Line data Source code
1 : // SpaceShower.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 : // Header file for the spacelike initial-state showers.
7 : // SpaceDipoleEnd: radiating dipole end in ISR.
8 : // SpaceShower: handles the showering description.
9 :
10 : #ifndef Pythia8_SpaceShower_H
11 : #define Pythia8_SpaceShower_H
12 :
13 : #include "Pythia8/Basics.h"
14 : #include "Pythia8/BeamParticle.h"
15 : #include "Pythia8/Event.h"
16 : #include "Pythia8/Info.h"
17 : #include "Pythia8/ParticleData.h"
18 : #include "Pythia8/PartonSystems.h"
19 : #include "Pythia8/PythiaStdlib.h"
20 : #include "Pythia8/Settings.h"
21 : #include "Pythia8/StandardModel.h"
22 : #include "Pythia8/UserHooks.h"
23 : #include "Pythia8/MergingHooks.h"
24 : #include "Pythia8/WeakShowerMEs.h"
25 :
26 : namespace Pythia8 {
27 :
28 : //==========================================================================
29 :
30 : // Data on radiating dipole ends, only used inside SpaceShower.
31 :
32 : class SpaceDipoleEnd {
33 :
34 : public:
35 :
36 : // Constructor.
37 : SpaceDipoleEnd( int systemIn = 0, int sideIn = 0, int iRadiatorIn = 0,
38 : int iRecoilerIn = 0, double pTmaxIn = 0., int colTypeIn = 0,
39 : int chgTypeIn = 0, int weakTypeIn = 0, int MEtypeIn = 0,
40 : bool normalRecoilIn = true, int weakPolIn = 0) :
41 0 : system(systemIn), side(sideIn), iRadiator(iRadiatorIn),
42 0 : iRecoiler(iRecoilerIn), pTmax(pTmaxIn), colType(colTypeIn),
43 0 : chgType(chgTypeIn), weakType(weakTypeIn), MEtype(MEtypeIn),
44 0 : normalRecoil(normalRecoilIn), weakPol(weakPolIn), nBranch(0),
45 0 : pT2Old(0.), zOld(0.5) { }
46 :
47 : // Store values for trial emission.
48 : void store( int idDaughterIn, int idMotherIn, int idSisterIn,
49 : double x1In, double x2In, double m2DipIn, double pT2In, double zIn,
50 : double xMoIn, double Q2In, double mSisterIn, double m2SisterIn,
51 0 : double pT2corrIn) {idDaughter = idDaughterIn; idMother = idMotherIn;
52 0 : idSister = idSisterIn; x1 = x1In; x2 = x2In; m2Dip = m2DipIn;
53 0 : pT2 = pT2In; z = zIn; xMo = xMoIn; Q2 = Q2In; mSister = mSisterIn;
54 0 : m2Sister = m2SisterIn; pT2corr = pT2corrIn;}
55 :
56 : // Basic properties related to evolution and matrix element corrections.
57 : int system, side, iRadiator, iRecoiler;
58 : double pTmax;
59 : int colType, chgType, weakType, MEtype;
60 : bool normalRecoil;
61 : int weakPol;
62 :
63 : // Properties specific to current trial emission.
64 : int nBranch, idDaughter, idMother, idSister, iFinPol;
65 : double x1, x2, m2Dip, pT2, z, xMo, Q2, mSister, m2Sister, pT2corr,
66 : pT2Old, zOld, asymPol;
67 :
68 : } ;
69 :
70 : //==========================================================================
71 :
72 : // The SpaceShower class does spacelike showers.
73 :
74 : class SpaceShower {
75 :
76 : public:
77 :
78 : // Constructor.
79 0 : SpaceShower() {beamOffset = 0;}
80 :
81 : // Destructor.
82 0 : virtual ~SpaceShower() {}
83 :
84 : // Initialize various pointers.
85 : // (Separated from rest of init since not virtual.)
86 : void initPtr(Info* infoPtrIn, Settings* settingsPtrIn,
87 : ParticleData* particleDataPtrIn, Rndm* rndmPtrIn, CoupSM* coupSMPtrIn,
88 : PartonSystems* partonSystemsPtrIn, UserHooks* userHooksPtrIn,
89 : MergingHooks* mergingHooksPtrIn = 0) {
90 0 : infoPtr = infoPtrIn; settingsPtr = settingsPtrIn;
91 0 : particleDataPtr = particleDataPtrIn; rndmPtr = rndmPtrIn;
92 0 : coupSMPtr = coupSMPtrIn; partonSystemsPtr = partonSystemsPtrIn;
93 0 : userHooksPtr = userHooksPtrIn; mergingHooksPtr = mergingHooksPtrIn;}
94 :
95 : // Initialize generation. Possibility to force re-initialization by hand.
