Line data Source code
1 : // StandardModel.h is a part of the PYTHIA event generator.
2 : // Copyright (C) 2015 Torbjorn Sjostrand.
3 : // PYTHIA is licenced under the GNU GPL version 2, see COPYING for details.
4 : // Please respect the MCnet Guidelines, see GUIDELINES for details.
5 :
6 : // This file gives access to some Standard Model parameters.
7 : // AlphaStrong: fix or first- or second-order running alpha_strong.
8 :
9 : #ifndef Pythia8_StandardModel_H
10 : #define Pythia8_StandardModel_H
11 :
12 : #include "Pythia8/Basics.h"
13 : #include "Pythia8/PythiaStdlib.h"
14 : #include "Pythia8/Settings.h"
15 :
16 : namespace Pythia8 {
17 :
18 : //==========================================================================
19 :
20 : // The AlphaStrong class calculates the alpha_strong value at an arbitrary
21 : // scale, given the value at m_Z, to zeroth, first or second order.
22 :
23 : class AlphaStrong {
24 :
25 : public:
26 :
27 : // Constructors.
28 0 : AlphaStrong() : isInit(false), order(0),
29 0 : Lambda3Save(0.), Lambda4Save(0.), Lambda5Save(0.), Lambda6Save(0.),
30 0 : Lambda3Save2(0.), Lambda4Save2(0.), Lambda5Save2(0.), Lambda6Save2(0.),
31 0 : scale2Min(0.), mc(0.), mb(0.), mt(0.), mc2(0.), mb2(0.), mt2(0.),
32 0 : lastCallToFull(false), valueRef(0.), valueNow(0.), scale2Now(0.) {}
33 :
34 : // Destructor.
35 0 : virtual ~AlphaStrong() {}
36 :
37 : // Initialization for given value at M_Z and given order.
38 : virtual void init(double valueIn = 0.12, int orderIn = 1, int nfmaxIn = 6,
39 : bool useCMWIn = false);
40 :
41 : // Set flavour threshold values: m_c, m_b, m_t.
42 : virtual void setThresholds(double mcIn, double mbIn, double mtIn) {
43 0 : mt=mtIn; mb=min(mt,mbIn); mc=min(mb,mcIn);}
44 :
45 : // alpha_S value and Lambda values.
46 : double alphaS(double scale2);
47 : double alphaS1Ord(double scale2);
48 : double alphaS2OrdCorr(double scale2);
49 0 : double Lambda3() const { return Lambda3Save; }
50 0 : double Lambda4() const { return Lambda4Save; }
51 0 : double Lambda5() const { return Lambda5Save; }
52 : double Lambda6() const { return (nfmax >= 6) ? Lambda6Save : Lambda5Save; }
53 :
54 : // Info: tell which scales we use for flavour thresholds.
55 : double muThres(int idQ);
56 : double muThres2(int idQ);
57 :
58 : // Return the CMW factor (for nF between 3 and 6).
59 : double facCMW( int nFin);
60 :
61 : // Protected data members: accessible to derived classes.
62 : protected:
63 :
64 : // Initialization data member.
65 : bool isInit;
66 :
67 : // Running order and max number of flavours to use in running.
68 : int order, nfmax;
69 :
70 : // Lambda values.
71 : double Lambda3Save, Lambda4Save, Lambda5Save, Lambda6Save;
72 : double Lambda3Save2, Lambda4Save2, Lambda5Save2, Lambda6Save2;
73 :
74 : // Smallest allowed renormalization scale.
75 : double scale2Min;
76 :
77 : // Flavour thresholds.
78 : static const double MZ;
79 : double mc, mb, mt;
80 : double mc2, mb2, mt2;
81 :
82 : // CMW rescaling factors.
83 : bool useCMW;
84 : static const double FACCMW3, FACCMW4, FACCMW5, FACCMW6;
85 :
86 : // Safety margins to avoid getting too close to LambdaQCD.
87 : static const double SAFETYMARGIN1, SAFETYMARGIN2;
88 :
89 : // Private data members: not accessible to derived classes.
90 : private:
91 :
92 : // Private constants: could only be changed in the code itself.
93 : static const int NITER;
94 :
95 : // Private data members.
96 : bool lastCallToFull;
97 : double valueRef, valueNow, scale2Now;
98 :
99 : };
100 :
101 : //==========================================================================
102 :
103 : // The AlphaEM class calculates the alpha_electromagnetic value at an
104 : // arbitrary scale, given the value at 0 and m_Z, to zeroth or first order.
105 :
106 : class AlphaEM {
107 :
108 : public:
109 :
110 : // Constructors.
111 0 : AlphaEM() {}
112 :
113 : // Initialization for a given order.
114 : void init(int orderIn, Settings* settingsPtr);
115 :
116 : // alpha_EM value.
117 : double alphaEM(double scale2);
118 :
119 : private:
120 :
121 : // Constants: could only be changed in the code itself.
