1 | // SigmaQCD.cc is a part of the PYTHIA event generator. |
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2 | // Copyright (C) 2012 Torbjorn Sjostrand. |
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3 | // PYTHIA is licenced under the GNU GPL version 2, see COPYING for details. |
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4 | // Please respect the MCnet Guidelines, see GUIDELINES for details. |
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5 | |
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6 | // Function definitions (not found in the header) for the |
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7 | // QCD simulation classes. |
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8 | |
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9 | #include "SigmaQCD.h" |
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10 | |
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11 | namespace Pythia8 { |
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12 | |
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13 | //========================================================================== |
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14 | |
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15 | // Sigma0AB2AB class. |
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16 | // Cross section for elastic scattering A B -> A B. |
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17 | |
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18 | //-------------------------------------------------------------------------- |
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19 | |
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20 | // Select identity, colour and anticolour. |
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21 | |
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22 | void Sigma0AB2AB::setIdColAcol() { |
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23 | |
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24 | // Flavours and colours are trivial. |
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25 | setId( idA, idB, idA, idB); |
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26 | setColAcol( 0, 0, 0, 0, 0, 0, 0, 0); |
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27 | } |
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28 | |
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29 | //========================================================================== |
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30 | |
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31 | // Sigma0AB2XB class. |
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32 | // Cross section for single diffractive scattering A B -> X B. |
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33 | |
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34 | //-------------------------------------------------------------------------- |
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35 | |
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36 | // Select identity, colour and anticolour. |
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37 | |
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38 | void Sigma0AB2XB::setIdColAcol() { |
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39 | |
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40 | // Flavours and colours are trivial. |
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41 | int idX = 10* (abs(idA) / 10) + 9900000; |
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42 | if (idA < 0) idX = -idX; |
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43 | setId( idA, idB, idX, idB); |
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44 | setColAcol( 0, 0, 0, 0, 0, 0, 0, 0); |
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45 | |
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46 | } |
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47 | |
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48 | //========================================================================== |
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49 | |
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50 | // Sigma0AB2AX class. |
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51 | // Cross section for single diffractive scattering A B -> A X. |
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52 | |
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53 | //-------------------------------------------------------------------------- |
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54 | |
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55 | // Select identity, colour and anticolour. |
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56 | |
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57 | void Sigma0AB2AX::setIdColAcol() { |
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58 | |
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59 | // Flavours and colours are trivial. |
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60 | int idX = 10* (abs(idB) / 10) + 9900000; |
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61 | if (idB < 0) idX = -idX; |
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62 | setId( idA, idB, idA, idX); |
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63 | setColAcol( 0, 0, 0, 0, 0, 0, 0, 0); |
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64 | |
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65 | } |
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66 | |
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67 | //========================================================================== |
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68 | |
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69 | // Sigma0AB2XX class. |
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70 | // Cross section for double diffractive scattering A B -> X X. |
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71 | |
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72 | //-------------------------------------------------------------------------- |
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73 | |
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74 | // Select identity, colour and anticolour. |
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75 | |
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76 | void Sigma0AB2XX::setIdColAcol() { |
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77 | |
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78 | // Flavours and colours are trivial. |
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79 | int idX1 = 10* (abs(idA) / 10) + 9900000; |
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80 | if (idA < 0) idX1 = -idX1; |
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81 | int idX2 = 10* (abs(idB) / 10) + 9900000; |
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82 | if (idB < 0) idX2 = -idX2; |
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83 | setId( idA, idB, idX1, idX2); |
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84 | setColAcol( 0, 0, 0, 0, 0, 0, 0, 0); |
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85 | |
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86 | } |
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87 | |
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88 | //========================================================================== |
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89 | |
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90 | // Sigma0AB2AXB class. |
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91 | // Cross section for central scattering A B -> A X B. |
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92 | |
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93 | //-------------------------------------------------------------------------- |
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94 | |
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95 | // Select identity, colour and anticolour. |
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96 | |
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97 | void Sigma0AB2AXB::setIdColAcol() { |
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98 | |
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99 | // Central diffractive state represented by rho_diffr0. Colours trivial. |
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100 | int idX = 9900110; |
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101 | setId( idA, idB, idA, idB,idX); |
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102 | setColAcol( 0, 0, 0, 0, 0, 0, 0, 0, 0, 0); |
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103 | |
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104 | } |
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105 | |
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106 | //========================================================================== |
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107 | |
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108 | // Sigma2gg2gg class. |
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109 | // Cross section for g g -> g g. |
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110 | |
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111 | //-------------------------------------------------------------------------- |
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112 | |
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113 | // Evaluate d(sigmaHat)/d(tHat) - no incoming flavour dependence. |
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114 | |
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115 | void Sigma2gg2gg::sigmaKin() { |
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116 | |
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117 | // Calculate kinematics dependence. |
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118 | sigTS = (9./4.) * (tH2 / sH2 + 2. * tH / sH + 3. + 2. * sH / tH |
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119 | + sH2 / tH2); |
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120 | sigUS = (9./4.) * (uH2 / sH2 + 2. * uH / sH + 3. + 2. * sH / uH |
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121 | + sH2 / uH2); |
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122 | sigTU = (9./4.) * (tH2 / uH2 + 2. * tH / uH + 3. + 2. * uH / tH |
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123 | + uH2 / tH2); |
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124 | sigSum = sigTS + sigUS + sigTU; |
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125 | |
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126 | // Answer contains factor 1/2 from identical gluons. |
