1 | // SigmaProcess.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 |
---|
7 | // SigmaProcess class, and classes derived from it. |
---|
8 | |
---|
9 | #include "SigmaProcess.h" |
---|
10 | |
---|
11 | namespace Pythia8 { |
---|
12 | |
---|
13 | //========================================================================== |
---|
14 | |
---|
15 | // The SigmaProcess class. |
---|
16 | // Base class for cross sections. |
---|
17 | |
---|
18 | //-------------------------------------------------------------------------- |
---|
19 | |
---|
20 | // Constants: could be changed here if desired, but normally should not. |
---|
21 | // These are of technical nature, as described for each. |
---|
22 | |
---|
23 | // Conversion of GeV^{-2} to mb for cross section. |
---|
24 | const double SigmaProcess::CONVERT2MB = 0.389380; |
---|
25 | |
---|
26 | // The sum of outgoing masses must not be too close to the cm energy. |
---|
27 | const double SigmaProcess::MASSMARGIN = 0.1; |
---|
28 | |
---|
29 | // Parameters of momentum rescaling procedure: maximally allowed |
---|
30 | // relative energy error and number of iterations. |
---|
31 | const double SigmaProcess::COMPRELERR = 1e-10; |
---|
32 | const int SigmaProcess::NCOMPSTEP = 10; |
---|
33 | |
---|
34 | //-------------------------------------------------------------------------- |
---|
35 | |
---|
36 | // Perform simple initialization and store pointers. |
---|
37 | |
---|
38 | void SigmaProcess::init(Info* infoPtrIn, Settings* settingsPtrIn, |
---|
39 | ParticleData* particleDataPtrIn, Rndm* rndmPtrIn, BeamParticle* beamAPtrIn, |
---|
40 | BeamParticle* beamBPtrIn, Couplings* couplingsPtrIn, |
---|
41 | SigmaTotal* sigmaTotPtrIn, SusyLesHouches* slhaPtrIn) { |
---|
42 | |
---|
43 | // Store pointers. |
---|
44 | infoPtr = infoPtrIn; |
---|
45 | settingsPtr = settingsPtrIn; |
---|
46 | particleDataPtr = particleDataPtrIn; |
---|
47 | rndmPtr = rndmPtrIn; |
---|
48 | beamAPtr = beamAPtrIn; |
---|
49 | beamBPtr = beamBPtrIn; |
---|
50 | couplingsPtr = couplingsPtrIn; |
---|
51 | sigmaTotPtr = sigmaTotPtrIn; |
---|
52 | slhaPtr = slhaPtrIn; |
---|
53 | |
---|
54 | // Read out some properties of beams to allow shorthand. |
---|
55 | idA = (beamAPtr != 0) ? beamAPtr->id() : 0; |
---|
56 | idB = (beamBPtr != 0) ? beamBPtr->id() : 0; |
---|
57 | mA = (beamAPtr != 0) ? beamAPtr->m() : 0.; |
---|
58 | mB = (beamBPtr != 0) ? beamBPtr->m() : 0.; |
---|
59 | isLeptonA = (beamAPtr != 0) ? beamAPtr->isLepton() : false; |
---|
60 | isLeptonB = (beamBPtr != 0) ? beamBPtr->isLepton() : false; |
---|
61 | hasLeptonBeams = isLeptonA || isLeptonB; |
---|
62 | |
---|
63 | // K factor, multiplying resolved processes. (But not here for MPI.) |
---|
64 | Kfactor = settingsPtr->parm("SigmaProcess:Kfactor"); |
---|
65 | |
---|
66 | // Maximum incoming quark flavour. |
---|
67 | nQuarkIn = settingsPtr->mode("PDFinProcess:nQuarkIn"); |
---|
68 | |
---|
69 | // Medium heavy fermion masses set massless or not in ME expressions. |
---|
70 | mcME = (settingsPtr->flag("SigmaProcess:cMassiveME")) |
---|
71 | ? particleDataPtr->m0(4) : 0.; |
---|
72 | mbME = (settingsPtr->flag("SigmaProcess:bMassiveME")) |
---|
73 | ? particleDataPtr->m0(5) : 0.; |
---|
74 | mmuME = (settingsPtr->flag("SigmaProcess:muMassiveME")) |
---|
75 | ? particleDataPtr->m0(13) : 0.; |
---|
76 | mtauME = (settingsPtr->flag("SigmaProcess:tauMassiveME")) |
---|
77 | ? particleDataPtr->m0(15) : 0.; |
---|
78 | |
---|
79 | // Renormalization scale choice. |
---|
80 | renormScale1 = settingsPtr->mode("SigmaProcess:renormScale1"); |
---|
81 | renormScale2 = settingsPtr->mode("SigmaProcess:renormScale2"); |
---|
82 | renormScale3 = settingsPtr->mode("SigmaProcess:renormScale3"); |
---|
83 | renormScale3VV = settingsPtr->mode("SigmaProcess:renormScale3VV"); |
---|
84 | renormMultFac = settingsPtr->parm("SigmaProcess:renormMultFac"); |
---|
85 | renormFixScale = settingsPtr->parm("SigmaProcess:renormFixScale"); |
---|
86 | |
---|
87 | // Factorization scale choice. |
---|
88 | factorScale1 = settingsPtr->mode("SigmaProcess:factorScale1"); |
---|
89 | factorScale2 = settingsPtr->mode("SigmaProcess:factorScale2"); |
---|
90 | factorScale3 = settingsPtr->mode("SigmaProcess:factorScale3"); |
---|
91 | factorScale3VV = settingsPtr->mode("SigmaProcess:factorScale3VV"); |
---|
92 | factorMultFac = settingsPtr->parm("SigmaProcess:factorMultFac"); |
---|
93 | factorFixScale = settingsPtr->parm("SigmaProcess:factorFixScale"); |
---|
94 | |
---|
95 | // CP violation parameters for the BSM Higgs sector. |
---|
96 | higgsH1parity = settingsPtr->mode("HiggsH1:parity"); |
---|
97 | higgsH1eta = settingsPtr->parm("HiggsH1:etaParity"); |
---|
98 | higgsH2parity = settingsPtr->mode("HiggsH2:parity"); |
---|
99 | higgsH2eta = settingsPtr->parm("HiggsH2:etaParity"); |
---|
100 | higgsA3parity = settingsPtr->mode("HiggsA3:parity"); |
---|
101 | higgsA3eta = settingsPtr->parm("HiggsA3:etaParity"); |
---|
102 | |
---|
103 | // If BSM not switched on then H1 should have SM properties. |
---|
104 | if (!settingsPtr->flag("Higgs:useBSM")){ |
---|
105 | higgsH1parity = 1; |
---|
106 | higgsH1eta = 0.; |
---|
107 | } |
---|
108 | |
---|
109 | } |
---|
110 | |
---|
111 | //-------------------------------------------------------------------------- |
---|
112 | |
---|
113 | // Set up allowed flux of incoming partons. |
---|
114 | // addBeam: set up PDF's that need to be evaluated for the two beams. |
---|
115 | // addPair: set up pairs of incoming partons from the two beams. |
---|
116 | |
---|
117 | bool SigmaProcess::initFlux() { |
---|
118 | |
---|
119 | // Reset arrays (in case of several init's in same run). |
---|
120 | inBeamA.clear(); |
---|
121 | inBeamB.clear(); |
---|
122 | inPair.clear(); |
---|
123 | |
---|
124 | // Read in process-specific channel information. |
---|
125 | string fluxType = inFlux(); |
---|
126 | |
---|
127 | // Case with g g incoming state. |
---|
128 | if (fluxType == "gg") { |
---|
129 | addBeamA(21); |
---|
130 | addBeamB(21); |
---|
131 | addPair(21, 21); |
---|
132 | } |
---|
133 | |
---|
134 | // Case with q g incoming state. |
---|
135 | else if (fluxType == "qg") { |
---|
136 | for (int i = -nQuarkIn; i <= nQuarkIn; ++i) { |
---|
137 | int idNow = (i == 0) ? 21 : i; |
---|
138 | addBeamA(idNow); |
---|
139 | addBeamB(idNow); |
---|
140 | } |
---|
141 | for (int idNow = -nQuarkIn; idNow <= nQuarkIn; ++idNow) |
---|
142 | if (idNow != 0) { |
---|
143 | addPair(idNow, 21); |
---|
144 | addPair(21, idNow); |
---|
145 | } |
---|
146 | } |
---|
147 | |
---|
148 | // Case with q q', q qbar' or qbar qbar' incoming state. |
---|
149 | else if (fluxType == "qq") { |
---|
150 | for (int idNow = -nQuarkIn; idNow <= nQuarkIn; ++idNow) |
---|
151 | if (idNow != 0) { |
---|
152 | addBeamA(idNow); |
---|
153 | addBeamB(idNow); |
---|
154 | } |
---|
