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EnergyLossEstimator Class Reference

Helper struct to provide consistent energy loss estimation throughout the CDC track finding. More...

#include <EnergyLossEstimator.h>

Public Member Functions

 EnergyLossEstimator (double eDensity, double I, double bZ=NAN)
 Constructor from the material properties.
 
double getBetheStoppingPower (double p, int pdgCode) const
 Stopping power aka energy loss / arc length.
 
double getEnergyLoss (double p, int pdgCode, double arcLength) const
 Calculates the total energy loss after travelling the given distance.
 
double getMomentumLossFactor (double p, int pdgCode, double arcLength) const
 Calculates a factor applicable scaling the current momentum to the momentum after traveling given arc length.
 
double getLossDist2D (double pt, int pdgCode, double arcLength2D) const
 Calculates a correction term for the two dimensional distance undoing the energy loss after the given arc length.
 

Static Public Member Functions

static EnergyLossEstimator forCDC ()
 Create an energy loss estimator with the material properties of the CDC.
 
static double getMass (int pdgCode)
 Lookup the mass for the given pdg code.
 
static int getCharge (int pdgCode)
 Lookup the charge for the given pdg code.
 

Private Attributes

double m_eDensity
 Electron density in mol / cm^3.
 
double m_I
 Mean excitation energy in GeV.
 
double m_bZ
 B field to be used for the distance translation.
 

Detailed Description

Helper struct to provide consistent energy loss estimation throughout the CDC track finding.

Definition at line 22 of file EnergyLossEstimator.h.

Constructor & Destructor Documentation

◆ EnergyLossEstimator()

EnergyLossEstimator ( double eDensity,
double I,
double bZ = NAN )

Constructor from the material properties.

Parameters
eDensityElectron density in mol / cm ^ 3, e.g. from Z * density / A
IExcitation energy (must be given in standard GeV units)
bZMean magentic field in the z direction

Definition at line 122 of file EnergyLossEstimator.cc.

123 : m_eDensity(eDensity)
124 , m_I(I)
125 , m_bZ(bZ)
126{
127}
Belle2::TrackFindingCDC::EnergyLossEstimator::m_eDensity
double m_eDensity
Electron density in mol / cm^3.
Definition EnergyLossEstimator.h:75
Belle2::TrackFindingCDC::EnergyLossEstimator::m_bZ
double m_bZ
B field to be used for the distance translation.
Definition EnergyLossEstimator.h:81
Belle2::TrackFindingCDC::EnergyLossEstimator::m_I
double m_I
Mean excitation energy in GeV.
Definition EnergyLossEstimator.h:78

Member Function Documentation

◆ forCDC()

EnergyLossEstimator forCDC ( )
static

Create an energy loss estimator with the material properties of the CDC.

Definition at line 29 of file EnergyLossEstimator.cc.

