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0001 // -*- C++ -*- 0002 // 0003 // MEQCD2to2.h is a part of Herwig - A multi-purpose Monte Carlo event generator 0004 // Copyright (C) 2002-2019 The Herwig Collaboration 0005 // 0006 // Herwig is licenced under version 3 of the GPL, see COPYING for details. 0007 // Please respect the MCnet academic guidelines, see GUIDELINES for details. 0008 // 0009 #ifndef HERWIG_MEQCD2to2_H 0010 #define HERWIG_MEQCD2to2_H 0011 // 0012 // This is the declaration of the MEQCD2to2 class. 0013 // 0014 0015 #include "Herwig/MatrixElement/HwMEBase.h" 0016 #include "Herwig/MatrixElement/ProductionMatrixElement.h" 0017 #include "ThePEG/Helicity/Vertex/AbstractFFVVertex.h" 0018 #include "ThePEG/Helicity/Vertex/AbstractVVVVertex.h" 0019 #include "ThePEG/Helicity/Vertex/AbstractVVVVVertex.h" 0020 #include "ThePEG/Helicity/WaveFunction/SpinorWaveFunction.h" 0021 #include "ThePEG/Helicity/WaveFunction/VectorWaveFunction.h" 0022 #include "ThePEG/Helicity/WaveFunction/SpinorBarWaveFunction.h" 0023 0024 namespace Herwig { 0025 using namespace ThePEG; 0026 using namespace ThePEG::Helicity; 0027 0028 /** 0029 * The MEQCD2to2 class provides the matrix elements for \f$2\to2\f$ 0030 * QCD scattering processes in hadron-hadron collisions. 0031 * 0032 * @see \ref MEQCD2to2Interfaces "The interfaces" 0033 * defined for MEQCD2to2. 0034 */ 0035 class MEQCD2to2: public HwMEBase { 0036 0037 public: 0038 0039 /** 0040 * The default constructor. 0041 */ 0042 MEQCD2to2(); 0043 0044 /** @name Virtual functions required by the MEBase class. */ 0045 //@{ 0046 /** 0047 * Return the order in \f$\alpha_S\f$ in which this matrix 0048 * element is given. 0049 */ 0050 virtual unsigned int orderInAlphaS() const; 0051 0052 /** 0053 * Return the order in \f$\alpha_{EW}\f$ in which this matrix 0054 * element is given. 0055 */ 0056 virtual unsigned int orderInAlphaEW() const; 0057 0058 /** 0059 * The matrix element for the kinematical configuration 0060 * previously provided by the last call to setKinematics(), suitably 0061 * scaled by sHat() to give a dimension-less number. 0062 * @return the matrix element scaled with sHat() to give a 0063 * dimensionless number. 0064 */ 0065 virtual double me2() const; 0066 0067 /** 0068 * Return the scale associated with the last set phase space point. 0069 */ 0070 virtual Energy2 scale() const; 0071 0072 /** 0073 * Add all possible diagrams with the add() function. 0074 */ 0075 virtual void getDiagrams() const; 0076 0077 /** 0078 * Get diagram selector. With the information previously supplied with the 0079 * setKinematics method, a derived class may optionally 0080 * override this method to weight the given diagrams with their 0081 * (although certainly not physical) relative probabilities. 0082 * @param dv the diagrams to be weighted. 0083 * @return a Selector relating the given diagrams to their weights. 0084 */ 0085 virtual Selector<DiagramIndex> diagrams(const DiagramVector & dv) const; 0086 0087 /** 0088 * Return a Selector with possible colour geometries for the selected 0089 * diagram weighted by their relative probabilities. 0090 * @param diag the diagram chosen. 0091 * @return the possible colour geometries weighted by their 0092 * relative probabilities. 0093 */ 0094 virtual Selector<const ColourLines *> 0095 colourGeometries(tcDiagPtr diag) const; 0096 0097 /** 0098 * Construct the vertex of spin correlations. 0099 */ 0100 virtual void constructVertex(tSubProPtr); 0101 //@} 0102 0103 public: 0104 0105 /** @name Functions used by the persistent I/O system. */ 0106 //@{ 0107 /** 0108 * Function used to write out object persistently. 0109 * @param os the persistent output stream written to. 0110 */ 0111 void persistentOutput(PersistentOStream & os) const; 0112 0113 /** 0114 * Function used to read in object persistently. 