155 | for (int id1Now = -nQuarkIn; id1Now <= nQuarkIn; ++id1Now) |
---|
156 | if (id1Now != 0) |
---|
157 | for (int id2Now = -nQuarkIn; id2Now <= nQuarkIn; ++id2Now) |
---|
158 | if (id2Now != 0) |
---|
159 | addPair(id1Now, id2Now); |
---|
160 | } |
---|
161 | |
---|
162 | // Case with q qbar incoming state. |
---|
163 | else if (fluxType == "qqbarSame") { |
---|
164 | for (int idNow = -nQuarkIn; idNow <= nQuarkIn; ++idNow) |
---|
165 | if (idNow != 0) { |
---|
166 | addBeamA(idNow); |
---|
167 | addBeamB(idNow); |
---|
168 | } |
---|
169 | for (int idNow = -nQuarkIn; idNow <= nQuarkIn; ++idNow) |
---|
170 | if (idNow != 0) |
---|
171 | addPair(idNow, -idNow); |
---|
172 | } |
---|
173 | |
---|
174 | // Case with f f', f fbar', fbar fbar' incoming state. |
---|
175 | else if (fluxType == "ff") { |
---|
176 | // If beams are leptons then they are also the colliding partons. |
---|
177 | if ( isLeptonA && isLeptonB ) { |
---|
178 | addBeamA(idA); |
---|
179 | addBeamB(idB); |
---|
180 | addPair(idA, idB); |
---|
181 | // First beam is lepton and second is hadron. |
---|
182 | } else if ( isLeptonA ) { |
---|
183 | addBeamA(idA); |
---|
184 | for (int idNow = -nQuarkIn; idNow <= nQuarkIn; ++idNow) |
---|
185 | if (idNow != 0) { |
---|
186 | addBeamB(idNow); |
---|
187 | addPair(idA, idNow); |
---|
188 | } |
---|
189 | // First beam is hadron and second is lepton. |
---|
190 | } else if ( isLeptonB ) { |
---|
191 | addBeamB(idB); |
---|
192 | for (int idNow = -nQuarkIn; idNow <= nQuarkIn; ++idNow) |
---|
193 | if (idNow != 0) { |
---|
194 | addBeamA(idNow); |
---|
195 | addPair(idNow, idB); |
---|
196 | } |
---|
197 | // Hadron beams gives quarks. |
---|
198 | } else { |
---|
199 | for (int idNow = -nQuarkIn; idNow <= nQuarkIn; ++idNow) |
---|
200 | if (idNow != 0) { |
---|
201 | addBeamA(idNow); |
---|
202 | addBeamB(idNow); |
---|
203 | } |
---|
204 | for (int id1Now = -nQuarkIn; id1Now <= nQuarkIn; ++id1Now) |
---|
205 | if (id1Now != 0) |
---|
206 | for (int id2Now = -nQuarkIn; id2Now <= nQuarkIn; ++id2Now) |
---|
207 | if (id2Now != 0) |
---|
208 | addPair(id1Now, id2Now); |
---|
209 | } |
---|
210 | } |
---|
211 | |
---|
212 | // Case with f fbar incoming state. |
---|
213 | else if (fluxType == "ffbarSame") { |
---|
214 | // If beams are antiparticle pair and leptons then also colliding partons. |
---|
215 | if ( idA + idB == 0 && isLeptonA ) { |
---|
216 | addBeamA(idA); |
---|
217 | addBeamB(idB); |
---|
218 | addPair(idA, idB); |
---|
219 | // Else assume both to be hadrons, for better or worse. |
---|
220 | } else { |
---|
221 | for (int idNow = -nQuarkIn; idNow <= nQuarkIn; ++idNow) |
---|
222 | if (idNow != 0) { |
---|
223 | addBeamA(idNow); |
---|
224 | addBeamB(idNow); |
---|
225 | } |
---|
226 | for (int idNow = -nQuarkIn; idNow <= nQuarkIn; ++idNow) |
---|
227 | if (idNow != 0) |
---|
228 | addPair(idNow, -idNow); |
---|
229 | } |
---|
230 | } |
---|
231 | |
---|
232 | // Case with f fbar' charged(+-1) incoming state. |
---|
233 | else if (fluxType == "ffbarChg") { |
---|
234 | // If beams are leptons then also colliding partons. |
---|
235 | if ( isLeptonA && isLeptonB && abs( particleDataPtr->chargeType(idA) |
---|
236 | + particleDataPtr->chargeType(idB) ) == 3 ) { |
---|
237 | addBeamA(idA); |
---|
238 | addBeamB(idB); |
---|
239 | addPair(idA, idB); |
---|
240 | // Hadron beams gives quarks. |
---|
241 | } else { |
---|
242 | for (int idNow = -nQuarkIn; idNow <= nQuarkIn; ++idNow) |
---|
243 | if (idNow != 0) { |
---|
244 | addBeamA(idNow); |
---|
245 | addBeamB(idNow); |
---|
246 | } |
---|
247 | for (int id1Now = -nQuarkIn; id1Now <= nQuarkIn; ++id1Now) |
---|
248 | if (id1Now != 0) |
---|
249 | for (int id2Now = -nQuarkIn; id2Now <= nQuarkIn; ++id2Now) |
---|
250 | if (id2Now != 0 && id1Now * id2Now < 0 |
---|
251 | && (abs(id1Now) + abs(id2Now))%2 == 1) addPair(id1Now, id2Now); |
---|
252 | } |
---|
253 | } |
---|
254 | |
---|
255 | // Case with f fbar' generic incoming state. |
---|
256 | else if (fluxType == "ffbar") { |
---|
257 | // If beams are leptons then also colliding partons. |
---|
258 | if (isLeptonA && isLeptonB && idA * idB < 0) { |
---|
259 | addBeamA(idA); |
---|
260 | addBeamB(idB); |
---|
261 | addPair(idA, idB); |
---|
262 | // Hadron beams gives quarks. |
---|
263 | } else { |
---|
264 | for (int idNow = -nQuarkIn; idNow <= nQuarkIn; ++idNow) |
---|
265 | if (idNow != 0) { |
---|
266 | addBeamA(idNow); |
---|
267 | addBeamB(idNow); |
---|
268 | } |
---|
269 | for (int id1Now = -nQuarkIn; id1Now <= nQuarkIn; ++id1Now) |
---|
270 | if (id1Now != 0) |
---|
271 | for (int id2Now = -nQuarkIn; id2Now <= nQuarkIn; ++id2Now) |
---|
272 | if (id2Now != 0 && id1Now * id2Now < 0) |
---|
273 | addPair(id1Now, id2Now); |
---|
274 | } |
---|
275 | } |
---|
276 | |
---|
277 | // Case with f gamma incoming state. |
---|
278 | else if (fluxType == "fgm") { |
---|
279 | // Fermion from incoming side A. |
---|
280 | if ( isLeptonA ) { |
---|
281 | addBeamA(idA); |
---|
282 | addPair(idA, 22); |
---|
283 | } else { |
---|
284 | for (int idNow = -nQuarkIn; idNow <= nQuarkIn; ++idNow) |
---|
285 | if (idNow != 0) { |
---|
286 | addBeamA(idNow); |
---|
287 | addPair(idNow, 22); |
---|
288 | } |
---|
289 | } |
---|
290 | // Fermion from incoming side B. |
---|
291 | if ( isLeptonB ) { |
---|
292 | addBeamB( idB); |
---|
293 | addPair(22, idB); |
---|
294 | } else { |
---|
295 | for (int idNow = -nQuarkIn; idNow <= nQuarkIn; ++idNow) |
---|
296 | if (idNow != 0) { |
---|
297 | addBeamB(idNow); |
---|
298 | addPair(22, idNow); |
---|
299 | } |
---|
300 | } |
---|
301 | // Photons in the beams. |
---|
302 | addBeamA(22); |
---|
303 | addBeamB(22); |
---|
304 | } |
---|
305 | |
---|
306 | // Case with gamma gamma incoming state. |
---|
307 | else if (fluxType == "ggm") { |
---|
308 | addBeamA(21); |
---|
309 | addBeamA(22); |
---|
310 | addBeamB(21); |
---|
311 | addBeamB(22); |
---|
312 | addPair(21, 22); |
---|
313 | addPair(22, 21); |
---|
314 | } |
---|
315 | |
---|
316 | // Case with gamma gamma incoming state. |
---|
317 | else if (fluxType == "gmgm") { |
---|
318 | addBeamA(22); |
---|
319 | addBeamB(22); |
---|
320 | addPair(22, 22); |
---|
321 | } |
---|
322 | |
---|
323 | // Unrecognized fluxType is bad sign. Else done. |
---|
324 | else { |
---|
325 | infoPtr->errorMsg("Error in SigmaProcess::initFlux: " |
---|
326 | "unrecognized inFlux type", fluxType); |
---|
327 | return false; |
---|
328 | } |
---|
329 | return true; |
---|
330 | |
---|
331 | } |
---|
332 | |
---|
333 | //-------------------------------------------------------------------------- |
---|
334 | |
---|
335 | // Convolute matrix-element expression(s) with parton flux and K factor. |
---|
336 | |
---|
337 | double SigmaProcess::sigmaPDF() { |
---|
338 | |
---|
339 | // Evaluate and store the required parton densities. |
---|
340 | for (int j = 0; j < sizeBeamA(); ++j) |
