| 63ba5337 |
1 | // HadronLevel.cc is a part of the PYTHIA event generator. |
| 2 | // Copyright (C) 2012 Torbjorn Sjostrand. |
| 3 | // PYTHIA is licenced under the GNU GPL version 2, see COPYING for details. |
| 4 | // Please respect the MCnet Guidelines, see GUIDELINES for details. |
| 5 | |
| 6 | // Function definitions (not found in the header) for the HadronLevel class. |
| 7 | |
| 8 | #include "HadronLevel.h" |
| 9 | |
| 10 | namespace Pythia8 { |
| 11 | |
| 12 | //========================================================================== |
| 13 | |
| 14 | // The HadronLevel class. |
| 15 | |
| 16 | //-------------------------------------------------------------------------- |
| 17 | |
| 18 | // Constants: could be changed here if desired, but normally should not. |
| 19 | // These are of technical nature, as described for each. |
| 20 | |
| 21 | // For breaking J-J string, pick a Gamma by taking a step with fictitious mass. |
| 22 | const double HadronLevel::JJSTRINGM2MAX = 25.; |
| 23 | const double HadronLevel::JJSTRINGM2FRAC = 0.1; |
| 24 | |
| 25 | // Iterate junction rest frame boost until convergence or too many tries. |
| 26 | const double HadronLevel::CONVJNREST = 1e-5; |
| 27 | const int HadronLevel::NTRYJNREST = 20; |
| 28 | |
| 29 | // Typical average transvere primary hadron mass <mThad>. |
| 30 | const double HadronLevel::MTHAD = 0.9; |
| 31 | |
| 32 | //-------------------------------------------------------------------------- |
| 33 | |
| 34 | // Find settings. Initialize HadronLevel classes as required. |
| 35 | |
| 36 | bool HadronLevel::init(Info* infoPtrIn, Settings& settings, |
| 37 | ParticleData* particleDataPtrIn, Rndm* rndmPtrIn, |
| 38 | Couplings* couplingsPtrIn, TimeShower* timesDecPtr, |
| 39 | RHadrons* rHadronsPtrIn, DecayHandler* decayHandlePtr, |
| 40 | vector<int> handledParticles) { |
| 41 | |
| 42 | // Save pointers. |
| 43 | infoPtr = infoPtrIn; |
| 44 | particleDataPtr = particleDataPtrIn; |
| 45 | rndmPtr = rndmPtrIn; |
| 46 | couplingsPtr = couplingsPtrIn; |
| 47 | rHadronsPtr = rHadronsPtrIn; |
| 48 | |
| 49 | // Main flags. |
| 50 | doHadronize = settings.flag("HadronLevel:Hadronize"); |
| 51 | doDecay = settings.flag("HadronLevel:Decay"); |
| 52 | doBoseEinstein = settings.flag("HadronLevel:BoseEinstein"); |
| 53 | |
| 54 | // Boundary mass between string and ministring handling. |
| 55 | mStringMin = settings.parm("HadronLevel:mStringMin"); |
| 56 | |
| 57 | // For junction processing. |
| 58 | eNormJunction = settings.parm("StringFragmentation:eNormJunction"); |
| 59 | |
| 60 | // Allow R-hadron formation. |
| 61 | allowRH = settings.flag("RHadrons:allow"); |
| 62 | |
| 63 | // Particles that should decay or not before Bose-Einstein stage. |
| 64 | widthSepBE = settings.parm("BoseEinstein:widthSep"); |
| 65 | |
| 66 | // Hadron scattering --rjc |
| 67 | doHadronScatter = settings.flag("HadronScatter:scatter"); |
| 68 | hsAfterDecay = settings.flag("HadronScatter:afterDecay"); |
| 69 | |
| 70 | // Initialize auxiliary fragmentation classes. |
| 71 | flavSel.init(settings, rndmPtr); |
| 72 | pTSel.init(settings, *particleDataPtr, rndmPtr); |
| 73 | zSel.init(settings, *particleDataPtr, rndmPtr); |
| 74 | |
| 75 | // Initialize auxiliary administrative class. |
| 76 | colConfig.init(infoPtr, settings, &flavSel); |
| 77 | |
| 78 | // Initialize string and ministring fragmentation. |
| 79 | stringFrag.init(infoPtr, settings, particleDataPtr, rndmPtr, |
| 80 | &flavSel, &pTSel, &zSel); |
| 81 | ministringFrag.init(infoPtr, settings, particleDataPtr, rndmPtr, |
| 82 | &flavSel, &pTSel, &zSel); |
| 83 | |
| 84 | // Initialize particle decays. |
| 85 | decays.init(infoPtr, settings, particleDataPtr, rndmPtr, couplingsPtr, |
| 86 | timesDecPtr, &flavSel, decayHandlePtr, handledParticles); |
| 87 | |
| 88 | // Initialize BoseEinstein. |
| 89 | boseEinstein.init(infoPtr, settings, *particleDataPtr); |
| 90 | |
| 91 | // Initialize HadronScatter --rjc |
| 92 | if (doHadronScatter) |
| 93 | hadronScatter.init(infoPtr, settings, rndmPtr, particleDataPtr); |
| 94 | |
| 95 | // Initialize Hidden-Valley fragmentation, if necessary. |
| 96 | useHiddenValley = hiddenvalleyFrag.init(infoPtr, settings, |
| 97 | particleDataPtr, rndmPtr); |
| 98 | |
| 99 | // Send flavour and z selection pointers to R-hadron machinery. |
| 100 | rHadronsPtr->fragPtrs( &flavSel, &zSel); |
| 101 | |
| 102 | // Done. |
| 103 | return true; |
| 104 | |
| 105 | } |
| 106 | |
| 107 | //-------------------------------------------------------------------------- |
| 108 | |
| 109 | // Hadronize and decay the next parton-level. |
| 110 | |
| 111 | bool HadronLevel::next( Event& event) { |
| 112 | |
| 113 | // Do Hidden-Valley fragmentation, if necessary. |
| 114 | if (useHiddenValley) hiddenvalleyFrag.fragment(event); |
| 115 | |
| 116 | // Colour-octet onia states must be decayed to singlet + gluon. |
| 117 | if (!decayOctetOnia(event)) return false; |
| 118 | |
| 119 | // Possibility of hadronization inside decay, but then no BE second time. |
| 120 | // Hadron scattering, first pass only --rjc |
| 121 | bool moreToDo, firstPass = true; |
