MultipleScatteringUpdator Class Reference

#include <MultipleScatteringUpdator.h>

Inheritance diagram for MultipleScatteringUpdator:

Public Member Functions
virtual double	deltaP (const TrajectoryStateOnSurface &, const PropagationDirection) const
	reimplementation of deltaP (since always 0) More...
	MultipleScatteringUpdator (double mass, double ptMin=-1.)
	~MultipleScatteringUpdator ()
	destructor More...
Public Member Functions inherited from MaterialEffectsUpdator
virtual const AlgebraicSymMatrix55 &	deltaLocalError (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 MultipleScatteringUpdator *	clone () const
virtual void	compute (const TrajectoryStateOnSurface &, const PropagationDirection) const

Private Attributes
double	thePtMin

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

Detailed Description

Adds effects from multiple scattering (standard Highland formula) to a trajectory state. Uses radiation length from medium properties. Ported from ORCA.

Author

todorov, cerati

Definition at line 14 of file MultipleScatteringUpdator.h.

Constructor & Destructor Documentation

MultipleScatteringUpdator::MultipleScatteringUpdator ( double  mass, double  ptMin = -1.  )

inline

Specify assumed mass of particle for material effects. If ptMin > 0, then the rms muliple scattering angle will be calculated taking into account the uncertainty in the reconstructed track momentum. (By default, it is neglected). However, a lower limit on the possible value of the track Pt will be applied at ptMin, to avoid the rms multiple scattering becoming too big.

Definition at line 25 of file MultipleScatteringUpdator.h.

Referenced by clone().

                                                            :
    MaterialEffectsUpdator(mass),
    thePtMin(ptMin) {}

MultipleScatteringUpdator::~MultipleScatteringUpdator ( )

inline

destructor

Definition at line 29 of file MultipleScatteringUpdator.h.

{}

Member Function Documentation

virtual MultipleScatteringUpdator* MultipleScatteringUpdator::clone ( void  ) const

inlineprivatevirtual

Implements MaterialEffectsUpdator.

Definition at line 16 of file MultipleScatteringUpdator.h.

References MultipleScatteringUpdator().

                                                   {
    return new MultipleScatteringUpdator(*this);
  }

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

privatevirtual

Implements MaterialEffectsUpdator.

Definition at line 14 of file MultipleScatteringUpdator.cc.

References a, gather_cfg::cout, TrajectoryStateOnSurface::globalMomentum(), TrajectoryStateOnSurface::localError(), TrajectoryStateOnSurface::localMomentum(), funct::log(), PV3DBase< T, PVType, FrameType >::mag2(), MaterialEffectsUpdator::mass(), LocalTrajectoryError::matrix(), Surface::mediumProperties(), L1TEmulatorMonitor_cff::p, p2, PV3DBase< T, PVType, FrameType >::perp2(), ExpressReco_HICollisions_FallBack::pMin, MediumProperties::radLen(), mathSSE::sqrt(), TrajectoryStateOnSurface::surface(), MaterialEffectsUpdator::theDeltaCov, thePtMin, PV3DBase< T, PVType, FrameType >::x(), PV3DBase< T, PVType, FrameType >::y(), and PV3DBase< T, PVType, FrameType >::z().

{
  //
  // Get surface
  //
  const Surface& surface = TSoS.surface();
  //
  // Initialise the update to the covariance matrix
  // (dP is constantly 0).
  //
  theDeltaCov(1,1) = 0.;
  theDeltaCov(1,2) = 0.;
  theDeltaCov(2,2) = 0.;
  //
  // Now get information on medium
  //
  if (surface.mediumProperties()) {
    // Momentum vector
    LocalVector d = TSoS.localMomentum();
    double p2 = d.mag2();
    d *= 1./sqrt(p2);
    // MediumProperties mp(0.02, .5e-4);
    const MediumProperties& mp = *surface.mediumProperties();
    double xf = 1./fabs(d.z());         // increase of path due to angle of incidence
    // calculate general physics things
    const double amscon = 1.8496e-4;    // (13.6MeV)**2
    const double m2 = mass()*mass();            // use mass hypothesis from constructor
    double e2     = p2 + m2;
    double beta2  = p2/e2;
    // calculate the multiple scattering angle
    double radLen = mp.radLen()*xf;     // effective rad. length
    double sigt2 = 0.;                  // sigma(alpha)**2
    if (radLen > 0) {
      // Calculated rms scattering angle squared.
      double fact = 1. + 0.038*log(radLen); fact *=fact;
      double a = fact/(beta2*p2);
      sigt2 = amscon*radLen*a;
      if (thePtMin > 0) {
#ifdef DBG_MSU
        std::cout<<"Original rms scattering = "<<sqrt(sigt2);
#endif
        // Inflate estimated rms scattering angle, to take into account 
        // that 1/p is not known precisely.
        AlgebraicSymMatrix55 const & covMatrix = TSoS.localError().matrix();
        double error2_QoverP = covMatrix(0,0);
    // Formula valid for ultra-relativistic particles.
        //      sigt2 *= (1. + p2 * error2_QoverP);
    // Exact formula
        sigt2 *= (1. + p2 * error2_QoverP *
                       (1. + 5.*m2/e2 + 3.*m2*beta2*error2_QoverP));
#ifdef DBG_MSU
    std::cout<<" new = "<<sqrt(sigt2);
#endif
    // Convert Pt constraint to P constraint, neglecting uncertainty in 
    // track angle.
    double pMin2 = thePtMin*thePtMin*(p2/TSoS.globalMomentum().perp2());       
        // Use P constraint to calculate rms maximum scattering angle.
        double betaMin2 = pMin2/(pMin2 + m2);
        double a_max = fact/(betaMin2 * pMin2);
        double sigt2_max = amscon*radLen*a_max;
        if (sigt2 > sigt2_max) sigt2 = sigt2_max;
#ifdef DBG_MSU
    std::cout<<" after P constraint ("<<pMin<<") = "<<sqrt(sigt2);
    std::cout<<" for track with 1/p="<<1/p<<"+-"<<sqrt(error2_QoverP)<<std::endl;
#endif
      }
    }
    double sl2 = d.perp2();
    double cl2 = (d.z()*d.z());
    double cf2 = (d.x()*d.x())/sl2;
    double sf2 = (d.y()*d.y())/sl2;
    // Create update (transformation of independant variations
    //   on angle in orthogonal planes to local parameters.
    double den = 1./(cl2*cl2);
    theDeltaCov(1,1) = (den*sigt2)*(sf2*cl2 + cf2);
    theDeltaCov(1,2) = (den*sigt2)*(d.x()*d.y()  );
    theDeltaCov(2,2) = (den*sigt2)*(cf2*cl2 + sf2);

    /*
    std::cout << "new " <<  theDeltaCov(1,1) << " " <<  theDeltaCov(1,2)  << " " <<  theDeltaCov(2,2) << std::endl;
    oldMUcompute(TSoS,propDir, mass(), thePtMin);
    */
  }

}

virtual double MultipleScatteringUpdator::deltaP ( const TrajectoryStateOnSurface &  , const PropagationDirection    ) const

inlinevirtual

reimplementation of deltaP (since always 0)

Reimplemented from MaterialEffectsUpdator.

Definition at line 31 of file MultipleScatteringUpdator.h.

Referenced by CombinedMaterialEffectsUpdator::compute().

                                                                                            {
    return 0.;
  }

Member Data Documentation

double MultipleScatteringUpdator::thePtMin

private

Definition at line 42 of file MultipleScatteringUpdator.h.

Referenced by compute().