lhapdf is hosted by Hepforge, IPPP Durham
LHAPDF 6.5.1
AlphaS.h
1// -*- C++ -*-
2//
3// This file is part of LHAPDF
4// Copyright (C) 2012-2022 The LHAPDF collaboration (see AUTHORS for details)
5//
6#pragma once
7#ifndef LHAPDF_AlphaS_H
8#define LHAPDF_AlphaS_H
9
10#include "LHAPDF/Utils.h"
11#include "LHAPDF/Exceptions.h"
12#include "LHAPDF/KnotArray.h"
13
14namespace LHAPDF {
15
16
24 class AlphaS {
25 public:
26
29
31 virtual ~AlphaS() {};
32
35
37 double alphasQ(double q) const { return alphasQ2(q*q); }
38
41 virtual double alphasQ2(double q2) const = 0;
42
44
45
48
50 int numFlavorsQ(double q) const { return numFlavorsQ2(q*q); }
51
53 virtual int numFlavorsQ2(double q2) const;
54
56 double quarkMass(int id) const;
57
61 void setQuarkMass(int id, double value);
62
66 double quarkThreshold(int id) const;
67
71 void setQuarkThreshold(int id, double value);
72
76 int orderQCD() { return _qcdorder; }
77
81 void setOrderQCD(int order) { _qcdorder = order; }
82
86 void setMZ(double mz) { _mz = mz; }
87
91 void setAlphaSMZ(double alphas) { _alphas_mz = alphas; }
92
96 void setMassReference(double mref) { _mreference = mref; _customref = true; }
97
101 void setAlphaSReference(double alphas) { _alphas_reference = alphas; _customref = true; }
102
106 virtual void setLambda(unsigned int, double) {};
107
109 enum FlavorScheme { FIXED, VARIABLE };
110
112 virtual std::string type() const = 0;
113
115 void setFlavorScheme(FlavorScheme scheme, int nf = -1);
116
119
121
122
123 protected:
124
127
131 double _beta(int i, int nf) const;
132
135 std::vector<double> _betas(int nf) const;
136
138
139
140 protected:
141
144
146 double _mz;
147
150
153
156
159
163 std::map<int, double> _quarkmasses, _flavorthresholds;
164
167
170
171 };
172
173
174
176 class AlphaS_Analytic : public AlphaS {
177 public:
178
180 std::string type() const { return "analytic"; }
181
183 double alphasQ2(double q2) const;
184
186 int numFlavorsQ2(double q2) const;
187
189 void setLambda(unsigned int i, double lambda);
190
191
192 private:
193
195 double _lambdaQCD(int nf) const;
196
199
200
202 std::map<int, double> _lambdas;
203
208
209 };
210
211
212
216 class AlphaS_Ipol : public AlphaS {
217 public:
218
220 std::string type() const { return "ipol"; }
221
223 double alphasQ2(double q2) const;
224
228 void setQValues(const std::vector<double>& qs);
229
235 void setQ2Values(const std::vector<double>& q2s) { _q2s = q2s; }
236
242 void setAlphaSValues(const std::vector<double>& as) { _as = as; }
243
244
245 private:
246
248 double _interpolateCubic(double T, double VL, double VDL, double VH, double VDH) const;
250 double _ddq_central( size_t i ) const;
252 double _ddq_forward( size_t i ) const;
254 double _ddq_backward( size_t i ) const;
255
258 void _setup_grids() const;
259
260
263 mutable std::map<double, AlphaSArray> _knotarrays;
264
266 std::vector<double> _q2s;
268 std::vector<double> _as;
269
270 };
271
272
273
275 class AlphaS_ODE : public AlphaS {
276 public:
277
279 std::string type() const { return "ode"; }
280
282 double alphasQ2( double q2 ) const;
283
285 void setMZ( double mz ) { _mz = mz; _calculated = false; }
286
288 void setAlphaSMZ( double alphas ) { _alphas_mz = alphas; _calculated = false; }
289
291 void setMassReference( double mref ) { _mreference = mref; _calculated = false; _customref = true; }
292
294 void setAlphaSReference( double alphas ) { _alphas_reference = alphas; _calculated = false; _customref = true; }
295
297 void setQValues(const std::vector<double>& qs);
298
302 void setQ2Values( std::vector<double> q2s ) { _q2s = q2s; _calculated = false; }
303
304
305 private:
306
308 double _derivative(double t, double y, const std::vector<double>& beta) const;
309
312 double _decouple(double y, double t, unsigned int ni, unsigned int nf) const;
313
315 void _rk4(double& t, double& y, double h, const double allowed_change, const vector<double>& bs) const;
316
318 void _solve(double q2, double& t, double& y, const double& allowed_relative, double h, double accuracy) const;
319
321 void _interpolate() const;
322
323
325 mutable std::vector<double> _q2s;
326
328 mutable bool _calculated;
329
332
333 };
334
335
336}
337#endif
Calculate alpha_s(Q2) by an analytic approximation.