| 122 | bool doBoseEinsteinNow = doBoseEinstein; |
| 123 | do { |
| 124 | moreToDo = false; |
| 125 | |
| 126 | // First part: string fragmentation. |
| 127 | if (doHadronize) { |
| 128 | |
| 129 | // Find the complete colour singlet configuration of the event. |
| 130 | if (!findSinglets( event)) return false; |
| 131 | |
| 132 | // Fragment off R-hadrons, if necessary. |
| 133 | if (allowRH && !rHadronsPtr->produce( colConfig, event)) |
| 134 | return false; |
| 135 | |
| 136 | // Process all colour singlet (sub)system |
| 137 | for (int iSub = 0; iSub < colConfig.size(); ++iSub) { |
| 138 | |
| 139 | // Collect sequentially all partons in a colour singlet subsystem. |
| 140 | colConfig.collect(iSub, event); |
| 141 | |
| 142 | // String fragmentation of each colour singlet (sub)system. |
| 143 | if ( colConfig[iSub].massExcess > mStringMin ) { |
| 144 | if (!stringFrag.fragment( iSub, colConfig, event)) return false; |
| 145 | |
| 146 | // Low-mass string treated separately. Tell if diffractive system. |
| 147 | } else { |
| 148 | bool isDiff = infoPtr->isDiffractiveA() |
| 149 | || infoPtr->isDiffractiveB(); |
| 150 | if (!ministringFrag.fragment( iSub, colConfig, event, isDiff)) |
| 151 | return false; |
| 152 | } |
| 153 | } |
| 154 | } |
| 155 | |
| 156 | // Hadron scattering --rjc |
| 157 | if (doHadronScatter && !hsAfterDecay && firstPass) |
| 158 | hadronScatter.scatter(event); |
| 159 | |
| 160 | // Second part: sequential decays of short-lived particles (incl. K0). |
| 161 | if (doDecay) { |
| 162 | |
| 163 | // Loop through all entries to find those that should decay. |
| 164 | int iDec = 0; |
| 165 | do { |
| 166 | Particle& decayer = event[iDec]; |
| 167 | if ( decayer.isFinal() && decayer.canDecay() && decayer.mayDecay() |
| 168 | && (decayer.mWidth() > widthSepBE || decayer.idAbs() == 311) ) { |
| 169 | decays.decay( iDec, event); |
| 170 | if (decays.moreToDo()) moreToDo = true; |
| 171 | } |
| 172 | } while (++iDec < event.size()); |
| 173 | } |
| 174 | |
| 175 | // Hadron scattering --rjc |
| 176 | if (doHadronScatter && hsAfterDecay && firstPass) |
| 177 | hadronScatter.scatter(event); |
| 178 | |
| 179 | // Third part: include Bose-Einstein effects among current particles. |
| 180 | if (doBoseEinsteinNow) { |
| 181 | if (!boseEinstein.shiftEvent(event)) return false; |
| 182 | doBoseEinsteinNow = false; |
| 183 | } |
| 184 | |
| 185 | // Fourth part: sequential decays also of long-lived particles. |
| 186 | if (doDecay) { |
| 187 | |
| 188 | // Loop through all entries to find those that should decay. |
| 189 | int iDec = 0; |
| 190 | do { |
| 191 | Particle& decayer = event[iDec]; |
| 192 | if ( decayer.isFinal() && decayer.canDecay() && decayer.mayDecay() ) { |
| 193 | decays.decay( iDec, event); |
| 194 | if (decays.moreToDo()) moreToDo = true; |
| 195 | } |
| 196 | } while (++iDec < event.size()); |
| 197 | } |
| 198 | |
| 199 | // Normally done first time around, but sometimes not (e.g. Upsilon). |
| 200 | } while (moreToDo); |
| 201 | |
| 202 | // Done. |
| 203 | return true; |
| 204 | |
| 205 | } |
| 206 | |
| 207 | //-------------------------------------------------------------------------- |
| 208 | |
| 209 | // Allow more decays if on/off switches changed. |
| 210 | // Note: does not do sequential hadronization, e.g. for Upsilon. |
| 211 | |
| 212 | bool HadronLevel::moreDecays( Event& event) { |
| 213 | |
| 214 | // Colour-octet onia states must be decayed to singlet + gluon. |
| 215 | if (!decayOctetOnia(event)) return false; |
| 216 | |
| 217 | // Loop through all entries to find those that should decay. |
| 218 | int iDec = 0; |
| 219 | do { |
| 220 | if ( event[iDec].isFinal() && event[iDec].canDecay() |
| 221 | && event[iDec].mayDecay() ) decays.decay( iDec, event); |
| 222 | } while (++iDec < event.size()); |
| 223 | |
| 224 | // Done. |
| 225 | return true; |
| 226 | |
| 227 | } |
| 228 | |
| 229 | //-------------------------------------------------------------------------- |
| 230 | |
| 231 | // Decay colour-octet onium states. |
| 232 | |
| 233 | bool HadronLevel::decayOctetOnia(Event& event) { |
| 234 | |
| 235 | // Onium states to be decayed. |
| 236 | int idOnium[6] = { 9900443, 9900441, 9910441, |
| 237 | 9900553, 9900551, 9910551 }; |
| 238 | |
| 239 | // Loop over particles and identify onia. |
| 240 | for (int iDec = 0; iDec < event.size(); ++iDec) |
| 241 | if (event[iDec].isFinal()) { |
| 242 | int id = event[iDec].id(); |
| 243 | bool isOnium = false; |
| 244 | for (int j = 0; j < 6; ++j) if (id == idOnium[j]) isOnium = true; |
| 245 | |
| 246 | // Decay any onia encountered. |
| 247 | if (isOnium) { |
| 248 | if (!decays.decay( iDec, event)) return false; |
| 249 | |
| 250 | // Set colour flow by hand: gluon inherits octet-onium state. |
| 251 | int iGlu = event.size() - 1; |
| 252 | event[iGlu].cols( event[iDec].col(), event[iDec].acol() ); |
| 253 | } |
| 254 | } |
| 255 | |
| 256 | // Done. |
| 257 | return true; |
| 258 | |
| 259 | } |
| 260 | |
| 261 | //-------------------------------------------------------------------------- |
| 262 | |
