PartonLevel.h

// PartonLevel.h is a part of the PYTHIA event generator.
// Copyright (C) 2014 Torbjorn Sjostrand.
// PYTHIA is licenced under the GNU GPL version 2, see COPYING for details.
// Please respect the MCnet Guidelines, see GUIDELINES for details.

// This file contains the main class for parton-level event generation
// PartonLevel: administrates showers, multiparton interactions and remnants.

#ifndef Pythia8_PartonLevel_H
#define Pythia8_PartonLevel_H

#include "Pythia8/Basics.h"
#include "Pythia8/BeamParticle.h"
#include "Pythia8/BeamRemnants.h"
#include "Pythia8/Event.h"
#include "Pythia8/Info.h"
#include "Pythia8/MultipartonInteractions.h"
#include "Pythia8/ParticleData.h"
#include "Pythia8/PartonSystems.h"
#include "Pythia8/PythiaStdlib.h"
#include "Pythia8/ResonanceDecays.h"
#include "Pythia8/RHadrons.h"
#include "Pythia8/Settings.h"
#include "Pythia8/SigmaTotal.h"
#include "Pythia8/SpaceShower.h"
#include "Pythia8/StandardModel.h"
#include "Pythia8/TimeShower.h"
#include "Pythia8/UserHooks.h"
#include "Pythia8/MergingHooks.h"

namespace Pythia8 {
 
//==========================================================================

// The PartonLevel class contains the top-level routines to generate
// the partonic activity of an event.

class PartonLevel {

public:

  // Constructor.
  PartonLevel() : userHooksPtr(0) {}
 
  // Initialization of all classes at the parton level.
  bool init( Info* infoPtrIn, Settings& settings,
    ParticleData* particleDataPtrIn, Rndm* rndmPtrIn,
    BeamParticle* beamAPtrIn, BeamParticle* beamBPtrIn,
    BeamParticle* beamPomAPtrIn, BeamParticle* beamPomBPtrIn,
    Couplings* couplingsPtrIn, PartonSystems* partonSystemsPtrIn,
    SigmaTotal* sigmaTotPtr, TimeShower* timesDecPtrIn,
    TimeShower* timesPtrIn, SpaceShower* spacePtrIn,
    RHadrons* rHadronsPtrIn, UserHooks* userHooksPtrIn,
    MergingHooks* mergingHooksPtr, bool useAsTrial);
 
  // Generate the next parton-level process.
  bool next( Event& process, Event& event);

  // Perform showers in resonance decay chains. (For special cases.)
  void setupShowerSys( Event& process, Event& event);
  bool resonanceShowers( Event& process, Event& event, bool skipForR);

  // Perform decays and showers of W and Z emitted in shower.
  bool wzDecayShowers( Event& event);

  // Tell whether failure was due to vetoing.
  bool hasVetoed() const {return doVeto;}

  // Accumulate, print and reset statistics.
  void accumulate() {if (isResolved && !isDiff) multiPtr->accumulate();}
  void statistics(bool reset = false) {
    if (doMPI) multiMB.statistics(reset);}
    // For now no separate statistics for diffraction??
    //if (doMPISDA && doDiffraction) multiSDA.statistics(reset);
    //if (doMPISDB && doDiffraction) multiSDB.statistics(reset);}
  void resetStatistics() { if (doMPI) multiMB.resetStatistics(); }

  // Reset PartonLevel object for trial shower usage.
  void resetTrial();
  // Provide the pT scale of the last branching in the shower.
  double pTLastInShower(){ return pTLastBranch; }
  // Provide the type of the last branching in the shower.
  int typeLastInShower(){ return typeLastBranch; }

private:

  // Constants: could only be changed in the code itself.
  static const int NTRY;