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127 | sigma = (M_PI / sH2) * pow2(alpS) * 0.5 * sigSum; |
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128 | |
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129 | } |
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130 | |
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131 | //-------------------------------------------------------------------------- |
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132 | |
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133 | // Select identity, colour and anticolour. |
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134 | |
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135 | void Sigma2gg2gg::setIdColAcol() { |
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136 | |
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137 | // Flavours are trivial. |
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138 | setId( id1, id2, 21, 21); |
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139 | |
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140 | // Three colour flow topologies, each with two orientations. |
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141 | double sigRand = sigSum * rndmPtr->flat(); |
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142 | if (sigRand < sigTS) setColAcol( 1, 2, 2, 3, 1, 4, 4, 3); |
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143 | else if (sigRand < sigTS + sigUS) |
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144 | setColAcol( 1, 2, 3, 1, 3, 4, 4, 2); |
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145 | else setColAcol( 1, 2, 3, 4, 1, 4, 3, 2); |
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146 | if (rndmPtr->flat() > 0.5) swapColAcol(); |
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147 | |
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148 | } |
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149 | |
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150 | //========================================================================== |
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151 | |
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152 | // Sigma2gg2qqbar class. |
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153 | // Cross section for g g -> q qbar (q = u, d, s, i.e. almost massless). |
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154 | |
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155 | //-------------------------------------------------------------------------- |
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156 | |
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157 | // Initialize process. |
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158 | |
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159 | void Sigma2gg2qqbar::initProc() { |
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160 | |
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161 | // Read number of quarks to be considered in massless approximation. |
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162 | nQuarkNew = settingsPtr->mode("HardQCD:nQuarkNew"); |
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163 | |
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164 | } |
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165 | |
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166 | //-------------------------------------------------------------------------- |
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167 | |
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168 | // Evaluate d(sigmaHat)/d(tHat) - no incoming flavour dependence. |
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169 | |
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170 | void Sigma2gg2qqbar::sigmaKin() { |
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171 | |
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172 | // Pick new flavour. |
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173 | idNew = 1 + int( nQuarkNew * rndmPtr->flat() ); |
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174 | mNew = particleDataPtr->m0(idNew); |
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175 | m2New = mNew*mNew; |
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176 | |
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177 | // Calculate kinematics dependence. |
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178 | sigTS = 0.; |
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179 | sigUS = 0.; |
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180 | if (sH > 4. * m2New) { |
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181 | sigTS = (1./6.) * uH / tH - (3./8.) * uH2 / sH2; |
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182 | sigUS = (1./6.) * tH / uH - (3./8.) * tH2 / sH2; |
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183 | } |
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184 | sigSum = sigTS + sigUS; |
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185 | |
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186 | // Answer is proportional to number of outgoing flavours. |
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187 | sigma = (M_PI / sH2) * pow2(alpS) * nQuarkNew * sigSum; |
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188 | |
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189 | } |
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190 | |
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191 | //-------------------------------------------------------------------------- |
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192 | |
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193 | // Select identity, colour and anticolour. |
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194 | |
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195 | void Sigma2gg2qqbar::setIdColAcol() { |
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196 | |
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197 | // Flavours are trivial. |
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198 | setId( id1, id2, idNew, -idNew); |
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199 | |
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200 | // Two colour flow topologies. |
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201 | double sigRand = sigSum * rndmPtr->flat(); |
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202 | if (sigRand < sigTS) setColAcol( 1, 2, 2, 3, 1, 0, 0, 3); |
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203 | else setColAcol( 1, 2, 3, 1, 3, 0, 0, 2); |
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204 | |
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205 | } |
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206 | |
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207 | //========================================================================== |
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208 | |
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209 | // Sigma2qg2qg class. |
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210 | // Cross section for q g -> q g. |
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211 | |
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212 | //-------------------------------------------------------------------------- |
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213 | |
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214 | // Evaluate d(sigmaHat)/d(tHat) - no incoming flavour dependence. |
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215 | |
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216 | void Sigma2qg2qg::sigmaKin() { |
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217 | |
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218 | // Calculate kinematics dependence. |
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219 | sigTS = uH2 / tH2 - (4./9.) * uH / sH; |
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220 | sigTU = sH2 / tH2 - (4./9.) * sH / uH; |
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221 | sigSum = sigTS + sigTU; |
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222 | |
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223 | // Answer. |
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224 | sigma = (M_PI / sH2) * pow2(alpS) * sigSum; |
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225 | |
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226 | } |
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227 | |
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228 | //-------------------------------------------------------------------------- |
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229 | |
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230 | // Select identity, colour and anticolour. |
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231 | |
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232 | void Sigma2qg2qg::setIdColAcol() { |
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233 | |
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234 | // Outgoing = incoming flavours. |
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235 | setId( id1, id2, id1, id2); |
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236 | |
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237 | // Two colour flow topologies. Swap if first is gluon, or when antiquark. |
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238 | double sigRand = sigSum * rndmPtr->flat(); |
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239 | if (sigRand < sigTS) setColAcol( 1, 0, 2, 1, 3, 0, 2, 3); |
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240 | else setColAcol( 1, 0, 2, 3, 2, 0, 1, 3); |
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241 | if (id1 == 21) swapCol1234(); |
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242 | if (id1 < 0 || id2 < 0) swapColAcol(); |
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243 | |
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244 | } |
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245 | |
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246 | //========================================================================== |
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247 | |
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248 | // Sigma2qq2qq class. |
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249 | // Cross section for q qbar' -> q qbar' or q q' -> q q' |
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250 | // (qbar qbar' -> qbar qbar'), q' may be same as q. |
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251 | |
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252 | //-------------------------------------------------------------------------- |