---|
341 | inBeamA[j].pdf = beamAPtr->xfHard( inBeamA[j].id, x1Save, Q2FacSave); |
---|
342 | for (int j = 0; j < sizeBeamB(); ++j) |
---|
343 | inBeamB[j].pdf = beamBPtr->xfHard( inBeamB[j].id, x2Save, Q2FacSave); |
---|
344 | |
---|
345 | // Loop over allowed incoming channels. |
---|
346 | sigmaSumSave = 0.; |
---|
347 | for (int i = 0; i < sizePair(); ++i) { |
---|
348 | |
---|
349 | // Evaluate hard-scattering cross section. Include K factor. |
---|
350 | inPair[i].pdfSigma = Kfactor |
---|
351 | * sigmaHatWrap(inPair[i].idA, inPair[i].idB); |
---|
352 | |
---|
353 | // Multiply by respective parton densities. |
---|
354 | for (int j = 0; j < sizeBeamA(); ++j) |
---|
355 | if (inPair[i].idA == inBeamA[j].id) { |
---|
356 | inPair[i].pdfA = inBeamA[j].pdf; |
---|
357 | inPair[i].pdfSigma *= inBeamA[j].pdf; |
---|
358 | break; |
---|
359 | } |
---|
360 | for (int j = 0; j < sizeBeamB(); ++j) |
---|
361 | if (inPair[i].idB == inBeamB[j].id) { |
---|
362 | inPair[i].pdfB = inBeamB[j].pdf; |
---|
363 | inPair[i].pdfSigma *= inBeamB[j].pdf; |
---|
364 | break; |
---|
365 | } |
---|
366 | |
---|
367 | // Sum for all channels. |
---|
368 | sigmaSumSave += inPair[i].pdfSigma; |
---|
369 | } |
---|
370 | |
---|
371 | // Done. |
---|
372 | return sigmaSumSave; |
---|
373 | |
---|
374 | } |
---|
375 | |
---|
376 | //-------------------------------------------------------------------------- |
---|
377 | |
---|
378 | // Select incoming parton channel and extract parton densities (resolved). |
---|
379 | |
---|
380 | void SigmaProcess::pickInState(int id1in, int id2in) { |
---|
381 | |
---|
382 | // Multiparton interactions: partons already selected. |
---|
383 | if (id1in != 0 && id2in != 0) { |
---|
384 | id1 = id1in; |
---|
385 | id2 = id2in; |
---|
386 | } |
---|
387 | |
---|
388 | // Pick channel. Extract channel flavours and pdf's. |
---|
389 | double sigmaRand = sigmaSumSave * rndmPtr->flat(); |
---|
390 | for (int i = 0; i < sizePair(); ++i) { |
---|
391 | sigmaRand -= inPair[i].pdfSigma; |
---|
392 | if (sigmaRand <= 0.) { |
---|
393 | id1 = inPair[i].idA; |
---|
394 | id2 = inPair[i].idB; |
---|
395 | pdf1Save = inPair[i].pdfA; |
---|
396 | pdf2Save = inPair[i].pdfB; |
---|
397 | break; |
---|
398 | } |
---|
399 | } |
---|
400 | |
---|
401 | } |
---|
402 | |
---|
403 | //-------------------------------------------------------------------------- |
---|
404 | |
---|
405 | // Calculate incoming modified masses and four-vectors for matrix elements. |
---|
406 | |
---|
407 | bool SigmaProcess::setupForMEin() { |
---|
408 | |
---|
409 | // Initially assume it will work out to set up modified kinematics. |
---|
410 | bool allowME = true; |
---|
411 | |
---|
412 | // Correct incoming c, b, mu and tau to be massive or not. |
---|
413 | mME[0] = 0.; |
---|
414 | int id1Tmp = abs(id1); |
---|
415 | if (id1Tmp == 4) mME[0] = mcME; |
---|
416 | if (id1Tmp == 5) mME[0] = mbME; |
---|
417 | if (id1Tmp == 13) mME[0] = mmuME; |
---|
418 | if (id1Tmp == 15) mME[0] = mtauME; |
---|
419 | mME[1] = 0.; |
---|
420 | int id2Tmp = abs(id2); |
---|
421 | if (id2Tmp == 4) mME[1] = mcME; |
---|
422 | if (id2Tmp == 5) mME[1] = mbME; |
---|
423 | if (id2Tmp == 13) mME[1] = mmuME; |
---|
424 | if (id2Tmp == 15) mME[1] = mtauME; |
---|
425 | |
---|
426 | // If kinematically impossible return to massless case, but set error. |
---|
427 | if (mME[0] + mME[1] >= mH) { |
---|
428 | mME[0] = 0.; |
---|
429 | mME[1] = 0.; |
---|
430 | allowME = false; |
---|
431 | } |
---|
432 | |
---|
433 | // Do incoming two-body kinematics for massless or massive cases. |
---|
434 | if (mME[0] == 0. && mME[1] == 0.) { |
---|
435 | pME[0] = 0.5 * mH * Vec4( 0., 0., 1., 1.); |
---|
436 | pME[1] = 0.5 * mH * Vec4( 0., 0., -1., 1.); |
---|
437 | } else { |
---|
438 | double e0 = 0.5 * (mH * mH + mME[0] * mME[0] - mME[1] * mME[1]) / mH; |
---|
439 | double pz0 = sqrtpos(e0 * e0 - mME[0] * mME[0]); |
---|
440 | pME[0] = Vec4( 0., 0., pz0, e0); |
---|
441 | pME[1] = Vec4( 0., 0., -pz0, mH - e0); |
---|
442 | } |
---|
443 | |
---|
444 | // Done. |
---|
445 | return allowME; |
---|
446 | |
---|
447 | } |
---|
448 | |
---|
449 | //-------------------------------------------------------------------------- |
---|
450 | |
---|
451 | // Evaluate weight for W decay distribution in t -> W b -> f fbar b. |
---|
452 | |
---|
453 | double SigmaProcess::weightTopDecay( Event& process, int iResBeg, |
---|
454 | int iResEnd) { |
---|
455 | |
---|
456 | // If not pair W d/s/b and mother t then return unit weight. |
---|
457 | if (iResEnd - iResBeg != 1) return 1.; |
---|
458 | int iW1 = iResBeg; |
---|
459 | int iB2 = iResBeg + 1; |
---|
460 | int idW1 = process[iW1].idAbs(); |
---|
461 | int idB2 = process[iB2].idAbs(); |
---|
462 | if (idW1 != 24) { |
---|
463 | swap(iW1, iB2); |
---|
464 | swap(idW1, idB2); |
---|
465 | } |
---|
466 | if (idW1 != 24 || (idB2 != 1 && idB2 != 3 && idB2 != 5)) return 1.; |
---|
467 | int iT = process[iW1].mother1(); |
---|
468 | if (iT <= 0 || process[iT].idAbs() != 6) return 1.; |
---|
469 | |
---|
470 | // Find sign-matched order of W decay products. |
---|
471 | int iF = process[iW1].daughter1(); |
---|
472 | int iFbar = process[iW1].daughter2(); |
---|
473 | if (iFbar - iF != 1) return 1.; |
---|
474 | if (process[iT].id() * process[iF].id() < 0) swap(iF, iFbar); |
---|
475 | |
---|
476 | // Weight and maximum weight. |
---|
477 | double wt = (process[iT].p() * process[iFbar].p()) |
---|
478 | * (process[iF].p() * process[iB2].p()); |
---|
479 | double wtMax = ( pow4(process[iT].m()) - pow4(process[iW1].m()) ) / 8.; |
---|
480 | |
---|
481 | // Done. |
---|
482 | return wt / wtMax; |
---|
483 | |
---|
484 | } |
---|
485 | |
---|
486 | //-------------------------------------------------------------------------- |
---|
487 | |
---|
488 | // Evaluate weight for Z0/W+- decay distributions in H -> Z0/W+ Z0/W- -> 4f |
---|
489 | // and H -> gamma Z0 -> gamma f fbar. |
---|
490 | |
---|
491 | double SigmaProcess::weightHiggsDecay( Event& process, int iResBeg, |
---|
492 | int iResEnd) { |
---|
493 | |
---|
494 | // If not pair Z0 Z0, W+ W- or gamma Z0 then return unit weight. |
---|
495 | if (iResEnd - iResBeg != 1) return 1.; |
---|
496 | int iZW1 = iResBeg; |
---|
497 | int iZW2 = iResBeg + 1; |
---|
498 | int idZW1 = process[iZW1].id(); |
---|
499 | int idZW2 = process[iZW2].id(); |
---|
500 | if (idZW1 < 0 || idZW2 == 22) { |
---|
501 | swap(iZW1, iZW2); |
---|
502 | swap(idZW1, idZW2); |
---|
503 | } |
---|
504 | if ( (idZW1 != 23 || idZW2 != 23) && (idZW1 != 24 || idZW2 != -24) |
---|
505 | && (idZW1 != 22 || idZW2 != 23) ) return 1.; |
---|
506 | |
---|
507 | // If mother is not Higgs then return unit weight. |
---|
508 | int iH = process[iZW1].mother1(); |
---|
509 | if (iH <= 0) return 1.; |
---|
510 | int idH = process[iH].id(); |
---|