0115 * @param is the persistent input stream read from. 0116 * @param version the version number of the object when written. 0117 */ 0118 void persistentInput(PersistentIStream & is, int version); 0119 //@} 0120 0121 /** 0122 * The standard Init function used to initialize the interfaces. 0123 * Called exactly once for each class by the class description system 0124 * before the main function starts or 0125 * when this class is dynamically loaded. 0126 */ 0127 static void Init(); 0128 0129 protected: 0130 0131 /** 0132 * Members to calculate the matrix elements 0133 */ 0134 //@{ 0135 /** 0136 * Matrix element for \f$gg\to gg\f$. 0137 * @param g1 The wavefunctions for the first incoming gluon 0138 * @param g2 The wavefunctions for the second incoming gluon 0139 * @param g3 The wavefunctions for the first outgoing gluon 0140 * @param g4 The wavefunctions for the second outgoing gluon 0141 * @param flow The colour flow 0142 */ 0143 double gg2ggME(vector<VectorWaveFunction> &g1,vector<VectorWaveFunction> &g2, 0144 vector<VectorWaveFunction> &g3,vector<VectorWaveFunction> &g4, 0145 unsigned int flow) const; 0146 0147 /** 0148 * Matrix element for \f$gg\to q\bar{q}\f$ 0149 * @param g1 The wavefunctions for the first incoming gluon 0150 * @param g2 The wavefunctions for the second incoming gluon 0151 * @param q The wavefunction for the outgoing quark 0152 * @param qbar The wavefunction for the outgoing antiquark 0153 * @param flow The colour flow 0154 */ 0155 double gg2qqbarME(vector<VectorWaveFunction> &g1,vector<VectorWaveFunction> &g2, 0156 vector<SpinorBarWaveFunction> & q,vector<SpinorWaveFunction> & qbar, 0157 unsigned int flow) const; 0158 0159 /** 0160 * Matrix element for \f$q\bar{q}\to gg\f$ 0161 * @param q The wavefunction for the incoming quark 0162 * @param qbar The wavefunction for the incoming antiquark 0163 * @param g1 The wavefunctions for the first outgoing gluon 0164 * @param g2 The wavefunctions for the second outgoing gluon 0165 * @param flow The colour flow 0166 */ 0167 double qqbar2ggME(vector<SpinorWaveFunction> & q,vector<SpinorBarWaveFunction> & qbar, 0168 vector<VectorWaveFunction> &g1,vector<VectorWaveFunction> &g2, 0169 unsigned int flow) const; 0170 0171 /** 0172 * Matrix element for \f$qg\to qg\f$ 0173 * @param qin The wavefunction for the incoming quark 0174 * @param g2 The wavefunction for the incoming gluon 0175 * @param qout The wavefunction for the outgoing quark 0176 * @param g4 The wavefunction for the outgoing gluon 0177 * @param flow The colour flow 0178 */ 0179 double qg2qgME(vector<SpinorWaveFunction> & qin,vector<VectorWaveFunction> &g2, 0180 vector<SpinorBarWaveFunction> & qout,vector<VectorWaveFunction> &g4, 0181 unsigned int flow) const; 0182 0183 /** 0184 * Matrix elements for \f$\bar{q}g\to \bar{q}g\f$. 0185 * @param qin The wavefunction for the incoming antiquark 0186 * @param g2 The wavefunction for the incoming gluon 0187 * @param qout The wavefunction for the outgoing antiquark 0188 * @param g4 The wavefunction for the outgoing gluon 0189 * @param flow The colour flow 0190 */ 0191 double qbarg2qbargME(vector<SpinorBarWaveFunction> & qin, 0192 vector<VectorWaveFunction> &g2, 0193 vector<SpinorWaveFunction> & qout,vector<VectorWaveFunction> &g4, 0194 unsigned int flow) const; 0195 0196 /** 0197 * Matrix element for \f$qq\to qq\f$ 0198 * @param q1 The wavefunction for the first incoming quark 0199 * @param q2 The wavefunction for the second incoming quark 0200 * @param q3 The wavefunction for the first outgoing quark 0201 * @param q4 The wavefunction for the second outgoing quark 0202 * @param flow The colour flow 0203 */ 0204 double qq2qqME(vector<SpinorWaveFunction> & q1, vector<SpinorWaveFunction> & q2, 0205 vector<SpinorBarWaveFunction> & q3, vector<SpinorBarWaveFunction> & q4, 0206 unsigned int flow) const; 0207 0208 /** 0209 * Matrix element for \f$\bar{q}\bar{q}\to \bar{q}\bar{q}\f$ 0210 * @param q1 The wavefunction for the first