G4ElementaryParticleCollider.cc

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//
// $Id: G4ElementaryParticleCollider.cc 71940 2013-06-28 19:04:44Z mkelsey $
//
// 20100114  M. Kelsey -- Remove G4CascadeMomentum, use G4LorentzVector directly
// 20100316  D. Wright (restored by M. Kelsey) -- Replace original (incorrect)
//              pp, pn, nn 2-body to 2-body scattering angular distributions
//              with a new parametrization of elastic scattering data using
//              the sum of two exponentials.
// 20100319  M. Kelsey -- Use new generateWithRandomAngles for theta,phi stuff;
//              eliminate some unnecessary std::pow()
// 20100407  M. Kelsey -- Replace std::vector<>::resize(0) with ::clear()
//              Eliminate return-by-value std::vector<> by creating buffers
//              buffers for particles, momenta, and particle types.
//              The following functions now return void and are non-const:
//                ::generateSCMfinalState()
//                ::generateMomModules()
//                ::generateStrangeChannelPartTypes()
//                ::generateSCMpionAbsorption()
// 20100408  M. Kelsey -- Follow changes to G4*Sampler to pass particle_kinds
//              as input buffer.
// 20100413  M. Kelsey -- Pass G4CollisionOutput by ref to ::collide()
// 20100428  M. Kelsey -- Use G4InuclParticleNames enum
// 20100429  M. Kelsey -- Change "photon()" to "isPhoton()"
// 20100507  M. Kelsey -- Rationalize multiplicity returns to be actual value
// 20100511  M. Kelsey -- Replace G4PionSampler and G4NucleonSampler with new
//              pi-N and N-N classes, reorganize if-cascades 
// 20100511  M. Kelsey -- Eliminate three residual random-angles blocks.
// 20100511  M. Kelsey -- Bug fix: pi-N two-body final states not correctly
//              tested for charge-exchange case.
// 20100512  M. Kelsey -- Rationalize multiplicity returns to be actual value
// 20100512  M. Kelsey -- Add some additional debugging messages for 2-to-2
// 20100512  M. Kelsey -- Replace "if (is==)" cascades with switch blocks.
//              Use G4CascadeInterpolator for angular distributions.
// 20100517  M. Kelsey -- Inherit from common base class, make arrays static
// 20100519  M. Kelsey -- Use G4InteractionCase to compute "is" values.
// 20100625  M. Kelsey -- Two bugs in n-body momentum, last particle recoil
// 20100713  M. Kelsey -- Bump collide start message up to verbose > 1
// 20100714  M. Kelsey -- Move conservation checking to base class
// 20100714  M. Kelsey -- Add sanity check for two-body final state, to ensure
//              that final state total mass is below etot_scm; also compute
//              kinematics without "rescaling" (which led to non-conservation)
// 20100726  M. Kelsey -- Move remaining std::vector<> buffers to .hh file
// 20100804  M. Kelsey -- Add printing of final-state tables, protected by
//              G4CASCADE_DEBUG_SAMPLER preprocessor flag
// 20101019  M. Kelsey -- CoVerity report: check dynamic_cast<> for null
// 20110214  M. Kelsey -- Follow G4InuclParticle::Model enumerator migration
// 20110718  V. Uzhinskiy -- Drop IL,IM reset for multiplicity-three collisions
// 20110718  M. Kelsey -- Use enum names in switch blocks (c.f. G4NucleiModel)
// 20110720  M. Kelsey -- Follow interface change for cross-section tables,
//              eliminating switch blocks.
// 20110806  M. Kelsey -- Pre-allocate buffers to avoid memory churn
// 20110922  M. Kelsey -- Follow G4InuclParticle::print(ostream&) migration
// 20110926  M. Kelsey -- Protect sampleCMcosFor2to2 from unphysical arguments
// 20111003  M. Kelsey -- Prepare for gamma-N interactions by checking for
//              final-state tables instead of particle "isPhoton()"
// 20111007  M. Kelsey -- Add gamma-N final-state tables to printFinalState
// 20111107  M. Kelsey -- In sampleCMmomentumFor2to2(), hide message about
//              unrecognized gamma-N initial state behind verbosity.
// 20111216  M. Kelsey -- Add diagnostics to generateMomModulesFor2toMany(),
//              defer allocation of buffer in generateSCMfinalState() so that
//              multiplicity failures return zero output, and can be trapped.
// 20120308  M. Kelsey -- Allow photons to interact with dibaryons (see
//              changes in G4NucleiModel).
// 20120608  M. Kelsey -- Fix variable-name "shadowing" compiler warnings.
// 20121206  M. Kelsey -- Add Omega to printFinalStateTables(), remove line
//              about "preliminary" gamma-N.
// 20130129  M. Kelsey -- Add static arrays and interpolators for two-body
//              angular distributions (addresses MT thread-local issue)
// 20130221  M. Kelsey -- Move two-body angular dist classes to factory
// 20130306  M. Kelsey -- Use particle-name enums in if-blocks; add comments
//              to sections of momentum-coefficient matrix; move final state
//              table printing to G4CascadeChannelTables.
// 20130307  M. Kelsey -- Reverse order of dimensions for rmn array
// 20130307  M. Kelsey -- Use new momentum generator factory instead of rmn
// 20130308  M. Kelsey -- Move 3-body angle calc to G4InuclSpecialFunctions.
// 20130422  M. Kelsey -- Move kinematics to G4CascadeFinalStateAlgorithm;
//              reduce nesting and replicated code in collide().
// 20130508  D. Wright -- Implement muon capture
// 20130511  M. Kelsey -- Check for neutrinos and skip them in ::collide()
// 20141009  M. Kelsey -- Add pion absorption by single nucleons, with
//              nuclear recoil.  Improves pi- capture performance.
// 20141030  M. Kelsey -- Check flag for whether to do pi-N absorption
// 20141201  M. Kelsey -- Check for null vector return from G4GDecay3