| 263 | // Trace colour flow in the event to form colour singlet subsystems. |
| 264 | |
| 265 | bool HadronLevel::findSinglets(Event& event) { |
| 266 | |
| 267 | // Find a list of final partons and of all colour ends and gluons. |
| 268 | iColEnd.resize(0); |
| 269 | iAcolEnd.resize(0); |
| 270 | iColAndAcol.resize(0); |
| 271 | for (int i = 0; i < event.size(); ++i) if (event[i].isFinal()) { |
| 272 | if (event[i].col() > 0 && event[i].acol() > 0) iColAndAcol.push_back(i); |
| 273 | else if (event[i].col() > 0) iColEnd.push_back(i); |
| 274 | else if (event[i].acol() > 0) iAcolEnd.push_back(i); |
| 275 | } |
| 276 | |
| 277 | // Begin arrange the partons into separate colour singlets. |
| 278 | colConfig.clear(); |
| 279 | iPartonJun.resize(0); |
| 280 | iPartonAntiJun.resize(0); |
| 281 | |
| 282 | // Junctions: loop over them, and identify kind. |
| 283 | for (int iJun = 0; iJun < event.sizeJunction(); ++iJun) |
| 284 | if (event.remainsJunction(iJun)) { |
| 285 | event.remainsJunction(iJun, false); |
| 286 | int kindJun = event.kindJunction(iJun); |
| 287 | iParton.resize(0); |
| 288 | |
| 289 | // Loop over junction legs. |
| 290 | for (int iCol = 0; iCol < 3; ++iCol) { |
| 291 | int indxCol = event.colJunction(iJun, iCol); |
| 292 | iParton.push_back( -(10 + 10 * iJun + iCol) ); |
| 293 | // Junctions: find color ends. |
| 294 | if (kindJun % 2 == 1 && !traceFromAcol(indxCol, event, iJun, iCol)) |
| 295 | return false; |
| 296 | // Antijunctions: find anticolor ends. |
| 297 | if (kindJun % 2 == 0 && !traceFromCol(indxCol, event, iJun, iCol)) |
| 298 | return false; |
| 299 | } |
| 300 | |
| 301 | // Reject triple- and higher-junction systems (physics not implemented). |
| 302 | int otherJun = 0; |
| 303 | for (int i = 0; i < int(iParton.size()); ++i) |
| 304 | if (iParton[i] < 0 && abs(iParton[i]) / 10 != iJun + 1) { |
| 305 | if (otherJun == 0) otherJun = abs(iParton[i]) / 10; |
| 306 | else if (abs(iParton[i]) / 10 != otherJun) { |
| 307 | infoPtr->errorMsg("Error in HadronLevel::findSinglets: " |
| 308 | "too many junction-junction connections"); |
| 309 | return false; |
| 310 | } |
| 311 | } |
| 312 | |
| 313 | // Keep in memory a junction hooked up with an antijunction, |
| 314 | // else store found single-junction system. |
| 315 | int nNeg = 0; |
| 316 | for (int i = 0; i < int(iParton.size()); ++i) if (iParton[i] < 0) |
| 317 | ++nNeg; |
| 318 | if (nNeg > 3 && kindJun % 2 == 1) { |
| 319 | for (int i = 0; i < int(iParton.size()); ++i) |
| 320 | iPartonJun.push_back(iParton[i]); |
| 321 | } else if (nNeg > 3 && kindJun % 2 == 0) { |
| 322 | for (int i = 0; i < int(iParton.size()); ++i) |
| 323 | iPartonAntiJun.push_back(iParton[i]); |
| 324 | } else { |
| 325 | // A junction may be eliminated by insert if two quarks are nearby. |
| 326 | int nJunOld = event.sizeJunction(); |
| 327 | if (!colConfig.insert(iParton, event)) return false; |
| 328 | if (event.sizeJunction() < nJunOld) --iJun; |
| 329 | } |
| 330 | } |
| 331 | |
| 332 | // Split junction-antijunction system into two, and store those. |
| 333 | // (Only one system in extreme cases, and then second empty.) |
| 334 | if (iPartonJun.size() > 0 && iPartonAntiJun.size() > 0) { |
| 335 | if (!splitJunctionPair(event)) return false; |
| 336 | if (!colConfig.insert(iPartonJun, event)) return false; |
| 337 | if (iPartonAntiJun.size() > 0) |
| 338 | if (!colConfig.insert(iPartonAntiJun, event)) return false; |
| 339 | // Error if only one of junction and antijuction left here. |
| 340 | } else if (iPartonJun.size() > 0 || iPartonAntiJun.size() > 0) { |
| 341 | infoPtr->errorMsg("Error in HadronLevel::findSinglets: " |
| 342 | "unmatched (anti)junction"); |
| 343 | return false; |
| 344 | } |
| 345 | |
| 346 | // Open strings: pick up each colour end and trace to its anticolor end. |
| 347 | for (int iEnd = 0; iEnd < int(iColEnd.size()); ++iEnd) { |
| 348 | iParton.resize(0); |
| 349 | iParton.push_back( iColEnd[iEnd] ); |
| 350 | int indxCol = event[ iColEnd[iEnd] ].col(); |
| 351 | if (!traceFromCol(indxCol, event)) return false; |
| 352 | |
| 353 | // Store found open string system. Analyze its properties. |
| 354 | if (!colConfig.insert(iParton, event)) return false; |
| 355 | } |
| 356 | |
| 357 | // Closed strings : begin at any gluon and trace until back at it. |
| 358 | while (iColAndAcol.size() > 0) { |
| 359 | iParton.resize(0); |
| 360 | iParton.push_back( iColAndAcol[0] ); |
| 361 | int indxCol = event[ iColAndAcol[0] ].col(); |
| 362 | int indxAcol = event[ iColAndAcol[0] ].acol(); |
| 363 | iColAndAcol[0] = iColAndAcol.back(); |
| 364 | iColAndAcol.pop_back(); |
| 365 | if (!traceInLoop(indxCol, indxAcol, event)) return false; |
| 366 | |
| 367 | // Store found closed string system. Analyze its properties. |
| 368 | if (!colConfig.insert(iParton, event)) return false; |
| 369 | } |
| 370 | |
| 371 | // Done. |
| 372 | return true; |
| 373 | |
| 374 | } |
| 375 | |
| 376 | //-------------------------------------------------------------------------- |
| 377 | |
| 378 | // Trace a colour line, from a colour to an anticolour. |
| 379 | |
