This AthenaTool computes geometrical shifts for the initial GenEvent vertices. More...

#include <LongBeamspotVertexPositioner.h>

Inheritance diagram for Simulation::LongBeamspotVertexPositioner:

Collaboration diagram for Simulation::LongBeamspotVertexPositioner:

Public Member Functions
	LongBeamspotVertexPositioner (const std::string &t, const std::string &n, const IInterface *p)
	Constructor with parameters.
virtual	~LongBeamspotVertexPositioner ()=default
	Destructor.
StatusCode	initialize () override final
	Athena algtool's Hooks.
StatusCode	finalize () override final
	Athena algtool's Hooks.
CLHEP::HepLorentzVector *	generate (const EventContext &ctx) const override final
	computes the vertex displacement

Private Member Functions
double	heaviside (double val) const
double	getZpos (CLHEP::HepRandomEngine *) const
double	beamspotFunction (double z) const

Private Attributes
Gaudi::Property< double >	m_L {this, "LParameter", 150.}
	Parameter in the Z distribution of the beamspot - default 150.0 mm.
SG::ReadCondHandleKey< InDet::BeamSpotData >	m_beamSpotKey { this, "BeamSpotKey", "BeamSpotData", "SG key for beam spot" }
ServiceHandle< IAthRNGSvc >	m_rndGenSvc {this, "RandomSvc", "AthRNGSvc"}
ATHRNG::RNGWrapper *m_randomEngine	ATLAS_THREAD_SAFE {}
	Slot-local RNG.
Gaudi::Property< std::string >	m_randomEngineName {this, "RandomStream", "VERTEX"}
	Name of the random number stream.
Gaudi::Property< bool >	m_timeSmearing {this, "SimpleTimeSmearing", false}
	Do time smearing.

Detailed Description

This AthenaTool computes geometrical shifts for the initial GenEvent vertices.

based on function in: https://its.cern.ch/jira/ATLASSIM-265

Author: John.Chapman -at- cern.ch, Elmar.Ritsch -at- cern.ch

Definition at line 37 of file LongBeamspotVertexPositioner.h.

Constructor & Destructor Documentation

◆ LongBeamspotVertexPositioner()

Simulation::LongBeamspotVertexPositioner::LongBeamspotVertexPositioner	(	const std::string &	t,
		const std::string &	n,
		const IInterface *	p )

Constructor with parameters.

Constructor.

Definition at line 26 of file LongBeamspotVertexPositioner.cxx.

    : base_class(t,n,p)
  {
  }

◆ ~LongBeamspotVertexPositioner()

virtual Simulation::LongBeamspotVertexPositioner::~LongBeamspotVertexPositioner ( )

virtualdefault

Destructor.

Member Function Documentation

◆ beamspotFunction()

double Simulation::LongBeamspotVertexPositioner::beamspotFunction ( double z ) const

private

Definition at line 59 of file LongBeamspotVertexPositioner.cxx.

  {
    //double norm(1.0/232.06);
    double temp(1.0-std::abs(z)/m_L);
    return erf(2.5*temp)*heaviside(temp); // zero for |z|>150.0
  }

◆ finalize()

StatusCode Simulation::LongBeamspotVertexPositioner::finalize ( )

finaloverride

Athena algtool's Hooks.

Definition at line 53 of file LongBeamspotVertexPositioner.cxx.

  {
    ATH_MSG_VERBOSE("Finalizing ...");
    return StatusCode::SUCCESS;
  }

◆ generate()

CLHEP::HepLorentzVector * Simulation::LongBeamspotVertexPositioner::generate ( const EventContext & ctx ) const

finaloverride

computes the vertex displacement

Definition at line 81 of file LongBeamspotVertexPositioner.cxx.