96 : virtual void init(BeamParticle* beamAPtrIn, BeamParticle* beamBPtrIn);
97 :
98 : // New beams possible for handling of hard diffraction. (Not virtual.)
99 : void reassignBeamPtrs( BeamParticle* beamAPtrIn, BeamParticle* beamBPtrIn,
100 0 : int beamOffsetIn = 0) {beamAPtr = beamAPtrIn; beamBPtr = beamBPtrIn;
101 0 : beamOffset = beamOffsetIn;}
102 :
103 : // Find whether to limit maximum scale of emissions, and whether to dampen.
104 : virtual bool limitPTmax( Event& event, double Q2Fac = 0.,
105 : double Q2Ren = 0.);
106 :
107 : // Potential enhancement factor of pTmax scale for hardest emission.
108 0 : virtual double enhancePTmax() const {return pTmaxFudge;}
109 :
110 : // Prepare system for evolution; identify ME.
111 : virtual void prepare( int iSys, Event& event, bool limitPTmaxIn = true);
112 :
113 : // Update dipole list after each FSR emission.
114 : // Usage: update( iSys, event).
115 : virtual void update( int , Event&, bool hasWeakRad = false);
116 :
117 : // Select next pT in downwards evolution.
118 : virtual double pTnext( Event& event, double pTbegAll, double pTendAll,
119 : int nRadIn = -1);
120 :
121 : // ME corrections and kinematics that may give failure.
122 : virtual bool branch( Event& event);
123 :
124 : // Tell which system was the last processed one.
125 0 : int system() const {return iSysSel;}
126 :
127 : // Flag for failure in branch(...) that will force a retry of parton level.
128 0 : bool doRestart() const {return rescatterFail;}
129 :
130 : // Tell whether ISR has done a weak emission.
131 0 : bool getHasWeaklyRadiated() {return hasWeaklyRadiated;}
132 :
133 : // Print dipole list; for debug mainly.
134 : virtual void list(ostream& os = cout) const;
135 :
136 : protected:
137 :
138 : // Pointer to various information on the generation.
139 : Info* infoPtr;
140 :
141 : // Pointer to the settings database.
142 : Settings* settingsPtr;
143 :
144 : // Pointer to the particle data table.
145 : ParticleData* particleDataPtr;
146 :
147 : // Pointer to the random number generator.
148 : Rndm* rndmPtr;
149 :
150 : // Pointer to Standard Model couplings.
151 : CoupSM* coupSMPtr;
152 :
153 : // Pointers to the two incoming beams. Offset their location in event.
154 : BeamParticle* beamAPtr;
155 : BeamParticle* beamBPtr;
156 : int beamOffset;
157 :
158 : // Pointer to information on subcollision parton locations.
159 : PartonSystems* partonSystemsPtr;
160 :
161 : // Pointer to userHooks object for user interaction with program.
162 : UserHooks* userHooksPtr;
163 :
164 : // Weak matrix elements used for corrections both of ISR and FSR.
165 : WeakShowerMEs weakShowerMEs;
166 :
167 : // Store properties to be returned by methods.
168 : bool rescatterFail;
169 : int iSysSel;
170 : double pTmaxFudge;
171 :
172 : private:
173 :
174 : // Constants: could only be changed in the code itself.
175 : static const int MAXLOOPTINYPDF;
176 : static const double MCMIN, MBMIN, CTHRESHOLD, BTHRESHOLD, EVALPDFSTEP,
177 : TINYPDF, TINYKERNELPDF, TINYPT2, HEAVYPT2EVOL, HEAVYXEVOL,
178 : EXTRASPACEQ, LAMBDA3MARGIN, PT2MINWARN, LEPTONXMIN, LEPTONXMAX,
179 : LEPTONPT2MIN, LEPTONFUDGE, WEAKPSWEIGHT, HEADROOMQ2Q, HEADROOMQ2G,
180 : HEADROOMG2G, HEADROOMG2Q;
181 :
182 : // Initialization data, normally only set once.