#include "G4ElementaryParticleCollider.hh"
#include "G4CascadeChannel.hh"
#include "G4CascadeChannelTables.hh"
#include "G4CascadeParameters.hh"
#include "G4CollisionOutput.hh"
#include "G4GDecay3.hh"
#include "G4InuclParticleNames.hh"
#include "G4InuclSpecialFunctions.hh"
#include "G4LorentzConvertor.hh"
#include "G4MultiBodyMomentumDist.hh"
#include "G4NucleiModel.hh"
#include "G4ParticleLargerEkin.hh"
#include "G4TwoBodyAngularDist.hh"
#include "G4VMultiBodyMomDst.hh"
#include "G4VTwoBodyAngDst.hh"
#include "Randomize.hh"
#include <algorithm>
#include <cfloat>
#include <vector>

using namespace G4InuclParticleNames;
using namespace G4InuclSpecialFunctions;

typedef std::vector<G4InuclElementaryParticle>::iterator particleIterator;


G4ElementaryParticleCollider::G4ElementaryParticleCollider()
  : G4CascadeColliderBase("G4ElementaryParticleCollider"),
    nucleusA(0), nucleusZ(0) {;}


void
G4ElementaryParticleCollider::collide(G4InuclParticle* bullet,
                                      G4InuclParticle* target,
                                      G4CollisionOutput& output) 
{
  if (verboseLevel > 1)
    G4cout << " >>> G4ElementaryParticleCollider::collide" << G4endl;

  if (!useEPCollider(bullet,target)) {          // Sanity check
    G4cerr << " ElementaryParticleCollider -> can collide only particle with particle " 
           << G4endl;
    return;
  }

#ifdef G4CASCADE_DEBUG_SAMPLER
  static G4bool doPrintTables = true;   // Once and only once per job
  if (doPrintTables) {
    G4CascadeChannelTables::Print();
    doPrintTables = false;
  }
#endif

  interCase.set(bullet, target);        // To identify kind of collision

  if (verboseLevel > 1) G4cout << *bullet << G4endl << *target << G4endl;