  {
    // Prepare the random engine
    m_randomEngine->setSeed( name(), ctx );
    CLHEP::HepRandomEngine* randomEngine(m_randomEngine->getEngine(ctx));
    SG::ReadCondHandle<InDet::BeamSpotData> beamSpotHandle { m_beamSpotKey, ctx };
    // See jira issue ATLASSIM-497 for an explanation of why calling
    // shoot outside the CLHEP::HepLorentzVector constructor is
    // necessary/preferable.
    float vertexX = CLHEP::RandGaussZiggurat::shoot(randomEngine)*beamSpotHandle->beamSigma(0);
    float vertexY = CLHEP::RandGaussZiggurat::shoot(randomEngine)*beamSpotHandle->beamSigma(1);
    float vertexZ = getZpos(randomEngine);
    // calculate the vertexSmearing
    CLHEP::HepLorentzVector *vertexSmearing =
      new CLHEP::HepLorentzVector( vertexX, vertexY, vertexZ, 0. );
 
    // (1) code from: Simulation/G4Atlas/G4AtlasUtilities/VertexPositioner.cxx
    const double tx = tan( beamSpotHandle->beamTilt(1) );
    const double ty = tan( beamSpotHandle->beamTilt(0) );
 
    const double sqrt_abc = sqrt(1. + tx*tx + ty*ty);
    const double sqrt_fgh = sqrt(1. + ty*ty);
 
    const double a = ty/sqrt_abc;
    const double b = tx/sqrt_abc;
    const double c = 1./sqrt_abc;
 
    HepGeom::Point3D<double> from1(0,0,1);
    HepGeom::Point3D<double> to1(a,b,c);
 
    const double f = 1./sqrt_fgh;
    const double g = 0.;
    const double h = -(ty)/sqrt_fgh;
 
    HepGeom::Point3D<double> from2(1,0,0);
    HepGeom::Point3D<double> to2(f,g,h);
 
    // first rotation, then translation
    HepGeom::Transform3D transform(
        HepGeom::Rotate3D(from1, from2, to1, to2).getRotation(),
        CLHEP::Hep3Vector( beamSpotHandle->beamPos().x(),
                           beamSpotHandle->beamPos().y(),
                           beamSpotHandle->beamPos().z() )
        );
 
    // FIXME: don't use endl in MsgStream printouts
    ATH_MSG_VERBOSE("BeamSpotSvc reported beam position as " << beamSpotHandle->beamPos() << std::endl
                    << "\tWidth is (" << beamSpotHandle->beamSigma(0)
                    << ", " << beamSpotHandle->beamSigma(1) << ", "
                    << m_L << ")" << std::endl
                    << "\tTilts are " << beamSpotHandle->beamTilt(0) << " and " << beamSpotHandle->beamTilt(1) << std::endl
                    << "\tVertex Position before transform: " << *vertexSmearing);
 
    // update with the tilt
    *vertexSmearing = transform * HepGeom::Point3D<double>(*vertexSmearing);
 
    // See if we were asked to do time smearing as well
    if (m_timeSmearing) {
      /* This is ballpark code courtesy of Brian Amadio. He provided some functions based on beam parameters.
         He provided a little trick for pulling out the beam bunch width as well. Hard coding the crossing angle
         parameter for the time being, as the beam spot service doesn't really provide that yet.  */
      // Assumes that to make these funny beam spots we have a normal-looking bunch
      double bunch_length_z = (std::sqrt(2)*vertexZ)/0.9; // 0.9 is the crossing angle reduction factor
      //    double tLimit = 2.*(bunch_length_z+bunch_length_z)/Gaudi::Units::c_light;
      //    TF1 func = TF1("func","[0]*exp((-([3]-299792458*x)^2*[2]^2-([3]+299792458*x)^2*[1]^2)/(2*[1]^2*[2]^2))",-1*tLimit,tLimit);
      //    func.SetParameter(0,Gaudi::Units::c_light/(M_PI*bunch_length_z*bunch_length_z));
      //    func.SetParameter(1,bunch_length_z);
      //    func.SetParameter(2,bunch_length_z);
      //    func.SetParameter(3,vertexSmearing->z());
      //    double time_offset = func.GetRandom();
 
      // Time should be set in units of distance, which is a little funny
      double time_offset = CLHEP::RandGaussZiggurat::shoot(
          randomEngine, vertexSmearing->z()/Gaudi::Units::c_light,
          bunch_length_z/Gaudi::Units::c_light );
 
      vertexSmearing->setT( vertexSmearing->t() + time_offset*Gaudi::Units::c_light );
    }
 
    // and return it
    return vertexSmearing;
  }

◆ getZpos()

double Simulation::LongBeamspotVertexPositioner::getZpos ( CLHEP::HepRandomEngine * randomEngine ) const

private

Definition at line 66 of file LongBeamspotVertexPositioner.cxx.