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253 | |
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254 | // Evaluate d(sigmaHat)/d(tHat), part independent of incoming flavour. |
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255 | |
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256 | void Sigma2qq2qq::sigmaKin() { |
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257 | |
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258 | // Calculate kinematics dependence for different terms. |
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259 | sigT = (4./9.) * (sH2 + uH2) / tH2; |
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260 | sigU = (4./9.) * (sH2 + tH2) / uH2; |
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261 | sigTU = - (8./27.) * sH2 / (tH * uH); |
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262 | sigST = - (8./27.) * uH2 / (sH * tH); |
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263 | |
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264 | } |
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265 | |
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266 | //-------------------------------------------------------------------------- |
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267 | |
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268 | |
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269 | // Evaluate d(sigmaHat)/d(tHat), including incoming flavour dependence. |
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270 | |
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271 | double Sigma2qq2qq::sigmaHat() { |
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272 | |
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273 | // Combine cross section terms; factor 1/2 when identical quarks. |
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274 | if (id2 == id1) sigSum = 0.5 * (sigT + sigU + sigTU); |
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275 | else if (id2 == -id1) sigSum = sigT + sigST; |
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276 | else sigSum = sigT; |
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277 | |
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278 | // Answer. |
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279 | return (M_PI/sH2) * pow2(alpS) * sigSum; |
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280 | |
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281 | } |
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282 | |
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283 | //-------------------------------------------------------------------------- |
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284 | |
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285 | // Select identity, colour and anticolour. |
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286 | |
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287 | void Sigma2qq2qq::setIdColAcol() { |
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288 | |
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289 | // Outgoing = incoming flavours. |
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290 | setId( id1, id2, id1, id2); |
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291 | |
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292 | // Colour flow topologies. Swap when antiquarks. |
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293 | if (id1 * id2 > 0) setColAcol( 1, 0, 2, 0, 2, 0, 1, 0); |
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294 | else setColAcol( 1, 0, 0, 1, 2, 0, 0, 2); |
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295 | if (id2 == id1 && (sigT + sigU) * rndmPtr->flat() > sigT) |
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296 | setColAcol( 1, 0, 2, 0, 1, 0, 2, 0); |
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297 | if (id1 < 0) swapColAcol(); |
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298 | |
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299 | } |
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300 | |
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301 | //========================================================================== |
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302 | |
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303 | // Sigma2qqbar2gg class. |
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304 | // Cross section for q qbar -> g g. |
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305 | |
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306 | //-------------------------------------------------------------------------- |
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307 | |
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308 | // Evaluate d(sigmaHat)/d(tHat) - no incoming flavour dependence. |
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309 | |
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310 | void Sigma2qqbar2gg::sigmaKin() { |
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311 | |
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312 | // Calculate kinematics dependence. |
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313 | sigTS = (32./27.) * uH / tH - (8./3.) * uH2 / sH2; |
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314 | sigUS = (32./27.) * tH / uH - (8./3.) * tH2 / sH2; |
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315 | sigSum = sigTS + sigUS; |
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316 | |
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317 | // Answer contains factor 1/2 from identical gluons. |
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318 | sigma = (M_PI / sH2) * pow2(alpS) * 0.5 * sigSum; |
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319 | |
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320 | } |
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321 | |
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322 | //-------------------------------------------------------------------------- |
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323 | |
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324 | // Select identity, colour and anticolour. |
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325 | |
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326 | void Sigma2qqbar2gg::setIdColAcol() { |
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327 | |
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328 | // Outgoing flavours trivial. |
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329 | setId( id1, id2, 21, 21); |
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330 | |
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331 | // Two colour flow topologies. Swap if first is antiquark. |
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332 | double sigRand = sigSum * rndmPtr->flat(); |
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333 | if (sigRand < sigTS) setColAcol( 1, 0, 0, 2, 1, 3, 3, 2); |
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334 | else setColAcol( 1, 0, 0, 2, 3, 2, 1, 3); |
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335 | if (id1 < 0) swapColAcol(); |
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336 | |
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337 | } |
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338 | |
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339 | //========================================================================== |
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340 | |
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341 | // Sigma2qqbar2qqbarNew class. |
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342 | // Cross section q qbar -> q' qbar'. |
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343 | |
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344 | //-------------------------------------------------------------------------- |
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345 | |
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346 | // Initialize process. |
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347 | |
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348 | void Sigma2qqbar2qqbarNew::initProc() { |
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349 | |
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350 | // Read number of quarks to be considered in massless approximation. |
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351 | nQuarkNew = settingsPtr->mode("HardQCD:nQuarkNew"); |
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352 | |
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353 | } |
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354 | |
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355 | //-------------------------------------------------------------------------- |
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356 | |
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357 | // Evaluate d(sigmaHat)/d(tHat) - no incoming flavour dependence. |
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358 | |
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359 | void Sigma2qqbar2qqbarNew::sigmaKin() { |
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360 | |
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361 | // Pick new flavour. |
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362 | idNew = 1 + int( nQuarkNew * rndmPtr->flat() ); |
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363 | mNew = particleDataPtr->m0(idNew); |
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364 | m2New = mNew*mNew; |
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365 | |
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366 | // Calculate kinematics dependence. |
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367 | sigS = 0.; |
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368 | if (sH > 4. * m2New) sigS = (4./9.) * (tH2 + uH2) / sH2; |
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369 | |
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370 | // Answer is proportional to number of outgoing flavours. |
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371 | sigma = (M_PI / sH2) * pow2(alpS) * nQuarkNew * sigS; |
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372 | |
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373 | } |
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374 | |
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375 | //-------------------------------------------------------------------------- |
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376 | |
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377 | // Select identity, colour and anticolour. |
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378 | |