| 380 | bool HadronLevel::traceFromCol(int indxCol, Event& event, int iJun, |
| 381 | int iCol) { |
| 382 | |
| 383 | // Junction kind, if any. |
| 384 | int kindJun = (iJun >= 0) ? event.kindJunction(iJun) : 0; |
| 385 | |
| 386 | // Begin to look for a matching anticolour. |
| 387 | int loop = 0; |
| 388 | int loopMax = iColAndAcol.size() + 2; |
| 389 | bool hasFound = false; |
| 390 | do { |
| 391 | ++loop; |
| 392 | hasFound= false; |
| 393 | |
| 394 | // First check list of matching anticolour ends. |
| 395 | for (int i = 0; i < int(iAcolEnd.size()); ++i) |
| 396 | if (event[ iAcolEnd[i] ].acol() == indxCol) { |
| 397 | iParton.push_back( iAcolEnd[i] ); |
| 398 | indxCol = 0; |
| 399 | iAcolEnd[i] = iAcolEnd.back(); |
| 400 | iAcolEnd.pop_back(); |
| 401 | hasFound = true; |
| 402 | break; |
| 403 | } |
| 404 | |
| 405 | // Then check list of intermediate gluons. |
| 406 | if (!hasFound) |
| 407 | for (int i = 0; i < int(iColAndAcol.size()); ++i) |
| 408 | if (event[ iColAndAcol[i] ].acol() == indxCol) { |
| 409 | iParton.push_back( iColAndAcol[i] ); |
| 410 | |
| 411 | // Update to new colour. Remove gluon. |
| 412 | indxCol = event[ iColAndAcol[i] ].col(); |
| 413 | if (kindJun > 0) event.endColJunction(iJun, iCol, indxCol); |
| 414 | iColAndAcol[i] = iColAndAcol.back(); |
| 415 | iColAndAcol.pop_back(); |
| 416 | hasFound = true; |
| 417 | break; |
| 418 | } |
| 419 | |
| 420 | // In a pinch, check list of opposite-sign junction end colours. |
| 421 | // Store in iParton list as -(10 + 10 * iAntiJun + iAntiLeg). |
| 422 | if (!hasFound && kindJun % 2 == 0 && event.sizeJunction() > 1) |
| 423 | for (int iAntiJun = 0; iAntiJun < event.sizeJunction(); ++iAntiJun) |
| 424 | if (iAntiJun != iJun && event.kindJunction(iAntiJun) %2 == 1) |
| 425 | for (int iColAnti = 0; iColAnti < 3; ++iColAnti) |
| 426 | if (event.endColJunction(iAntiJun, iColAnti) == indxCol) { |
| 427 | iParton.push_back( -(10 + 10 * iAntiJun + iColAnti) ); |
| 428 | indxCol = 0; |
| 429 | hasFound = true; |
| 430 | break; |
| 431 | } |
| 432 | |
| 433 | // Keep on tracing via gluons until reached end of leg. |
| 434 | } while (hasFound && indxCol > 0 && loop < loopMax); |
| 435 | |
| 436 | // Something went wrong in colour tracing. |
| 437 | if (!hasFound || loop == loopMax) { |
| 438 | infoPtr->errorMsg("Error in HadronLevel::traceFromCol: " |
| 439 | "colour tracing failed"); |
| 440 | return false; |
| 441 | } |
| 442 | |
| 443 | // Done. |
| 444 | return true; |
| 445 | |
| 446 | } |
| 447 | |
| 448 | //-------------------------------------------------------------------------- |
| 449 | |
| 450 | // Trace a colour line, from an anticolour to a colour. |
| 451 | |
| 452 | bool HadronLevel::traceFromAcol(int indxCol, Event& event, int iJun, |
| 453 | int iCol) { |
| 454 | |
| 455 | // Junction kind, if any. |
| 456 | int kindJun = (iJun >= 0) ? event.kindJunction(iJun) : 0; |
| 457 | |
| 458 | // Begin to look for a matching colour. |
| 459 | int loop = 0; |
| 460 | int loopMax = iColAndAcol.size() + 2; |
| 461 | bool hasFound = false; |
| 462 | do { |
| 463 | ++loop; |
| 464 | hasFound= false; |
| 465 | |
| 466 | // First check list of matching colour ends. |
| 467 | for (int i = 0; i < int(iColEnd.size()); ++i) |
| 468 | if (event[ iColEnd[i] ].col() == indxCol) { |
| 469 | iParton.push_back( iColEnd[i] ); |
| 470 | indxCol = 0; |
| 471 | iColEnd[i] = iColEnd.back(); |
| 472 | iColEnd.pop_back(); |
| 473 | hasFound = true; |
| 474 | break; |
| 475 | } |
| 476 | |
| 477 | // Then check list of intermediate gluons. |
| 478 | if (!hasFound) |
| 479 | for (int i = 0; i < int(iColAndAcol.size()); ++i) |
| 480 | if (event[ iColAndAcol[i] ].col() == indxCol) { |
| 481 | iParton.push_back( iColAndAcol[i] ); |
| 482 | // Update to new colour. Remove gluon. |
| 483 | indxCol = event[ iColAndAcol[i] ].acol(); |
| 484 | if (kindJun > 0) event.endColJunction(iJun, iCol, indxCol); |
| 485 | iColAndAcol[i] = iColAndAcol.back(); |
| 486 | iColAndAcol.pop_back(); |
| 487 | hasFound = true; |
| 488 | break; |
| 489 | } |
| 490 | |
| 491 | // In a pinch, check list of opposite-sign junction end colours. |
| 492 | // Store in iParton list as -(10 + 10 * iAntiJun + iLeg). |
| 493 | if (!hasFound && kindJun % 2 == 1 && event.sizeJunction() > 1) |
| 494 | for (int iAntiJun = 0; iAntiJun < event.sizeJunction(); ++iAntiJun) |
| 495 | if (iAntiJun != iJun && event.kindJunction(iAntiJun) % 2 == 0) |
| 496 | for (int iColAnti = 0; iColAnti < 3; ++iColAnti) |
| 497 | if (event.endColJunction(iAntiJun, iColAnti) == indxCol) { |
| 498 | iParton.push_back( -(10 + 10 * iAntiJun + iColAnti) ); |
| 499 | indxCol = 0; |
| 500 | hasFound = true; |
| 501 | break; |
| 502 | } |
| 503 | |
| 504 | // Keep on tracing via gluons until reached end of leg. |
| 505 | } while (hasFound && indxCol > 0 && loop < loopMax); |
| 506 | |
| 507 | // Something went wrong in colour tracing. |
| 508 | if (!hasFound || loop == loopMax) { |
| 509 | infoPtr->errorMsg("Error in HadronLevel::traceFromAcol: " |
| 510 | "colour tracing failed"); |
| 511 | return false; |
| 512 | } |
| 513 | |
| 514 | // Done. |
| 515 | return true; |
| 516 | |
| 517 | } |