30{
31
32 // Look up material properties from the Belle2 geometry
33 G4Navigator g4Nav;
34 G4VPhysicalVolume* g4World = geometry::GeometryManager::getInstance().getTopVolume();
35 g4Nav.SetWorldVolume(g4World);
36
37 // Choose position well inside the CDC
38 double posX = 0;
39 double posY = 50;
40 double posZ = 0;
41
42 G4ThreeVector g4Pos(posX * CLHEP::cm, posY * CLHEP::cm, posZ * CLHEP::cm);
43 const G4VPhysicalVolume* g4Volume = g4Nav.LocateGlobalPointAndSetup(g4Pos);
44 const G4Material* g4Mat = g4Volume->GetLogicalVolume()->GetMaterial();
45
46 double A = 0;
47 double Z = 0;
48
49 if (g4Mat->GetNumberOfElements() == 1) {
50 A = g4Mat->GetA() * CLHEP::mole / CLHEP::g;
51 Z = g4Mat->GetZ();
52 } else {
53 // Calculate weight-averaged A, Z
54 for (unsigned i = 0; i < g4Mat->GetNumberOfElements(); ++i) {
55 const G4Element* element = (*g4Mat->GetElementVector())[i];
56 const double elementA = element->GetA() * CLHEP::mole / CLHEP::g;
57 const double elementZ = element->GetZ();
58 const double frac = g4Mat->GetFractionVector()[i];
59 B2RESULT("Part " << i << " Z=" << elementZ << " A=" << elementA << " (" << frac << ")");
60 Z += elementZ * frac;
61 A += elementA * frac;
62 }
63 }
64
65 // Make sure to translate to Belle units from the Geant4 / CLHEP units
66 // Z has correct units (is unitless)
67 const double density = g4Mat->GetDensity() / CLHEP::g * CLHEP::cm3;
68 const double radiationLength = g4Mat->GetRadlen() / CLHEP::cm;
69 const double mEE = g4Mat->GetIonisation()->GetMeanExcitationEnergy() / CLHEP::GeV;
70
71 B2RESULT("Received Z " << Z);
72 B2RESULT("Received A " << A);
73 B2RESULT("Received density " << density);
74 B2RESULT("Received radiation length " << radiationLength);
75 B2RESULT("Received mean excitation energy " << mEE);
76
77 const double eDensity = Z * density / A;
78 B2RESULT("Received electron density " << eDensity);
79
80 const double bZ = CDCBFieldUtil::getBFieldZ();
81
82 return EnergyLossEstimator(eDensity, mEE, bZ);
83}
Belle2::TrackFindingCDC::EnergyLossEstimator::EnergyLossEstimator
EnergyLossEstimator(double eDensity, double I, double bZ=NAN)
Constructor from the material properties.
Definition EnergyLossEstimator.cc:122
Belle2::TrackingUtilities::CDCBFieldUtil::getBFieldZ
static double getBFieldZ()
Getter for the signed magnetic field strength in z direction at the origin ( in Tesla )
Definition CDCBFieldUtil.cc:37
Belle2::geometry::GeometryManager::getTopVolume
G4VPhysicalVolume * getTopVolume()
Return a pointer to the top volume.
Definition GeometryManager.h:56
Belle2::geometry::GeometryManager::getInstance
static GeometryManager & getInstance()
Return a reference to the instance.
Definition GeometryManager.cc:96

◆ getBetheStoppingPower()

double getBetheStoppingPower ( double p,
int pdgCode ) const

Stopping power aka energy loss / arc length.

Parameters
pabsolute momentum
pdgCode

Definition at line 129 of file EnergyLossEstimator.cc.

130{
131 static const double eMass = getMass(11);
132
133 const double M = getMass(pdgCode);
134
135 const double E = std::sqrt(p * p + M * M);
136 const double gamma = E / M;
137 const double beta = p / E;
138
139 const double beta2 = beta * beta;
140 const double gamma2 = gamma * gamma;
141
142 const double Wmax = 2 * eMass * beta2 * gamma2 / (1 + 2 * gamma * eMass / M);
143 const double I2 = m_I * m_I;
144
145 static const double K = 0.307075 * Unit::MeV * Unit::cm2;
146 const double dEdx = K * m_eDensity / beta2 *
147 (1.0 / 2.0 * std::log(2 * eMass * beta2 * gamma2 * Wmax / I2) - beta2);
148 return dEdx;
149}
E
R E
internal precision of FFTW codelets
Definition DiscreteCosineTransform_31points.cc:36
K
#define K(x)
macro autogenerated by FFTW
Definition DiscreteCosineTransform_31points.cc:37
Belle2::TrackFindingCDC::EnergyLossEstimator::getMass
static double getMass(int pdgCode)
Lookup the mass for the given pdg code.
Definition EnergyLossEstimator.cc:85
Belle2::Unit::MeV
static const double MeV
[megaelectronvolt]
Definition Unit.h:114
Belle2::Unit::cm2
static const double cm2
[square centimeters]
Definition Unit.h:78

◆ getCharge()

int getCharge ( int pdgCode)
static

Lookup the charge for the given pdg code.

Definition at line 106 of file EnergyLossEstimator.cc.

107{
108 if (std::abs(pdgCode) == Const::electron.getPDGCode()) {
109 return -sign(pdgCode);
110 } else if (std::abs(pdgCode) == Const::muon.getPDGCode()) {
111 return -sign(pdgCode);
112 } else if (std::abs(pdgCode) == Const::kaon.getPDGCode()) {
113 return sign(pdgCode);
114 } else if (std::abs(pdgCode) == Const::pion.getPDGCode()) {
115 return sign(pdgCode);
116 } else if (std::abs(pdgCode) == Const::proton.getPDGCode()) {
117 return sign(pdgCode);
118 }
119 return 0;
120}
Belle2::Const::muon
static const ChargedStable muon
muon particle
Definition Const.h:660
Belle2::Const::pion
static const ChargedStable pion
charged pion particle
Definition Const.h:661
Belle2::Const::proton
static const ChargedStable proton
proton particle
Definition Const.h:663
Belle2::Const::kaon
static const ChargedStable kaon
charged kaon particle
Definition Const.h:662
Belle2::Const::electron
static const ChargedStable electron
electron particle
Definition Const.h:659

◆ getEnergyLoss()

double getEnergyLoss ( double p,
int pdgCode,
double arcLength ) const

Calculates the total energy loss after travelling the given distance.