  G4InuclElementaryParticle* particle1 =
    dynamic_cast<G4InuclElementaryParticle*>(bullet);
  G4InuclElementaryParticle* particle2 =        
    dynamic_cast<G4InuclElementaryParticle*>(target);

  if (!particle1 || !particle2) {       // Redundant with useEPCollider()
    G4cerr << " ElementaryParticleCollider -> can only collide hadrons"
           << G4endl;
    return;
  }

  if (particle1->isNeutrino() || particle2->isNeutrino()) return;

  // Check for available interaction, or pion+dibaryon special case
  if (!G4CascadeChannelTables::GetTable(interCase.hadrons()) &&
      !particle1->quasi_deutron() && !particle2->quasi_deutron()) {
    G4cerr << " ElementaryParticleCollider -> cannot collide " 
           << particle1->getDefinition()->GetParticleName() << " with "
           << particle2->getDefinition()->GetParticleName() << G4endl;
    return;
  }

  G4LorentzConvertor convertToSCM;      // Utility to handle frame manipulation
  if (particle2->nucleon() || particle2->quasi_deutron()) {
    convertToSCM.setBullet(particle1);
    convertToSCM.setTarget(particle2);
  } else {
    convertToSCM.setBullet(particle2);
    convertToSCM.setTarget(particle1);
  }

  convertToSCM.setVerbose(verboseLevel);
  convertToSCM.toTheCenterOfMass();

  // Generate any particle collision with nucleon
  if (particle1->nucleon() || particle2->nucleon()) {
    G4double ekin = convertToSCM.getKinEnergyInTheTRS();
    G4double etot_scm = convertToSCM.getTotalSCMEnergy();

    // SPECIAL:  Very low energy pions may be absorbed by a nucleon
    if (pionNucleonAbsorption(ekin)) {
      generateSCMpionNAbsorption(etot_scm, particle1, particle2);
    } else {
      generateSCMfinalState(ekin, etot_scm, particle1, particle2);
    }
  }

  // Generate pion or photon collision with quasi-deuteron
  if (particle1->quasi_deutron() || particle2->quasi_deutron()) {
    if (!G4NucleiModel::useQuasiDeuteron(particle1->type(),particle2->type()) &&
        !G4NucleiModel::useQuasiDeuteron(particle2->type(),particle1->type())) {
      G4cerr << " ElementaryParticleCollider -> can only collide pi,mu,gamma with"
             << " dibaryons " << G4endl;
      return;
    }

    G4double etot_scm = convertToSCM.getTotalSCMEnergy();

    if (particle1->isMuon() || particle2->isMuon()) {
      generateSCMmuonAbsorption(etot_scm, particle1, particle2);
    } else {            // Currently, pion absoprtion also handles gammas
      generateSCMpionAbsorption(etot_scm, particle1, particle2);
    }
  }    

  if (particles.empty()) {      // No final state possible, pass bullet through
    if (verboseLevel) {
      G4cerr << " ElementaryParticleCollider -> failed to collide " 
             << particle1->getMomModule() << " GeV/c " 
             << particle1->getDefinition()->GetParticleName() << " with "
             << particle2->getDefinition()->GetParticleName() << G4endl;
    }
    return;
  }

  // Convert final state back to lab frame
  G4LorentzVector mom;          // Buffer to avoid memory churn
  particleIterator ipart;
  for(ipart = particles.begin(); ipart != particles.end(); ipart++) {   
    mom = convertToSCM.backToTheLab(ipart->getMomentum());
    ipart->setMomentum(mom); 
  };
  
  // Check conservation in multibody final state
  if (verboseLevel && !validateOutput(bullet, target, particles)) {
    G4cout << " incoming particles: \n" << *particle1 << G4endl
           << *particle2 << G4endl
           << " outgoing particles: " << G4endl;
    for(ipart = particles.begin(); ipart != particles.end(); ipart++)
      G4cout << *ipart << G4endl;
    
    G4cout << " <<< Non-conservation in G4ElementaryParticleCollider"
           << G4endl;
  }
    
  std::sort(particles.begin(), particles.end(), G4ParticleLargerEkin());
  output.addOutgoingParticles(particles);
}