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379 | void Sigma2qqbar2qqbarNew::setIdColAcol() { |
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380 | |
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381 | // Set outgoing flavours ones. |
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382 | id3 = (id1 > 0) ? idNew : -idNew; |
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383 | setId( id1, id2, id3, -id3); |
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384 | |
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385 | // Colour flow topologies. Swap when antiquarks. |
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386 | setColAcol( 1, 0, 0, 2, 1, 0, 0, 2); |
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387 | if (id1 < 0) swapColAcol(); |
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388 | |
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389 | } |
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390 | |
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391 | //========================================================================== |
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392 | |
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393 | // Sigma2gg2QQbar class. |
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394 | // Cross section g g -> Q Qbar (Q = c, b or t). |
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395 | // Only provided for fixed m3 = m4 so do some gymnastics: |
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396 | // i) s34Avg picked so that beta34 same when s3, s4 -> s34Avg. |
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397 | // ii) tHQ = tH - mQ^2 = -0.5 sH (1 - beta34 cos(thetaH)) for m3 = m4 = mQ, |
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398 | // but tH - uH = sH beta34 cos(thetaH) also for m3 != m4, so use |
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399 | // tH, uH selected for m3 != m4 to derive tHQ, uHQ valid for m3 = m4. |
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400 | |
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401 | //-------------------------------------------------------------------------- |
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402 | |
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403 | // Initialize process. |
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404 | |
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405 | void Sigma2gg2QQbar::initProc() { |
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406 | |
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407 | // Process name. |
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408 | nameSave = "g g -> Q Qbar"; |
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409 | if (idNew == 4) nameSave = "g g -> c cbar"; |
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410 | if (idNew == 5) nameSave = "g g -> b bbar"; |
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411 | if (idNew == 6) nameSave = "g g -> t tbar"; |
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412 | if (idNew == 7) nameSave = "g g -> b' b'bar"; |
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413 | if (idNew == 8) nameSave = "g g -> t' t'bar"; |
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414 | |
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415 | // Secondary open width fraction. |
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416 | openFracPair = particleDataPtr->resOpenFrac(idNew, -idNew); |
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417 | |
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418 | } |
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419 | |
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420 | //-------------------------------------------------------------------------- |
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421 | |
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422 | // Evaluate d(sigmaHat)/d(tHat) - no incoming flavour dependence. |
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423 | |
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424 | void Sigma2gg2QQbar::sigmaKin() { |
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425 | |
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426 | // Modified Mandelstam variables for massive kinematics with m3 = m4. |
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427 | double s34Avg = 0.5 * (s3 + s4) - 0.25 * pow2(s3 - s4) / sH; |
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428 | double tHQ = -0.5 * (sH - tH + uH); |
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429 | double uHQ = -0.5 * (sH + tH - uH); |
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430 | double tHQ2 = tHQ * tHQ; |
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431 | double uHQ2 = uHQ * uHQ; |
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432 | |
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433 | // Calculate kinematics dependence. |
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434 | double tumHQ = tHQ * uHQ - s34Avg * sH; |
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435 | sigTS = ( uHQ / tHQ - 2.25 * uHQ2 / sH2 + 4.5 * s34Avg * tumHQ |
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436 | / ( sH * tHQ2) + 0.5 * s34Avg * (tHQ + s34Avg) / tHQ2 |
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437 | - s34Avg*s34Avg / (sH * tHQ) ) / 6.; |
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438 | sigUS = ( tHQ / uHQ - 2.25 * tHQ2 / sH2 + 4.5 * s34Avg * tumHQ |
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439 | / ( sH * uHQ2) + 0.5 * s34Avg * (uHQ + s34Avg) / uHQ2 |
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440 | - s34Avg*s34Avg / (sH * uHQ) ) / 6.; |
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441 | sigSum = sigTS + sigUS; |
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442 | |
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443 | // Answer. |
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444 | sigma = (M_PI / sH2) * pow2(alpS) * sigSum * openFracPair; |
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445 | |
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446 | } |
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447 | |
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448 | //-------------------------------------------------------------------------- |
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449 | |
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450 | // Select identity, colour and anticolour. |
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451 | |
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452 | void Sigma2gg2QQbar::setIdColAcol() { |
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453 | |
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454 | // Flavours are trivial. |
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455 | setId( id1, id2, idNew, -idNew); |
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456 | |
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457 | // Two colour flow topologies. |
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458 | double sigRand = sigSum * rndmPtr->flat(); |
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459 | if (sigRand < sigTS) setColAcol( 1, 2, 2, 3, 1, 0, 0, 3); |
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460 | else setColAcol( 1, 2, 3, 1, 3, 0, 0, 2); |
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461 | |
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462 | } |
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463 | |
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464 | //-------------------------------------------------------------------------- |
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465 | |
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466 | // Evaluate weight for decay angles of W in top decay. |
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467 | |
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468 | double Sigma2gg2QQbar::weightDecay( Event& process, int iResBeg, |
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469 | int iResEnd) { |
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470 | |
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471 | // For top decay hand over to standard routine, else done. |
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472 | if (idNew == 6 && process[process[iResBeg].mother1()].idAbs() == 6) |
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473 | return weightTopDecay( process, iResBeg, iResEnd); |
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474 | else return 1.; |
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475 | |
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476 | } |
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477 | |
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478 | //========================================================================== |
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479 | |
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480 | // Sigma2qqbar2QQbar class. |
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481 | // Cross section q qbar -> Q Qbar (Q = c, b or t). |
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482 | // Only provided for fixed m3 = m4 so do some gymnastics: |
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483 | // i) s34Avg picked so that beta34 same when s3, s4 -> s34Avg. |
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484 | // ii) tHQ = tH - mQ^2 = -0.5 sH (1 - beta34 cos(thetaH)) for m3 = m4 = mQ, |
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485 | // but tH - uH = sH beta34 cos(thetaH) also for m3 != m4, so use |
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486 | // tH, uH selected for m3 != m4 to derive tHQ, uHQ valid for m3 = m4. |
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487 | |
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488 | //-------------------------------------------------------------------------- |
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489 | |
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490 | // Initialize process, especially parton-flux object. |
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491 | |
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492 | void Sigma2qqbar2QQbar::initProc() { |
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493 | |
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494 | // Process name. |
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495 | nameSave = "q qbar -> Q Qbar"; |
---|
496 | if (idNew == 4) nameSave = "q qbar -> c cbar"; |
---|
497 | if (idNew == 5) nameSave = "q qbar -> b bbar"; |
---|
498 | if (idNew == 6) nameSave = "q qbar -> t tbar"; |
---|
499 | if (idNew == 7) nameSave = "q qbar -> b' b'bar"; |
---|
