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

#include <AlphaS.h>

Inheritance diagram for LHAPDF::AlphaS_ODE:

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.

Public Member Functions inherited from LHAPDF::AlphaS
	AlphaS ()
	Base class constructor for default param setup.

virtual	~AlphaS ()
	Destructor.

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.

double	quarkThreshold (int id) const
	Get a flavor scale threshold by PDG code.

void	setQuarkThreshold (int id, double value)
	Set a flavor threshold by PDG code (= quark masses by default)

int	orderQCD ()

void	setOrderQCD (int order)
	Set the order of QCD (expressed as number of loops)

void	setMZ (double mz)
	Set the Z mass used in this alpha_s.

void	setAlphaSMZ (double alphas)
	Set the alpha_s(MZ) used in this alpha_s.

void	setMassReference (double mref)
	Set the Z mass used in this alpha_s.

void	setAlphaSReference (double alphas)
	Set the alpha_s(MZ) used in this alpha_s.

virtual void	setLambda (unsigned int, double)
	Set the {i}th Lambda constant for i active flavors.

void	setFlavorScheme (FlavorScheme scheme, int nf=-1)
	Set flavor scheme of alpha_s solver.

FlavorScheme	flavorScheme () const
	Get flavor scheme.

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.

Member Function Documentation

◆ _decouple()

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

◆ alphasQ2()

double LHAPDF::AlphaS_ODE::alphasQ2 ( double q2 ) const

virtual

Calculate alphaS(Q2)

Implements LHAPDF::AlphaS.

◆ setQ2Values()

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.

◆ type()

std::string LHAPDF::AlphaS_ODE::type ( ) const

inlinevirtual

Implementation type of this solver.

Implements LHAPDF::AlphaS.

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

/builddir/build/BUILD/LHAPDF-6.5.5/include/LHAPDF/AlphaS.h

Public Member Functions

Private Member Functions