122 : static const double MZ, Q2STEP[5], BRUNDEF[5];
123 :
124 : // Data members.
125 : int order;
126 : double alpEM0, alpEMmZ, mZ2, bRun[5], alpEMstep[5];
127 :
128 : };
129 :
130 : //==========================================================================
131 :
132 : // The CoupSM class stores and returns electroweak couplings,
133 : // including Cabibbo-Kobayashi-Maskawa mass mixing matrix elements.
134 :
135 0 : class CoupSM {
136 :
137 : public:
138 :
139 : // Constructor.
140 0 : CoupSM() {}
141 :
142 : // Initialize, normally from Pythia::init().
143 : void init(Settings& settings, Rndm* rndmPtrIn);
144 :
145 : // alpha_S value and Lambda values.
146 0 : double alphaS(double scale2) {return alphaSlocal.alphaS(scale2);}
147 : double alphaS1Ord(double scale2) {return alphaSlocal.alphaS1Ord(scale2);}
148 : double alphaS2OrdCorr(double scale2) {
149 : return alphaSlocal.alphaS2OrdCorr(scale2);}
150 : double Lambda3() const {return alphaSlocal.Lambda3();}
151 : double Lambda4() const {return alphaSlocal.Lambda4();}
152 : double Lambda5() const {return alphaSlocal.Lambda5();}
153 :
154 : // Return alpha_EM value.
155 0 : double alphaEM(double scale2) {return alphaEMlocal.alphaEM(scale2);}
156 :
157 : // Return electroweak mixing angle and Fermi constant.
158 0 : double sin2thetaW() {return s2tW;}
159 0 : double cos2thetaW() {return c2tW;}
160 : double sin2thetaWbar() {return s2tWbar;}
161 0 : double GF() {return GFermi;}
162 :
163 : // Return electroweak couplings of quarks and leptons.
164 0 : double ef(int idAbs) {return efSave[idAbs];}
165 0 : double vf(int idAbs) {return vfSave[idAbs];}
166 0 : double af(int idAbs) {return afSave[idAbs];}
167 0 : double t3f(int idAbs) {return 0.5*afSave[idAbs];}
168 0 : double lf(int idAbs) {return lfSave[idAbs];}
169 0 : double rf(int idAbs) {return rfSave[idAbs];}
170 :
171 : // Return some squared couplings and other combinations.
172 0 : double ef2(int idAbs) {return ef2Save[idAbs];}
173 0 : double vf2(int idAbs) {return vf2Save[idAbs];}
174 0 : double af2(int idAbs) {return af2Save[idAbs];}
175 0 : double efvf(int idAbs) {return efvfSave[idAbs];}
176 0 : double vf2af2(int idAbs) {return vf2af2Save[idAbs];}
177 :
178 : // Return CKM value or square:
179 : // first index 1/2/3/4 = u/c/t/t', second 1/2/3/4 = d/s/b/b'.
180 0 : double VCKMgen(int genU, int genD) {return VCKMsave[genU][genD];}
181 : double V2CKMgen(int genU, int genD) {return V2CKMsave[genU][genD];}
182 :
183 : // Return CKM value or square for incoming flavours (sign irrelevant).
184 : double VCKMid(int id1, int id2);
185 : double V2CKMid(int id1, int id2);
186 :
187 : // Return CKM sum of squares for given inflavour, or random outflavour.
188 0 : double V2CKMsum(int id) {return V2CKMout[abs(id)];}
189 : int V2CKMpick(int id);
190 :
191 : protected:
192 :
193 : // Constants: could only be changed in the code itself.
194 : static const double efSave[20], afSave[20];
195 :
196 : // Couplings and VCKM matrix (index 0 not used).
197 : double s2tW, c2tW, s2tWbar, GFermi, vfSave[20], lfSave[20], rfSave[20],
198 : ef2Save[20], vf2Save[20], af2Save[20], efvfSave[20],
199 : vf2af2Save[20], VCKMsave[5][5], V2CKMsave[5][5], V2CKMout[20];
200 :
201 : // Pointer to the random number generator.
202 : Rndm* rndmPtr;
203 :
204 : // An AlphaStrong instance for general use (but not MPI, ISR, FSR).
205 : AlphaStrong alphaSlocal;
206 :
207 : // An AlphaEM instance for general use (but not MPI, ISR, FSR).
208 : AlphaEM alphaEMlocal;
209 :
210 : };
211 :
212 : //==========================================================================
213 :
214 : // Generic couplings class
215 :
216 0 : class Couplings : public CoupSM {
217 :
218 : public:
219 :
220 0 : Couplings() : isSUSY(false) {}
221 : bool isSUSY;
222 :
223 : };
224 :
225 : //==========================================================================
226 :
227 : } // end namespace Pythia8
228 :
229 : #endif // Pythia8_StandardModel_H
|