511 | if (idH != 25 && idH != 35 && idH !=36) return 1.; |
---|
512 | |
---|
513 | // H -> gamma Z0 -> gamma f fbar is 1 + cos^2(theta) in Z rest frame. |
---|
514 | if (idZW1 == 22) { |
---|
515 | int i5 = process[iZW2].daughter1(); |
---|
516 | int i6 = process[iZW2].daughter2(); |
---|
517 | double pgmZ = process[iZW1].p() * process[iZW2].p(); |
---|
518 | double pgm5 = process[iZW1].p() * process[i5].p(); |
---|
519 | double pgm6 = process[iZW1].p() * process[i6].p(); |
---|
520 | return (pow2(pgm5) + pow2(pgm6)) / pow2(pgmZ); |
---|
521 | } |
---|
522 | |
---|
523 | // Parameters depend on Higgs type: H0(H_1), H^0(H_2) or A^0(H_3). |
---|
524 | int higgsParity = higgsH1parity; |
---|
525 | double higgsEta = higgsH1eta; |
---|
526 | if (idH == 35) { |
---|
527 | higgsParity = higgsH2parity; |
---|
528 | higgsEta = higgsH2eta; |
---|
529 | } else if (idH == 36) { |
---|
530 | higgsParity = higgsA3parity; |
---|
531 | higgsEta = higgsA3eta; |
---|
532 | } |
---|
533 | |
---|
534 | // Option with isotropic decays. |
---|
535 | if (higgsParity == 0) return 1.; |
---|
536 | |
---|
537 | // Maximum and initial weight. |
---|
538 | double wtMax = pow4(process[iH].m()); |
---|
539 | double wt = wtMax; |
---|
540 | |
---|
541 | // Find sign-matched order of Z0/W+- decay products. |
---|
542 | int i3 = process[iZW1].daughter1(); |
---|
543 | int i4 = process[iZW1].daughter2(); |
---|
544 | if (process[i3].id() < 0) swap( i3, i4); |
---|
545 | int i5 = process[iZW2].daughter1(); |
---|
546 | int i6 = process[iZW2].daughter2(); |
---|
547 | if (process[i5].id() < 0) swap( i5, i6); |
---|
548 | |
---|
549 | // Evaluate four-vector products and find masses.. |
---|
550 | double p35 = 2. * process[i3].p() * process[i5].p(); |
---|
551 | double p36 = 2. * process[i3].p() * process[i6].p(); |
---|
552 | double p45 = 2. * process[i4].p() * process[i5].p(); |
---|
553 | double p46 = 2. * process[i4].p() * process[i6].p(); |
---|
554 | double p34 = 2. * process[i3].p() * process[i4].p(); |
---|
555 | double p56 = 2. * process[i5].p() * process[i6].p(); |
---|
556 | double mZW1 = process[iZW1].m(); |
---|
557 | double mZW2 = process[iZW2].m(); |
---|
558 | |
---|
559 | // For mixed CP states need epsilon product and gauge boson masses. |
---|
560 | double epsilonProd = 0.; |
---|
561 | if (higgsParity == 3) { |
---|
562 | double p[4][4]; |
---|
563 | for (int i = 0; i < 4; ++i) { |
---|
564 | int ii = i3; |
---|
565 | if (i == 1) ii = i4; |
---|
566 | if (i == 2) ii = i5; |
---|
567 | if (i == 3) ii = i6; |
---|
568 | p[i][0] = process[ii].e(); |
---|
569 | p[i][1] = process[ii].px(); |
---|
570 | p[i][2] = process[ii].py(); |
---|
571 | p[i][3] = process[ii].pz(); |
---|
572 | } |
---|
573 | epsilonProd |
---|
574 | = p[0][0]*p[1][1]*p[2][2]*p[3][3] - p[0][0]*p[1][1]*p[2][3]*p[3][2] |
---|
575 | - p[0][0]*p[1][2]*p[2][1]*p[3][3] + p[0][0]*p[1][2]*p[2][3]*p[3][1] |
---|
576 | + p[0][0]*p[1][3]*p[2][1]*p[3][2] - p[0][0]*p[1][3]*p[2][2]*p[3][1] |
---|
577 | - p[0][1]*p[1][0]*p[2][2]*p[3][3] + p[0][1]*p[1][0]*p[2][3]*p[3][2] |
---|
578 | + p[0][1]*p[1][2]*p[2][0]*p[3][3] - p[0][1]*p[1][2]*p[2][3]*p[3][0] |
---|
579 | - p[0][1]*p[1][3]*p[2][0]*p[3][2] + p[0][1]*p[1][3]*p[2][2]*p[3][0] |
---|
580 | + p[0][2]*p[1][0]*p[2][1]*p[3][3] - p[0][2]*p[1][0]*p[2][3]*p[3][1] |
---|
581 | - p[0][2]*p[1][1]*p[2][0]*p[3][3] + p[0][2]*p[1][1]*p[2][3]*p[3][0] |
---|
582 | + p[0][2]*p[1][3]*p[2][0]*p[3][1] - p[0][2]*p[1][3]*p[2][1]*p[3][0] |
---|
583 | - p[0][3]*p[1][0]*p[2][1]*p[3][2] + p[0][3]*p[1][0]*p[2][2]*p[3][1] |
---|
584 | + p[0][3]*p[1][1]*p[2][0]*p[3][2] - p[0][3]*p[1][1]*p[2][2]*p[3][0] |
---|
585 | - p[0][3]*p[1][2]*p[2][0]*p[3][1] + p[0][3]*p[1][2]*p[2][1]*p[3][0]; |
---|
586 | } |
---|
587 | |
---|
588 | // Z0 Z0 decay: vector and axial couplings of two fermion pairs. |
---|
589 | if (idZW1 == 23) { |
---|
590 | double vf1 = couplingsPtr->vf(process[i3].idAbs()); |
---|
591 | double af1 = couplingsPtr->af(process[i3].idAbs()); |
---|
592 | double vf2 = couplingsPtr->vf(process[i5].idAbs()); |
---|
593 | double af2 = couplingsPtr->af(process[i5].idAbs()); |
---|
594 | double va12asym = 4. * vf1 * af1 * vf2 * af2 |
---|
595 | / ( (vf1*vf1 + af1*af1) * (vf2*vf2 + af2*af2) ); |
---|
596 | double etaMod = higgsEta / pow2( particleDataPtr->m0(23) ); |
---|
597 | |
---|
598 | // Normal CP-even decay. |
---|
599 | if (higgsParity == 1) wt = 8. * (1. + va12asym) * p35 * p46 |
---|
600 | + 8. * (1. - va12asym) * p36 * p45; |
---|
601 | |
---|
602 | // CP-odd decay (normal for A0(H_3)). |
---|
603 | else if (higgsParity == 2) wt = ( pow2(p35 + p46) |
---|
604 | + pow2(p36 + p45) - 2. * p34 * p56 |
---|
605 | - 2. * pow2(p35 * p46 - p36 * p45) / (p34 * p56) |
---|
606 | + va12asym * (p35 + p36 - p45 - p46) * (p35 + p45 - p36 - p46) ) |
---|
607 | / (1. + va12asym); |
---|
608 | |
---|
609 | // Mixed CP states. |
---|
610 | else wt = 32. * ( 0.25 * ( (1. + va12asym) * p35 * p46 |
---|
611 | + (1. - va12asym) * p36 * p45 ) - 0.5 * etaMod * epsilonProd |
---|
612 | * ( (1. + va12asym) * (p35 + p46) - (1. - va12asym) * (p36 + p45) ) |
---|
613 | + 0.0625 * etaMod * etaMod * (-2. * pow2(p34 * p56) |
---|
614 | - 2. * pow2(p35 * p46 - p36 * p45) |
---|
615 | + p34 * p56 * (pow2(p35 + p46) + pow2(p36 + p45)) |
---|
616 | + va12asym * p34 * p56 * (p35 + p36 - p45 - p46) |
---|
617 | * (p35 + p45 - p36 - p46) ) ) / ( 1. + 2. * etaMod * mZW1 * mZW2 |
---|
618 | + 2. * pow2(etaMod * mZW1 * mZW2) * (1. + va12asym) ); |
---|
619 | |
---|
620 | // W+ W- decay. |
---|
621 | } else if (idZW1 == 24) { |
---|
622 | double etaMod = higgsEta / pow2( particleDataPtr->m0(24) ); |
---|
623 | |
---|
624 | // Normal CP-even decay. |
---|
625 | if (higgsParity == 1) wt = 16. * p35 * p46; |
---|
626 | |
---|
627 | // CP-odd decay (normal for A0(H_3)). |
---|
628 | else if (higgsParity == 2) wt = 0.5 * ( pow2(p35 + p46) |
---|
629 | + pow2(p36 + p45) - 2. * p34 * p56 |
---|
630 | - 2. * pow2(p35 * p46 - p36 * p45) / (p34 * p56) |
---|
631 | + (p35 + p36 - p45 - p46) * (p35 + p45 - p36 - p46) ); |
---|
632 | |
---|
633 | // Mixed CP states. |
---|
634 | else wt = 32. * ( 0.25 * 2. * p35 * p46 |
---|
635 | - 0.5 * etaMod * epsilonProd * 2. * (p35 + p46) |
---|
636 | + 0.0625 * etaMod * etaMod * (-2. * pow2(p34 * p56) |
---|
637 | - 2. * pow2(p35 * p46 - p36 * p45) |
---|
638 | + p34 * p56 * (pow2(p35 + p46) + pow2(p36 + p45)) |
---|
639 | + p34 * p56 * (p35 + p36 - p45 - p46) * (p35 + p45 - p36 - p46) ) ) |
---|
640 | / ( 1. * 2. * etaMod * mZW1 * mZW2 + 2. * pow2(etaMod * mZW1 * mZW2) ); |
---|
641 | } |
---|
642 | |
---|
643 | // Done. |
---|
644 | return wt / wtMax; |
---|
645 | |
---|
646 | } |
---|
647 | |
---|
648 | //========================================================================== |
---|
649 | |
---|
650 | // The Sigma1Process class. |
---|
651 | // Base class for resolved 2 -> 1 cross sections; derived from SigmaProcess. |