G4int 
G4ElementaryParticleCollider::generateMultiplicity(G4int is, 
                                                   G4double ekin) const 
{
  G4int mul = 0;

  const G4CascadeChannel* xsecTable = G4CascadeChannelTables::GetTable(is);

  if (xsecTable) mul = xsecTable->getMultiplicity(ekin);
  else {
    G4cerr << " G4ElementaryParticleCollider: Unknown interaction channel "
           << is << " - multiplicity not generated " << G4endl;
  }

  if(verboseLevel > 3){
    G4cout << " G4ElementaryParticleCollider::generateMultiplicity: "  
           << " multiplicity = " << mul << G4endl; 
  }

  return mul;
}

 
void 
G4ElementaryParticleCollider::generateOutgoingPartTypes(G4int is, G4int mult,
                                                        G4double ekin)
{
  particle_kinds.clear();       // Initialize buffer for generation

  const G4CascadeChannel* xsecTable = G4CascadeChannelTables::GetTable(is);

  if (xsecTable)
    xsecTable->getOutgoingParticleTypes(particle_kinds, mult, ekin);
  else {
    G4cerr << " G4ElementaryParticleCollider: Unknown interaction channel "
           << is << " - outgoing kinds not generated " << G4endl;
  }

  return;
}


void
G4ElementaryParticleCollider::generateSCMfinalState(G4double ekin, 
                                     G4double etot_scm, 
                                     G4InuclElementaryParticle* particle1,
                                     G4InuclElementaryParticle* particle2) {
  if (verboseLevel > 2) {
    G4cout << " >>> G4ElementaryParticleCollider::generateSCMfinalState" 
           << G4endl;
  }

  fsGenerator.SetVerboseLevel(verboseLevel);

  const G4int itry_max = 10;

  G4int type1 = particle1->type();
  G4int type2 = particle2->type();

  G4int is = type1 * type2;

  if (verboseLevel > 3) G4cout << " is " << is << G4endl;

  G4int multiplicity = 0;
  G4bool generate = true;

  G4int itry = 0;
  while (generate && itry++ < itry_max) {
    particles.clear();          // Initialize buffers for this event
    particle_kinds.clear();

    // Generate list of final-state particles
    multiplicity = generateMultiplicity(is, ekin);

    generateOutgoingPartTypes(is, multiplicity, ekin);
    if (particle_kinds.empty()) {
      if (verboseLevel > 3) {
        G4cout << " generateOutgoingPartTypes failed mult " << multiplicity
               << G4endl;
      }
      continue;
    }

    fillOutgoingMasses();       // Fill mass buffer from particle types

    // Attempt to produce final state kinematics
    fsGenerator.Configure(particle1, particle2, particle_kinds);
    generate = !fsGenerator.Generate(etot_scm, masses, scm_momentums);
  }     // while (generate) 

  if (itry >= itry_max) {               // Unable to generate valid final state
    if (verboseLevel > 2)
      G4cout << " generateSCMfinalState failed " << itry << " attempts"
             << G4endl;
    return;
  }

  // Store generated momenta into outgoing particles

  particles.resize(multiplicity);               // Preallocate buffer
  for (G4int i=0; i<multiplicity; i++) {
    particles[i].fill(scm_momentums[i], particle_kinds[i],
                      G4InuclParticle::EPCollider);
  }

  if (verboseLevel > 3) {
    G4cout << " <<< G4ElementaryParticleCollider::generateSCMfinalState"
           << G4endl;
  }

  return;       // Particles buffer filled
}


// Use generated list of final states to fill mass buffers

void G4ElementaryParticleCollider::fillOutgoingMasses() {
  G4int mult = particle_kinds.size();

  masses.resize(mult,0.);
  masses2.resize(mult,0.);              // Allows direct [i] setting

  for (G4int i = 0; i < mult; i++) {
    masses[i] = G4InuclElementaryParticle::getParticleMass(particle_kinds[i]);
    masses2[i] = masses[i] * masses[i];
  }
}