Definition at line 151 of file EnergyLossEstimator.cc.

152{
153 const double dEdx = getBetheStoppingPower(p, pdgCode);
154 const double eLoss = arcLength * dEdx;
155 return eLoss;
156}
Belle2::TrackFindingCDC::EnergyLossEstimator::getBetheStoppingPower
double getBetheStoppingPower(double p, int pdgCode) const
Stopping power aka energy loss / arc length.
Definition EnergyLossEstimator.cc:129

◆ getLossDist2D()

double getLossDist2D ( double pt,
int pdgCode,
double arcLength2D ) const

Calculates a correction term for the two dimensional distance undoing the energy loss after the given arc length.

Definition at line 171 of file EnergyLossEstimator.cc.

172{
173 const double eLoss = getEnergyLoss(pt, pdgCode, arcLength2D);
174
175 const int q = getCharge(pdgCode);
176 const double radius = q * CDCBFieldUtil::absMom2DToBendRadius(pt, m_bZ);;
177 return radius * eLoss / (pt - eLoss);
178
179 // const double pFactor = getMomentumLossFactor(p, pdgCode, arcLength2D);
180 // return radius * (1 / pFactor - 1);
181}
Belle2::TrackFindingCDC::EnergyLossEstimator::getCharge
static int getCharge(int pdgCode)
Lookup the charge for the given pdg code.
Definition EnergyLossEstimator.cc:106
Belle2::TrackFindingCDC::EnergyLossEstimator::getEnergyLoss
double getEnergyLoss(double p, int pdgCode, double arcLength) const
Calculates the total energy loss after travelling the given distance.
Definition EnergyLossEstimator.cc:151
Belle2::TrackingUtilities::CDCBFieldUtil::absMom2DToBendRadius
static double absMom2DToBendRadius(double absMom2D, double bZ)
Conversion helper for momenta to two dimensional (absolute) bend radius.
Definition CDCBFieldUtil.cc:89

◆ getMass()

double getMass ( int pdgCode)
static

Lookup the mass for the given pdg code.

Definition at line 85 of file EnergyLossEstimator.cc.

86{
87 if (std::abs(pdgCode) == Const::electron.getPDGCode()) {
88 const double electronMass = 0.511 * Unit::MeV;
89 return electronMass;
90 } else if (std::abs(pdgCode) == Const::muon.getPDGCode()) {
91 const double muonMass = 105.658 * Unit::MeV;
92 return muonMass;
93 } else if (std::abs(pdgCode) == Const::kaon.getPDGCode()) {
94 const double kaonMass = 0.493677;
95 return kaonMass;
96 } else if (std::abs(pdgCode) == Const::pion.getPDGCode()) {
97 const double pionMass = 0.13957;
98 return pionMass;
99 } else if (std::abs(pdgCode) == Const::proton.getPDGCode()) {
100 const double protonMass = 0.938272;
101 return protonMass;
102 }
103 return NAN;
104}

◆ getMomentumLossFactor()

double getMomentumLossFactor ( double p,
int pdgCode,
double arcLength ) const

Calculates a factor applicable scaling the current momentum to the momentum after traveling given arc length.

Definition at line 158 of file EnergyLossEstimator.cc.

159{
160 const double eLoss = getEnergyLoss(p, pdgCode, arcLength);
161 return (p - eLoss) / p;
162
163 const double mass = getMass(pdgCode);
164
165 const double eBefore = std::sqrt(p * p + mass * mass);
166 const double eAfter = eBefore - eLoss;
167 const double pAfter = std::sqrt(eAfter * eAfter - mass * mass);
168 return pAfter / p;
169}

Member Data Documentation

◆ m_bZ

double m_bZ
private

B field to be used for the distance translation.

Definition at line 81 of file EnergyLossEstimator.h.

◆ m_eDensity

double m_eDensity
private

Electron density in mol / cm^3.

Definition at line 75 of file EnergyLossEstimator.h.

◆ m_I

double m_I
private

Mean excitation energy in GeV.

Definition at line 78 of file EnergyLossEstimator.h.

The documentation for this class was generated from the following files: