apfel::AlphaQCDxi Class Reference

The AlphaQCDxi is a specialization class of the MatchedEvolution class for the computation of the QCD coupling running with the possibility to vary the resummation scale through the parameter xi. More...

#include <alphaqcdxi.h>

Inheritance diagram for apfel::AlphaQCDxi:

Public Member Functions
double	MatchObject (bool const &Up, int const &nf, double const &Coup) const
	Function for the computation of the matching.
double	Derivative (int const &nf, double const &, double const &as) const
	Function that returns QCD function.
double	betaQCD (int const &pt, int const &nf, double const &lambda) const
	Function for the computation of the single coefficients of the expansion of the QCD function.
Constructors
List of constructors.
	AlphaQCDxi ()=delete
	AlphaQCDxi (double const &AlphaRef, double const &MuRef, std::vector< double > const &Masses, std::vector< double > const &Thresholds, int const &pt, double const &xi=1, int const &nsteps=10)
	AlphaQCDxi constructor.
	AlphaQCDxi (double const &AlphaRef, double const &MuRef, std::vector< double > const &Masses, int const &pt, double const &xi=1, int const &nsteps=10)
	AlphaQCDxi constructor.
Public Member Functions inherited from apfel::MatchedEvolution< double >
	MatchedEvolution ()=delete
	MatchedEvolution (double const &ObjRef, double const &MuRef, std::vector< double > const &Thresholds, int const &nsteps=10)
	The MatchedEvolution constructor.
virtual	~MatchedEvolution ()=default
virtual double	EvolveObject (int const &nf, double const &t0, double const &t1, double const &Obj0) const
	Virtual function for the computation of the evolution.
double	Evaluate (double const &mu) const
	Function that returns the evolved object.
double	GetObjectRef () const
	Function that returns the reference value of the object.
double	GetMuRef () const
	Function that returns the reference scale.
std::vector< double >	GetThresholds () const
	Function that returns the values of the thresholds.
int	GetNumberOfSteps () const
	Function that returns the number of steps.
void	SetObjectRef (double ObjRef)
	Function that sets the reference value of the object.
void	SetMuRef (double const &MuRef)
	Function that sets the reference scale.
void	SetNumberOfSteps (int const &nsteps)
	Function that sets the number of steps of the RK algorithm.

Private Attributes
int const	_pt
	Perturbative order.
double const	_xi
	Resummation-scale paremeter.
std::function< double(bool const &, int const &, double const &)>	_MatchingConditions
	Matching condition functions.
std::function< double(int const &, double const &)>	_BetaFunction
	Beta function.

Additional Inherited Members
Protected Attributes inherited from apfel::MatchedEvolution< double >
double	_ObjRef
double	_MuRef
double	_MuRef2
double	_LogMuRef2
std::vector< double >	_Thresholds
int	_nsteps
std::vector< double >	_Thresholds2
std::vector< double >	_LogThresholds2

Detailed Description

The AlphaQCDxi is a specialization class of the MatchedEvolution class for the computation of the QCD coupling running with the possibility to vary the resummation scale through the parameter xi.

Examples

coupling_test.cc.

Constructor & Destructor Documentation

AlphaQCDxi() [1/3]

apfel::AlphaQCDxi::AlphaQCDxi ( )

delete

AlphaQCDxi() [2/3]

apfel::AlphaQCDxi::AlphaQCDxi	(	double const &	AlphaRef,
		double const &	MuRef,
		std::vector< double > const &	Masses,
		std::vector< double > const &	Thresholds,
		int const &	pt,
		double const &	xi = 1,
		int const &	nsteps = 10 )

AlphaQCDxi constructor.

Parameters

AlphaRef	the reference value of the coupling
MuRef	the reference value of the scale
Masses	vector of masses
Thresholds	vector of thresholds
pt	perturbative order
xi	resummation-scale parameter (default: 1)
nsteps	number of steps of the ODE solver (default: 10)

AlphaQCDxi() [3/3]

apfel::AlphaQCDxi::AlphaQCDxi	(	double const &	AlphaRef,
		double const &	MuRef,
		std::vector< double > const &	Masses,
		int const &	pt,
		double const &	xi = 1,
		int const &	nsteps = 10 )

AlphaQCDxi constructor.

Parameters

AlphaRef	the reference value of the coupling
MuRef	the reference value of the scale
Masses	vector of masses
pt	perturbative order
xi	resummation-scale parameter (default: 1)
nsteps	number of steps of the ODE solver (default: 10)

Note

This constructor assumes that masses and thresholds coincide.

Member Function Documentation

betaQCD()

double apfel::AlphaQCDxi::betaQCD	(	int const &	pt,
		int const &	nf,
		double const &	lambda ) const

Function for the computation of the single coefficients of the expansion of the QCD function.

Parameters

pt	perturbative order
nf	number of active flavours
lambda	argument of the g-functions

Returns

The pt-th coefficient of the QCD function.

Derivative()

double apfel::AlphaQCDxi::Derivative ( int const & nf, double const & , double const & as ) const

virtual

Function that returns QCD function.

Parameters

nf	number of active flavours
as	value of the coupling

Returns

The the value of the QCD function

Implements apfel::MatchedEvolution< double >.

MatchObject()

double apfel::AlphaQCDxi::MatchObject ( bool const & Up, int const & nf, double const & Coup ) const

virtual

Function for the computation of the matching.

Parameters

Up	tells whether the matching is upward or not (downward)
nf	number of active flavours
Coup	value of the coupling to be matched

Returns

The matched value of the strong coupling at the threshold

Implements apfel::MatchedEvolution< double >.

Member Data Documentation

_BetaFunction

std::function<double(int const&, double const&)> apfel::AlphaQCDxi::_BetaFunction

private

Beta function.

_MatchingConditions

std::function<double(bool const&, int const&, double const&)> apfel::AlphaQCDxi::_MatchingConditions

private

Matching condition functions.

_pt

int const apfel::AlphaQCDxi::_pt

private

Perturbative order.

_xi

double const apfel::AlphaQCDxi::_xi

private

Resummation-scale paremeter.

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

• /Users/vb262523/Codes/apfelxx/inc/apfel/alphaqcdxi.h