  {
    size_t ntries(0);
    double yval(CLHEP::RandFlat::shoot(randomEngine, 0.0, 1.0));
    double zval(CLHEP::RandFlat::shoot(randomEngine, -150.0, 150.0));
    while (this->beamspotFunction(zval)<yval) {
      if(ntries>1000000) return 0.0; //just so we don't sit in this loop forever
      yval = CLHEP::RandFlat::shoot(randomEngine, 0.0, 1.0);
      zval = CLHEP::RandFlat::shoot(randomEngine, -150.0, 150.0);
      ++ntries;
    }
    return zval;
  }

◆ heaviside()

double Simulation::LongBeamspotVertexPositioner::heaviside ( double val ) const

inlineprivate

Definition at line 57 of file LongBeamspotVertexPositioner.h.

57{return (val >= 0.0) ? 1.0 : 0.0;};

◆ initialize()

StatusCode Simulation::LongBeamspotVertexPositioner::initialize ( )

finaloverride

Athena algtool's Hooks.

Definition at line 34 of file LongBeamspotVertexPositioner.cxx.

  {
    ATH_MSG_VERBOSE("Initializing ...");
 
    ATH_CHECK(m_beamSpotKey.initialize());
    // prepare the RandonNumber generation
    ATH_CHECK(m_rndGenSvc.retrieve());
    m_randomEngine = m_rndGenSvc->getEngine(this, m_randomEngineName);
    if (!m_randomEngine) {
      ATH_MSG_ERROR("Could not get random number engine from RandomNumberService. Abort.");
      return StatusCode::FAILURE;
    }
 
    // everything set up properly
    return StatusCode::SUCCESS;
  }

Member Data Documentation

◆ ATLAS_THREAD_SAFE

ATHRNG::RNGWrapper* m_randomEngine Simulation::LongBeamspotVertexPositioner::ATLAS_THREAD_SAFE {}

private

Slot-local RNG.

Definition at line 63 of file LongBeamspotVertexPositioner.h.

63{};

◆ m_beamSpotKey

SG::ReadCondHandleKey<InDet::BeamSpotData> Simulation::LongBeamspotVertexPositioner::m_beamSpotKey { this, "BeamSpotKey", "BeamSpotData", "SG key for beam spot" }

private

Definition at line 61 of file LongBeamspotVertexPositioner.h.

61{ this, "BeamSpotKey", "BeamSpotData", "SG key for beam spot" };

◆ m_L

Gaudi::Property<double> Simulation::LongBeamspotVertexPositioner::m_L {this, "LParameter", 150.}

private

Parameter in the Z distribution of the beamspot - default 150.0 mm.

Definition at line 60 of file LongBeamspotVertexPositioner.h.

60{this, "LParameter", 150.};

◆ m_randomEngineName

Gaudi::Property<std::string> Simulation::LongBeamspotVertexPositioner::m_randomEngineName {this, "RandomStream", "VERTEX"}

private

Name of the random number stream.

Definition at line 65 of file LongBeamspotVertexPositioner.h.

65{this, "RandomStream", "VERTEX"};

◆ m_rndGenSvc

ServiceHandle<IAthRNGSvc> Simulation::LongBeamspotVertexPositioner::m_rndGenSvc {this, "RandomSvc", "AthRNGSvc"}

private

Definition at line 62 of file LongBeamspotVertexPositioner.h.

62{this, "RandomSvc", "AthRNGSvc"};

◆ m_timeSmearing

Gaudi::Property<bool> Simulation::LongBeamspotVertexPositioner::m_timeSmearing {this, "SimpleTimeSmearing", false}

private

Do time smearing.

Definition at line 66 of file LongBeamspotVertexPositioner.h.

66{this, "SimpleTimeSmearing", false};

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

Public Member Functions

Private Member Functions

Private Attributes

Detailed Description

Constructor & Destructor Documentation

◆ LongBeamspotVertexPositioner()

◆ ~LongBeamspotVertexPositioner()

Member Function Documentation

◆ beamspotFunction()

◆ finalize()

◆ generate()

◆ getZpos()

◆ heaviside()

◆ initialize()

Member Data Documentation

◆ ATLAS_THREAD_SAFE

◆ m_beamSpotKey

◆ m_L

◆ m_randomEngineName

◆ m_rndGenSvc

◆ m_timeSmearing