libthepeg-dev 1.8.0-1 / usr / include / ThePEG / Vectors / HepMCTraits.h

// -*- C++ -*-
//
// HepMCTraits.h is a part of ThePEG - Toolkit for HEP Event Generation
// Copyright (C) 1999-2011 Leif Lonnblad
//
// ThePEG is licenced under version 2 of the GPL, see COPYING for details.
// Please respect the MCnet academic guidelines, see GUIDELINES for details.
//
#ifndef ThePEG_HepMCTraits_H
#define ThePEG_HepMCTraits_H

#include "HepMC/GenEvent.h"

namespace HepMC {

class GenEvent;
class GenParticle;
class GenVertex;
class Polarization;
class PdfInfo;

}

namespace ThePEG {

/**
 * HepMCTraitsBase is a convenient base class for specializing the
 * HepMCTraits class to deal with different flavours of HepMC in the
 * HepMCConverter class. The default version will work for the CLHEP
 * implementation of HepMC. To use the HepMCConverter class for any
 * flavour of HepMC you have to specialize the HepMCTraits class
 * accordingly, possibly inheriting the functionality from the
 * HepMCTraitsBase class and only overriding the functions and
 * typedefs which are different. For the CLHEP flavour of HepMC you
 * only need to do <code>template&lt;&gt; struct
 * HepMCTraits&lt;HepMC::GenEvent&gt;: public
 * HepMCTraitsBase&lt;HepMC::GenEvent,HepMC::GenParticle,HepMC::GenVertex,
 * HepMC::Polarization&gt; {};</code> somewhere inside the ThePEG
 * namespace.  The boolean template argument determines whether the
 * HepMC implementation is specifying units or not.
 */
template <typename HepMCEventT, typename HepMCParticleT,
	  typename HepMCVertexT, typename HepMCPolarizationT,
	  typename HepMCPdfInfoT>

struct HepMCTraitsBase {

  /** Typedef of the particle class. */
  typedef HepMCParticleT ParticleT;

  /** Typedef of the event class. */
  typedef HepMCEventT EventT;

  /** Typedef of the vertex class. */
  typedef HepMCVertexT VertexT;

  /** Typedef of the polarization class. */
  typedef HepMCPolarizationT PolarizationT;

  /** Typedef of the PdfInfo class. */
  typedef HepMCPdfInfoT PdfInfoT;

  /** Create an event object with number \a evno and \a weight. */
  static EventT * newEvent(long evno, double weight,
			   const map<string,double>& optionalWeights) {
    EventT * e = new EventT();
    e->set_event_number(evno);
    e->weights().push_back(weight);
    for ( map<string,double>::const_iterator w = optionalWeights.begin();
	  w != optionalWeights.end(); ++w ) {
#ifdef HEPMC_HAS_NAMED_WEIGHTS
      e->weights()[w->first] = w->second;
#else
      e->weights().push_back(w->second);
#endif
    }
    return e;
  }

  /** Reset event weight and number of a re-used GenEvent. */
  static void resetEvent(EventT * e, long evno, double weight,
			 const map<string,double>& optionalWeights) {
    e->set_event_number(evno);
    e->weights().clear();
    e->weights().push_back(weight);
    for ( map<string,double>::const_iterator w = optionalWeights.begin();
	  w != optionalWeights.end(); ++w ) {
#ifdef HEPMC_HAS_NAMED_WEIGHTS
      e->weights()[w->first] = w->second;
#else
      e->weights().push_back(w->second);
#endif
    }
  }

  /**
   * Return true if this version of HepMC accept user-defined units.
   */
  static bool hasUnits() {
#ifdef HEPMC_HAS_UNITS   
    return true;
#else
    return false;
#endif
  }

  /**
   * Return the energy unit used in the installed version of HepMC.
   */
  static Energy defaultEnergyUnit() {
#ifndef HEPMC_HAS_UNITS
    return GeV;
#else
    return HepMC::Units::default_momentum_unit() == HepMC::Units::GEV? GeV: MeV;
#endif
  }

  /**
   * Return the length unit used in the installed version of HepMC.
   */
  static Length defaultLengthUnit() {
#ifndef HEPMC_HAS_UNITS
    return millimeter;
#else
    return HepMC::Units::default_length_unit() == HepMC::Units::MM?
      millimeter: 10.0*millimeter;
#endif
  }

  /**
   * Return the momentum unit used by a given GenEvent object. If
   * HepMC does not support units this must return GeV.
   */
  static Energy momentumUnit(const EventT & e) {
#ifdef HEPMC_HAS_UNITS   
    return e.momentum_unit() == HepMC::Units::MEV? MeV: GeV;
#else
    return GeV;
#endif
  }

  /**
   * Return the length unit used by a given GenEvent object. If
   * HepMC does not support units this must return millimeter.
   */
  static Length lengthUnit(const EventT & e) {
#ifdef HEPMC_HAS_UNITS   
    return e.length_unit() == HepMC::Units::CM? centimeter: millimeter;
#else
    return millimeter;
#endif
  }

