NievesSimoVacasMECPXSec2016.cxx

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//_________________________________________________________________________
/*
 Copyright (c) 2003-2025, The GENIE Collaboration
 For the full text of the license visit http://copyright.genie-mc.org
 
 Original code contributed by J. Schwehr, D. Cherdack, R. Gran
 Substantial code refactorizations by the core GENIE group.
*/
//_________________________________________________________________________
 
#include "Framework/Algorithm/AlgConfigPool.h"
#include "Framework/Conventions/Constants.h"
#include "Framework/Conventions/Units.h"
#include "Framework/Messenger/Messenger.h"
#include "Framework/ParticleData/PDGCodes.h"
#include "Framework/ParticleData/PDGLibrary.h"
#include "Framework/ParticleData/PDGUtils.h"
#include "Framework/Utils/KineUtils.h"
#include "Physics/HadronTensors/NievesMECHadronTensorModel.h"
#include "Physics/HadronTensors/LabFrameHadronTensorI.h"
#include "Physics/Multinucleon/XSection/NievesSimoVacasMECPXSec2016.h"
#include "Physics/Multinucleon/XSection/MECUtils.h"
#include "Physics/XSectionIntegration/XSecIntegratorI.h"
 
using namespace genie;
using namespace genie::constants;
 
//_________________________________________________________________________
NievesSimoVacasMECPXSec2016::NievesSimoVacasMECPXSec2016() :
XSecAlgorithmI("genie::NievesSimoVacasMECPXSec2016")
{
 
}
//_________________________________________________________________________
NievesSimoVacasMECPXSec2016::NievesSimoVacasMECPXSec2016(string config) :
XSecAlgorithmI("genie::NievesSimoVacasMECPXSec2016", config)
{
 
}
//_________________________________________________________________________
NievesSimoVacasMECPXSec2016::~NievesSimoVacasMECPXSec2016()
{
 
}
//_________________________________________________________________________
double NievesSimoVacasMECPXSec2016::XSec(
  const Interaction * interaction, KinePhaseSpace_t kps) const
{
  // If {W,Q2} have been supplied instead, compute {Tl, ctl}
  // NOTE: The expressions used here neglect Fermi motion and
  // should eventually be revisited. See the "important note"
  // in src/Framework/Utils/KineUtils.cxx about the
  // Jacobian for transforming {W,Q2} --> {Tl, ctl}.
  // - S. Gardiner, 29 July 2020
  if ( kps == kPSWQ2fE ) {
 
    double Q2 = interaction->Kine().GetKV( kKVQ2 );
    double W = interaction->Kine().GetKV( kKVW );
 
    // Probe properties (mass, energy, momentum)
    const InitialState& init_state = interaction->InitState();
    double mv = init_state.Probe()->Mass();
    double Ev = init_state.ProbeE( kRfLab );
    double pv = std::sqrt( std::max(0., Ev*Ev - mv*mv) );
 
    // Invariant mass of the initial hit nucleon
    const TLorentzVector& hit_nuc_P4 = init_state.Tgt().HitNucP4();
    double M = hit_nuc_P4.M();
 
    // Get the outgoing lepton kinetic energy
    double ml = interaction->FSPrimLepton()->Mass();
    double Tl = Ev - ml - ( (W*W + Q2 - M*M) / (2.*M) );
 
    // Get the outgoing lepton scattering cosine
    double El = Tl + ml;
    double pl = std::sqrt( std::max(0., El*El - ml*ml) );
    double ctl = ( 2.*Ev*El - Q2 - mv*mv - ml*ml ) / ( 2. * pv * pl );
 
    // Set Tl, ctl in the interaction
    interaction->KinePtr()->SetKV( kKVTl, Tl );
    interaction->KinePtr()->SetKV( kKVctl, ctl );
  }
 
  // This function returns d2sigma/(dTmu dcos_mu) in GeV^(-3)
  int target_pdg = interaction->InitState().Tgt().Pdg();
 
  int A_request = pdg::IonPdgCodeToA(target_pdg);
  int Z_request = pdg::IonPdgCodeToZ(target_pdg);
 
  // To generate cross-sections for nuclei other than those with hadron
  // tensors we need to pull both the full cross-section and
  // the pn initial state fraction.
  // Non-isoscalar nuclei are beyond the original published Valencia model
  // and scale with A according to the number of pp, pn, or nn pairs
  // the probe is expected to find.
  // There is some by-hand optimization here, skipping the delta part when
  // only the total cross-section is requested.
  // Possible future models without a Delta had tensor would also use that
  // flag to call this without computing the Delta part.
 