Definition: AlphaS.h:176
int _nfmin
Min number of flavors.
Definition: AlphaS.h:207
int _nfmax
Max number of flavors.
Definition: AlphaS.h:205
int numFlavorsQ2(double q2) const
Analytic has its own numFlavorsQ2 which respects the min/max nf set by the Lambdas.
void setLambda(unsigned int i, double lambda)
Set lambda_i (for i = flavour number)
std::string type() const
Implementation type of this solver.
Definition: AlphaS.h:180
double alphasQ2(double q2) const
Calculate alphaS(Q2)
double _lambdaQCD(int nf) const
Get lambdaQCD for nf.
void _setFlavors()
Recalculate min/max flavors in case lambdas have changed.
std::map< int, double > _lambdas
LambdaQCD values.
Definition: AlphaS.h:202
Definition: AlphaS.h:216
double _interpolateCubic(double T, double VL, double VDL, double VH, double VDH) const
Standard cubic interpolation formula.
void setQValues(const std::vector< double > &qs)
double alphasQ2(double q2) const
Calculate alphaS(Q2)
double _ddq_central(size_t i) const
Get the gradient for a patch in the middle of the grid.
double _ddq_forward(size_t i) const
Get the gradient for a patch at the low end of the grid.
double _ddq_backward(size_t i) const
Get the gradient for a patch at the high end of the grid.
std::map< double, AlphaSArray > _knotarrays
Definition: AlphaS.h:263
void _setup_grids() const
void setAlphaSValues(const std::vector< double > &as)
Definition: AlphaS.h:242
std::string type() const
Implementation type of this solver.
Definition: AlphaS.h:220
std::vector< double > _as
Array of alpha_s values for the Q2 knots.
Definition: AlphaS.h:268
std::vector< double > _q2s
Array of ipol knots in Q2.
Definition: AlphaS.h:266
void setQ2Values(const std::vector< double > &q2s)
Definition: AlphaS.h:235
Solve the differential equation in alphaS using an implementation of RK4.
Definition: AlphaS.h:275
AlphaS_Ipol _ipol
The interpolation used to get Alpha_s after the ODE has been solved.
Definition: AlphaS.h:331
void _interpolate() const
Create interpolation grid.
void setAlphaSMZ(double alphas)
Set alpha_s(MZ), and also the caching flag.
Definition: AlphaS.h:288
void setMassReference(double mref)
Set reference mass, and also the caching flag.
Definition: AlphaS.h:291
void setMZ(double mz)
Set MZ, and also the caching flag.
Definition: AlphaS.h:285
void _solve(double q2, double &t, double &y, const double &allowed_relative, double h, double accuracy) const
Solve alpha_s for q2 using RK4.
double alphasQ2(double q2) const
Calculate alphaS(Q2)
bool _calculated
Whether or not the ODE has been solved yet.