// generate nucleons momenta for pion or photon absorption by dibaryon
// the nucleon distribution assumed to be isotropic in SCM

void
G4ElementaryParticleCollider::generateSCMpionAbsorption(G4double etot_scm,
                                     G4InuclElementaryParticle* particle1,
                                     G4InuclElementaryParticle* particle2) {
  if (verboseLevel > 3)
    G4cout << " >>> G4ElementaryParticleCollider::generateSCMpionAbsorption" 
           << G4endl;

  particles.clear();            // Initialize buffers for this event
  particles.resize(2);

  particle_kinds.clear();

  G4int type1 = particle1->type();
  G4int type2 = particle2->type();

  // Ensure that absportion is valid (charge conservable)
  if (!G4NucleiModel::useQuasiDeuteron(type1, type2)) {
    G4cerr << " pion absorption: "
           << particle1->getDefinition()->GetParticleName() << " + "
           << particle2->getDefinition()->GetParticleName() << " -> ?"
           << G4endl;
    return;
  }

  if (!splitQuasiDeuteron(type2)) return;       // Get constituents of [NN]

  fillOutgoingMasses();

  G4double a = 0.5 * (etot_scm * etot_scm - masses2[0] - masses2[1]);

  G4double pmod = std::sqrt((a*a - masses2[0]*masses2[1])
                            / (masses2[0] + masses2[1] + 2.0*a));
  G4LorentzVector mom1 = generateWithRandomAngles(pmod, masses[0]);
  G4LorentzVector mom2;
  mom2.setVectM(-mom1.vect(), masses[1]);

  particles[0].fill(mom1, particle_kinds[0], G4InuclParticle::EPCollider);
  particles[1].fill(mom2, particle_kinds[1], G4InuclParticle::EPCollider);
}


// generate nucleons momenta for muon absorption by dibaryon
// the nucleon distribution assumed to be isotropic in SCM

void
G4ElementaryParticleCollider::generateSCMmuonAbsorption(G4double etot_scm,
                                     G4InuclElementaryParticle* particle1,
                                     G4InuclElementaryParticle* particle2)
{
  if (verboseLevel > 3)
    G4cout << " >>> G4ElementaryParticleCollider::generateSCMmuonAbsorption"
           << G4endl;

  // A phase space generator is required for the 3-body final state

  particles.clear();            // Initialize buffers for this event
  particles.resize(3);

  scm_momentums.clear();
  scm_momentums.resize(3);

  particle_kinds.clear();

  G4int type1 = particle1->type();
  G4int type2 = particle2->type();

  if (type1 != muonMinus) return;       // Sanity check, only mu- absorption

  // Ensure that absportion is valid (charge conservable)
  if (!G4NucleiModel::useQuasiDeuteron(type1, type2)) {
    G4cerr << " mu- absorption: "
           << particle1->getDefinition()->GetParticleName() << " + "
           << particle2->getDefinition()->GetParticleName() << " -> ?"
           << G4endl;
    return;
  }

  if (!splitQuasiDeuteron(type2)) return;       // Get constituents of [NN]
  particle_kinds.push_back(mnu);
  
  fillOutgoingMasses();

  G4GDecay3 breakup(etot_scm, masses[0], masses[1], masses[2]);
  std::vector<G4ThreeVector> theMomenta = breakup.GetThreeBodyMomenta();

  if (theMomenta.empty()) {
    G4cerr << " generateSCMmuonAbsorption: GetThreeBodyMomenta() failed"
           << " for " << type2 << " dibaryon" << G4endl;
    particle_kinds.clear();
    masses.clear();
    return;
  }

  for (size_t i=0; i<3; i++) {
    scm_momentums[i].setVectM(theMomenta[i], masses[i]);
    particles[i].fill(scm_momentums[i], particle_kinds[i], G4InuclParticle::EPCollider);
  }
} 


// generate nucleons momenta for pion absorption by single nucleon

void
G4ElementaryParticleCollider::generateSCMpionNAbsorption(G4double etot_scm,
                                     G4InuclElementaryParticle* particle1,
                                     G4InuclElementaryParticle* particle2) {
  if (verboseLevel > 3)
    G4cout << " >>> G4ElementaryParticleCollider::generateSCMpionNAbsorption" 
           << G4endl;

  particles.clear();            // Initialize buffers for this event
  particles.resize(1);

  particle_kinds.clear();