500 | if (idNew == 8) nameSave = "q qbar -> t' t'bar"; |
---|
501 | |
---|
502 | // Secondary open width fraction. |
---|
503 | openFracPair = particleDataPtr->resOpenFrac(idNew, -idNew); |
---|
504 | |
---|
505 | } |
---|
506 | |
---|
507 | //-------------------------------------------------------------------------- |
---|
508 | |
---|
509 | // Evaluate d(sigmaHat)/d(tHat) - no incoming flavour dependence. |
---|
510 | |
---|
511 | void Sigma2qqbar2QQbar::sigmaKin() { |
---|
512 | |
---|
513 | // Modified Mandelstam variables for massive kinematics with m3 = m4. |
---|
514 | double s34Avg = 0.5 * (s3 + s4) - 0.25 * pow2(s3 - s4) / sH; |
---|
515 | double tHQ = -0.5 * (sH - tH + uH); |
---|
516 | double uHQ = -0.5 * (sH + tH - uH); |
---|
517 | double tHQ2 = tHQ * tHQ; |
---|
518 | double uHQ2 = uHQ * uHQ; |
---|
519 | |
---|
520 | // Calculate kinematics dependence. |
---|
521 | double sigS = (4./9.) * ((tHQ2 + uHQ2) / sH2 + 2. * s34Avg / sH); |
---|
522 | |
---|
523 | // Answer. |
---|
524 | sigma = (M_PI / sH2) * pow2(alpS) * sigS * openFracPair; |
---|
525 | |
---|
526 | } |
---|
527 | |
---|
528 | //-------------------------------------------------------------------------- |
---|
529 | |
---|
530 | // Select identity, colour and anticolour. |
---|
531 | |
---|
532 | void Sigma2qqbar2QQbar::setIdColAcol() { |
---|
533 | |
---|
534 | // Set outgoing flavours. |
---|
535 | id3 = (id1 > 0) ? idNew : -idNew; |
---|
536 | setId( id1, id2, id3, -id3); |
---|
537 | |
---|
538 | // Colour flow topologies. Swap when antiquarks. |
---|
539 | setColAcol( 1, 0, 0, 2, 1, 0, 0, 2); |
---|
540 | if (id1 < 0) swapColAcol(); |
---|
541 | |
---|
542 | } |
---|
543 | |
---|
544 | //-------------------------------------------------------------------------- |
---|
545 | |
---|
546 | // Evaluate weight for decay angles of W in top decay. |
---|
547 | |
---|
548 | double Sigma2qqbar2QQbar::weightDecay( Event& process, int iResBeg, |
---|
549 | int iResEnd) { |
---|
550 | |
---|
551 | // For top decay hand over to standard routine, else done. |
---|
552 | if (idNew == 6 && process[process[iResBeg].mother1()].idAbs() == 6) |
---|
553 | return weightTopDecay( process, iResBeg, iResEnd); |
---|
554 | else return 1.; |
---|
555 | |
---|
556 | } |
---|
557 | |
---|
558 | |
---|
559 | //========================================================================== |
---|
560 | |
---|
561 | // Sigma3gg2ggg class. |
---|
562 | // Cross section for g g -> g g g. |
---|
563 | |
---|
564 | //-------------------------------------------------------------------------- |
---|
565 | |
---|
566 | // Evaluate |M|^2 - no incoming flavour dependence. |
---|
567 | |
---|
568 | void Sigma3gg2ggg::sigmaKin() { |
---|
569 | |
---|
570 | // Calculate all four-vector products. |
---|
571 | Vec4 p1cm( 0., 0., 0.5 * mH, 0.5 * mH); |
---|
572 | Vec4 p2cm( 0., 0., -0.5 * mH, 0.5 * mH); |
---|
573 | pp[1][2] = p1cm * p2cm; |
---|
574 | pp[1][3] = p1cm * p3cm; |
---|
575 | pp[1][4] = p1cm * p4cm; |
---|
576 | pp[1][5] = p1cm * p5cm; |
---|
577 | pp[2][3] = p2cm * p3cm; |
---|
578 | pp[2][4] = p2cm * p4cm; |
---|
579 | pp[2][5] = p2cm * p5cm; |
---|
580 | pp[3][4] = p3cm * p4cm; |
---|
581 | pp[3][5] = p3cm * p5cm; |
---|
582 | pp[4][5] = p4cm * p5cm; |
---|
583 | for (int i = 1; i < 5; ++i) |
---|
584 | for (int j = i + 1; j < 6; ++j) pp[j][i] = pp[i][j]; |
---|
585 | |
---|
586 | // Cross section, in three main sections. |
---|
587 | double num1 = cycle(1,2,3,4,5) + cycle(1,2,3,5,4) + cycle(1,2,4,3,5) |
---|
588 | + cycle(1,2,4,5,3) + cycle(1,2,5,3,4) + cycle(1,2,5,4,3) |
---|
589 | + cycle(1,3,2,4,5) + cycle(1,3,2,5,4) + cycle(1,3,4,2,5) |
---|
590 | + cycle(1,3,5,2,4) + cycle(1,4,2,3,5) + cycle(1,4,3,2,5); |
---|
591 | double num2 = pow4(pp[1][2]) + pow4(pp[1][3]) + pow4(pp[1][4]) |
---|
592 | + pow4(pp[1][5]) + pow4(pp[2][3]) + pow4(pp[2][4]) |
---|
593 | + pow4(pp[2][5]) + pow4(pp[3][4]) + pow4(pp[3][5]) |
---|
594 | + pow4(pp[4][5]); |
---|
595 | double den = pp[1][2] * pp[1][3] * pp[1][4] * pp[1][5] * pp[2][3] |
---|
596 | * pp[2][4] * pp[2][5] * pp[3][4] * pp[3][5] * pp[4][5]; |
---|
597 | |
---|
598 | // Answer has a factor 6 due to identical gluons |
---|
599 | // This is cancelled by phase space factor (1 / 6) |
---|
600 | sigma = pow3(4. * M_PI * alpS) * (27./16.) * num1 * num2 / den; |
---|
601 | |
---|
602 | } |
---|
603 | |
---|
604 | //-------------------------------------------------------------------------- |
---|
605 | |
---|
606 | // Select identity, colour and anticolour. |
---|
607 | |
---|
608 | void Sigma3gg2ggg::setIdColAcol() { |
---|
609 | |
---|
610 | // Flavours are trivial. |
---|
611 | setId( id1, id2, 21, 21, 21); |
---|
612 | |
---|
613 | // Three colour flow topologies, each with two orientations. |
---|
614 | /* |
---|
615 | double sigRand = sigSum * rndmPtr->flat(); |
---|
616 | if (sigRand < sigTS) setColAcol( 1, 2, 2, 3, 1, 4, 4, 3); |
---|
617 | else if (sigRand < sigTS + sigUS) |
---|
618 | setColAcol( 1, 2, 3, 1, 3, 4, 4, 2); |
---|
619 | else setColAcol( 1, 2, 3, 4, 1, 4, 3, 2); |
---|
620 | if (rndmPtr->flat() > 0.5) swapColAcol(); |
---|
621 | */ |
---|
622 | |
---|
623 | // Temporary solution. |
---|
624 | setColAcol( 1, 2, 2, 3, 1, 4, 4, 5, 5, 3); |
---|
625 | } |
---|
626 | |
---|
627 | |
---|
628 | //========================================================================== |
---|
629 | |
---|
630 | // Sigma3qqbar2ggg class. |
---|
631 | // Cross section for q qbar -> g g g. |
---|
632 | |
---|
633 | //-------------------------------------------------------------------------- |
---|
634 | |
---|
635 | // Evaluate |M|^2 - no incoming flavour dependence. |
---|
636 | void Sigma3qqbar2ggg::sigmaKin() { |
---|
637 | |
---|
638 | // Setup four-vectors |
---|
639 | pCM[0] = Vec4( 0., 0., 0.5 * mH, 0.5 * mH); |
---|
640 | pCM[1] = Vec4( 0., 0., -0.5 * mH, 0.5 * mH); |
---|
641 | pCM[2] = p3cm; |
---|
642 | pCM[3] = p4cm; |
---|
643 | pCM[4] = p5cm; |
---|
644 | |
---|
645 | // Calculate |M|^2 |
---|
646 | // Answer has a factor 6 due to identical gluons, |
---|
647 | // which is cancelled by phase space factor (1 / 6) |
---|
648 | sigma = m2Calc(); |
---|
649 | |
---|
650 | } |
---|
651 | |
---|
652 | //-------------------------------------------------------------------------- |
---|
653 | |
---|
654 | // |M|^2 |
---|
655 | |
---|
656 | inline double Sigma3qqbar2ggg::m2Calc() { |
---|
657 | |
---|
658 | // Calculate four-products |
---|
659 | double sHnow = (pCM[0] + pCM[1]).m2Calc(); |
---|
660 | double sHhalf = sH / 2.; |
---|
661 | |
---|
662 | // qbar (p+) + q(p-) -> g(k1) g(k2) g(k3) |
---|
663 | // a_i = (p+ . ki), i = 1, 2, 3 |
---|
664 | // b_i = (p- . ki), i = 1, 2, 3 |
---|
665 | a[0] = pCM[0] * pCM[2]; |
---|
666 | a[1] = pCM[0] * pCM[3]; |
---|
667 | a[2] = pCM[0] * pCM[4]; |
---|
668 | b[0] = pCM[1] * pCM[2]; |
---|
669 | b[1] = pCM[1] * pCM[3]; |
---|
670 | b[2] = pCM[1] * pCM[4]; |
---|
671 | |
---|
672 | pp[0][1] = pCM[2] * pCM[3]; |
---|
673 | pp[1][2] = pCM[3] * pCM[4]; |
---|
674 | pp[2][0] = pCM[4] * pCM[2]; |
---|
675 | |
---|
676 | // ab[i][j] = a_i * b_j + a_j * b_i |
---|
677 | ab[0][1] = a[0] * b[1] + a[1] * b[0]; |
---|
678 | ab[1][2] = a[1] * b[2] + a[2] * b[1]; |
---|
679 | ab[2][0] = a[2] * b[0] + a[0] * b[2]; |
---|
680 | |
---|
681 | // Cross section |
---|
682 | double num1 = a[0] * b[0] * (a[0] * a[0] + b[0] * b[0]) + |
---|
683 | a[1] * b[1] * (a[1] * a[1] + b[1] * b[1]) + |
---|
684 | a[2] * b[2] * (a[2] * a[2] + b[2] * b[2]); |
---|
685 | double den1 = a[0] * a[1] * a[2] * b[0] * b[1] * b[2]; |
---|
686 | double num2 = - ( ab[0][1] / pp[0][1] ) |
---|
687 | - ( ab[1][2] / pp[1][2] ) |
---|
688 | - ( ab[2][0] / pp[2][0] ); |
---|
689 | double num3 = a[2] * b[2] * ab[0][1] / (pp[1][2] * pp[2][0] ) + |
---|
690 | a[0] * b[0] * ab[1][2] / (pp[2][0] * pp[0][1] ) + |
---|
691 | a[1] * b[1] * ab[2][0] / (pp[0][1] * pp[1][2] ); |
---|
692 | |
---|
693 | // Final answer |
---|
694 | return pow3(4. * M_PI * alpS) * (8. / 324.) * (num1 / den1) * |
---|
695 | ( sHhalf + 9. * (sHhalf + num2) + (2. * 81. / sHnow) * num3 ); |
---|
696 | |
---|
697 | } |
---|
698 | |
---|
699 | //-------------------------------------------------------------------------- |
---|
700 | |
---|
701 | // Select identity, colour and anticolour. |
---|
702 | |
---|
703 | void Sigma3qqbar2ggg::setIdColAcol(){ |
---|
704 | |
---|
705 | // Flavours are trivial. |
---|
706 | setId( id1, id2, 21, 21, 21); |
---|
707 | |
---|
708 | // Temporary solution. |
---|
709 | setColAcol( 1, 0, 0, 2, 1, 3, 3, 4, 4, 2); |
---|
710 | if (id1 < 0) swapColAcol(); |
---|
711 | } |
---|
712 | |
---|
713 | //-------------------------------------------------------------------------- |
---|
714 | |
---|
715 | // Map a final state configuration |
---|
716 | |
---|
717 | inline void Sigma3qqbar2ggg::mapFinal() { |
---|
718 | switch (config) { |
---|
719 | case 0: pCM[2] = p3cm; pCM[3] = p4cm; pCM[4] = p5cm; break; |
---|
720 | case 1: pCM[2] = p3cm; pCM[3] = p5cm; pCM[4] = p4cm; break; |
---|
721 | case 2: pCM[2] = p4cm; pCM[3] = p3cm; pCM[4] = p5cm; break; |
---|
722 | case 3: pCM[2] = p4cm; pCM[3] = p5cm; pCM[4] = p3cm; break; |
---|
723 | case 4: pCM[2] = p5cm; pCM[3] = p3cm; pCM[4] = p4cm; break; |
---|
724 | case 5: pCM[2] = p5cm; pCM[3] = p4cm; pCM[4] = p3cm; break; |
---|
725 | } |
---|
726 | } |
---|
727 | |
---|
728 | //========================================================================== |
---|
729 | |
---|
730 | // Sigma3qg2qgg class. |
---|
731 | // Cross section for q g -> q g g. |
---|
732 | // Crossed relation from q qbar -> g g g: |
---|
733 | // qbar(p+) q(p-) -> g(k1) g(k2) g(k3) |
---|
734 | |
---|
735 | //-------------------------------------------------------------------------- |
---|
736 | |
---|
737 | // Evaluate |M|^2 - no incoming flavour dependence |
---|
738 | // Note: two different contributions from gq and qg incoming |
---|
739 | |
---|
740 | void Sigma3qg2qgg::sigmaKin() { |
---|
741 | |
---|
742 | // Pick a final state configuration |
---|
743 | pickFinal(); |
---|
744 | |
---|
745 | // gq and qg incoming |
---|
746 | for (int i = 0; i < 2; i++) { |
---|
747 | |
---|
748 | // Map incoming four-vectors to p+, p-, k1, k2, k3 |
---|
749 | pCM[0] = Vec4( 0., 0., 0.5 * mH, 0.5 * mH); |
---|
750 | pCM[1] = Vec4( 0., 0., -0.5 * mH, 0.5 * mH); |
---|
751 | mapFinal(); |
---|
752 | |
---|
753 | // Crossing |
---|
754 | swap(pCM[i], pCM[2]); |
---|
755 | |
---|
756 | // |M|^2 |
---|
757 | // XXX - Extra factor of (3) from selecting a final state |
---|
758 | // configuration (already a factor of 2 in the original |
---|
759 | // answer due to two identical final state gluons)??? |
---|
760 | // Extra factor of (3 / 8) as average over incoming gluon |
---|
761 | sigma[i] = 3. * (3. / 8.) * m2Calc(); |
---|
762 | |
---|
763 | } // for (int i = 0; i < 2; i++) |
---|
764 | |
---|
765 | } |
---|
766 | |
---|
767 | //-------------------------------------------------------------------------- |
---|
768 | |
---|