| 518 | |
| 519 | //-------------------------------------------------------------------------- |
| 520 | |
| 521 | // Trace a colour loop, from a colour back to the anticolour of the same. |
| 522 | |
| 523 | bool HadronLevel::traceInLoop(int indxCol, int indxAcol, Event& event) { |
| 524 | |
| 525 | // Move around until back where begun. |
| 526 | int loop = 0; |
| 527 | int loopMax = iColAndAcol.size() + 2; |
| 528 | bool hasFound = false; |
| 529 | do { |
| 530 | ++loop; |
| 531 | hasFound= false; |
| 532 | |
| 533 | // Check list of gluons. |
| 534 | for (int i = 0; i < int(iColAndAcol.size()); ++i) |
| 535 | if (event[ iColAndAcol[i] ].acol() == indxCol) { |
| 536 | iParton.push_back( iColAndAcol[i] ); |
| 537 | indxCol = event[ iColAndAcol[i] ].col(); |
| 538 | iColAndAcol[i] = iColAndAcol.back(); |
| 539 | iColAndAcol.pop_back(); |
| 540 | hasFound = true; |
| 541 | break; |
| 542 | } |
| 543 | } while (hasFound && indxCol != indxAcol && loop < loopMax); |
| 544 | |
| 545 | // Something went wrong in colour tracing. |
| 546 | if (!hasFound || loop == loopMax) { |
| 547 | infoPtr->errorMsg("Error in HadronLevel::traceInLoop: " |
| 548 | "colour tracing failed"); |
| 549 | return false; |
| 550 | } |
| 551 | |
| 552 | // Done. |
| 553 | return true; |
| 554 | |
| 555 | } |
| 556 | |
| 557 | //-------------------------------------------------------------------------- |
| 558 | |
| 559 | // Split junction-antijunction system into two, or simplify other way. |
| 560 | |
| 561 | bool HadronLevel::splitJunctionPair(Event& event) { |
| 562 | |
| 563 | // Construct separate index arrays for the three junction legs. |
| 564 | int identJun = (-iPartonJun[0])/10; |
| 565 | iJunLegA.resize(0); |
| 566 | iJunLegB.resize(0); |
| 567 | iJunLegC.resize(0); |
| 568 | int leg = -1; |
| 569 | for (int i = 0; i < int(iPartonJun.size()); ++ i) { |
| 570 | if ( (-iPartonJun[i])/10 == identJun) ++leg; |
| 571 | if (leg == 0) iJunLegA.push_back( iPartonJun[i] ); |
| 572 | else if (leg == 1) iJunLegB.push_back( iPartonJun[i] ); |
| 573 | else iJunLegC.push_back( iPartonJun[i] ); |
| 574 | } |
| 575 | |
| 576 | // Construct separate index arrays for the three antijunction legs. |
| 577 | int identAnti = (-iPartonAntiJun[0])/10; |
| 578 | iAntiLegA.resize(0); |
| 579 | iAntiLegB.resize(0); |
| 580 | iAntiLegC.resize(0); |
| 581 | leg = -1; |
| 582 | for (int i = 0; i < int(iPartonAntiJun.size()); ++ i) { |
| 583 | if ( (-iPartonAntiJun[i])/10 == identAnti) ++leg; |
| 584 | if (leg == 0) iAntiLegA.push_back( iPartonAntiJun[i] ); |
| 585 | else if (leg == 1) iAntiLegB.push_back( iPartonAntiJun[i] ); |
| 586 | else iAntiLegC.push_back( iPartonAntiJun[i] ); |
| 587 | } |
| 588 | |
| 589 | // Find interjunction legs, i.e. between junction and antijunction. |
| 590 | int nMatch = 0; |
| 591 | int legJun[3], legAnti[3], nGluLeg[3]; |
| 592 | if (iJunLegA.back() < 0) { legJun[nMatch] = 0; |
| 593 | legAnti[nMatch] = (-iJunLegA.back())%10; ++nMatch;} |
| 594 | if (iJunLegB.back() < 0) { legJun[nMatch] = 1; |
| 595 | legAnti[nMatch] = (-iJunLegB.back())%10; ++nMatch;} |
| 596 | if (iJunLegC.back() < 0) { legJun[nMatch] = 2; |
| 597 | legAnti[nMatch] = (-iJunLegC.back())%10; ++nMatch;} |
| 598 | |
| 599 | // Loop over interjunction legs. |
| 600 | for (int iMatch = 0; iMatch < nMatch; ++iMatch) { |
| 601 | vector<int>& iJunLeg = (legJun[iMatch] == 0) ? iJunLegA |
| 602 | : ( (legJun[iMatch] == 1) ? iJunLegB : iJunLegC ); |
| 603 | vector<int>& iAntiLeg = (legAnti[iMatch] == 0) ? iAntiLegA |
| 604 | : ( (legAnti[iMatch] == 1) ? iAntiLegB : iAntiLegC ); |
| 605 | |
| 606 | // Find number of gluons on each. Do nothing for now if none. |
| 607 | nGluLeg[iMatch] = iJunLeg.size() + iAntiLeg.size() - 4; |
| 608 | if (nGluLeg[iMatch] == 0) continue; |
| 609 | |
| 610 | // Else pick up the gluons on the interjunction leg in order. |
| 611 | iGluLeg.resize(0); |
| 612 | for (int i = 1; i < int(iJunLeg.size()) - 1; ++i) |
| 613 | iGluLeg.push_back( iJunLeg[i] ); |
| 614 | for (int i = int(iAntiLeg.size()) - 2; i > 0; --i) |
| 615 | iGluLeg.push_back( iAntiLeg[i] ); |
| 616 | |
| 617 | // Remove those gluons from the junction/antijunction leg lists. |
| 618 | iJunLeg.resize(1); |
| 619 | iAntiLeg.resize(1); |
| 620 | |
| 621 | // Pick a new quark at random; for simplicity no diquarks. |
| 622 | int idQ = flavSel.pickLightQ(); |
| 623 | int colQ, acolQ; |
| 624 | |
| 625 | // If one gluon on leg, split it into a collinear q-qbar pair. |
| 626 | if (iGluLeg.size() == 1) { |
| 627 | |
| 628 | // Store the new q qbar pair, sharing gluon colour and momentum. |
| 629 | colQ = event[ iGluLeg[0] ].col(); |
| 630 | acolQ = event[ iGluLeg[0] ].acol(); |
| 631 | Vec4 pQ = 0.5 * event[ iGluLeg[0] ].p(); |
| 632 | double mQ = 0.5 * event[ iGluLeg[0] ].m(); |
| 633 | int iQ = event.append( idQ, 75, iGluLeg[0], 0, 0, 0, colQ, 0, pQ, mQ ); |
| 634 | int iQbar = event.append( -idQ, 75, iGluLeg[0], 0, 0, 0, 0, acolQ, |
| 635 | pQ, mQ ); |
| 636 | |
| 637 | // Mark split gluon and update junction and antijunction legs. |
| 638 | event[ iGluLeg[0] ].statusNeg(); |
| 639 | event[ iGluLeg[0] ].daughters( iQ, iQbar); |