  G4int type1 = particle1->type();
  G4int type2 = particle2->type();

  // Ensure that single-nucleon absportion is valid (charge exchangeable)
  if ((type1*type2 != pim*pro && type1*type2 != pip*neu)) {
    G4cerr << " pion-nucleon absorption: "
           << particle1->getDefinition()->GetParticleName() << " + "
           << particle2->getDefinition()->GetParticleName() << " -> ?"
           << G4endl;
    return;
  }

  // Get outgoing nucleon type using charge exchange
  // Proton code is 1, neutron code is 2, so 3-# swaps them
  G4int ntype = (particle2->nucleon() ? type2 : type1);
  G4int outType = 3 - ntype;
  particle_kinds.push_back(outType);

  fillOutgoingMasses();

  // Get mass of residual nucleus (2-ntype = 1 for proton, 0 for neutron)
  G4double mRecoil =
    G4InuclNuclei::getNucleiMass(nucleusA-1, nucleusZ-(2-ntype));
  G4double mRecoil2 = mRecoil*mRecoil;

  // Recompute Ecm to include nucleus (for recoil kinematics)
  G4LorentzVector vsum(0.,0.,0.,mRecoil);
  vsum += particle1->getMomentum() + particle2->getMomentum();
  etot_scm = vsum.m();

  // Two-body kinematics (nucleon against nucleus)
  G4double a = 0.5 * (etot_scm*etot_scm - masses2[0] - mRecoil2);

  G4double pmod = std::sqrt((a*a - masses2[0]*mRecoil2)
                            / (masses2[0] + mRecoil2 + 2.0*a));
  G4LorentzVector mom1 = generateWithRandomAngles(pmod, masses[0]);

  if (verboseLevel > 3) {
    G4cout << " outgoing type " << outType << " recoiling on nuclear mass "
           << mRecoil << " a " << a << " p(SCM) " << pmod << " Ekin "
           << mom1.e()-masses[0] << G4endl;
  }

  // Nuclear recoil four momentum, for boosting back
  G4LorentzVector mom2;
  mom2.setVectM(-mom1.vect(), mRecoil);
  mom1.boost(-mom2.boostVector());

  if (verboseLevel > 3) {
    G4cout << " after nuclear recoil p " << mom1.rho() << " Ekin "
           << mom1.e()-masses[0] << G4endl;
  }

  // Fill only the ejected nucleon
  particles[0].fill(mom1, particle_kinds[0], G4InuclParticle::EPCollider);
}


// Evaluate whether interaction is candidate for absorption on nucleon

G4bool 
G4ElementaryParticleCollider::pionNucleonAbsorption(G4double ekin) const {
  if (!G4CascadeParameters::piNAbsorption()) return false;

  if (verboseLevel > 3)
    G4cout << " >>> G4ElementaryParticleCollider::pionNucleonAbsorption ?"
           << " ekin " << ekin << " is " << interCase.hadrons() << G4endl;

  const G4double mpi0 = G4InuclElementaryParticle::getParticleMass(pionZero);

  // Absorption occurs only for pi- p -> n, or pi+ n -> p
  // Restrict to "very slow" pions, to allow for some normal scattering
  G4bool isAbsorbable = ((interCase.hadrons() == pim*pro ||
                          interCase.hadrons() == pip*neu)
                         && ekin < 0.5*mpi0);

  // FIXME:  Should have an effective cross-section to throw random here
  return isAbsorbable;
}


// generate constituents of dibaryon for "explosion"

G4bool G4ElementaryParticleCollider::splitQuasiDeuteron(G4int qdtype) {
  if (qdtype != diproton && qdtype != unboundPN && qdtype != dineutron) {
    G4cerr << " type " << qdtype << " not dibaryon!" << G4endl;
    return false;
  }

  G4int b2 = qdtype % 10;       // Dibaryon codes are 1ab (a=1,2; b=1,2)
  G4int b1 = (qdtype/10) % 10;

  particle_kinds.push_back(b1);
  particle_kinds.push_back(b2);

  return true;
}