769 | // Evaluate |M|^2 - incoming flavour dependence |
---|
770 | // Pick from two configurations calculated previously |
---|
771 | |
---|
772 | double Sigma3qg2qgg::sigmaHat() { |
---|
773 | // gq or qg incoming |
---|
774 | return (id1 == 21) ? sigma[0] : sigma[1]; |
---|
775 | } |
---|
776 | |
---|
777 | //-------------------------------------------------------------------------- |
---|
778 | |
---|
779 | // Select identity, colour and anticolour. |
---|
780 | |
---|
781 | void Sigma3qg2qgg::setIdColAcol(){ |
---|
782 | // Outgoing flavours; only need to know where the quark is |
---|
783 | int qIdx = config / 2; |
---|
784 | int idTmp[3] = { 21, 21, 21 }; |
---|
785 | idTmp[qIdx] = (id1 == 21) ? id2 : id1; |
---|
786 | setId( id1, id2, idTmp[0], idTmp[1], idTmp[2]); |
---|
787 | |
---|
788 | // Temporary solution |
---|
789 | if (qIdx == 0) setColAcol(1, 0, 2, 1, 4, 0, 3, 4, 2, 3); |
---|
790 | else if (qIdx == 1) setColAcol(1, 0, 2, 1, 3, 4, 4, 0, 2, 3); |
---|
791 | else setColAcol(1, 0, 2, 1, 3, 4, 2, 3, 4, 0); |
---|
792 | // gq or qg incoming |
---|
793 | if (id1 == 21) { |
---|
794 | swap( colSave[1], colSave[2]); |
---|
795 | swap(acolSave[1], acolSave[2]); |
---|
796 | } |
---|
797 | // qbar rather than q incoming |
---|
798 | if (id1 < 0 || id2 < 0) swapColAcol(); |
---|
799 | |
---|
800 | } |
---|
801 | |
---|
802 | //========================================================================== |
---|
803 | |
---|
804 | // Sigma3gg2qqbarg class. |
---|
805 | // Cross section for g g -> q qbar g |
---|
806 | // Crossed relation from q qbar -> g g g |
---|
807 | |
---|
808 | //-------------------------------------------------------------------------- |
---|
809 | |
---|
810 | // Initialize process. |
---|
811 | |
---|
812 | void Sigma3gg2qqbarg::initProc() { |
---|
813 | |
---|
814 | // Read number of quarks to be considered in massless approximation. |
---|
815 | nQuarkNew = settingsPtr->mode("HardQCD:nQuarkNew"); |
---|
816 | |
---|
817 | } |
---|
818 | |
---|
819 | //-------------------------------------------------------------------------- |
---|
820 | |
---|
821 | // Evaluate |M|^2 - no incoming flavour dependence. |
---|
822 | |
---|
823 | void Sigma3gg2qqbarg::sigmaKin() { |
---|
824 | |
---|
825 | // Incoming four-vectors |
---|
826 | pCM[0] = Vec4( 0., 0., 0.5 * mH, 0.5 * mH); |
---|
827 | pCM[1] = Vec4( 0., 0., -0.5 * mH, 0.5 * mH); |
---|
828 | |
---|
829 | // Pick and map a final state configuration |
---|
830 | pickFinal(); |
---|
831 | mapFinal(); |
---|
832 | |
---|
833 | // Crossing |
---|
834 | swap(pCM[0], pCM[2]); |
---|
835 | swap(pCM[1], pCM[3]); |
---|
836 | |
---|
837 | // |M|^2 |
---|
838 | // Extra factor of (6.) from picking a final state configuration |
---|
839 | // Extra factor of nQuarkNew |
---|
840 | // Extra factor of (3. / 8.) ^ 2 as averaging over two incoming gluons |
---|
841 | sigma = 6. * nQuarkNew * (3. / 8.) * (3. / 8.) * m2Calc(); |
---|
842 | |
---|
843 | } |
---|
844 | |
---|
845 | //-------------------------------------------------------------------------- |
---|
846 | |
---|
847 | // Select identity, colour and anticolour. |
---|
848 | |
---|
849 | void Sigma3gg2qqbarg::setIdColAcol(){ |
---|
850 | |
---|
851 | // Pick new flavour |
---|
852 | int idNew = 1 + int( nQuarkNew * rndmPtr->flat() ); |
---|
853 | |
---|
854 | // Outgoing flavours; easiest just to map by hand |
---|
855 | switch (config) { |
---|
856 | case 0: id3 = idNew; id4 = -idNew; id5 = 21; break; |
---|
857 | case 1: id3 = idNew; id4 = 21; id5 = -idNew; break; |
---|
858 | case 2: id3 = -idNew; id4 = idNew; id5 = 21; break; |
---|
859 | case 3: id3 = 21; id4 = idNew; id5 = -idNew; break; |
---|
860 | case 4: id3 = -idNew; id4 = 21; id5 = idNew; break; |
---|
861 | case 5: id3 = 21; id4 = -idNew; id5 = idNew; break; |
---|
862 | } |
---|
863 | setId(id1, id2, id3, id4, id5); |
---|
864 | |
---|
865 | // Temporary solution |
---|
866 | switch (config) { |
---|
867 | case 0: setColAcol( 1, 2, 2, 3, 4, 0, 0, 3, 1, 4 ); break; |
---|
868 | case 1: setColAcol( 1, 2, 2, 3, 4, 0, 1, 4, 0, 3 ); break; |
---|
869 | case 2: setColAcol( 1, 2, 2, 3, 0, 3, 4, 0, 1, 4 ); break; |
---|
870 | case 3: setColAcol( 1, 2, 2, 3, 1, 4, 4, 0, 0, 3 ); break; |
---|
871 | case 4: setColAcol( 1, 2, 2, 3, 0, 3, 1, 4, 4, 0 ); break; |
---|
872 | case 5: setColAcol( 1, 2, 2, 3, 1, 4, 0, 3, 4, 0 ); break; |
---|
873 | } |
---|
874 | |
---|
875 | } |
---|
876 | |
---|
877 | //========================================================================== |
---|
878 | |
---|
879 | // Sigma3qq2qqgDiff class. |
---|
880 | // Cross section for q q' -> q q' g, q != q' |
---|
881 | |
---|
882 | //-------------------------------------------------------------------------- |
---|
883 | |
---|
884 | // Evaluate |M|^2 - no incoming flavour dependence |
---|
885 | |
---|
886 | void Sigma3qq2qqgDiff::sigmaKin() { |
---|
887 | |
---|
888 | // q1(p+) q2(p-) -> q1(q+) q2(q-) g(k) |
---|
889 | |
---|
890 | // Incoming four-vectors |
---|
891 | pCM[0] = Vec4( 0., 0., 0.5 * mH, 0.5 * mH); |
---|
892 | pCM[1] = Vec4( 0., 0., -0.5 * mH, 0.5 * mH); |
---|
893 | // Pick and map a final state configuration |
---|
894 | pickFinal(); |
---|
895 | mapFinal(); |
---|
896 | |
---|
897 | // |M|^2 |
---|
898 | // Extra factor of (6.) from picking a final state configuration |
---|
899 | sigma = 6. * m2Calc(); |
---|
900 | } |
---|
901 | |
---|
902 | //-------------------------------------------------------------------------- |
---|
903 | |
---|
904 | // |M|^2 |
---|
905 | |
---|
906 | inline double Sigma3qq2qqgDiff::m2Calc() { |
---|
907 | |
---|
908 | // Four-products |
---|
909 | s = (pCM[0] + pCM[1]).m2Calc(); |
---|
910 | t = (pCM[0] - pCM[2]).m2Calc(); |
---|
911 | u = (pCM[0] - pCM[3]).m2Calc(); |
---|
912 | up = (pCM[1] - pCM[2]).m2Calc(); |
---|
913 | sp = (pCM[2] + pCM[3]).m2Calc(); |
---|
914 | tp = (pCM[1] - pCM[3]).m2Calc(); |
---|
915 | |
---|
916 | // |M|^2 |
---|
917 | double num1 = (s * s + sp * sp + u * u + up * up) / (t * tp); |
---|
918 | double den1 = (pCM[0] * pCM[4]) * (pCM[1] * pCM[4]) * |
---|
919 | (pCM[2] * pCM[4]) * (pCM[3] * pCM[4]); |
---|
920 | double num2 = (u + up) * (s * sp + t * tp - u * up) + |
---|
921 | u * (s * t + sp * tp) + up * (s * tp + sp * t); |
---|
922 | double num3 = (s + sp) * (s * sp - t * tp - u * up) + |
---|
923 | 2. * t * tp * (u + up) + 2. * u * up * (t + tp); |
---|
924 | |
---|
925 | // (N^2 - 1)^2 / 4N^3 = 16. / 27. |
---|
926 | // (N^2 - 1) / 4N^3 = 2. / 27. |
---|
927 | return (1. / 8.) * pow3(4. * M_PI * alpS) * num1 / den1 * |
---|
928 | ( (16. / 27.) * num2 - (2. / 27.) * num3 ); |
---|
929 | |
---|
930 | } |
---|
931 | |
---|
932 | //-------------------------------------------------------------------------- |
---|
933 | |
---|
934 | // Evaluate |M|^2 - incoming flavour dependence |
---|
935 | |
---|
936 | double Sigma3qq2qqgDiff::sigmaHat() { |
---|
937 | // Different incoming flavours only |
---|
938 | if (abs(id1) == abs(id2)) return 0.; |
---|
939 | return sigma; |
---|
940 | } |
---|
941 | |
---|
942 | //-------------------------------------------------------------------------- |
---|
943 | |
---|
944 | // Select identity, colour and anticolour. |
---|
945 | |
---|
946 | void Sigma3qq2qqgDiff::setIdColAcol(){ |
---|
947 | |
---|
948 | // Outgoing flavours; easiest just to map by hand |
---|
949 | switch (config) { |
---|
950 | case 0: id3 = id1; id4 = id2; id5 = 21; break; |
---|
951 | case 1: id3 = id1; id4 = 21; id5 = id2; break; |
---|
952 | case 2: id3 = id2; id4 = id1; id5 = 21; break; |
---|
953 | case 3: id3 = 21; id4 = id1; id5 = id2; break; |
---|
954 | case 4: id3 = id2; id4 = 21; id5 = id1; break; |
---|
955 | case 5: id3 = 21; id4 = id2; id5 = id1; break; |
---|
956 | } |
---|
957 | setId(id1, id2, id3, id4, id5); |
---|
958 | |
---|
959 | // Temporary solution; id1 and id2 can be q/qbar independently |
---|
960 | int cols[5][2]; |
---|
961 | if (id1 > 0) { |
---|
962 | cols[0][0] = 1; cols[0][1] = 0; |
---|
963 | cols[2][0] = 1; cols[2][1] = 0; |
---|
964 | } else { |
---|
965 | cols[0][0] = 0; cols[0][1] = 1; |
---|
966 | cols[2][0] = 0; cols[2][1] = 1; |
---|
967 | } |
---|
968 | if (id2 > 0) { |
---|
969 | cols[1][0] = 2; cols[1][1] = 0; |
---|
970 | cols[3][0] = 3; cols[3][1] = 0; |
---|
971 | cols[4][0] = 2; cols[4][1] = 3; |
---|
972 | } else { |
---|
973 | cols[1][0] = 0; cols[1][1] = 2; |
---|
974 | cols[3][0] = 0; cols[3][1] = 3; |
---|
975 | cols[4][0] = 3; cols[4][1] = 2; |
---|
976 | } |
---|
977 | // Map correct final state configuration |
---|
978 | int i3 = 0, i4 = 0, i5 = 0; |
---|
979 | switch (config) { |
---|
980 | case 0: i3 = 2; i4 = 3; i5 = 4; break; |
---|
981 | case 1: i3 = 2; i4 = 4; i5 = 3; break; |
---|
982 | case 2: i3 = 3; i4 = 2; i5 = 4; break; |
---|
983 | case 3: i3 = 4; i4 = 2; i5 = 3; break; |
---|
984 | case 4: i3 = 3; i4 = 4; i5 = 2; break; |
---|
985 | case 5: i3 = 4; i4 = 3; i5 = 2; break; |
---|
986 | } |
---|
987 | // Put colours in place |
---|
988 | setColAcol(cols[0][0], cols[0][1], cols[1][0], cols[1][1], |
---|
989 | cols[i3][0], cols[i3][1], cols[i4][0], cols[i4][1], |
---|
990 | cols[i5][0], cols[i5][1]); |
---|
991 | |
---|
992 | } |
---|
993 | |
---|
994 | //-------------------------------------------------------------------------- |
---|
995 | |
---|
996 | // Map a final state configuration |
---|
997 | |
---|
998 | inline void Sigma3qq2qqgDiff::mapFinal() { |
---|
999 | switch (config) { |
---|
1000 | case 0: pCM[2] = p3cm; pCM[3] = p4cm; pCM[4] = p5cm; break; |
---|
1001 | case 1: pCM[2] = p3cm; pCM[3] = p5cm; pCM[4] = p4cm; break; |
---|
1002 | case 2: pCM[2] = p4cm; pCM[3] = p3cm; pCM[4] = p5cm; break; |
---|
1003 | case 3: pCM[2] = p4cm; pCM[3] = p5cm; pCM[4] = p3cm; break; |
---|
1004 | case 4: pCM[2] = p5cm; pCM[3] = p3cm; pCM[4] = p4cm; break; |
---|
1005 | case 5: pCM[2] = p5cm; pCM[3] = p4cm; pCM[4] = p3cm; break; |
---|
1006 | } |
---|
1007 | } |
---|
1008 | |
---|
1009 | |
---|
1010 | //========================================================================== |
---|
1011 | |
---|
1012 | // Sigma3qqbar2qqbargDiff |
---|
1013 | // Cross section for q qbar -> q' qbar' g |
---|
1014 | // Crossed relation from q q' -> q q' g, q != q' |
---|
1015 | |
---|
1016 | //-------------------------------------------------------------------------- |
---|
1017 | |
---|
1018 | // Initialize process. |
---|
1019 | |
---|
1020 | void Sigma3qqbar2qqbargDiff::initProc() { |
---|
1021 | |
---|
1022 | // Read number of quarks to be considered in massless approximation. |
---|
1023 | nQuarkNew = settingsPtr->mode("HardQCD:nQuarkNew"); |
---|
1024 | |
---|
1025 | } |
---|
1026 | |
---|
1027 | //-------------------------------------------------------------------------- |
---|
1028 | |
---|
1029 | // Evaluate |M|^2 - no incoming flavour dependence. |
---|
1030 | |
---|
1031 | void Sigma3qqbar2qqbargDiff::sigmaKin() { |
---|
1032 | // Overall 6 possibilities for final state ordering |
---|
1033 | // To keep symmetry between final states, always map to: |
