MultipleScatteringUpdator Class Reference

#include <MultipleScatteringUpdator.h>

Inheritance diagram for MultipleScatteringUpdator:

Public Member Functions
virtual void	compute (const TrajectoryStateOnSurface &, const PropagationDirection, Effect &effect) const
	MultipleScatteringUpdator (double mass, double ptMin=-1.)
	~MultipleScatteringUpdator ()
	destructor More...
Public Member Functions inherited from MaterialEffectsUpdator
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

Private Attributes
double	thePtMin

Additional Inherited Members
Public Types inherited from MaterialEffectsUpdator
typedef materialEffect::Covariance	Covariance
typedef materialEffect::CovIndex	CovIndex
typedef materialEffect::Effect	Effect

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 15 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 26 of file MultipleScatteringUpdator.h.

Referenced by clone().

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

MultipleScatteringUpdator::~MultipleScatteringUpdator ( )

inline

destructor

Definition at line 30 of file MultipleScatteringUpdator.h.

{}

Member Function Documentation

virtual MultipleScatteringUpdator* MultipleScatteringUpdator::clone ( void  ) const

inlineprivatevirtual

Implements MaterialEffectsUpdator.

Definition at line 17 of file MultipleScatteringUpdator.h.

References MultipleScatteringUpdator().

                                                              {
    return new MultipleScatteringUpdator(*this);
  }

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

virtual

Implements MaterialEffectsUpdator.

Definition at line 15 of file MultipleScatteringUpdator.cc.

References a, funct::abs(), GetRecoTauVFromDQM_MC_cff::cl2, constexpr, gather_cfg::cout, ztail::d, materialEffect::Effect::deltaCov, reco::e2, fact, TrajectoryStateOnSurface::globalMomentum(), TrajectoryStateOnSurface::localError(), TrajectoryStateOnSurface::localMomentum(), MaterialEffectsUpdator::mass(), LocalTrajectoryError::matrix(), Surface::mediumProperties(), materialEffect::msxx, materialEffect::msxy, materialEffect::msyy, AlCaHLTBitMon_ParallelJobs::p, p2, PV3DBase< T, PVType, FrameType >::perp2(), HLT_25ns10e33_v2_cff::pMin, MediumProperties::radLen(), mathSSE::sqrt(), TrajectoryStateOnSurface::surface(), thePtMin, and unlikely.

Referenced by CombinedMaterialEffectsUpdator::compute().

{
  //
  // Get surface
  //
  const Surface& surface = TSoS.surface();
  //
  //
  // Now get information on medium
  //
  const MediumProperties& mp = surface.mediumProperties();
  if unlikely(mp.radLen()==0) return;

  // Momentum vector
  LocalVector d = TSoS.localMomentum();
  float p2 = d.mag2();
  d *= 1.f/sqrt(p2);
  float xf = 1.f/std::abs(d.z());         // increase of path due to angle of incidence
  // calculate general physics things
  constexpr float amscon = 1.8496e-4;    // (13.6MeV)**2
  const float m2 = mass()*mass();            // use mass hypothesis from constructor
  float e2     = p2 + m2;
  float beta2  = p2/e2;
  // calculate the multiple scattering angle
  float radLen = mp.radLen()*xf;     // effective rad. length
  float sigt2 = 0.;                  // sigma(alpha)**2

  // Calculated rms scattering angle squared.
  float fact = 1.f + 0.038f*unsafe_logf<2>(radLen); fact *=fact;
  float 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();
    float error2_QoverP = covMatrix(0,0);
    // Formula valid for ultra-relativistic particles.
    //      sigt2 *= (1. + p2 * error2_QoverP);
    // Exact formula
    sigt2 *= 1.f +  error2_QoverP *( p2 + m2*beta2*(5.f + 3.f*p2*error2_QoverP) ) ;
#ifdef DBG_MSU
    std::cout<<" new = "<<sqrt(sigt2);
#endif
    // Convert Pt constraint to P constraint, neglecting uncertainty in 
    // track angle.
    float pMin2 = thePtMin*thePtMin*(p2/TSoS.globalMomentum().perp2());       
    // Use P constraint to calculate rms maximum scattering angle.
    float betaMin2 = pMin2/(pMin2 + m2);
    float a_max = fact/(betaMin2 * pMin2);
    float 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
  }
  
  float isl2 = 1.f/d.perp2();
  float cl2 = (d.z()*d.z());
  float cf2 = (d.x()*d.x())*isl2;
  float sf2 = (d.y()*d.y())*isl2;
  // Create update (transformation of independant variations
  //   on angle in orthogonal planes to local parameters.
  float den = 1.f/(cl2*cl2);
  using namespace materialEffect;
  effect.deltaCov[msxx] += (den*sigt2)*(sf2*cl2 + cf2);
  effect.deltaCov[msxy] += (den*sigt2)*(d.x()*d.y()  );
  effect.deltaCov[msyy] += (den*sigt2)*(cf2*cl2 + sf2);
  
  /*
    std::cout << "new " <<  theDeltaCov(1,1) << " " <<  theDeltaCov(1,2)  << " " <<  theDeltaCov(2,2) << std::endl;
    oldMUcompute(TSoS,propDir, mass(), thePtMin);
  */
    
}

Member Data Documentation

double MultipleScatteringUpdator::thePtMin

private

Definition at line 39 of file MultipleScatteringUpdator.h.

Referenced by compute().