---|
652 | |
---|
653 | //-------------------------------------------------------------------------- |
---|
654 | |
---|
655 | // Wrapper to sigmaHat, to (a) store current incoming flavours, |
---|
656 | // (b) convert from GeV^-2 to mb where required, and |
---|
657 | // (c) convert from |M|^2 to d(sigmaHat)/d(tHat) where required. |
---|
658 | |
---|
659 | double Sigma1Process::sigmaHatWrap(int id1in, int id2in) { |
---|
660 | |
---|
661 | id1 = id1in; |
---|
662 | id2 = id2in; |
---|
663 | double sigmaTmp = sigmaHat(); |
---|
664 | if (convertM2()) { |
---|
665 | sigmaTmp /= 2. * sH; |
---|
666 | // Convert 2 * pi * delta(p^2 - m^2) to Breit-Wigner with same area. |
---|
667 | int idTmp = resonanceA(); |
---|
668 | double mTmp = particleDataPtr->m0(idTmp); |
---|
669 | double GamTmp = particleDataPtr->mWidth(idTmp); |
---|
670 | sigmaTmp *= 2. * mTmp * GamTmp / ( pow2(sH - mTmp * mTmp) |
---|
671 | + pow2(mTmp * GamTmp) ); |
---|
672 | } |
---|
673 | if (convert2mb()) sigmaTmp *= CONVERT2MB; |
---|
674 | return sigmaTmp; |
---|
675 | |
---|
676 | } |
---|
677 | |
---|
678 | //-------------------------------------------------------------------------- |
---|
679 | |
---|
680 | // Input and complement kinematics for resolved 2 -> 1 process. |
---|
681 | |
---|
682 | void Sigma1Process::store1Kin( double x1in, double x2in, double sHin) { |
---|
683 | |
---|
684 | // Default value only sensible for these processes. |
---|
685 | swapTU = false; |
---|
686 | |
---|
687 | // Incoming parton momentum fractions and sHat. |
---|
688 | x1Save = x1in; |
---|
689 | x2Save = x2in; |
---|
690 | sH = sHin; |
---|
691 | mH = sqrt(sH); |
---|
692 | sH2 = sH * sH; |
---|
693 | |
---|
694 | // Different options for renormalization scale, but normally sHat. |
---|
695 | Q2RenSave = renormMultFac * sH; |
---|
696 | if (renormScale1 == 2) Q2RenSave = renormFixScale; |
---|
697 | |
---|
698 | // Different options for factorization scale, but normally sHat. |
---|
699 | Q2FacSave = factorMultFac * sH; |
---|
700 | if (factorScale1 == 2) Q2FacSave = factorFixScale; |
---|
701 | |
---|
702 | // Evaluate alpha_strong and alpha_EM. |
---|
703 | alpS = couplingsPtr->alphaS(Q2RenSave); |
---|
704 | alpEM = couplingsPtr->alphaEM(Q2RenSave); |
---|
705 | |
---|
706 | } |
---|
707 | |
---|
708 | //-------------------------------------------------------------------------- |
---|
709 | |
---|
710 | // Calculate modified masses and four-vectors for matrix elements. |
---|
711 | |
---|
712 | bool Sigma1Process::setupForME() { |
---|
713 | |
---|
714 | // Common initial-state handling. |
---|
715 | bool allowME = setupForMEin(); |
---|
716 | |
---|
717 | // Final state trivial here. |
---|
718 | mME[2] = mH; |
---|
719 | pME[2] = Vec4( 0., 0., 0., mH); |
---|
720 | |
---|
721 | // Done. |
---|
722 | return allowME; |
---|
723 | |
---|
724 | } |
---|
725 | |
---|
726 | //========================================================================== |
---|
727 | |
---|
728 | // The Sigma2Process class. |
---|
729 | // Base class for resolved 2 -> 2 cross sections; derived from SigmaProcess. |
---|
730 | |
---|
731 | //-------------------------------------------------------------------------- |
---|
732 | |
---|
733 | // Input and complement kinematics for resolved 2 -> 2 process. |
---|
734 | |
---|
735 | void Sigma2Process::store2Kin( double x1in, double x2in, double sHin, |
---|
736 | double tHin, double m3in, double m4in, double runBW3in, double runBW4in) { |
---|
737 | |
---|
738 | // Default ordering of particles 3 and 4. |
---|
739 | swapTU = false; |
---|
740 | |
---|
741 | // Incoming parton momentum fractions. |
---|
742 | x1Save = x1in; |
---|
743 | x2Save = x2in; |
---|
744 | |
---|
745 | // Incoming masses and their squares. |
---|
746 | bool masslessKin = (id3Mass() == 0) && (id4Mass() == 0); |
---|
747 | if (masslessKin) { |
---|
748 | m3 = 0.; |
---|
749 | m4 = 0.; |
---|
750 | } else { |
---|
751 | m3 = m3in; |
---|
752 | m4 = m4in; |
---|
753 | } |
---|
754 | mSave[3] = m3; |
---|
755 | mSave[4] = m4; |
---|
756 | s3 = m3 * m3; |
---|
757 | s4 = m4 * m4; |
---|
758 | |
---|
759 | // Standard Mandelstam variables and their squares. |
---|
760 | sH = sHin; |
---|
761 | tH = tHin; |
---|
762 | uH = (masslessKin) ? -(sH + tH) : s3 + s4 - (sH + tH); |
---|
763 | mH = sqrt(sH); |
---|
764 | sH2 = sH * sH; |
---|
765 | tH2 = tH * tH; |
---|
766 | uH2 = uH * uH; |
---|
767 | |
---|
768 | // The nominal Breit-Wigner factors with running width. |
---|
769 | runBW3 = runBW3in; |
---|
770 | runBW4 = runBW4in; |
---|
771 | |
---|
772 | // Calculate squared transverse momentum. |
---|
773 | pT2 = (masslessKin) ? tH * uH / sH : (tH * uH - s3 * s4) / sH; |
---|
774 | |
---|
775 | // Special case: pick scale as if 2 -> 1 process in disguise. |
---|
776 | if (isSChannel()) { |
---|
777 | |
---|
778 | // Different options for renormalization scale, but normally sHat. |
---|
779 | Q2RenSave = renormMultFac * sH; |
---|
780 | if (renormScale1 == 2) Q2RenSave = renormFixScale; |
---|
781 | |
---|
782 | // Different options for factorization scale, but normally sHat. |
---|
783 | Q2FacSave = factorMultFac * sH; |
---|
784 | if (factorScale1 == 2) Q2FacSave = factorFixScale; |
---|
785 | |
---|
786 | // Normal case with "true" 2 -> 2. |
---|
787 | } else { |
---|
788 | |
---|
789 | // Different options for renormalization scale. |
---|
790 | if (masslessKin) Q2RenSave = (renormScale2 < 4) ? pT2 : sH; |
---|
791 | else if (renormScale2 == 1) Q2RenSave = pT2 + min(s3, s4); |
---|
792 | else if (renormScale2 == 2) Q2RenSave = sqrt((pT2 + s3) * (pT2 + s4)); |
---|
793 | else if (renormScale2 == 3) Q2RenSave = pT2 + 0.5 * (s3 + s4); |
---|
794 | else Q2RenSave = sH; |
---|
795 | Q2RenSave *= renormMultFac; |
---|
796 | if (renormScale2 == 5) Q2RenSave = renormFixScale; |
---|
797 | |
---|
798 | // Different options for factorization scale. |
---|
799 | if (masslessKin) Q2FacSave = (factorScale2 < 4) ? pT2 : sH; |
---|
800 | else if (factorScale2 == 1) Q2FacSave = pT2 + min(s3, s4); |
---|
801 | else if (factorScale2 == 2) Q2FacSave = sqrt((pT2 + s3) * (pT2 + s4)); |
---|
802 | else if (factorScale2 == 3) Q2FacSave = pT2 + 0.5 * (s3 + s4); |
---|
803 | else Q2FacSave = sH; |
---|
804 | Q2FacSave *= factorMultFac; |
---|
805 | if (factorScale2 == 5) Q2FacSave = factorFixScale; |
---|
806 | } |
---|
807 | |
---|
808 | // Evaluate alpha_strong and alpha_EM. |
---|
809 | alpS = couplingsPtr->alphaS(Q2RenSave); |
---|
810 | alpEM = couplingsPtr->alphaEM(Q2RenSave); |
---|
811 | |
---|
812 | } |
---|
813 | |
---|
814 | //-------------------------------------------------------------------------- |
---|
815 | |
---|
816 | // As above, special kinematics for multiparton interactions. |
---|
817 | |
---|
818 | void Sigma2Process::store2KinMPI( double x1in, double x2in, |
---|
