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LabFrameHadronTensorI.cxx
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1 // standard library includes
2 #include <cmath>
3 
4 // GENIE includes
10 
12  const Interaction* interaction, double Q_value) const
13 {
14  // Don't do anything if you've been handed a nullptr
15  if ( !interaction ) return 0.;
16 
17  int probe_pdg = interaction->InitState().ProbePdg();
18  double E_probe = interaction->InitState().ProbeE(kRfLab);
19  double m_probe = interaction->InitState().Probe()->Mass();
20  double Tl = interaction->Kine().GetKV(kKVTl);
21  double cos_l = interaction->Kine().GetKV(kKVctl);
22  double ml = interaction->FSPrimLepton()->Mass();
23 
24  return contraction(probe_pdg, E_probe, m_probe, Tl, cos_l, ml, Q_value);
25 }
26 
27 double genie::LabFrameHadronTensorI::contraction(int probe_pdg, double E_probe,
28  double m_probe, double Tl, double cos_l, double ml, double Q_value) const
29 {
30  // Final state lepton total energy
31  double El = Tl + ml;
32 
33  // Energy transfer (uncorrected)
34  double q0 = E_probe - El;
35 
36  // The corrected energy transfer takes into account the binding
37  // energy of the struck nucleon(s)
38  double q0_corrected = q0 - Q_value;
39 
40  // Magnitude of the initial state lepton 3-momentum
41  double k_initial = std::sqrt( std::max(0., std::pow(E_probe, 2)
42  - std::pow(m_probe, 2) ));
43 
44  // Magnitude of the final state lepton 3-momentum
45  double k_final = std::sqrt( std::max(0., std::pow(Tl, 2) + 2*ml*Tl) );
46 
47  // Square of the magnitude of the 3-momentum transfer
48  double q_mag2 = std::pow(k_initial, 2) + std::pow(k_final, 2)
49  - 2.*k_initial*k_final*cos_l;
50 
51  // Square of the magnitude of the 4-momentum transfer
52  double q2 = q0_corrected*q0_corrected - q_mag2;
53 
54  // Differential cross section
55  double xs = dSigma_dT_dCosTheta(probe_pdg, E_probe, m_probe, Tl, cos_l, ml,
56  Q_value);
57 
58  if ( pdg::IsNeutrino(probe_pdg) || pdg::IsAntiNeutrino(probe_pdg) ) {
59  /// See equation (3) of Nieves, Amaro, and Valverde, Phys. Rev. C 70,
60  /// 055503 (2004)
61  xs *= 2. * genie::constants::kPi * k_initial
62  / (k_final * genie::constants::kGF2);
63  }
64  else if ( probe_pdg == kPdgElectron ) {
65  /// See equation (82) of Gil, Nieves, and Oset, Nucl. Phys. A 627, 543
66  /// (1997)
67  xs *= std::pow(q2 / genie::constants::kAem, 2) * k_initial / k_final
68  / (2. * genie::constants::kPi);
69  }
70  else {
71  LOG("TabulatedHadronTensor", pERROR)
72  << "Unknown probe PDG code " << probe_pdg
73  << "encountered.";
74  return 0.;
75  }
76 
77  return xs;
78 }
bool IsNeutrino(int pdgc)
Definition: PDGUtils.cxx:110
#define pERROR
Definition: Messenger.h:59
TParticlePDG * Probe(void) const
const int kPdgElectron
Definition: PDGCodes.h:35
Summary information for an interaction.
Definition: Interaction.h:56
#define LOG(stream, priority)
A macro that returns the requested log4cpp::Category appending a string (using the FILE...
Definition: Messenger.h:96
bool IsAntiNeutrino(int pdgc)
Definition: PDGUtils.cxx:118
const Kinematics & Kine(void) const
Definition: Interaction.h:71
int ProbePdg(void) const
Definition: InitialState.h:64
double GetKV(KineVar_t kv) const
Definition: Kinematics.cxx:323
TParticlePDG * FSPrimLepton(void) const
final state primary lepton
virtual double contraction(const Interaction *interaction, double Q_value) const
const InitialState & InitState(void) const
Definition: Interaction.h:69
double ProbeE(RefFrame_t rf) const
Most commonly used PDG codes. A set of utility functions to handle PDG codes is provided in PDGUtils...