---|
1034 | // 1) q1(p+) qbar1(p-) -> qbar2(q+) q2(q-) g(k) |
---|
1035 | // 2) qbar1(p+) q1(p-) -> q2(q+) qbar2(q-) g(k) |
---|
1036 | // Crossing p- and q+ gives: |
---|
1037 | // 1) q1(p+) q2(-q+) -> q1(-p-) q2(q-) g(k) |
---|
1038 | // 2) qbar1(p+) qbar2(-q+) -> qbar1(-p-) qbar2(q-) g(k) |
---|
1039 | |
---|
1040 | // Incoming four-vectors |
---|
1041 | pCM[0] = Vec4( 0., 0., 0.5 * mH, 0.5 * mH); |
---|
1042 | pCM[1] = Vec4( 0., 0., -0.5 * mH, 0.5 * mH); |
---|
1043 | // Pick and map a final state configuration |
---|
1044 | pickFinal(); |
---|
1045 | mapFinal(); |
---|
1046 | |
---|
1047 | // Crossing |
---|
1048 | swap(pCM[1], pCM[2]); |
---|
1049 | pCM[1] = -pCM[1]; |
---|
1050 | pCM[2] = -pCM[2]; |
---|
1051 | |
---|
1052 | // |M|^2 |
---|
1053 | // Extra factor of (6.) from picking a final state configuration |
---|
1054 | // Extra factor of (nQuarkNew - 1) from new q/qbar pairs |
---|
1055 | // XXX - Extra factor of (2.) from second possible crossing??? |
---|
1056 | sigma = 6. * (nQuarkNew - 1) * 2. * m2Calc(); |
---|
1057 | |
---|
1058 | } |
---|
1059 | |
---|
1060 | //-------------------------------------------------------------------------- |
---|
1061 | |
---|
1062 | // Select identity, colour and anticolour. |
---|
1063 | |
---|
1064 | void Sigma3qqbar2qqbargDiff::setIdColAcol(){ |
---|
1065 | |
---|
1066 | // Pick new q qbar flavour with incoming flavour disallowed |
---|
1067 | int idNew = 1 + int( (nQuarkNew - 1) * rndmPtr->flat() ); |
---|
1068 | if (idNew >= abs(id1)) ++idNew; |
---|
1069 | // For qbar q incoming, q+ is always mapped to q2 |
---|
1070 | // For q qbar incoming, q+ is always mapped to qbar2 |
---|
1071 | if (id1 > 0) idNew = -idNew; |
---|
1072 | |
---|
1073 | // Outgoing flavours; easiest just to map by hand |
---|
1074 | switch (config) { |
---|
1075 | case 0: id3 = idNew; id4 = -idNew; id5 = 21; break; |
---|
1076 | case 1: id3 = idNew; id4 = 21; id5 = -idNew; break; |
---|
1077 | case 2: id3 = -idNew; id4 = idNew; id5 = 21; break; |
---|
1078 | case 3: id3 = 21; id4 = idNew; id5 = -idNew; break; |
---|
1079 | case 4: id3 = -idNew; id4 = 21; id5 = idNew; break; |
---|
1080 | case 5: id3 = 21; id4 = -idNew; id5 = idNew; break; |
---|
1081 | } |
---|
1082 | setId(id1, id2, id3, id4, id5); |
---|
1083 | |
---|
1084 | // Temporary solution; start with q qbar -> qbar q g |
---|
1085 | int cols[5][2]; |
---|
1086 | cols[0][0] = 1; cols[0][1] = 0; |
---|
1087 | cols[1][0] = 0; cols[1][1] = 2; |
---|
1088 | cols[2][0] = 0; cols[2][1] = 3; |
---|
1089 | cols[3][0] = 1; cols[3][1] = 0; |
---|
1090 | cols[4][0] = 3; cols[4][1] = 2; |
---|
1091 | // Map into correct place |
---|
1092 | int i3 = 0, i4 = 0, i5 = 0; |
---|
1093 | switch (config) { |
---|
1094 | case 0: i3 = 2; i4 = 3; i5 = 4; break; |
---|
1095 | case 1: i3 = 2; i4 = 4; i5 = 3; break; |
---|
1096 | case 2: i3 = 3; i4 = 2; i5 = 4; break; |
---|
1097 | case 3: i3 = 4; i4 = 2; i5 = 3; break; |
---|
1098 | case 4: i3 = 3; i4 = 4; i5 = 2; break; |
---|
1099 | case 5: i3 = 4; i4 = 3; i5 = 2; break; |
---|
1100 | } |
---|
1101 | setColAcol(cols[0][0], cols[0][1], cols[1][0], cols[1][1], |
---|
1102 | cols[i3][0], cols[i3][1], cols[i4][0], cols[i4][1], |
---|
1103 | cols[i5][0], cols[i5][1]); |
---|
1104 | // Swap for qbar q incoming |
---|
1105 | if (id1 < 0) swapColAcol(); |
---|
1106 | |
---|
1107 | } |
---|
1108 | |
---|
1109 | //========================================================================== |
---|
1110 | |
---|
1111 | // Sigma3qg2qqqbarDiff class. |
---|
1112 | // Cross section for q g -> q q' qbar' |
---|
1113 | // Crossed relation from q q' -> q q' g, q != q' |
---|
1114 | // q1(p+) q2(p-) -> q1(q+) q2(q-) g(k) |
---|
1115 | |
---|
1116 | //-------------------------------------------------------------------------- |
---|
1117 | |
---|
1118 | // Initialize process. |
---|
1119 | |
---|
1120 | void Sigma3qg2qqqbarDiff::initProc() { |
---|
1121 | |
---|
1122 | // Read number of quarks to be considered in massless approximation. |
---|
1123 | nQuarkNew = settingsPtr->mode("HardQCD:nQuarkNew"); |
---|
1124 | |
---|
1125 | } |
---|
1126 | |
---|
1127 | //-------------------------------------------------------------------------- |
---|
1128 | |
---|
1129 | // Evaluate |M|^2 - no incoming flavour dependence |
---|
1130 | |
---|
1131 | void Sigma3qg2qqqbarDiff::sigmaKin() { |
---|
1132 | |
---|
1133 | // Pick a final state configuration |
---|
1134 | pickFinal(); |
---|
1135 | |
---|
1136 | // gq or qg incoming |
---|
1137 | for (int i = 0; i < 2; i++) { |
---|
1138 | |
---|
1139 | // Map incoming four-vectors |
---|
1140 | pCM[0] = Vec4( 0., 0., 0.5 * mH, 0.5 * mH); |
---|
1141 | pCM[1] = Vec4( 0., 0., -0.5 * mH, 0.5 * mH); |
---|
1142 | mapFinal(); |
---|
1143 | |
---|
1144 | // Crossing (note extra -ve sign in total sigma) |
---|
1145 | swap(pCM[i], pCM[4]); |
---|
1146 | pCM[i] = -pCM[i]; |
---|
1147 | pCM[4] = -pCM[4]; |
---|
1148 | |
---|
1149 | // |M|^2 |
---|
1150 | // Extra factor of (6) from picking a final state configuration |
---|
1151 | // Extra factor of (3 / 8) as averaging over incoming gluon |
---|
1152 | // Extra factor of (nQuarkNew - 1) due to new q/qbar pair |
---|
1153 | sigma[i] = -6. * (3. / 8.) * (nQuarkNew - 1) * m2Calc(); |
---|
1154 | |
---|
1155 | } |
---|
1156 | |
---|
1157 | } |
---|
1158 | |
---|
1159 | //-------------------------------------------------------------------------- |
---|
1160 | |
---|
1161 | // Evaluate |M|^2 - incoming flavour dependence |
---|
1162 | |
---|
1163 | double Sigma3qg2qqqbarDiff::sigmaHat() { |
---|
1164 | // gq or qg incoming |
---|
1165 | return (id1 == 21) ? sigma[0] : sigma[1]; |
---|
1166 | } |
---|
1167 | |
---|
1168 | //-------------------------------------------------------------------------- |
---|
1169 | |
---|
1170 | // Select identity, colour and anticolour. |
---|
1171 | |
---|
1172 | void Sigma3qg2qqqbarDiff::setIdColAcol(){ |
---|
1173 | // Pick new q qbar flavour with incoming flavour disallowed |
---|
1174 | int sigmaIdx = (id1 == 21) ? 0 : 1; |
---|
1175 | int idIn = (id1 == 21) ? id2 : id1; |
---|
1176 | int idNew = 1 + int( (nQuarkNew - 1) * rndmPtr->flat() ); |
---|
1177 | if (idNew >= abs(idIn)) ++idNew; |
---|
1178 | |
---|
1179 | // qbar instead of q incoming means swap outgoing q/qbar pair |
---|
1180 | int id3Tmp = idIn, id4Tmp = idNew, id5Tmp = -idNew; |
---|
1181 | if (idIn < 0) swap(id4Tmp, id5Tmp); |
---|
1182 | // If g q incoming rather than q g, idIn and idNew |
---|
1183 | // should be exchanged (see sigmaKin) |
---|
1184 | if (sigmaIdx == 0) swap(id3Tmp, id4Tmp); |
---|
1185 | // Outgoing flavours; now just map as if q g incoming |
---|
1186 | switch (config) { |
---|
1187 | case 0: id3 = id3Tmp; id4 = id4Tmp; id5 = id5Tmp; break; |
---|
1188 | case 1: id3 = id3Tmp; id4 = id5Tmp; id5 = id4Tmp; break; |
---|
1189 | case 2: id3 = id4Tmp; id4 = id3Tmp; id5 = id5Tmp; break; |
---|
1190 | case 3: id3 = id5Tmp; id4 = id3Tmp; id5 = id4Tmp; break; |
---|
1191 | case 4: id3 = id4Tmp; id4 = id5Tmp; id5 = id3Tmp; break; |
---|
1192 | case 5: id3 = id5Tmp; id4 = id4Tmp; id5 = id3Tmp; break; |
---|
1193 | } |
---|
1194 | setId(id1, id2, id3, id4, id5); |
---|
1195 | |
---|
1196 | // Temporary solution; start with either |
---|
1197 | // g q1 -> q1 q2 qbar2 |
---|
1198 | // g qbar1 -> qbar1 qbar2 q2 |
---|
1199 | int cols[5][2]; |
---|
1200 | cols[0][0] = 1; cols[0][1] = 2; |
---|
1201 | if (idIn > 0) { |
---|
1202 | cols[1][0] = 3; cols[1][1] = 0; |
---|
1203 | cols[2][0] = 1; cols[2][1] = 0; |
---|
1204 | cols[3][0] = 3; cols[3][1] = 0; |
---|
1205 | cols[4][0] = 0; cols[4][1] = 2; |
---|
1206 | } else { |
---|
1207 | cols[1][0] = 0; cols[1][1] = 3; |
---|
1208 | cols[2][0] = 0; cols[2][1] = 2; |
---|
1209 | cols[3][0] = 0; cols[3][1] = 3; |
---|
1210 | cols[4][0] = 1; cols[4][1] = 0; |
---|
1211 | } |
---|
1212 | // Swap incoming if q/qbar g instead |
---|
1213 | if (id2 == 21) { |
---|
1214 | swap(cols[0][0], cols[1][0]); |
---|
1215 | swap(cols[0][1], cols[1][1]); |
---|
1216 | } |
---|
1217 | // Map final state |
---|
1218 | int i3 = 0, i4 = 0, i5 = 0; |
---|
1219 | if (sigmaIdx == 0) { |
---|
1220 | switch (config) { |
---|
1221 | case 0: i3 = 3; i4 = 2; i5 = 4; break; |
---|
1222 | case 1: i3 = 3; i4 = 4; i5 = 2; break; |
---|
1223 | case 2: i3 = 2; i4 = 3; i5 = 4; break; |
---|
1224 | case 3: i3 = 4; i4 = 3; i5 = 2; break; |
---|
1225 | case 4: i3 = 2; i4 = 4; i5 = 3; break; |
---|
1226 | case 5: i3 = 4; i4 = 2; i5 = 3; break; |
---|
1227 | } |
---|
1228 | } else { |
---|
1229 | switch (config) { |
---|
1230 | case 0: i3 = 2; i4 = 3; i5 = 4; break; |
---|
1231 | case 1: i3 = 2; i4 = 4; i5 = 3; break; |
---|
1232 | case 2: i3 = 3; i4 = 2; i5 = 4; break; |
---|
1233 | case 3: i3 = 4; i4 = 2; i5 = 3; break; |
---|
1234 | case 4: i3 = 3; i4 = 4; i5 = 2; break; |
---|
1235 | case 5: i3 = 4; i4 = 3; i5 = 2; break; |
---|
1236 | } |
---|
1237 | } |
---|
1238 | setColAcol(cols[0][0], cols[0][1], cols[1][0], cols[1][1], |
---|
1239 | cols[i3][0], cols[i3][1], cols[i4][0], cols[i4][1], |
---|
1240 | cols[i5][0], cols[i5][1]); |
---|
1241 | } |
---|
1242 | |
---|
1243 | //========================================================================== |
---|
1244 | |
---|
1245 | // Sigma3qq2qqgSame class. |
---|
1246 | // Cross section for q q' -> q q' g, q == q'. |
---|
1247 | |
---|
1248 | //-------------------------------------------------------------------------- |
---|
1249 | |
---|
1250 | // Evaluate |M|^2 - no incoming flavour dependence |
---|
1251 | |
---|
1252 | void Sigma3qq2qqgSame::sigmaKin() { |
---|
1253 | // q1(p+) q2(p-) -> q1(q+) q2(q-) g(k) |
---|
1254 | |
---|
1255 | // Incoming four-vectors |
---|
1256 | pCM[0] = Vec4( 0., 0., 0.5 * mH, 0.5 * mH); |
---|
1257 | pCM[1] = Vec4( 0., 0., -0.5 * mH, 0.5 * mH); |
---|
1258 | // Pick/map a final state configuration |
---|
1259 | pickFinal(); |
---|
1260 | mapFinal(); |
---|
1261 | |
---|
1262 | // |M|^2 |
---|
1263 | // Extra factor (3) from picking final state configuration |
---|
1264 | // (original answer already has a factor 2 from identical |
---|
1265 | // quarks in the final state) |
---|
1266 | sigma = 3. * m2Calc(); |
---|
1267 | |
---|
1268 | } |
---|
1269 | |
---|
1270 | //-------------------------------------------------------------------------- |
---|
1271 | |
---|
1272 | // |M|^2 |
---|
1273 | |
---|
1274 | inline double Sigma3qq2qqgSame::m2Calc() { |
---|
1275 | |
---|
1276 | // Four-products |
---|
1277 | s = (pCM[0] + pCM[1]).m2Calc(); |
---|
1278 | t = (pCM[0] - pCM[2]).m2Calc(); |
---|
1279 | u = (pCM[0] - pCM[3]).m2Calc(); |
---|
1280 | sp = (pCM[2] + pCM[3]).m2Calc(); |
---|
1281 | tp = (pCM[1] - pCM[3]).m2Calc(); |
---|
1282 | up = (pCM[1] - pCM[2]).m2Calc(); |
---|
1283 | |
---|
1284 | // |M|^2 |
---|
1285 | ssp = s * sp; |
---|
1286 | ttp = t * tp; |
---|
1287 | uup = u * up; |
---|
1288 | s_sp = s + sp; |
---|
1289 | t_tp = t + tp; |
---|
1290 | u_up = u + up; |
---|
1291 | |
---|
1292 | double den1 = (pCM[0] * pCM[4]) * (pCM[1] * pCM[4]) * |