| 640 | iJunLeg.push_back(iQ); |
| 641 | iAntiLeg.push_back(iQbar); |
| 642 | |
| 643 | // If several gluons on the string, decide which g-g region to split up. |
| 644 | } else { |
| 645 | |
| 646 | // Evaluate mass-squared for all adjacent gluon pairs. |
| 647 | m2Pair.resize(0); |
| 648 | double m2Sum = 0.; |
| 649 | for (int i = 0; i < int(iGluLeg.size()) - 1; ++i) { |
| 650 | double m2Now = 0.5 * event[ iGluLeg[i] ].p() |
| 651 | * event[ iGluLeg[i + 1] ].p(); |
| 652 | m2Pair.push_back(m2Now); |
| 653 | m2Sum += m2Now; |
| 654 | } |
| 655 | |
| 656 | // Pick breakup region with probability proportional to mass-squared. |
| 657 | double m2Reg = m2Sum * rndmPtr->flat(); |
| 658 | int iReg = -1; |
| 659 | do m2Reg -= m2Pair[++iReg]; |
| 660 | while (m2Reg > 0. && iReg < int(iGluLeg.size()) - 1); |
| 661 | m2Reg = m2Pair[iReg]; |
| 662 | |
| 663 | // Pick breaking point of string in chosen region (symmetrically). |
| 664 | double m2Temp = min( JJSTRINGM2MAX, JJSTRINGM2FRAC * m2Reg); |
| 665 | double xPos = 0.5; |
| 666 | double xNeg = 0.5; |
| 667 | do { |
| 668 | double zTemp = zSel.zFrag( idQ, 0, m2Temp); |
| 669 | xPos = 1. - zTemp; |
| 670 | xNeg = m2Temp / (zTemp * m2Reg); |
| 671 | } while (xNeg > 1.); |
| 672 | if (rndmPtr->flat() > 0.5) swap(xPos, xNeg); |
| 673 | |
| 674 | // Pick up two "mother" gluons of breakup. Mark them decayed. |
| 675 | Particle& gJun = event[ iGluLeg[iReg] ]; |
| 676 | Particle& gAnti = event[ iGluLeg[iReg + 1] ]; |
| 677 | gJun.statusNeg(); |
| 678 | gAnti.statusNeg(); |
| 679 | int dau1 = event.size(); |
| 680 | gJun.daughters(dau1, dau1 + 3); |
| 681 | gAnti.daughters(dau1, dau1 + 3); |
| 682 | int mother1 = min( iGluLeg[iReg], iGluLeg[iReg + 1]); |
| 683 | int mother2 = max( iGluLeg[iReg], iGluLeg[iReg + 1]); |
| 684 | |
| 685 | // Can keep one of old colours but need one new so unambiguous. |
| 686 | colQ = gJun.acol(); |
| 687 | acolQ = event.nextColTag(); |
| 688 | |
| 689 | // Store copied gluons with reduced momenta. |
| 690 | int iGjun = event.append( 21, 75, mother1, mother2, 0, 0, |
| 691 | gJun.col(), gJun.acol(), (1. - 0.5 * xPos) * gJun.p(), |
| 692 | (1. - 0.5 * xPos) * gJun.m()); |
| 693 | int iGanti = event.append( 21, 75, mother1, mother2, 0, 0, |
| 694 | acolQ, gAnti.acol(), (1. - 0.5 * xNeg) * gAnti.p(), |
| 695 | (1. - 0.5 * xNeg) * gAnti.m()); |
| 696 | |
| 697 | // Store the new q qbar pair with remaining momenta. |
| 698 | int iQ = event.append( idQ, 75, mother1, mother2, 0, 0, |
| 699 | colQ, 0, 0.5 * xNeg * gAnti.p(), 0.5 * xNeg * gAnti.m() ); |
| 700 | int iQbar = event.append( -idQ, 75, mother1, mother2, 0, 0, |
| 701 | 0, acolQ, 0.5 * xPos * gJun.p(), 0.5 * xPos * gJun.m() ); |
| 702 | |
| 703 | // Update junction and antijunction legs with gluons and quarks. |
| 704 | for (int i = 0; i < iReg; ++i) |
| 705 | iJunLeg.push_back( iGluLeg[i] ); |
| 706 | iJunLeg.push_back(iGjun); |
| 707 | iJunLeg.push_back(iQ); |
| 708 | for (int i = int(iGluLeg.size()) - 1; i > iReg + 1; --i) |
| 709 | iAntiLeg.push_back( iGluLeg[i] ); |
| 710 | iAntiLeg.push_back(iGanti); |
| 711 | iAntiLeg.push_back(iQbar); |
| 712 | } |
| 713 | |
| 714 | // Update end colours for both g -> q qbar and g g -> g g q qbar. |
| 715 | event.endColJunction(identJun - 1, legJun[iMatch], colQ); |
| 716 | event.endColJunction(identAnti - 1, legAnti[iMatch], acolQ); |
| 717 | } |
| 718 | |
| 719 | // Update list of interjunction legs after splittings above. |
| 720 | int iMatchUp = 0; |
| 721 | while (iMatchUp < nMatch) { |
| 722 | if (nGluLeg[iMatchUp] > 0) { |
| 723 | for (int i = iMatchUp; i < nMatch - 1; ++i) { |
| 724 | legJun[i] = legJun[i + 1]; |
| 725 | legAnti[i] = legAnti[i + 1]; |
| 726 | nGluLeg[i] = nGluLeg[i + 1]; |
| 727 | } --nMatch; |
| 728 | } else ++iMatchUp; |
| 729 | } |
| 730 | |
| 731 | // Should not ever have three empty interjunction legs. |
| 732 | if (nMatch == 3) { |
| 733 | infoPtr->errorMsg("Error in HadronLevel::splitJunctionPair: " |
| 734 | "three empty junction-junction legs"); |
| 735 | return false; |
| 736 | } |
| 737 | |
| 738 | // If two legs are empty, then collapse system to a single string. |
| 739 | if (nMatch == 2) { |
| 740 | int legJunLeft = 3 - legJun[0] - legJun[1]; |
| 741 | int legAntiLeft = 3 - legAnti[0] - legAnti[1]; |
| 742 | vector<int>& iJunLeg = (legJunLeft == 0) ? iJunLegA |
| 743 | : ( (legJunLeft == 1) ? iJunLegB : iJunLegC ); |
| 744 | vector<int>& iAntiLeg = (legAntiLeft == 0) ? iAntiLegA |
| 745 | : ( (legAntiLeft == 1) ? iAntiLegB : iAntiLegC ); |
| 746 | iPartonJun.resize(0); |
| 747 | for (int i = int(iJunLeg.size()) - 1; i > 0; --i) |
| 748 | iPartonJun.push_back( iJunLeg[i] ); |
| 749 | for (int i = 1; i < int(iAntiLeg.size()); ++i) |
| 750 | iPartonJun.push_back( iAntiLeg[i] ); |
| 751 | |
| 752 | // Match up the colours where the strings are joined. |
| 753 | int iColJoin = iJunLeg[1]; |
| 754 | int iAcolJoin = iAntiLeg[1]; |
| 755 | event[iAcolJoin].acol( event[iColJoin].col() ); |
| 756 | |
| 757 | // Other string system empty. Remove junctions from their list. Done. |
| 758 | iPartonAntiJun.resize(0); |