819 | double sHin, double tHin, double uHin, double alpSin, double alpEMin, |
---|
820 | bool needMasses, double m3in, double m4in) { |
---|
821 | |
---|
822 | // Default ordering of particles 3 and 4. |
---|
823 | swapTU = false; |
---|
824 | |
---|
825 | // Incoming x values. |
---|
826 | x1Save = x1in; |
---|
827 | x2Save = x2in; |
---|
828 | |
---|
829 | // Standard Mandelstam variables and their squares. |
---|
830 | sH = sHin; |
---|
831 | tH = tHin; |
---|
832 | uH = uHin; |
---|
833 | mH = sqrt(sH); |
---|
834 | sH2 = sH * sH; |
---|
835 | tH2 = tH * tH; |
---|
836 | uH2 = uH * uH; |
---|
837 | |
---|
838 | // Strong and electroweak couplings. |
---|
839 | alpS = alpSin; |
---|
840 | alpEM = alpEMin; |
---|
841 | |
---|
842 | // Assume vanishing masses. (Will be modified in final kinematics.) |
---|
843 | m3 = 0.; |
---|
844 | s3 = 0.; |
---|
845 | m4 = 0.; |
---|
846 | s4 = 0.; |
---|
847 | sHBeta = sH; |
---|
848 | |
---|
849 | // Scattering angle. |
---|
850 | cosTheta = (tH - uH) / sH; |
---|
851 | sinTheta = 2. * sqrtpos( tH * uH ) / sH; |
---|
852 | |
---|
853 | // In some cases must use masses and redefine meaning of tHat and uHat. |
---|
854 | if (needMasses) { |
---|
855 | m3 = m3in; |
---|
856 | s3 = m3 * m3; |
---|
857 | m4 = m4in; |
---|
858 | s4 = m4 * m4; |
---|
859 | sHMass = sH - s3 - s4; |
---|
860 | sHBeta = sqrtpos(sHMass*sHMass - 4. * s3 * s4); |
---|
861 | tH = -0.5 * (sHMass - sHBeta * cosTheta); |
---|
862 | uH = -0.5 * (sHMass + sHBeta * cosTheta); |
---|
863 | tH2 = tH * tH; |
---|
864 | uH2 = uH * uH; |
---|
865 | } |
---|
866 | |
---|
867 | // pT2 with masses (at this stage) included. |
---|
868 | pT2Mass = 0.25 * sHBeta * pow2(sinTheta); |
---|
869 | |
---|
870 | } |
---|
871 | |
---|
872 | //-------------------------------------------------------------------------- |
---|
873 | |
---|
874 | // Perform kinematics for a multiparton interaction, including a rescattering. |
---|
875 | |
---|
876 | bool Sigma2Process::final2KinMPI( int i1Res, int i2Res, Vec4 p1Res, Vec4 p2Res, |
---|
877 | double m1Res, double m2Res) { |
---|
878 | |
---|
879 | // Have to set flavours and colours. |
---|
880 | setIdColAcol(); |
---|
881 | |
---|
882 | // Check that masses of outgoing particles not too big. |
---|
883 | m3 = particleDataPtr->m0(idSave[3]); |
---|
884 | m4 = particleDataPtr->m0(idSave[4]); |
---|
885 | mH = sqrt(sH); |
---|
886 | if (m3 + m4 + MASSMARGIN > mH) return false; |
---|
887 | s3 = m3 * m3; |
---|
888 | s4 = m4 * m4; |
---|
889 | |
---|
890 | // Do kinematics of the production; without or with masses. |
---|
891 | double e1In = 0.5 * mH; |
---|
892 | double e2In = e1In; |
---|
893 | double pzIn = e1In; |
---|
894 | if (i1Res > 0 || i2Res > 0) { |
---|
895 | double s1 = m1Res * m1Res; |
---|
896 | double s2 = m2Res * m2Res; |
---|
897 | e1In = 0.5 * (sH + s1 - s2) / mH; |
---|
898 | e2In = 0.5 * (sH + s2 - s1) / mH; |
---|
899 | pzIn = sqrtpos( e1In*e1In - s1 ); |
---|
900 | } |
---|
901 | |
---|
902 | // Do kinematics of the decay. |
---|
903 | double e3 = 0.5 * (sH + s3 - s4) / mH; |
---|
904 | double e4 = 0.5 * (sH + s4 - s3) / mH; |
---|
905 | double pAbs = sqrtpos( e3*e3 - s3 ); |
---|
906 | phi = 2. * M_PI * rndmPtr->flat(); |
---|
907 | double pZ = pAbs * cosTheta; |
---|
908 | pTFin = pAbs * sinTheta; |
---|
909 | double pX = pTFin * sin(phi); |
---|
910 | double pY = pTFin * cos(phi); |
---|
911 | double scale = 0.5 * mH * sinTheta; |
---|
912 | |
---|
913 | // Fill particle info. |
---|
914 | int status1 = (i1Res == 0) ? -31 : -34; |
---|
915 | int status2 = (i2Res == 0) ? -31 : -34; |
---|
916 | parton[1] = Particle( idSave[1], status1, 0, 0, 3, 4, |
---|
917 | colSave[1], acolSave[1], 0., 0., pzIn, e1In, m1Res, scale); |
---|
918 | parton[2] = Particle( idSave[2], status2, 0, 0, 3, 4, |
---|
919 | colSave[2], acolSave[2], 0., 0., -pzIn, e2In, m2Res, scale); |
---|
920 | parton[3] = Particle( idSave[3], 33, 1, 2, 0, 0, |
---|
921 | colSave[3], acolSave[3], pX, pY, pZ, e3, m3, scale); |
---|
922 | parton[4] = Particle( idSave[4], 33, 1, 2, 0, 0, |
---|
923 | colSave[4], acolSave[4], -pX, -pY, -pZ, e4, m4, scale); |
---|
924 | |
---|
925 | // Boost particles from subprocess rest frame to event rest frame. |
---|
926 | // Normal multiparton interaction: only longitudinal boost. |
---|
927 | if (i1Res == 0 && i2Res == 0) { |
---|
928 | double betaZ = (x1Save - x2Save) / (x1Save + x2Save); |
---|
929 | for (int i = 1; i <= 4; ++i) parton[i].bst(0., 0., betaZ); |
---|
930 | // Rescattering: generic rotation and boost required. |
---|
931 | } else { |
---|
932 | RotBstMatrix M; |
---|
933 | M.fromCMframe( p1Res, p2Res); |
---|
934 | for (int i = 1; i <= 4; ++i) parton[i].rotbst(M); |
---|
935 | } |
---|
936 | |
---|
937 | // Done. |
---|
938 | return true; |
---|
939 | |
---|
940 | } |
---|
941 | |
---|
942 | //-------------------------------------------------------------------------- |
---|
943 | |
---|
944 | // Calculate modified masses and four-vectors for matrix elements. |
---|
945 | |
---|
946 | bool Sigma2Process::setupForME() { |
---|
947 | |
---|
948 | // Common initial-state handling. |
---|
949 | bool allowME = setupForMEin(); |
---|
950 | |
---|
951 | // Correct outgoing c, b, mu and tau to be massive or not. |
---|
952 | mME[2] = m3; |
---|
953 | int id3Tmp = abs(id3Mass()); |
---|
954 | if (id3Tmp == 4) mME[2] = mcME; |
---|
955 | if (id3Tmp == 5) mME[2] = mbME; |
---|
956 | if (id3Tmp == 13) mME[2] = mmuME; |
---|
957 | if (id3Tmp == 15) mME[2] = mtauME; |
---|
958 | mME[3] = m4; |
---|
959 | int id4Tmp = abs(id4Mass()); |
---|
960 | if (id4Tmp == 4) mME[3] = mcME; |
---|
961 | if (id4Tmp == 5) mME[3] = mbME; |
---|
962 | if (id4Tmp == 13) mME[3] = mmuME; |
---|
963 | if (id4Tmp == 15) mME[3] = mtauME; |
---|
964 | |
---|
965 | // If kinematically impossible turn to massless case, but set error. |
---|
966 | if (mME[2] + mME[3] >= mH) { |
---|
967 | mME[2] = 0.; |
---|
968 | mME[3] = 0.; |
---|
969 | allowME = false; |
---|
970 | } |
---|
971 | |
---|
972 | // Calculate scattering angle in subsystem rest frame. |
---|
973 | double sH34 = sqrtpos( pow2(sH - s3 - s4) - 4. * s3 * s4); |
---|
974 | double cThe = (tH - uH) / sH34; |
---|
975 | double sThe = sqrtpos(1. - cThe * cThe); |
---|
976 | |
---|
977 | // Setup massive kinematics with preserved scattering angle. |
---|
978 | double s3ME = pow2(mME[2]); |
---|
979 | double s4ME = pow2(mME[3]); |
---|
980 | double sH34ME = sqrtpos( pow2(sH - s3ME - s4ME) - 4. * s3ME * s4ME); |
---|
981 | double pAbsME = 0.5 * sH34ME / mH; |
---|
982 | |
---|
983 | // Normally allowed with unequal (or vanishing) masses. |
---|
984 | if (id3Tmp == 0 || id3Tmp != id4Tmp) { |
---|
985 | pME[2] = Vec4( pAbsME * sThe, 0., pAbsME * cThe, |
---|
986 | 0.5 * (sH + s3ME - s4ME) / mH); |
---|
987 | pME[3] = Vec4( -pAbsME * sThe, 0., -pAbsME * cThe, |
---|