  // Initialization data, mainly read from Settings.
  bool   doNonDiff, doDiffraction, doMPI, doMPIMB, doMPISDA, doMPISDB,
         doMPICD, doMPIinit, doISR, doFSRduringProcess, doFSRafterProcess,
         doFSRinResonances, doRemnants, doSecondHard, hasLeptonBeams,
         hasPointLeptons, canVetoPT, canVetoStep, canVetoMPIStep,
         canVetoEarly, canSetScale, allowRH, earlyResDec, vetoWeakJets,
         canReconResSys;
  double mMinDiff, mWidthDiff, pMaxDiff, vetoWeakDeltaR2;

  // Event generation strategy. Number of steps. Maximum pT scales.
  bool   doVeto;
  int    nMPI, nISR, nFSRinProc, nFSRinRes, nISRhard, nFSRhard,
         typeLatest, nVetoStep, typeVetoStep, nVetoMPIStep, iSysNow;
  double pTsaveMPI, pTsaveISR, pTsaveFSR, pTvetoPT;

  // Current event properties.
  bool   isNonDiff, isDiffA, isDiffB, isDiffC, isDiff, isSingleDiff,
         isDoubleDiff, isCentralDiff, isResolved, isResolvedA,
         isResolvedB, isResolvedC;
  int    sizeProcess, sizeEvent, nHardDone, nHardDoneRHad, iDS;
  double eCMsave;
  vector<bool> inRHadDecay;
  vector<int>  iPosBefShow;

  // Pointer to various information on the generation.
  Info*          infoPtr;

  // Pointer to the particle data table.
  ParticleData*  particleDataPtr;

  // Pointer to the random number generator.
  Rndm*          rndmPtr;

  // Pointers to the two incoming beams.
  BeamParticle*  beamAPtr;
  BeamParticle*  beamBPtr;

  // Spare copies of normal pointers. Pointers to Pomeron beam-inside-beam.
  BeamParticle*  beamHadAPtr;
  BeamParticle*  beamHadBPtr;
  BeamParticle*  beamPomAPtr;
  BeamParticle*  beamPomBPtr;

  // Pointers to Standard Model couplings.
  Couplings*     couplingsPtr;
  
  // Pointer to information on subcollision parton locations.
  PartonSystems* partonSystemsPtr;

  // Pointer to userHooks object for user interaction with program.
  UserHooks*     userHooksPtr;

  // Pointers to timelike showers for resonance decays and the rest.
  TimeShower*    timesDecPtr;
  TimeShower*    timesPtr;

  // Pointer to spacelike showers.
  SpaceShower*   spacePtr;

  // The generator classes for multiparton interactions.
  MultipartonInteractions  multiMB;
  MultipartonInteractions  multiSDA;
  MultipartonInteractions  multiSDB;
  MultipartonInteractions  multiCD;
  MultipartonInteractions* multiPtr;

  // The generator class to construct beam-remnant kinematics.
  BeamRemnants remnants;
  // Separate instance for central diffraction.
  BeamRemnants remnantsCD;
  
  // The RHadrons class is used to fragment off and decay R-hadrons.
  RHadrons*    rHadronsPtr;

  // ResonanceDecay object does sequential resonance decays.
  ResonanceDecays resonanceDecays;

  // Resolved diffraction: find how many systems should have it.
  int decideResolvedDiff( Event& process);

  // Set up an unresolved process, i.e. elastic or diffractive.
  bool setupUnresolvedSys( Event& process, Event& event);

  // Set up the hard process, excluding subsequent resonance decays.
  void setupHardSys( Event& process, Event& event);

  // Resolved diffraction: pick whether to have it and set up for it.
  void setupResolvedDiff( Event& process);

  // Resolved diffraction: restore normal behaviour.
  void leaveResolvedDiff( int iHardLoop, Event& process, Event& event);

  // Pointer to MergingHooks object for user interaction with the merging.
  MergingHooks* mergingHooksPtr;
  // Parameters to specify trial shower usage
  bool doTrial;
  int nTrialEmissions;
  // Parameters to store to veto trial showers
  double pTLastBranch;
  int typeLastBranch;
  // Parameters to specify merging usage
  bool canRemoveEvent, canRemoveEmission;

};

//==========================================================================

} // end namespace Pythia8

#endif // Pythia8_PartonLevel_H