incoming antiquark 0211 * @param q2 The wavefunction for the second incoming antiquark 0212 * @param q3 The wavefunction for the first outgoing antiquark 0213 * @param q4 The wavefunction for the second outgoing antiquark 0214 * @param flow The colour flow 0215 */ 0216 double qbarqbar2qbarqbarME(vector<SpinorBarWaveFunction> & q1, 0217 vector<SpinorBarWaveFunction> & q2, 0218 vector<SpinorWaveFunction> & q3, 0219 vector<SpinorWaveFunction> & q4, 0220 unsigned int flow) const; 0221 0222 /** 0223 * Matrix element for \f$q\bar{q}\to q\bar{q}\f$ 0224 * @param q1 The wavefunction for the incoming quark 0225 * @param q2 The wavefunction for the incoming antiquark 0226 * @param q3 The wavefunction for the outgoing quark 0227 * @param q4 The wavefunction for the outgoing antiquark 0228 * @param flow The colour flow 0229 */ 0230 double qqbar2qqbarME(vector<SpinorWaveFunction> & q1, 0231 vector<SpinorBarWaveFunction> & q2, 0232 vector<SpinorBarWaveFunction> & q3, 0233 vector<SpinorWaveFunction> & q4, 0234 unsigned int flow) const; 0235 //@} 0236 0237 protected: 0238 0239 /** @name Clone Methods. */ 0240 //@{ 0241 /** 0242 * Make a simple clone of this object. 0243 * @return a pointer to the new object. 0244 */ 0245 virtual IBPtr clone() const { return new_ptr(*this); } 0246 0247 /** Make a clone of this object, possibly modifying the cloned object 0248 * to make it sane. 0249 * @return a pointer to the new object. 0250 */ 0251 virtual IBPtr fullclone() const { return new_ptr(*this); } 0252 //@} 0253 0254 protected: 0255 0256 /** @name Standard Interfaced functions. */ 0257 //@{ 0258 /** 0259 * Initialize this object after the setup phase before saving an 0260 * EventGenerator to disk. 0261 * @throws InitException if object could not be initialized properly. 0262 */ 0263 virtual void doinit(); 0264 0265 /** 0266 * Rebind pointer to other Interfaced objects. Called in the setup phase 0267 * after all objects used in an EventGenerator has been cloned so that 0268 * the pointers will refer to the cloned objects afterwards. 0269 * @param trans a TranslationMap relating the original objects to 0270 * their respective clones. 0271 * @throws RebindException if no cloned object was found for a given 0272 * pointer. 0273 */ 0274 virtual void rebind(const TranslationMap & trans) 0275 ; 0276 0277 /** 0278 * Return a vector of all pointers to Interfaced objects used in this 0279 * object. 0280 * @return a vector of pointers. 0281 */ 0282 virtual IVector getReferences(); 0283 //@} 0284 0285 0286 private: 0287 0288 /** 0289 * The assignment operator is private and must never be called. 0290 * In fact, it should not even be implemented. 0291 */ 0292 MEQCD2to2 & operator=(const MEQCD2to2 &) = delete; 0293 0294 private: 0295 0296 /** 0297 * Vertices needed to compute the diagrams 0298 */ 0299 //@{ 0300 /** 0301 * \f$gggg\f$ vertex 0302 */ 0303 AbstractVVVVVertexPtr _ggggvertex; 0304 0305 /** 0306 * \f$ggg\f$ vertex 0307 */ 0308 AbstractVVVVertexPtr _gggvertex; 0309 0310 /** 0311 * \f$q\bar{q}g\f$ vertex 0312 */ 0313 AbstractFFVVertexPtr _qqgvertex; 0314 //@} 0315 0316 /** 0317 * Maximum numbere of quark flavours to include 0318 */ 0319 unsigned int _maxflavour; 0320 0321 /** 0322 * Processes to include 0323 */ 0324 unsigned int _process; 0325 0326 /** 0327 * Colour flow 0328 */ 0329 mutable unsigned int _flow; 0330 0331 /** 0332 * Diagram 0333 */ 0334 mutable unsigned int _diagram; 0335 0336 /** 0337 * Matrix element 0338 */ 0339 mutable ProductionMatrixElement _me; 0340 0341 /** 0342 * ParticleData objects of the partons 0343 */ 0344 //@{ 0345 /** 0346 * The gluon 0347 */ 0348 PDPtr _gluon; 0349 0350 /** 0351 * the quarks 0352 */ 0353 vector<PDPtr> _quark; 0354 0355 /** 0356 * the antiquarks 0357 */ 0358 vector<PDPtr> _antiquark; 0359 //@} 0360 }; 0361 0362 } 0363 0364 #endif /* HERWIG_MEQCD2to2_H */
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