183 : bool doQCDshower, doQEDshowerByQ, doQEDshowerByL, useSamePTasMPI,
184 : doWeakShower, doMEcorrections, doMEafterFirst, doPhiPolAsym,
185 : doPhiIntAsym, doRapidityOrder, useFixedFacScale, doSecondHard,
186 : canVetoEmission, alphaSuseCMW, singleWeakEmission, vetoWeakJets;
187 : int pTmaxMatch, pTdampMatch, alphaSorder, alphaSnfmax, alphaEMorder,
188 : nQuarkIn, enhanceScreening, weakMode;
189 : double pTdampFudge, mc, mb, m2c, m2b, renormMultFac, factorMultFac,
190 : fixedFacScale2, alphaSvalue, alphaS2pi, Lambda3flav, Lambda4flav,
191 : Lambda5flav, Lambda3flav2, Lambda4flav2, Lambda5flav2, pT0Ref,
192 : ecmRef, ecmPow, pTmin, sCM, eCM, pT0, pTminChgQ, pTminChgL, pT20,
193 : pT2min, pT2minChgQ, pT2minChgL, pTweakCut, pT2weakCut, pTmaxFudgeMPI,
194 : strengthIntAsym, weakEnhancement, mZ, gammaZ, thetaWRat, mW, gammaW,
195 : weakMaxWt, vetoWeakDeltaR2;
196 :
197 : // alphaStrong and alphaEM calculations.
198 : AlphaStrong alphaS;
199 : AlphaEM alphaEM;
200 :
201 : // Some current values.
202 : bool sideA, dopTlimit1, dopTlimit2, dopTdamp, hasWeaklyRadiated, tChannel;
203 : int iNow, iRec, idDaughter, nRad, idResFirst, idResSecond;
204 : double xDaughter, x1Now, x2Now, m2Dip, m2Rec, pT2damp, pTbegRef, pdfScale2;
205 :
206 : // List of emissions in different sides in different systems:
207 : vector<int> nRadA,nRadB;
208 :
209 : // All dipole ends
210 : vector<SpaceDipoleEnd> dipEnd;
211 :
212 : // Pointers to the current and hardest (so far) dipole ends.
213 : int iDipNow, iSysNow;
214 : SpaceDipoleEnd* dipEndNow;
215 : int iDipSel;
216 : SpaceDipoleEnd* dipEndSel;
217 :
218 : // Evolve a QCD dipole end.
219 : void pT2nextQCD( double pT2begDip, double pT2endDip);
220 :
221 : // Evolve a QCD dipole end near heavy quark threshold region.
222 : void pT2nearQCDthreshold( BeamParticle& beam, double m2Massive,
223 : double m2Threshold, double xMaxAbs, double zMinAbs,
224 : double zMaxMassive);
225 :
226 : // Evolve a QED dipole end.
227 : void pT2nextQED( double pT2begDip, double pT2endDip);
228 :
229 : // Evolve a Weak dipole end.
230 : void pT2nextWeak( double pT2begDip, double pT2endDip);
231 :
232 : // Find class of ME correction.
233 : int findMEtype( int iSys, Event& event, bool weakRadiation = false);
234 :
235 : // Provide maximum of expected ME weight; for preweighting of evolution.
236 : double calcMEmax( int MEtype, int idMother, int idDaughterIn);
237 :
238 : // Provide actual ME weight for current branching.
239 : double calcMEcorr(int MEtype, int idMother, int idDaughterIn, double M2,
240 : double z, double Q2,double m2Sister);
241 :
242 : // Provide actual ME weight for t-channel weak emissions.
243 : double calcMEcorrWeak(int MEtype, double m2, double z,
244 : double pT2, Vec4 pMother, Vec4 pB, Vec4 pDaughter,
245 : Vec4 pB0, Vec4 p1, Vec4 p2, Vec4 pSister);
246 :
247 : // Find coefficient of azimuthal asymmetry from gluon polarization.
248 : void findAsymPol( Event& event, SpaceDipoleEnd* dip);
249 :
250 : // Pointer to MergingHooks object for NLO merging.
251 : MergingHooks* mergingHooksPtr;
252 :
253 : };
254 :
255 : //==========================================================================
256 :
257 : } // end namespace Pythia8
258 :
259 : #endif // Pythia8_SpaceShower_H
|