Definition: AlphaS.h:328
void setQ2Values(std::vector< double > q2s)
Set the array of Q2 values for interpolation, and also the caching flag.
Definition: AlphaS.h:302
double _decouple(double y, double t, unsigned int ni, unsigned int nf) const
std::string type() const
Implementation type of this solver.
Definition: AlphaS.h:279
double _derivative(double t, double y, const std::vector< double > &beta) const
Calculate the derivative at Q2 = t, alpha_S = y.
std::vector< double > _q2s
Vector of Q2s in case specific anchor points are used.
Definition: AlphaS.h:325
void setQValues(const std::vector< double > &qs)
Set the array of Q values for interpolation, and also the caching flag.
void setAlphaSReference(double alphas)
Set alpha_s(MZ), and also the caching flag.
Definition: AlphaS.h:294
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.
Calculator interface for computing alpha_s(Q2) in various ways.
Definition: AlphaS.h:24
int numFlavorsQ(double q) const
Calculate the number of active flavours at energy scale Q.
Definition: AlphaS.h:50
double quarkMass(int id) const
Get a quark mass by PDG code.
virtual std::string type() const =0
Get the implementation type of this AlphaS.
void setQuarkMass(int id, double value)
Set quark masses by PDG code.
AlphaS()
Base class constructor for default param setup.
virtual ~AlphaS()
Destructor.
Definition: AlphaS.h:31
double quarkThreshold(int id) const
Get a flavor scale threshold by PDG code.
double _mz
Mass of the Z boson in GeV.
Definition: AlphaS.h:146
FlavorScheme
Enum of flavor schemes.
Definition: AlphaS.h:109
double alphasQ(double q) const
Calculate alphaS(Q)
Definition: AlphaS.h:37
virtual int numFlavorsQ2(double q2) const
Calculate the number of active flavours at energy scale Q2.
void setMassReference(double mref)
Set the Z mass used in this alpha_s.
Definition: AlphaS.h:96
virtual void setLambda(unsigned int, double)
Set the {i}th Lambda constant for i active flavors.
Definition: AlphaS.h:106
int orderQCD()
Definition: AlphaS.h:76
double _mreference
Reference mass in GeV.
Definition: AlphaS.h:152
int _qcdorder
Order of QCD evolution (expressed as number of loops)
Definition: AlphaS.h:143
bool _customref
Decides whether to use custom reference values or fall back on MZ/AlphaS_MZ.
Definition: AlphaS.h:158
FlavorScheme _flavorscheme
The flavor scheme in use.
Definition: AlphaS.h:166
void setAlphaSMZ(double alphas)
Set the alpha_s(MZ) used in this alpha_s.
Definition: AlphaS.h:91
void setOrderQCD(int order)
Set the order of QCD (expressed as number of loops)
Definition: AlphaS.h:81
std::vector< double > _betas(int nf) const
double _alphas_reference
Value of alpha_s(reference mass)
Definition: AlphaS.h:155
double _alphas_mz
Value of alpha_s(MZ)
Definition: AlphaS.h:149
int _fixflav
The allowed numbers of flavours in a fixed scheme.
Definition: AlphaS.h:169
void setQuarkThreshold(int id, double value)
Set a flavor threshold by PDG code (= quark masses by default)
double _beta(int i, int nf) const
void setAlphaSReference(double alphas)
Set the alpha_s(MZ) used in this alpha_s.
Definition: AlphaS.h:101
void setMZ(double mz)
Set the Z mass used in this alpha_s.
Definition: AlphaS.h:86
virtual double alphasQ2(double q2) const =0
FlavorScheme flavorScheme() const
Get flavor scheme.
Definition: AlphaS.h:118
void setFlavorScheme(FlavorScheme scheme, int nf=-1)
Set flavor scheme of alpha_s solver.
std::map< int, double > _quarkmasses
Definition: AlphaS.h:163
Namespace for all LHAPDF functions and classes.
Definition: AlphaS.h:14