  /**
   * Set the units to be used by the given GenEvent object. If
   * HepMC does not support units this should be a no-op.
   */
#ifdef HEPMC_HAS_UNITS   
  static void setUnits(EventT & e, Energy momu, Length lenu) {
    e.use_units(momu == MeV? HepMC::Units::MEV: HepMC::Units::GEV,
		lenu == centimeter? HepMC::Units::CM: HepMC::Units::MM);
  }
#else
  static void setUnits(EventT &, Energy, Length) {}
#endif


  /** Set the \a scale, \f$\alpha_S\f$ (\a aS) and \f$\alpha_{EM}\f$
      (\a aEM) for the event \a e. The scale will be scaled with \a
      unit before given to the GenEvent. */
  static void setScaleAndAlphas(EventT & e, Energy2 scale,
				double aS,  double aEM, Energy unit) {
    e.set_event_scale(sqrt(scale)/unit);
    e.set_alphaQCD(aS);
    e.set_alphaQED(aEM);
  }

  /** Set the primary vertex, \a v, for the event \a e. */
  static void setSignalProcessVertex(EventT & e, VertexT * v) {
    e.set_signal_process_vertex(v);
  }

  /** Set a vertex, \a v, for the event \a e. */
  static void addVertex(EventT & e, VertexT * v) {
    e.add_vertex(v);
  }

  /** Create a new particle object with momentum \a p, PDG number \a
      id and status code \a status. The momentum will be scaled with
      \a unit which according to the HepMC documentation should be
      GeV. */
  static ParticleT * newParticle(const Lorentz5Momentum & p,
				 long id, int status, Energy unit) {
    // Note that according to the documentation the momentum is stored in a
    // HepLorentzVector in GeV (event though the CLHEP standard is MeV).
    LorentzVector<double> p_scalar = p/unit;
    ParticleT * genp = new ParticleT(p_scalar, id, status);
    genp->setGeneratedMass(p.mass()/unit);
    return genp;
  }

  /** Set the polarization directions, \a the and \a phi, for particle
      \a p. */
  static void setPolarization(ParticleT & genp, double the, double phi) {
    genp.set_polarization(PolarizationT(the, phi));
  }

  /** Set the colour line (with index \a indx) to \a coline for
      particle \a p. */
  static void setColourLine(ParticleT & p, int indx, int coline) {
    p.set_flow(indx, coline);
  }

  /** Create a new vertex. */
  static VertexT * newVertex() {
    return new VertexT();
  }

  /** Add an incoming particle, \a p, to the vertex, \a v. */
  static void addIncoming(VertexT & v, ParticleT * p) {
    v.add_particle_in(p);
  }

  /** Add an outgoing particle, \a p, to the vertex, \a v. */
  static void addOutgoing(VertexT & v, ParticleT * p) {
    v.add_particle_out(p);
  }

  /** Set the position \a p for the vertex, \a v. The length will be
      scaled with \a unit which normally should be millimeters. */
  static void setPosition(VertexT & v, const LorentzPoint & p, Length unit) {
    LorentzVector<double> p_scaled = p/unit;
    v.set_position(p_scaled);
  }

  /** Set the beam particles for the event.*/
  static void setBeamParticles(EventT & e, ParticleT * p1, ParticleT * p2) {
    e.set_beam_particles(p1,p2);
    p1->set_status(4);
    p2->set_status(4);
  }

  /** Set the PDF info for the event. */
#ifdef HEPMC_HAS_PDF_INFO
  static void setPdfInfo(EventT & e, int id1, int id2, double x1, double x2,
			 double scale, double xf1, double xf2) {
    e.set_pdf_info(PdfInfoT(id1, id2, x1, x2, scale, xf1, xf2));
  }
#else
  static void setPdfInfo(EventT &, int, int, double, double,
			 double, double, double) {}
#endif

  /** Set the cross section info for the event. */
#ifdef HEPMC_HAS_CROSS_SECTION
  static void setCrossSection(EventT & ev, double xs, double xserr) {
    HepMC::GenCrossSection x;
    x.set_cross_section(xs, xserr);
    ev.set_cross_section(x);
  }
#else
  static void setCrossSection(EventT &, double, double) {}
#endif

};

/**
 * The HepMCTraits class is used to deal with different flavours of
 * HepMC in the HepMCConverter class. To use the HepMCConverter class
 * for any flavour of HepMC you have to specialize the
 * HepMCTraits class accordingly, possibly inheriting the
 * functionality from the HepMCTraitsBase class and only overriding
 * the functions and typedefs which are different. For the CLHEP
 * flavour of HepMC you only need to do <code>template&lt;&gt; struct
 * HepMCTraits&lt;HepMC::GenEvent&gt;: public
 * HepMCTraitsBase&lt;HepMC::GenEvent,HepMC::GenParticle,HepMC::GenVertex,
 * HepMC::Polarization,HepMC::PdfInfo&gt; {};</code> somewhere inside the ThePEG
 * namespace.
 */
template <typename HepMCEventT>
struct HepMCTraits {};
}

#endif