| 759 | event.eraseJunction( max(identJun, identAnti) - 1); |
| 760 | event.eraseJunction( min(identJun, identAnti) - 1); |
| 761 | return true; |
| 762 | } |
| 763 | |
| 764 | // If one leg is empty then, depending on string length, either |
| 765 | // (a) annihilate junction and antijunction into two simple strings, or |
| 766 | // (b) split the empty leg by borrowing energy from nearby legs. |
| 767 | if (nMatch == 1) { |
| 768 | |
| 769 | // Identify the two external legs of either junction. |
| 770 | vector<int>& iJunLeg0 = (legJun[0] == 0) ? iJunLegB : iJunLegA; |
| 771 | vector<int>& iJunLeg1 = (legJun[0] == 2) ? iJunLegB : iJunLegC; |
| 772 | vector<int>& iAntiLeg0 = (legAnti[0] == 0) ? iAntiLegB : iAntiLegA; |
| 773 | vector<int>& iAntiLeg1 = (legAnti[0] == 2) ? iAntiLegB : iAntiLegC; |
| 774 | |
| 775 | // Simplified procedure: mainly study first parton on each leg. |
| 776 | Vec4 pJunLeg0 = event[ iJunLeg0[1] ].p(); |
| 777 | Vec4 pJunLeg1 = event[ iJunLeg1[1] ].p(); |
| 778 | Vec4 pAntiLeg0 = event[ iAntiLeg0[1] ].p(); |
| 779 | Vec4 pAntiLeg1 = event[ iAntiLeg1[1] ].p(); |
| 780 | |
| 781 | // Starting frame hopefully intermediate to two junction directions. |
| 782 | Vec4 pStart = pJunLeg0 / pJunLeg0.e() + pJunLeg1 / pJunLeg1.e() |
| 783 | + pAntiLeg0 / pAntiLeg0.e() + pAntiLeg1 / pAntiLeg1.e(); |
| 784 | |
| 785 | // Loop over iteration to junction/antijunction rest frames (JRF/ARF). |
| 786 | RotBstMatrix MtoJRF, MtoARF; |
| 787 | Vec4 pInJRF[3], pInARF[3]; |
| 788 | for (int iJun = 0; iJun < 2; ++iJun) { |
| 789 | int offset = (iJun == 0) ? 0 : 2; |
| 790 | |
| 791 | // Iterate from system rest frame towards the junction rest frame. |
| 792 | RotBstMatrix MtoRF, Mstep; |
| 793 | MtoRF.bstback(pStart); |
| 794 | Vec4 pInRF[4]; |
| 795 | int iter = 0; |
| 796 | do { |
| 797 | ++iter; |
| 798 | |
| 799 | // Find rest-frame momenta on the three sides of the junction. |
| 800 | // Only consider first parton on each leg, for simplicity. |
| 801 | pInRF[0 + offset] = pJunLeg0; |
| 802 | pInRF[1 + offset] = pJunLeg1; |
| 803 | pInRF[2 - offset] = pAntiLeg0; |
| 804 | pInRF[3 - offset] = pAntiLeg1; |
| 805 | for (int i = 0; i < 4; ++i) pInRF[i].rotbst(MtoRF); |
| 806 | |
| 807 | // For third side add both legs beyond other junction, weighted. |
| 808 | double wt2 = 1. - exp( -pInRF[2].e() / eNormJunction); |
| 809 | double wt3 = 1. - exp( -pInRF[3].e() / eNormJunction); |
| 810 | pInRF[2] = wt2 * pInRF[2] + wt3 * pInRF[3]; |
| 811 | |
| 812 | // Find new junction rest frame from the set of momenta. |
| 813 | Mstep = stringFrag.junctionRestFrame( pInRF[0], pInRF[1], pInRF[2]); |
| 814 | MtoRF.rotbst( Mstep ); |
| 815 | } while (iter < 3 || (Mstep.deviation() > CONVJNREST |
| 816 | && iter < NTRYJNREST) ); |
| 817 | |
| 818 | // Store final boost and rest-frame (weighted) momenta. |
| 819 | if (iJun == 0) { |
| 820 | MtoJRF = MtoRF; |
| 821 | for (int i = 0; i < 3; ++i) pInJRF[i] = pInRF[i]; |
| 822 | } else { |
| 823 | MtoARF = MtoRF; |
| 824 | for (int i = 0; i < 3; ++i) pInARF[i] = pInRF[i]; |
| 825 | } |
| 826 | } |
| 827 | |
| 828 | // Opposite operations: boost from JRF/ARF to original system. |
| 829 | RotBstMatrix MfromJRF = MtoJRF; |
| 830 | MfromJRF.invert(); |
| 831 | RotBstMatrix MfromARF = MtoARF; |
| 832 | MfromARF.invert(); |
| 833 | |
| 834 | // Velocity vectors of junctions and momentum of legs in lab frame. |
| 835 | Vec4 vJun(0., 0., 0., 1.); |
| 836 | vJun.rotbst(MfromJRF); |
| 837 | Vec4 vAnti(0., 0., 0., 1.); |
| 838 | vAnti.rotbst(MfromARF); |
| 839 | Vec4 pLabJ[3], pLabA[3]; |
| 840 | for (int i = 0; i < 3; ++i) { |
| 841 | pLabJ[i] = pInJRF[i]; |
| 842 | pLabJ[i].rotbst(MfromJRF); |
| 843 | pLabA[i] = pInARF[i]; |
| 844 | pLabA[i].rotbst(MfromARF); |
| 845 | } |
| 846 | |
| 847 | // Calculate Lambda-measure length of three possible topologies. |
| 848 | double vJvA = vJun * vAnti; |
| 849 | double vJvAe2y = vJvA + sqrt(vJvA*vJvA - 1.); |
| 850 | double LambdaJA = (2. * pInJRF[0].e()) * (2. * pInJRF[1].e()) |
| 851 | * (2. * pInARF[0].e()) * (2. * pInARF[1].e()) * vJvAe2y; |
| 852 | double Lambda00 = (2. * pLabJ[0] * pLabA[0]) |
| 853 | * (2. * pLabJ[1] * pLabA[1]); |
| 854 | double Lambda01 = (2. * pLabJ[0] * pLabA[1]) |
| 855 | * (2. * pLabJ[1] * pLabA[0]); |
| 856 | |
| 857 | // Case when either topology without junctions is the shorter one. |
| 858 | if (LambdaJA > min( Lambda00, Lambda01)) { |
| 859 | vector<int>& iAntiMatch0 = (Lambda00 < Lambda01) |
| 860 | ? iAntiLeg0 : iAntiLeg1; |
| 861 | vector<int>& iAntiMatch1 = (Lambda00 < Lambda01) |
| 862 | ? iAntiLeg1 : iAntiLeg0; |
| 863 | |
| 864 | // Define two quark-antiquark strings. |
| 865 | iPartonJun.resize(0); |
| 866 | for (int i = int(iJunLeg0.size()) - 1; i > 0; --i) |
| 867 | iPartonJun.push_back( iJunLeg0[i] ); |
| 868 | for (int i = 1; i < int(iAntiMatch0.size()); ++i) |
| 869 | iPartonJun.push_back( iAntiMatch0[i] ); |
| 870 | iPartonAntiJun.resize(0); |
| 871 | for (int i = int(iJunLeg1.size()) - 1; i > 0; --i) |
| 872 | iPartonAntiJun.push_back( iJunLeg1[i] ); |
| 873 | for (int i = 1; i < int(iAntiMatch1.size()); ++i) |
