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LHAPDF  6.1.6
LHAPDF::AlphaS_ODE Class Reference

Solve the differential equation in alphaS using an implementation of RK4. More...

#include <AlphaS.h>

Inheritance diagram for LHAPDF::AlphaS_ODE:
LHAPDF::AlphaS

Public Member Functions

std::string type () const
 Implementation type of this solver.
 
double alphasQ2 (double q2) const
 Calculate alphaS(Q2)
 
void setMZ (double mz)
 Set MZ, and also the caching flag.
 
void setAlphaSMZ (double alphas)
 Set alpha_s(MZ), and also the caching flag.
 
void setMassReference (double mref)
 Set reference mass, and also the caching flag.
 
void setAlphaSReference (double alphas)
 Set alpha_s(MZ), and also the caching flag.
 
void setQValues (const std::vector< double > &qs)
 Set the array of Q values for interpolation, and also the caching flag.
 
void setQ2Values (std::vector< double > q2s)
 Set the array of Q2 values for interpolation, and also the caching flag. More...
 
- Public Member Functions inherited from LHAPDF::AlphaS
 AlphaS ()
 Base class constructor for default param setup.
 
virtual ~AlphaS ()
 Destructor.
 
void setFlavorScheme (FlavorScheme scheme, int nf=-1)
 Set flavor scheme of alpha_s solver.
 
FlavorScheme flavorScheme () const
 Get flavor scheme.
 
double alphasQ (double q) const
 Calculate alphaS(Q)
 
int numFlavorsQ (double q) const
 Calculate the number of active flavours at energy scale Q.
 
virtual int numFlavorsQ2 (double q2) const
 Calculate the number of active flavours at energy scale Q2.
 
double quarkMass (int id) const
 Get a quark mass by PDG code.
 
void setQuarkMass (int id, double value)
 Set quark masses by PDG code. More...
 
double quarkThreshold (int id) const
 Get a flavor scale threshold by PDG code. More...
 
void setQuarkThreshold (int id, double value)
 Set a flavor threshold by PDG code (= quark masses by default) More...
 
int orderQCD ()
 
void setOrderQCD (int order)
 Set the order of QCD (expressed as number of loops) More...
 
void setMZ (double mz)
 Set the Z mass used in this alpha_s. More...
 
void setAlphaSMZ (double alphas)
 Set the alpha_s(MZ) used in this alpha_s. More...
 
void setMassReference (double mref)
 Set the Z mass used in this alpha_s. More...
 
void setAlphaSReference (double alphas)
 Set the alpha_s(MZ) used in this alpha_s. More...
 
virtual void setLambda (unsigned int, double)
 Set the {i}th Lambda constant for i active flavors. More...
 

Private Member Functions

double _derivative (double t, double y, const std::vector< double > &beta) const
 Calculate the derivative at Q2 = t, alpha_S = y.
 
double _decouple (double y, double t, unsigned int ni, unsigned int nf) const
 
void _rk4 (double &t, double &y, double h, const double allowed_change, const vector< double > &bs) const
 Calculate the next step using RK4 with adaptive step size.
 
void _solve (double q2, double &t, double &y, const double &allowed_relative, double h, double accuracy) const
 Solve alpha_s for q2 using RK4.
 
void _interpolate () const
 Create interpolation grid.
 

Private Attributes

std::vector< double > _q2s
 Vector of Q2s in case specific anchor points are used.
 
bool _calculated
 Whether or not the ODE has been solved yet.
 
AlphaS_Ipol _ipol
 The interpolation used to get Alpha_s after the ODE has been solved.
 

Additional Inherited Members

- Public Types inherited from LHAPDF::AlphaS
enum  FlavorScheme { FIXED, VARIABLE }
 enum of flavor schemes
 
- Protected Member Functions inherited from LHAPDF::AlphaS
double _beta (int i, int nf) const
 
std::vector< double > _betas (int nf) const
 
- Protected Attributes inherited from LHAPDF::AlphaS
int _qcdorder
 Order of QCD evolution (expressed as number of loops)
 
double _mz
 Mass of the Z boson in GeV.
 
double _alphas_mz
 Value of alpha_s(MZ)
 
double _mreference
 Reference mass in GeV.
 
double _alphas_reference
 Value of alpha_s(reference mass)
 
bool _customref
 Decides whether to use custom reference values or fall back on MZ/AlphaS_MZ.
 
std::map< int, double > _quarkmasses
 
std::map< int, double > _flavorthresholds
 
FlavorScheme _flavorscheme
 The flavor scheme in use.
 
int _fixflav
 The allowed numbers of flavours in a fixed scheme.
 

Detailed Description

Solve the differential equation in alphaS using an implementation of RK4.

Examples:
/tests/testalphas.cc.

Member Function Documentation

double LHAPDF::AlphaS_ODE::_decouple ( double  y,
double  t,
unsigned int  ni,
unsigned int  nf 
) const
private

Calculate the decoupling relation when going from num. flav. = ni -> nf abs(ni - nf) must be = 1

void LHAPDF::AlphaS_ODE::setQ2Values ( std::vector< double >  q2s)
inline

Set the array of Q2 values for interpolation, and also the caching flag.

Writes to the same internal array as setQValues, appropriately transformed.


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