  // Try to look up a hadron tensor in the pool that is an exact match for
  // the target nucleus. If an exact match cannot be found, decide upon a
  // suitable substitute based on the mass number A and proton number Z.
 
  int tensor_pdg = target_pdg;
 
  /// \todo Replace these hard-coded replacements with an equivalent XML
  /// configuration
  if ( ! fHadronTensorModel->GetTensor(tensor_pdg, genie::kHT_MEC_FullAll) )
  {
 
    if ( A_request == 4 && Z_request == 2 ) {
      tensor_pdg = kPdgTgtC12;
      // This is for helium 4, but use carbon tensor
      // the use of nuclear density parameterization is suspicious
      // but some users (MINERvA) need something not nothing.
      // The pn will be exactly 1/3, but pp and nn will be ~1/4
      // Because the combinatorics are different.
      // Could do lithium beryllium boron which you don't need
    }
    else if (A_request < 9) {
      // refuse to do D, T, He3, Li, and some Be, B
      // actually it would work technically, maybe except D, T
      MAXLOG("NievesSimoVacasMEC", pWARN, 10)
          << "Asked to scale to deuterium through boron "
          << target_pdg << " nope, lets not do that.";
      return 0;
    }
    else if (A_request >= 9 && A_request < 15) {
      tensor_pdg = kPdgTgtC12;
      //}
      // could explicitly put in nitrogen for air
      //else if ( A_request >= 14 && A < 15) { // AND CHANGE <=14 to <14.
      //  tensor_pdg = kPdgTgtN14;
    }
    else if (A_request >= 15 && A_request < 22) {
      tensor_pdg = kPdgTgtO16;
    }
    else if (A_request >= 22 && A_request < 33) {
      // of special interest, this gets Al27 and Si28
      tensor_pdg = 1000140280;
    }
    else if (A_request >= 33 && A_request < 50) {
      // of special interest, this gets Ar40 and Ti48
      tensor_pdg = kPdgTgtCa40;
    }
    else if (A_request >= 50 && A_request < 90) {
      // pseudoFe56, also covers many other ferrometals and Ge
      tensor_pdg = 1000280560;
    }
    else if (A_request >= 90 && A_request < 160) {
      // use Ba112 = PseudoCd.  Row5 of Periodic table useless. Ag, Xe?
      tensor_pdg = 1000561120;
    }
    else if (A_request >= 160) {
      // use Rf208 = pseudoPb
      tensor_pdg = 1001042080;
    }
    else {
      MAXLOG("NievesSimoVacasMEC", pWARN, 10)
          << "Asked to scale to a nucleus "
          << target_pdg << " which we don't know yet.";
      return 0;
    }
  }
 
  // Check that the input kinematical point is within the range
  // in which hadron tensors are known (for chosen target)
  double Ev    = interaction->InitState().ProbeE(kRfLab);
  double Tl    = interaction->Kine().GetKV(kKVTl);
  double costl = interaction->Kine().GetKV(kKVctl);
  double ml    = interaction->FSPrimLepton()->Mass();
  double Q0    = interaction->Kine().GetKV(kKVQ0);
  double Q3    = interaction->Kine().GetKV(kKVQ3);
 
  const LabFrameHadronTensorI* tensor
    = dynamic_cast<const LabFrameHadronTensorI*>(
    fHadronTensorModel->GetTensor(tensor_pdg, genie::kHT_MEC_FullAll) );
 
  // If retrieving the tensor failed, complain and return zero
  if ( !tensor ) {
    LOG("NievesSimoVacasMEC", pWARN) << "Failed to load a"
      " hadronic tensor for the nuclide " << tensor_pdg;
    return 0.;
  }
 
  // Assume for now that the range of validity for the "FullAll" hadron
  // tensor is the same as for the partial hadron tensors
  /// \todo Revisit this assumption, and perhaps implement something
  /// more robust
  double Q0min = tensor->q0Min();
  double Q0max = tensor->q0Max();
  double Q3min = tensor->qMagMin();
  double Q3max = tensor->qMagMax();
  if (Q0 < Q0min || Q0 > Q0max || Q3 < Q3min || Q3 > Q3max) {
    return 0.0;
  }
 
  // Get the Q-value needed to calculate the cross sections using the
  // hadron tensor.
  /// \todo Shouldn't we get this from the nuclear model?
  int nu_pdg = interaction->InitState().ProbePdg();
  double Q_value = genie::utils::mec::Qvalue(target_pdg, nu_pdg);
 
  // Apply Qvalue relative shift if needed:
  if( fQvalueShifter ) Q_value += Q_value * fQvalueShifter -> Shift( interaction->InitState().Tgt() ) ;
 
  // By default, we will compute the full cross-section. If a resonance is
  // set, we will calculate the part of the cross-section with an internal
  // Delta line without a final state pion (usually called PPD for pioness
  // Delta decay). If a {p,n} hit dinucleon was set we will calculate the
  // cross-section for that component only (either full or PDD cross-section)
  bool delta = interaction->ExclTag().KnownResonance();
  bool pn    = (interaction->InitState().Tgt().HitNucPdg() == kPdgClusterNP);
 
  double xsec_all = 0.;
  double xsec_pn  = 0.;
  if ( delta ) {
 
    const LabFrameHadronTensorI* tensor_delta_all
      = dynamic_cast<const LabFrameHadronTensorI*>(
      fHadronTensorModel->GetTensor(tensor_pdg, genie::kHT_MEC_DeltaAll) );
 
    if ( !tensor_delta_all ) {
      LOG("NievesSimoVacasMEC", pWARN) << "Failed to load a \"DeltaAll\""
        << " hadronic tensor for nuclide " << tensor_pdg;
      return 0.;
    }
 
    const LabFrameHadronTensorI* tensor_delta_pn
      = dynamic_cast<const LabFrameHadronTensorI*>(
      fHadronTensorModel->GetTensor(tensor_pdg, genie::kHT_MEC_Deltapn) );
 
    if ( !tensor_delta_pn ) {
      LOG("NievesSimoVacasMEC", pWARN) << "Failed to load a \"Deltapn\""
        << " hadronic tensor for nuclide " << tensor_pdg;
      return 0.;
    }
 
    xsec_all = tensor_delta_all->dSigma_dT_dCosTheta(interaction, Q_value);
    xsec_pn = tensor_delta_pn->dSigma_dT_dCosTheta(interaction, Q_value);
 
  }
  else {
 
    const LabFrameHadronTensorI* tensor_full_all
      = dynamic_cast<const LabFrameHadronTensorI*>(
      fHadronTensorModel->GetTensor(tensor_pdg, genie::kHT_MEC_FullAll) );
 
    if ( !tensor_full_all ) {
      LOG("NievesSimoVacasMEC", pWARN) << "Failed to load a \"FullAll\""
        << " hadronic tensor for nuclide " << tensor_pdg;
      return 0.;
    }
 
    const LabFrameHadronTensorI* tensor_full_pn
      = dynamic_cast<const LabFrameHadronTensorI*>(
      fHadronTensorModel->GetTensor(tensor_pdg, genie::kHT_MEC_Fullpn) );
 
    if ( !tensor_full_pn ) {
      LOG("NievesSimoVacasMEC", pWARN) << "Failed to load a \"Fullpn\""
        << " hadronic tensor for nuclide " << tensor_pdg;
      return 0.;
    }
 
    xsec_all = tensor_full_all->dSigma_dT_dCosTheta(interaction, Q_value);
    xsec_pn = tensor_full_pn->dSigma_dT_dCosTheta(interaction, Q_value);
  }
 
  // We need to scale the cross section appropriately if
  // we are using a hadronic tensor for a nuclide that is different
  // from the actual target
  bool need_to_scale = (target_pdg != tensor_pdg);
 
  // would need to trap and treat He3, T, D special here.
  if ( need_to_scale ) {
 
    double PP = Z_request;
    double NN = A_request - PP;
    double P  = pdg::IonPdgCodeToZ(tensor_pdg);
    double N  = pdg::IonPdgCodeToA(tensor_pdg) - P;
 
    double scale_pn = TMath::Sqrt( (PP*NN)/(P*N) );
    double scale_pp = TMath::Sqrt( (PP * (PP - 1.)) / (P * (P - 1.)) );
    double scale_nn = TMath::Sqrt( (NN * (NN - 1.)) / (N * (N - 1.)) );
 
    LOG("NievesSimoVacasMEC", pDEBUG)
        << "Scale pn pp nn for (" << target_pdg << ", " << tensor_pdg << ")"
        << " : " << scale_pn << " " << scale_pp << " " << scale_nn;
 
    // This is an approximation in at least three senses:
    // 1. We are scaling from an isoscalar nucleus using p and n counting
    // 2. We are not using the right qvalue in the had tensor
    // 3. We are not scaling the Delta faster than the non-Delta.
    // The guess is that these are good approximations.
    // A test we could document is to scale from O16 to N14 or C12 using this
    // algorithm and see how many percent deviation we see from the full
    // calculation.
    double temp_all = xsec_all;
    double temp_pn  = xsec_pn * scale_pn;
    if (nu_pdg > 0) {
      // matter neutrinos
      temp_all = xsec_pn * scale_pn + (xsec_all - xsec_pn) * scale_nn;
    }
    else {
      // antineutrinos
      temp_all = xsec_pn * scale_pn + (xsec_all - xsec_pn) * scale_pp;
    }
 
    xsec_all = temp_all;
    xsec_pn  = temp_pn;
 
  }
 
  // Choose the right kind of cross section ("all" or "pn") to return
  // based on whether a {p, n} dinucleon was hit
  double xsec = (pn) ? xsec_pn : xsec_all;
 
  // Apply given scaling factor
  const ProcessInfo& proc_info = interaction->ProcInfo();
  if( proc_info.IsWeakCC() ) xsec *= fXSecCCScale;
  else if( proc_info.IsWeakNC() ) xsec *= fXSecNCScale;
 
  if( fMECScaleAlg ) xsec *= fMECScaleAlg->GetScaling( * interaction ) ;
 
  if ( kps != kPSTlctl && kps != kPSWQ2fE ) {
      LOG("NievesSimoVacasMEC", pWARN)
          << "Doesn't support transformation from "
          << KinePhaseSpace::AsString(kPSTlctl) << " to "
          << KinePhaseSpace::AsString(kps);
      xsec = 0;
  }
  else if ( kps == kPSWQ2fE && xsec != 0. ) {
    double J = utils::kinematics::Jacobian( interaction, kPSTlctl, kps );
    xsec *= J;
  }
 
  return xsec;
}
//_________________________________________________________________________
double NievesSimoVacasMECPXSec2016::Integral(
        const Interaction * interaction) const
{
    double xsec = fXSecIntegrator->Integrate(this,interaction);
    return xsec;
}
//_________________________________________________________________________
bool NievesSimoVacasMECPXSec2016::ValidProcess(
        const Interaction * interaction) const
{
    if (interaction->TestBit(kISkipProcessChk)) return true;
 
    const ProcessInfo & proc_info = interaction->ProcInfo();
    if (!proc_info.IsMEC()) {
        return false;
    }
    return true;
}
//_________________________________________________________________________
void NievesSimoVacasMECPXSec2016::Configure(const Registry & config)
{
    Algorithm::Configure(config);
    this->LoadConfig();
}
//____________________________________________________________________________
void NievesSimoVacasMECPXSec2016::Configure(string config)
{
    Algorithm::Configure(config);
    this->LoadConfig();
}
//_________________________________________________________________________
void NievesSimoVacasMECPXSec2016::LoadConfig(void)
{
  bool good_config = true;
 
  // Cross section scaling factor
  GetParam( "MEC-CC-XSecScale", fXSecCCScale ) ;
  GetParam( "MEC-NC-XSecScale", fXSecNCScale ) ;
 
  fHadronTensorModel = dynamic_cast<const HadronTensorModelI *> ( this->SubAlg("HadronTensorAlg") );
  if( !fHadronTensorModel ) {
    good_config = false ;
    LOG("NievesSimoVacasMECPXSec2016", pERROR) << "The required HadronTensorAlg does not exist. AlgID is : " << SubAlg("HadronTensorAlg")->Id() ;
  }
 
  fXSecIntegrator = dynamic_cast<const XSecIntegratorI *> (this->SubAlg("NumericalIntegrationAlg"));
  if( !fXSecIntegrator ) {
    good_config = false ;
    LOG("NievesSimoVacasMECPXSec2016", pERROR) << "The required NumericalIntegrationAlg does not exist. AlgID is : " << SubAlg("NumericalIntegrationAlg")->Id();
  }
 
  // Read optional QvalueShifter:
  fQvalueShifter = nullptr;
  if( GetConfig().Exists("QvalueShifterAlg") ) {
    fQvalueShifter = dynamic_cast<const QvalueShifter *> ( this->SubAlg("QvalueShifterAlg") );
    if( !fQvalueShifter ) {
      good_config = false ;
      LOG("NievesSimoVacasMECPXSec2016", pERROR) << "The required QvalueShifterAlg does not exist. AlgID is : " << SubAlg("QvalueShifterAlg")->Id() ;
    }
  }
 
  // Read optional MECScaleVsW:
  fMECScaleAlg = nullptr;
  if( GetConfig().Exists("MECScaleAlg") ) {
    fMECScaleAlg = dynamic_cast<const XSecScaleI *> ( this->SubAlg("MECScaleAlg") );
    if( !fMECScaleAlg ) {
      good_config = false ;
      LOG("NievesSimoVacasMECPXSec2016", pERROR) << "The required MECScaleAlg cannot be casted. AlgID is : " << SubAlg("MECScaleAlg")->Id() ;
    }
  }
 
  if( ! good_config ) {
    LOG("NievesSimoVacasMECPXSec2016", pERROR) << "Configuration has failed.";
    exit(78) ;
  }
 
}