propDir) const
virtual	~MaterialEffectsUpdator ()

Private Member Functions
virtual void	compute (const TrajectoryStateOnSurface &, const PropagationDirection) const
void	computeBetheBloch (const LocalVector &, const MediumProperties &) const
void	computeElectrons (const LocalVector &, const MediumProperties &, const PropagationDirection) const

Additional Inherited Members
Protected Attributes inherited from MaterialEffectsUpdator
AlgebraicSymMatrix55	theDeltaCov
double	theDeltaP
Static Protected Attributes inherited from MaterialEffectsUpdator
static AlgebraicSymMatrix55	theNullMatrix

Detailed Description

Energy loss according to Bethe-Bloch + special treatment for electrons. Adds effects from energy loss according to Bethe-Bloch formula without density effect. Assumes silicon as material. For electrons energy loss due to radiation added according to formulae by Bethe & Heitler. Ported from ORCA.

Definition at line 20 of file EnergyLossUpdator.h.

Constructor & Destructor Documentation

EnergyLossUpdator::EnergyLossUpdator ( double  mass )

inline

Definition at line 28 of file EnergyLossUpdator.h.

Referenced by clone().

                                   :
    MaterialEffectsUpdator(mass) {}

Member Function Documentation

virtual EnergyLossUpdator* EnergyLossUpdator::clone ( void  ) const

inlinevirtual

Implements MaterialEffectsUpdator.

Definition at line 23 of file EnergyLossUpdator.h.

References EnergyLossUpdator().

                                           {
    return new EnergyLossUpdator(*this);
  }

void EnergyLossUpdator::compute ( const TrajectoryStateOnSurface &  TSoS, const PropagationDirection  propDir  ) const

privatevirtual

Implements MaterialEffectsUpdator.

Definition at line 9 of file EnergyLossUpdator.cc.

References alongMomentum, computeBetheBloch(), computeElectrons(), TrajectoryStateOnSurface::localMomentum(), MaterialEffectsUpdator::mass(), Surface::mediumProperties(), TrajectoryStateOnSurface::surface(), MaterialEffectsUpdator::theDeltaCov, and MaterialEffectsUpdator::theDeltaP.

{
  //
  // Get surface
  //
  const Surface& surface = TSoS.surface();
  //
  // Initialise dP and the update to the covariance matrix
  //
  theDeltaP = 0.;
  theDeltaCov(0,0) = 0.;
  //
  // Now get information on medium
  //
  if (surface.mediumProperties()) {
    //
    // Bethe-Bloch
    //
    if ( mass()>0.001 )
      computeBetheBloch(TSoS.localMomentum(),*surface.mediumProperties());
    //
    // Special treatment for electrons (currently rather crude
    // distinction using mass)
    //
    else
      computeElectrons(TSoS.localMomentum(),*surface.mediumProperties(),
               propDir);
    if (propDir != alongMomentum) theDeltaP *= -1.;
  }
}

void EnergyLossUpdator::computeBetheBloch ( const LocalVector &  localP, const MediumProperties &  materialConstants  ) const

private

Definition at line 44 of file EnergyLossUpdator.cc.

References beta, alignCSCRings::e, create_public_lumi_plots::log, m, PV3DBase< T, PVType, FrameType >::mag(), MaterialEffectsUpdator::mass(), AlCaHLTBitMon_ParallelJobs::p, mathSSE::sqrt(), MaterialEffectsUpdator::theDeltaCov, MaterialEffectsUpdator::theDeltaP, MediumProperties::xi(), and PV3DBase< T, PVType, FrameType >::z().

Referenced by compute().

                                                                       {
  //
  // calculate absolute momentum and correction to path length from angle 
  // of incidence
  //
  double p = localP.mag();
  double xf = fabs(p/localP.z());
  // constants
  const double m = mass();            // use mass hypothesis from constructor

  const double emass = 0.511e-3;
  const double poti = 16.e-9 * 10.75; // = 16 eV * Z**0.9, for Si Z=14
  const double eplasma = 28.816e-9 * sqrt(2.33*0.498); // 28.816 eV * sqrt(rho*(Z/A)) for Si
  const double delta0 = 2*log(eplasma/poti) - 1.;

  // calculate general physics things
  double e     = sqrt(p*p + m*m);
  double beta  = p/e;
  double gamma = e/m;
  double eta2  = beta*gamma; eta2 *= eta2;
  //  double lnEta2 = log(eta2);
  double ratio = emass/m;
  double emax  = 2.*emass*eta2/(1. + 2.*ratio*gamma + ratio*ratio);
  // double delta = delta0 + lnEta2;

  // calculate the mean and sigma of energy loss
  // xi = d[g/cm2] * 0.307075MeV/(g/cm2) * Z/A * 1/2
  double xi = materialConstants.xi()*xf; xi /= (beta*beta);

//   double dEdx = xi*(log(2.*emass*eta2*emax/(poti*poti)) - 2.*(beta*beta));
  //double dEdx = xi*(log(2.*emass*emax/(poti*poti))+lnEta2 - 2.*(beta*beta) - delta);

  double dEdx = xi*(log(2.*emass*emax/(poti*poti)) - 2.*(beta*beta) - delta0);
  double dEdx2 = xi*emax*(1.-0.5*(beta*beta));
  double dP    = dEdx/beta;
  double sigp2 = dEdx2*e*e/(p*p*p*p*p*p);
  theDeltaP += -dP;
  theDeltaCov(0,0) += sigp2;
}

void EnergyLossUpdator::computeElectrons ( const LocalVector &  localP, const MediumProperties &  materialConstants, const PropagationDirection  propDir  ) const

private

Definition at line 88 of file EnergyLossUpdator.cc.

References create_public_lumi_plots::exp, f, create_public_lumi_plots::log, PV3DBase< T, PVType, FrameType >::mag(), oppositeToMomentum, AlCaHLTBitMon_ParallelJobs::p, MediumProperties::radLen(), MaterialEffectsUpdator::theDeltaCov, MaterialEffectsUpdator::theDeltaP, detailsBasic3DVector::z, and PV3DBase< T, PVType, FrameType >::z().

Referenced by compute().

                                                               {
  //
  // calculate absolute momentum and correction to path length from angle 
  // of incidence
  //
  double p = localP.mag();
  double normalisedPath = fabs(p/localP.z())*materialConstants.radLen();
  //
  // Energy loss and variance according to Bethe and Heitler, see also
  // Comp. Phys. Comm. 79 (1994) 157. 
  //
  double z = exp(-normalisedPath);
  double varz = exp(-normalisedPath*log(3.)/log(2.))- 
                z*z;
        // exp(-2*normalisedPath);

  if ( propDir==oppositeToMomentum ) {
    //
    // for backward propagation: delta(1/p) is linear in z=p_outside/p_inside
    // convert to obtain equivalent delta(p). Sign of deltaP is corrected
    // in method compute -> deltaP<0 at this place!!!
    //
    theDeltaP += -p*(1/z-1);
    theDeltaCov(0,0) += varz/(p*p);
  }
  else {    
    //
    // for forward propagation: calculate in p (linear in 1/z=p_inside/p_outside),
    // then convert sig(p) to sig(1/p). 
    //
    theDeltaP += p*(z-1);
    //    double f = 1/p/z/z;
    // patch to ensure consistency between for- and backward propagation
    double f = 1./(p*z);
    theDeltaCov(0,0) += f*f*varz;
  }
}