---|
1293 | (pCM[2] * pCM[4]) * (pCM[3] * pCM[4]); |
---|
1294 | |
---|
1295 | double fac1 = s * (t * u + tp * up) + sp * (t * up + tp * u); |
---|
1296 | double fac2 = ssp - ttp - uup; |
---|
1297 | double fac3 = 2. * (ttp * u_up + uup * t_tp); |
---|
1298 | |
---|
1299 | double num1 = u_up * (ssp + ttp - uup) + fac1; |
---|
1300 | double num2 = s_sp * fac2 + fac3; |
---|
1301 | double num3 = (s * s + sp * sp + u * u + up * up) / (t * tp); |
---|
1302 | |
---|
1303 | double num4 = t_tp * (ssp - ttp + uup) + fac1; |
---|
1304 | double num5 = (s * s + sp * sp + t * t + tp * tp) / (u * up); |
---|
1305 | |
---|
1306 | double num6 = s_sp * fac2 - fac3 - 2. * fac1; |
---|
1307 | double num7 = (s * s + sp * sp) * fac2; |
---|
1308 | double den7 = (ttp * uup); |
---|
1309 | |
---|
1310 | // C1 = (N^2 - 1)^2 / 4N^3 = 16. / 27. |
---|
1311 | // C2 = (N^2 - 1) / 4N^3 = 2. / 27. |
---|
1312 | // C3 = (N^4 - 1) / 8N^4 = 10. / 81. |
---|
1313 | // C4 = (N^2 - 1)^2 / 8N^4 = 8. / 81. |
---|
1314 | return (1. / 8.) * pow3(4. * M_PI * alpS) * |
---|
1315 | ( ( (16. / 27.) * num1 - (2. / 27.) * num2 ) * num3 + |
---|
1316 | ( (16. / 27.) * num4 - (2. / 27.) * num2 ) * num5 + |
---|
1317 | ( (10. / 81.) * num2 + (8. / 81.) * num6 ) * |
---|
1318 | ( num7 / den7 ) ) / den1; |
---|
1319 | |
---|
1320 | } |
---|
1321 | |
---|
1322 | //-------------------------------------------------------------------------- |
---|
1323 | |
---|
1324 | // Evaluate |M|^2 - incoming flavour dependence |
---|
1325 | |
---|
1326 | double Sigma3qq2qqgSame::sigmaHat() { |
---|
1327 | // q q / qbar qbar incoming states only |
---|
1328 | if (id1 != id2) return 0.; |
---|
1329 | return sigma; |
---|
1330 | } |
---|
1331 | |
---|
1332 | //-------------------------------------------------------------------------- |
---|
1333 | |
---|
1334 | // Select identity, colour and anticolour. |
---|
1335 | |
---|
1336 | void Sigma3qq2qqgSame::setIdColAcol(){ |
---|
1337 | |
---|
1338 | // Need to know where the gluon was mapped (pCM[4]) |
---|
1339 | int gIdx = 0; |
---|
1340 | switch (config) { |
---|
1341 | case 3: case 5: gIdx = 0; break; |
---|
1342 | case 1: case 4: gIdx = 1; break; |
---|
1343 | case 0: case 2: gIdx = 2; break; |
---|
1344 | } |
---|
1345 | |
---|
1346 | // Outgoing flavours |
---|
1347 | int idTmp[3] = { id1, id1, id1 }; |
---|
1348 | idTmp[gIdx] = 21; |
---|
1349 | setId(id1, id2, idTmp[0], idTmp[1], idTmp[2]); |
---|
1350 | |
---|
1351 | // Temporary solution; start with q q -> q q g |
---|
1352 | setColAcol(1, 0, 2, 0, 1, 0, 3, 0, 2, 3); |
---|
1353 | // Map gluon |
---|
1354 | swap( colSave[5], colSave[gIdx + 3]); |
---|
1355 | swap(acolSave[5], acolSave[gIdx + 3]); |
---|
1356 | // Swap if qbar qbar incoming |
---|
1357 | if (id1 < 0) swapColAcol(); |
---|
1358 | |
---|
1359 | } |
---|
1360 | |
---|
1361 | //-------------------------------------------------------------------------- |
---|
1362 | |
---|
1363 | // Map a final state configuration |
---|
1364 | inline void Sigma3qq2qqgSame::mapFinal() { |
---|
1365 | switch (config) { |
---|
1366 | case 0: pCM[2] = p3cm; pCM[3] = p4cm; pCM[4] = p5cm; break; |
---|
1367 | case 1: pCM[2] = p3cm; pCM[3] = p5cm; pCM[4] = p4cm; break; |
---|
1368 | case 2: pCM[2] = p4cm; pCM[3] = p3cm; pCM[4] = p5cm; break; |
---|
1369 | case 3: pCM[2] = p4cm; pCM[3] = p5cm; pCM[4] = p3cm; break; |
---|
1370 | case 4: pCM[2] = p5cm; pCM[3] = p3cm; pCM[4] = p4cm; break; |
---|
1371 | case 5: pCM[2] = p5cm; pCM[3] = p4cm; pCM[4] = p3cm; break; |
---|
1372 | } |
---|
1373 | } |
---|
1374 | |
---|
1375 | //========================================================================== |
---|
1376 | |
---|
1377 | // Sigma3qqbar2qqbargSame class. |
---|
1378 | // Cross section for q qbar -> q qbar g |
---|
1379 | // Crossed relation from q(bar) q(bar) -> q(bar) q(bar) g: |
---|
1380 | // q1(p+) q2(p-) -> q1(q+) q2(q-) g(k) |
---|
1381 | //-------------------------------------------------------------------------- |
---|
1382 | |
---|
1383 | // Evaluate |M|^2 - no incoming flavour dependence |
---|
1384 | |
---|
1385 | void Sigma3qqbar2qqbargSame::sigmaKin() { |
---|
1386 | |
---|
1387 | // Incoming four-vectors |
---|
1388 | pCM[0] = Vec4( 0., 0., 0.5 * mH, 0.5 * mH); |
---|
1389 | pCM[1] = Vec4( 0., 0., -0.5 * mH, 0.5 * mH); |
---|
1390 | |
---|
1391 | // Pick and map a final state configuration |
---|
1392 | pickFinal(); |
---|
1393 | mapFinal(); |
---|
1394 | |
---|
1395 | // Crossing |
---|
1396 | swap(pCM[1], pCM[3]); |
---|
1397 | pCM[1] = -pCM[1]; |
---|
1398 | pCM[3] = -pCM[3]; |
---|
1399 | |
---|
1400 | // |M|^2 |
---|
1401 | // Extra factor of (6) from picking a final state configuration |
---|
1402 | sigma = 6. * m2Calc(); |
---|
1403 | |
---|
1404 | } |
---|
1405 | |
---|
1406 | //-------------------------------------------------------------------------- |
---|
1407 | |
---|
1408 | // Select identity, colour and anticolour. |
---|
1409 | |
---|
1410 | void Sigma3qqbar2qqbargSame::setIdColAcol(){ |
---|
1411 | // Outgoing flavours; easiest to map by hand |
---|
1412 | switch (config) { |
---|
1413 | case 0: id3 = id1; id4 = id2; id5 = 21; break; |
---|
1414 | case 1: id3 = id1; id4 = 21; id5 = id2; break; |
---|
1415 | case 2: id3 = id2; id4 = id1; id5 = 21; break; |
---|
1416 | case 3: id3 = 21; id4 = id1; id5 = id2; break; |
---|
1417 | case 4: id3 = id2; id4 = 21; id5 = id1; break; |
---|
1418 | case 5: id3 = 21; id4 = id2; id5 = id1; break; |
---|
1419 | } |
---|
1420 | setId(id1, id2, id3, id4, id5); |
---|
1421 | |
---|
1422 | // Temporary solution; start with q qbar -> q qbar g |
---|
1423 | int cols[5][2]; |
---|
1424 | cols[0][0] = 1; cols[0][1] = 0; |
---|
1425 | cols[1][0] = 0; cols[1][1] = 2; |
---|
1426 | cols[2][0] = 1; cols[2][1] = 0; |
---|
1427 | cols[3][0] = 0; cols[3][1] = 3; |
---|
1428 | cols[4][0] = 3; cols[4][1] = 2; |
---|
1429 | // Map final state |
---|
1430 | int i3 = 0, i4 = 0, i5 = 0; |
---|
1431 | switch (config) { |
---|
1432 | case 0: i3 = 2; i4 = 3; i5 = 4; break; |
---|
1433 | case 1: i3 = 2; i4 = 4; i5 = 3; break; |
---|
1434 | case 2: i3 = 3; i4 = 2; i5 = 4; break; |
---|
1435 | case 3: i3 = 4; i4 = 2; i5 = 3; break; |
---|
1436 | case 4: i3 = 3; i4 = 4; i5 = 2; break; |
---|
1437 | case 5: i3 = 4; i4 = 3; i5 = 2; break; |
---|
1438 | } |
---|
1439 | setColAcol(cols[0][0], cols[0][1], cols[1][0], cols[1][1], |
---|
1440 | cols[i3][0], cols[i3][1], cols[i4][0], cols[i4][1], |
---|
1441 | cols[i5][0], cols[i5][1]); |
---|
1442 | // Swap for qbar q incoming |
---|
1443 | if (id1 < 0) swapColAcol(); |
---|
1444 | } |
---|
1445 | |
---|
1446 | //========================================================================== |
---|
1447 | |
---|
1448 | // Sigma3qg2qqqbarSame class. |
---|
1449 | // Cross section for q g -> q q qbar. |
---|
1450 | // Crossed relation from q(bar) q(bar) -> q(bar) q(bar) g: |
---|
1451 | // q1(p+) q1(p-) -> q1(q+) q1(q-) g(k) |
---|
1452 | |
---|
1453 | //-------------------------------------------------------------------------- |
---|
1454 | |
---|
1455 | // Evaluate |M|^2 - no incoming flavour dependence |
---|
1456 | |
---|
1457 | void Sigma3qg2qqqbarSame::sigmaKin() { |
---|
1458 | |
---|
1459 | // Pick a final state configuration |
---|
1460 | pickFinal(); |
---|
1461 | |
---|
1462 | // gq and qg incoming |
---|
1463 | for (int i = 0; i < 2; i++) { |
---|
1464 | |
---|
1465 | // Map incoming four-vectors |
---|
1466 | pCM[0] = Vec4( 0., 0., 0.5 * mH, 0.5 * mH); |
---|
1467 | pCM[1] = Vec4( 0., 0., -0.5 * mH, 0.5 * mH); |
---|
1468 | mapFinal(); |
---|
1469 | |
---|
1470 | // Crossing (note extra -ve sign in total sigma) |
---|
1471 | swap(pCM[i], pCM[4]); |
---|
1472 | pCM[i] = -pCM[i]; |
---|
1473 | pCM[4] = -pCM[4]; |
---|
1474 | |
---|
1475 | // |M|^2 |
---|
1476 | // XXX - Extra factor of (3) from picking a final state configuration??? |
---|
1477 | // Extra factor of (3 / 8) as averaging over incoming gluon |
---|
1478 | sigma[i] = -3. * (3. / 8.) * m2Calc(); |
---|
1479 | |
---|
1480 | } |
---|
1481 | |
---|
1482 | } |
---|
1483 | |
---|
1484 | //-------------------------------------------------------------------------- |
---|
1485 | |
---|
1486 | // Evaluate |M|^2 - incoming flavour dependence |
---|
1487 | |
---|
1488 | double Sigma3qg2qqqbarSame::sigmaHat() { |
---|
1489 | // gq or qg incoming |
---|
1490 | return (id1 == 21) ? sigma[0] : sigma[1]; |
---|
1491 | } |
---|
1492 | |
---|
1493 | //-------------------------------------------------------------------------- |
---|
1494 | |
---|
1495 | // Select identity, colour and anticolour. |
---|
1496 | |
---|
1497 | void Sigma3qg2qqqbarSame::setIdColAcol(){ |
---|
1498 | |
---|
1499 | // Pick outgoing flavour configuration |
---|
1500 | int idIn = (id1 == 21) ? id2 : id1; |
---|
1501 | |
---|
1502 | // Outgoing flavours; easiest just to map by hand |
---|
1503 | switch (config) { |
---|
1504 | case 0: id3 = idIn; id4 = idIn; id5 = -idIn; break; |
---|
1505 | case 1: id3 = idIn; id4 = -idIn; id5 = idIn; break; |
---|
1506 | case 2: id3 = idIn; id4 = idIn; id5 = -idIn; break; |
---|
1507 | case 3: id3 = -idIn; id4 = idIn; id5 = idIn; break; |
---|
1508 | case 4: id3 = idIn; id4 = -idIn; id5 = idIn; break; |
---|
1509 | case 5: id3 = -idIn; id4 = idIn; id5 = idIn; break; |
---|
1510 | } |
---|
1511 | setId(id1, id2, id3, id4, id5); |
---|
1512 | |
---|
1513 | // Temporary solution; start with either |
---|
1514 | // g q1 -> q1 q2 qbar2 |
---|
1515 | // g qbar1 -> qbar1 qbar2 q2 |
---|
1516 | int cols[5][2]; |
---|
1517 | cols[0][0] = 1; cols[0][1] = 2; |
---|
1518 | if (idIn > 0) { |
---|
1519 | cols[1][0] = 3; cols[1][1] = 0; |
---|
1520 | cols[2][0] = 1; cols[2][1] = 0; |
---|
1521 | cols[3][0] = 3; cols[3][1] = 0; |
---|
1522 | cols[4][0] = 0; cols[4][1] = 2; |
---|
1523 | } else { |
---|
1524 | cols[1][0] = 0; cols[1][1] = 3; |
---|
1525 | cols[2][0] = 0; cols[2][1] = 2; |
---|
1526 | cols[3][0] = 0; cols[3][1] = 3; |
---|
1527 | cols[4][0] = 1; cols[4][1] = 0; |
---|
1528 | } |
---|
1529 | // Swap incoming if q/qbar g instead |
---|
1530 | if (id2 == 21) { |
---|
1531 | swap(cols[0][0], cols[1][0]); |
---|
1532 | swap(cols[0][1], cols[1][1]); |
---|
1533 | } |
---|
1534 | // Map final state |
---|
1535 | int i3 = 0, i4 = 0, i5 = 0; |
---|
1536 | switch (config) { |
---|
1537 | case 0: i3 = 2; i4 = 3; i5 = 4; break; |
---|
1538 | case 1: i3 = 2; i4 = 4; i5 = 3; break; |
---|
1539 | case 2: i3 = 3; i4 = 2; i5 = 4; break; |
---|
1540 | case 3: i3 = 4; i4 = 2; i5 = 3; break; |
---|
1541 | case 4: i3 = 3; i4 = 4; i5 = 2; break; |
---|
1542 | case 5: i3 = 4; i4 = 3; i5 = 2; break; |
---|
1543 | } |
---|
1544 | setColAcol(cols[0][0], cols[0][1], cols[1][0], cols[1][1], |
---|
1545 | cols[i3][0], cols[i3][1], cols[i4][0], cols[i4][1], |
---|
1546 | cols[i5][0], cols[i5][1]); |
---|
1547 | } |
---|
1548 | |
---|
1549 | //========================================================================== |
---|
1550 | |
---|
1551 | } // end namespace Pythia8 |
---|