| 874 | iPartonAntiJun.push_back( iAntiMatch1[i] ); |
| 875 | |
| 876 | // Match up the colours where the strings are joined. |
| 877 | int iColJoin = iJunLeg0[1]; |
| 878 | int iAcolJoin = iAntiMatch0[1]; |
| 879 | event[iAcolJoin].acol( event[iColJoin].col() ); |
| 880 | iColJoin = iJunLeg1[1]; |
| 881 | iAcolJoin = iAntiMatch1[1]; |
| 882 | event[iAcolJoin].acol( event[iColJoin].col() ); |
| 883 | |
| 884 | // Remove junctions from their list. Done. |
| 885 | event.eraseJunction( max(identJun, identAnti) - 1); |
| 886 | event.eraseJunction( min(identJun, identAnti) - 1); |
| 887 | return true; |
| 888 | } |
| 889 | |
| 890 | // Case where junction and antijunction to be separated. |
| 891 | // Shuffle (p+/p-) momentum of order <mThad> between systems, |
| 892 | // times 2/3 for 120 degree in JRF, times 1/2 for two legs, |
| 893 | // but not more than half of what nearest parton carries. |
| 894 | double eShift = MTHAD / (3. * sqrt(vJvAe2y)); |
| 895 | double fracJ0 = min(0.5, eShift / pInJRF[0].e()); |
| 896 | double fracJ1 = min(0.5, eShift / pInJRF[0].e()); |
| 897 | Vec4 pFromJun = fracJ0 * pJunLeg0 + fracJ1 * pJunLeg1; |
| 898 | double fracA0 = min(0.5, eShift / pInARF[0].e()); |
| 899 | double fracA1 = min(0.5, eShift / pInARF[0].e()); |
| 900 | Vec4 pFromAnti = fracA0 * pAntiLeg0 + fracA1 * pAntiLeg1; |
| 901 | |
| 902 | // Pick a new quark at random; for simplicity no diquarks. |
| 903 | int idQ = flavSel.pickLightQ(); |
| 904 | |
| 905 | // Copy junction partons with scaled-down momenta and update legs. |
| 906 | int mother1 = min(iJunLeg0[1], iJunLeg1[1]); |
| 907 | int mother2 = max(iJunLeg0[1], iJunLeg1[1]); |
| 908 | int iNew1 = event.copy(iJunLeg0[1], 76); |
| 909 | event[iNew1].rescale5(1. - fracJ0); |
| 910 | iJunLeg0[1] = iNew1; |
| 911 | int iNew2 = event.copy(iJunLeg1[1], 76); |
| 912 | event[iNew2].rescale5(1. - fracJ1); |
| 913 | iJunLeg1[1] = iNew2; |
| 914 | |
| 915 | // Update junction colour and store quark with antijunction momentum. |
| 916 | // Store history as 2 -> 3 step for consistency. |
| 917 | int colQ = event.nextColTag(); |
| 918 | event.endColJunction(identJun - 1, legJun[0], colQ); |
| 919 | int iNewJ = event.append( idQ, 76, mother1, mother2, 0, 0, |
| 920 | colQ, 0, pFromAnti, pFromAnti.mCalc() ); |
| 921 | event[mother1].daughters( iNew1, iNewJ); |
| 922 | event[mother2].daughters( iNew1, iNewJ); |
| 923 | event[iNew1].mothers( mother1, mother2); |
| 924 | event[iNew2].mothers( mother1, mother2); |
| 925 | |
| 926 | // Copy anti junction partons with scaled-down momenta and update legs. |
| 927 | mother1 = min(iAntiLeg0[1], iAntiLeg1[1]); |
| 928 | mother2 = max(iAntiLeg0[1], iAntiLeg1[1]); |
| 929 | iNew1 = event.copy(iAntiLeg0[1], 76); |
| 930 | event[iNew1].rescale5(1. - fracA0); |
| 931 | iAntiLeg0[1] = iNew1; |
| 932 | iNew2 = event.copy(iAntiLeg1[1], 76); |
| 933 | event[iNew2].rescale5(1. - fracA1); |
| 934 | iAntiLeg1[1] = iNew2; |
| 935 | |
| 936 | // Update antijunction anticolour and store antiquark with junction |
| 937 | // momentum. Store history as 2 -> 3 step for consistency. |
| 938 | int acolQ = event.nextColTag(); |
| 939 | event.endColJunction(identAnti - 1, legAnti[0], acolQ); |
| 940 | int iNewA = event.append( -idQ, 76, mother1, mother2, 0, 0, |
| 941 | 0, acolQ, pFromJun, pFromJun.mCalc() ); |
| 942 | event[mother1].daughters( iNew1, iNewA); |
| 943 | event[mother2].daughters( iNew1, iNewA); |
| 944 | event[iNew1].mothers( mother1, mother2); |
| 945 | event[iNew2].mothers( mother1, mother2); |
| 946 | |
| 947 | // Bookkeep new quark and antiquark on third legs. |
| 948 | if (legJun[0] == 0) iJunLegA[1] = iNewJ; |
| 949 | else if (legJun[0] == 1) iJunLegB[1] = iNewJ; |
| 950 | else iJunLegC[1] = iNewJ; |
| 951 | if (legAnti[0] == 0) iAntiLegA[1] = iNewA; |
| 952 | else if (legAnti[0] == 1) iAntiLegB[1] = iNewA; |
| 953 | else iAntiLegC[1] = iNewA; |
| 954 | |
| 955 | // Done with splitting junction from antijunction. |
| 956 | } |
| 957 | |
| 958 | // Put together new junction parton list. |
| 959 | iPartonJun.resize(0); |
| 960 | for (int i = 0; i < int(iJunLegA.size()); ++i) |
| 961 | iPartonJun.push_back( iJunLegA[i] ); |
| 962 | for (int i = 0; i < int(iJunLegB.size()); ++i) |
| 963 | iPartonJun.push_back( iJunLegB[i] ); |
| 964 | for (int i = 0; i < int(iJunLegC.size()); ++i) |
| 965 | iPartonJun.push_back( iJunLegC[i] ); |
| 966 | |
| 967 | // Put together new antijunction parton list. |
| 968 | iPartonAntiJun.resize(0); |
| 969 | for (int i = 0; i < int(iAntiLegA.size()); ++i) |
| 970 | iPartonAntiJun.push_back( iAntiLegA[i] ); |
| 971 | for (int i = 0; i < int(iAntiLegB.size()); ++i) |
| 972 | iPartonAntiJun.push_back( iAntiLegB[i] ); |
| 973 | for (int i = 0; i < int(iAntiLegC.size()); ++i) |
| 974 | iPartonAntiJun.push_back( iAntiLegC[i] ); |
| 975 | |
| 976 | // Now the two junction systems are separated and can be stored. |
| 977 | return true; |
| 978 | |
| 979 | } |
| 980 | |
| 981 | //========================================================================== |
| 982 | |
| 983 | } // end namespace Pythia8 |
| 984 | |
git://git.uio.no / u / mrichter / AliRoot.git / blame