988 | 0.5 * (sH + s4ME - s3ME) / mH); |
---|
989 | |
---|
990 | // For equal (anti)particles (e.g. W+ W-) use averaged mass. |
---|
991 | } else { |
---|
992 | mME[2] = sqrtpos(0.5 * (s3ME + s4ME) - 0.25 * pow2(s3ME - s4ME) / sH); |
---|
993 | mME[3] = mME[2]; |
---|
994 | pME[2] = Vec4( pAbsME * sThe, 0., pAbsME * cThe, 0.5 * mH); |
---|
995 | pME[3] = Vec4( -pAbsME * sThe, 0., -pAbsME * cThe, 0.5 * mH); |
---|
996 | } |
---|
997 | |
---|
998 | // Done. |
---|
999 | return allowME; |
---|
1000 | |
---|
1001 | } |
---|
1002 | |
---|
1003 | //========================================================================== |
---|
1004 | |
---|
1005 | // The Sigma3Process class. |
---|
1006 | // Base class for resolved 2 -> 3 cross sections; derived from SigmaProcess. |
---|
1007 | |
---|
1008 | //-------------------------------------------------------------------------- |
---|
1009 | |
---|
1010 | // Input and complement kinematics for resolved 2 -> 3 process. |
---|
1011 | |
---|
1012 | void Sigma3Process::store3Kin( double x1in, double x2in, double sHin, |
---|
1013 | Vec4 p3cmIn, Vec4 p4cmIn, Vec4 p5cmIn, double m3in, double m4in, |
---|
1014 | double m5in, double runBW3in, double runBW4in, double runBW5in) { |
---|
1015 | |
---|
1016 | // Default ordering of particles 3 and 4 - not relevant here. |
---|
1017 | swapTU = false; |
---|
1018 | |
---|
1019 | // Incoming parton momentum fractions. |
---|
1020 | x1Save = x1in; |
---|
1021 | x2Save = x2in; |
---|
1022 | |
---|
1023 | // Incoming masses and their squares. |
---|
1024 | if (id3Mass() == 0 && id4Mass() == 0 && id5Mass() == 0) { |
---|
1025 | m3 = 0.; |
---|
1026 | m4 = 0.; |
---|
1027 | m5 = 0.; |
---|
1028 | } else { |
---|
1029 | m3 = m3in; |
---|
1030 | m4 = m4in; |
---|
1031 | m5 = m5in; |
---|
1032 | } |
---|
1033 | mSave[3] = m3; |
---|
1034 | mSave[4] = m4; |
---|
1035 | mSave[5] = m5; |
---|
1036 | s3 = m3 * m3; |
---|
1037 | s4 = m4 * m4; |
---|
1038 | s5 = m5 * m5; |
---|
1039 | |
---|
1040 | // Standard Mandelstam variables and four-momenta in rest frame. |
---|
1041 | sH = sHin; |
---|
1042 | mH = sqrt(sH); |
---|
1043 | sH2 = sH * sH; |
---|
1044 | p3cm = p3cmIn; |
---|
1045 | p4cm = p4cmIn; |
---|
1046 | p5cm = p5cmIn; |
---|
1047 | |
---|
1048 | // The nominal Breit-Wigner factors with running width. |
---|
1049 | runBW3 = runBW3in; |
---|
1050 | runBW4 = runBW4in; |
---|
1051 | runBW5 = runBW5in; |
---|
1052 | |
---|
1053 | // Special case: pick scale as if 2 -> 1 process in disguise. |
---|
1054 | if (isSChannel()) { |
---|
1055 | |
---|
1056 | // Different options for renormalization scale, but normally sHat. |
---|
1057 | Q2RenSave = renormMultFac * sH; |
---|
1058 | if (renormScale1 == 2) Q2RenSave = renormFixScale; |
---|
1059 | |
---|
1060 | // Different options for factorization scale, but normally sHat. |
---|
1061 | Q2FacSave = factorMultFac * sH; |
---|
1062 | if (factorScale1 == 2) Q2RenSave = factorFixScale; |
---|
1063 | |
---|
1064 | // "Normal" 2 -> 3 processes, i.e. not vector boson fusion. |
---|
1065 | } else if ( idTchan1() != 23 && idTchan1() != 24 && idTchan2() != 23 |
---|
1066 | && idTchan2() != 24 ) { |
---|
1067 | double mT3S = s3 + p3cm.pT2(); |
---|
1068 | double mT4S = s4 + p4cm.pT2(); |
---|
1069 | double mT5S = s5 + p5cm.pT2(); |
---|
1070 | |
---|
1071 | // Different options for renormalization scale. |
---|
1072 | if (renormScale3 == 1) Q2RenSave = min( mT3S, min(mT4S, mT5S) ); |
---|
1073 | else if (renormScale3 == 2) Q2RenSave = sqrt( mT3S * mT4S * mT5S |
---|
1074 | / max( mT3S, max(mT4S, mT5S) ) ); |
---|
1075 | else if (renormScale3 == 3) Q2RenSave = pow( mT3S * mT4S * mT5S, |
---|
1076 | 1./3. ); |
---|
1077 | else if (renormScale3 == 4) Q2RenSave = (mT3S + mT4S + mT5S) / 3.; |
---|
1078 | else Q2RenSave = sH; |
---|
1079 | Q2RenSave *= renormMultFac; |
---|
1080 | if (renormScale3 == 6) Q2RenSave = renormFixScale; |
---|
1081 | |
---|
1082 | // Different options for factorization scale. |
---|
1083 | if (factorScale3 == 1) Q2FacSave = min( mT3S, min(mT4S, mT5S) ); |
---|
1084 | else if (factorScale3 == 2) Q2FacSave = sqrt( mT3S * mT4S * mT5S |
---|
1085 | / max( mT3S, max(mT4S, mT5S) ) ); |
---|
1086 | else if (factorScale3 == 3) Q2FacSave = pow( mT3S * mT4S * mT5S, |
---|
1087 | 1./3. ); |
---|
1088 | else if (factorScale3 == 4) Q2FacSave = (mT3S + mT4S + mT5S) / 3.; |
---|
1089 | else Q2FacSave = sH; |
---|
1090 | Q2FacSave *= factorMultFac; |
---|
1091 | if (factorScale3 == 6) Q2FacSave = factorFixScale; |
---|
1092 | |
---|
1093 | // Vector boson fusion 2 -> 3 processes; recoils in positions 4 and 5. |
---|
1094 | } else { |
---|
1095 | double sV4 = pow2( particleDataPtr->m0(idTchan1()) ); |
---|
1096 | double sV5 = pow2( particleDataPtr->m0(idTchan2()) ); |
---|
1097 | double mT3S = s3 + p3cm.pT2(); |
---|
1098 | double mTV4S = sV4 + p4cm.pT2(); |
---|
1099 | double mTV5S = sV5 + p5cm.pT2(); |
---|
1100 | |
---|
1101 | // Different options for renormalization scale. |
---|
1102 | if (renormScale3VV == 1) Q2RenSave = max( sV4, sV5); |
---|
1103 | else if (renormScale3VV == 2) Q2RenSave = sqrt( mTV4S * mTV5S ); |
---|
1104 | else if (renormScale3VV == 3) Q2RenSave = pow( mT3S * mTV4S * mTV5S, |
---|
1105 | 1./3. ); |
---|
1106 | else if (renormScale3VV == 4) Q2RenSave = (mT3S * mTV4S * mTV5S) / 3.; |
---|
1107 | else Q2RenSave = sH; |
---|
1108 | Q2RenSave *= renormMultFac; |
---|
1109 | if (renormScale3VV == 6) Q2RenSave = renormFixScale; |
---|
1110 | |
---|
1111 | // Different options for factorization scale. |
---|
1112 | if (factorScale3VV == 1) Q2FacSave = max( sV4, sV5); |
---|
1113 | else if (factorScale3VV == 2) Q2FacSave = sqrt( mTV4S * mTV5S ); |
---|
1114 | else if (factorScale3VV == 3) Q2FacSave = pow( mT3S * mTV4S * mTV5S, |
---|
1115 | 1./3. ); |
---|
1116 | else if (factorScale3VV == 4) Q2FacSave = (mT3S * mTV4S * mTV5S) / 3.; |
---|
1117 | else Q2FacSave = sH; |
---|
1118 | Q2FacSave *= factorMultFac; |
---|
1119 | if (factorScale3VV == 6) Q2FacSave = factorFixScale; |
---|
1120 | } |
---|
1121 | |
---|
1122 | // Evaluate alpha_strong and alpha_EM. |
---|
1123 | alpS = couplingsPtr->alphaS(Q2RenSave); |
---|
1124 | alpEM = couplingsPtr->alphaEM(Q2RenSave); |
---|
1125 | |
---|
1126 | } |
---|
1127 | |
---|
1128 | //-------------------------------------------------------------------------- |
---|
1129 | |
---|
1130 | // Calculate modified masses and four-vectors for matrix elements. |
---|
1131 | |
---|
1132 | bool Sigma3Process::setupForME() { |
---|
1133 | |
---|
1134 | // Common initial-state handling. |
---|
1135 | bool allowME = setupForMEin(); |
---|
1136 | |
---|
1137 | // Correct outgoing c, b, mu and tau to be massive or not. |
---|
1138 | mME[2] = m3; |
---|
1139 | int id3Tmp = abs(id3Mass()); |
---|
1140 | if (id3Tmp == 4) mME[2] = mcME; |
---|
1141 | if (id3Tmp == 5) mME[2] = mbME; |
---|
1142 | if (id3Tmp == 13) mME[2] = mmuME; |
---|
1143 | if (id3Tmp == 15) mME[2] = mtauME; |
---|
1144 | mME[3] = m4; |
---|
1145 | int id4Tmp = abs(id4Mass()); |
---|
1146 | if (id4Tmp == 4) mME[3] = mcME; |
---|
1147 | if (id4Tmp == 5) mME[3] = mbME; |
---|
1148 | if (id4Tmp == 13) mME[3] = mmuME; |
---|
1149 | if (id4Tmp == 15) mME[3] = mtauME; |
---|
1150 | mME[4] = m5; |
---|
1151 | int id5Tmp = abs(id5Mass()); |
---|
1152 | if (id5Tmp == 4) mME[4] = mcME; |
---|
1153 | if (id5Tmp == 5) mME[4] = mbME; |
---|
1154 | if (id5Tmp == 13) mME[4] = mmuME; |
---|
1155 | if (id5Tmp == 15) mME[4] = mtauME; |
---|
1156 | |
---|
1157 | // If kinematically impossible turn to massless case, but set error. |
---|
1158 | if (mME[2] + mME[3] + mME[4] >= mH) { |
---|
1159 | mME[2] = 0.; |
---|
1160 | mME[3] = 0.; |
---|
1161 | mME[4] = 0.; |
---|
1162 | allowME = false; |
---|
1163 | } |
---|
1164 | |
---|
1165 | // Form new average masses if identical particles. |
---|
1166 | if (id3Tmp != 0 && id4Tmp == id3Tmp && id5Tmp == id3Tmp) { |
---|
1167 | double mAvg = (mME[2] + mME[3] + mME[4]) / 3.; |
---|
1168 | mME[2] = mAvg; |
---|
1169 | mME[3] = mAvg; |
---|
1170 | mME[4] = mAvg; |
---|
1171 | } else if (id3Tmp != 0 && id4Tmp == id3Tmp) { |
---|
1172 | mME[2] = sqrtpos(0.5 * (pow2(mME[2]) + pow2(mME[3])) |
---|
1173 | - 0.25 * pow2(pow2(mME[2]) - pow2(mME[3])) / sH); |
---|
1174 | mME[3] = mME[2]; |
---|
1175 | } else if (id3Tmp != 0 && id5Tmp == id3Tmp) { |
---|
1176 | mME[2] = sqrtpos(0.5 * (pow2(mME[2]) + pow2(mME[4])) |
---|
1177 | - 0.25 * pow2(pow2(mME[2]) - pow2(mME[4])) / sH); |
---|
1178 | mME[4] = mME[2]; |
---|
1179 | } else if (id4Tmp != 0 && id5Tmp == id4Tmp) { |
---|
1180 | mME[3] = sqrtpos(0.5 * (pow2(mME[3]) + pow2(mME[4])) |
---|
1181 | - 0.25 * pow2(pow2(mME[3]) - pow2(mME[4])) / sH); |
---|
1182 | mME[4] = mME[2]; |
---|
1183 | } |
---|
1184 | |
---|
1185 | // Iterate rescaled three-momenta until convergence. |
---|
1186 | double m2ME3 = pow2(mME[2]); |
---|
1187 | double m2ME4 = pow2(mME[3]); |
---|
1188 | double m2ME5 = pow2(mME[4]); |
---|
1189 | double p2ME3 = p3cm.pAbs2(); |
---|
1190 | double p2ME4 = p4cm.pAbs2(); |
---|
1191 | double p2ME5 = p5cm.pAbs2(); |
---|
1192 | double p2sum = p2ME3 + p2ME4 + p2ME5; |
---|
1193 | double eME3 = sqrt(m2ME3 + p2ME3); |
---|
1194 | double eME4 = sqrt(m2ME4 + p2ME4); |
---|
1195 | double eME5 = sqrt(m2ME5 + p2ME5); |
---|
1196 | double esum = eME3 + eME4 + eME5; |
---|
1197 | double p2rat = p2ME3 / eME3 + p2ME4 / eME4 + p2ME5 / eME5; |
---|
1198 | int iStep = 0; |
---|
1199 | while ( abs(esum - mH) > COMPRELERR * mH && iStep < NCOMPSTEP ) { |
---|
1200 | ++iStep; |
---|
1201 | double compFac = 1. + 2. * (mH - esum) / p2rat; |
---|
1202 | p2ME3 *= compFac; |
---|
1203 | p2ME4 *= compFac; |
---|
1204 | p2ME5 *= compFac; |
---|
1205 | eME3 = sqrt(m2ME3 + p2ME3); |
---|
1206 | eME4 = sqrt(m2ME4 + p2ME4); |
---|
1207 | eME5 = sqrt(m2ME5 + p2ME5); |
---|
1208 | esum = eME3 + eME4 + eME5; |
---|
1209 | p2rat = p2ME3 / eME3 + p2ME4 / eME4 + p2ME5 / eME5; |
---|
1210 | } |
---|
1211 | |
---|
1212 | // If failed convergence set error flag. |
---|
1213 | if (abs(esum - mH) > COMPRELERR * mH) allowME = false; |
---|
1214 | |
---|
1215 | // Set up accepted kinematics. |
---|
1216 | double totFac = sqrt( (p2ME3 + p2ME4 + p2ME5) / p2sum); |
---|
1217 | pME[2] = totFac * p3cm; |
---|
1218 | pME[2].e( eME3); |
---|
1219 | pME[3] = totFac * p4cm; |
---|
1220 | pME[3].e( eME4); |
---|
1221 | pME[4] = totFac * p5cm; |
---|
1222 | pME[4].e( eME5); |
---|
1223 | |
---|
1224 | // Done. |
---|
1225 | return allowME; |
---|
1226 | |
---|
1227 | } |
---|
1228 | |
---|
1229 | //========================================================================== |
---|
1230 | |
---|
1231 | // The SigmaLHAProcess class. |
---|
1232 | // Wrapper for Les Houches Accord external input; derived from SigmaProcess. |
---|
1233 | // Note: arbitrary subdivision into PhaseSpaceLHA and SigmaLHAProcess tasks. |
---|
1234 | |
---|
1235 | //-------------------------------------------------------------------------- |
---|
1236 | |
---|
1237 | // Evaluate weight for decay angles. |
---|
1238 | |
---|
1239 | double SigmaLHAProcess::weightDecay( Event& process, int iResBeg, |
---|
1240 | int iResEnd) { |
---|
1241 | |
---|
1242 | // Do nothing if decays present already at input. |
---|
1243 | if (iResBeg < process.savedSizeValue()) return 1.; |
---|
1244 | |
---|
1245 | // Identity of mother of decaying reseonance(s). |
---|
1246 | int idMother = process[process[iResBeg].mother1()].idAbs(); |
---|
1247 | |
---|
1248 | // For Higgs decay hand over to standard routine. |
---|
1249 | if (idMother == 25 || idMother == 35 || idMother == 36) |
---|
1250 | return weightHiggsDecay( process, iResBeg, iResEnd); |
---|
1251 | |
---|
1252 | // For top decay hand over to standard routine. |
---|
1253 | if (idMother == 6) |
---|
1254 | return weightTopDecay( process, iResBeg, iResEnd); |
---|
1255 | |
---|
1256 | // Else done. |
---|
1257 | return 1.; |
---|
1258 | |
---|
1259 | } |
---|
1260 | |
---|
1261 | //-------------------------------------------------------------------------- |
---|
1262 | |
---|
1263 | // Set scale, alpha_strong and alpha_EM when not set. |
---|
1264 | |
---|
1265 | void SigmaLHAProcess::setScale() { |
---|
1266 | |
---|
1267 | // If scale has not been set, then to set. |
---|
1268 | double scaleLHA = lhaUpPtr->scale(); |
---|
1269 | if (scaleLHA < 0.) { |
---|
1270 | |
---|
1271 | // Final-state partons and their invariant mass. |
---|
1272 | vector<int> iFin; |
---|
1273 | Vec4 pFinSum; |
---|
1274 | for (int i = 3; i < lhaUpPtr->sizePart(); ++i) |
---|
1275 | if (lhaUpPtr->mother1(i) == 1) { |
---|
1276 | iFin.push_back(i); |
---|
1277 | pFinSum += Vec4( lhaUpPtr->px(i), lhaUpPtr->py(i), |
---|
1278 | lhaUpPtr->pz(i), lhaUpPtr->e(i) ); |
---|
1279 | } |
---|
1280 | int nFin = iFin.size(); |
---|
1281 | sH = pFinSum * pFinSum; |
---|
1282 | mH = sqrt(sH); |
---|
1283 | sH2 = sH * sH; |
---|
1284 | |
---|
1285 | // If 1 final-state particle then use Sigma1Process logic. |
---|
1286 | if (nFin == 1) { |
---|
1287 | Q2RenSave = renormMultFac * sH; |
---|
1288 | if (renormScale1 == 2) Q2RenSave = renormFixScale; |
---|
1289 | Q2FacSave = factorMultFac * sH; |
---|
1290 | if (factorScale1 == 2) Q2FacSave = factorFixScale; |
---|
1291 | |
---|
1292 | // If 2 final-state particles then use Sigma2Process logic. |
---|
1293 | } else if (nFin == 2) { |
---|
1294 | double s3 = pow2(lhaUpPtr->m(iFin[0])); |
---|
1295 | double s4 = pow2(lhaUpPtr->m(iFin[1])); |
---|
1296 | double pT2 = pow2(lhaUpPtr->px(iFin[0])) + pow2(lhaUpPtr->py(iFin[0])); |
---|
1297 | if (renormScale2 == 1) Q2RenSave = pT2 + min(s3, s4); |
---|
1298 | else if (renormScale2 == 2) Q2RenSave = sqrt((pT2 + s3) * (pT2 + s4)); |
---|
1299 | else if (renormScale2 == 3) Q2RenSave = pT2 + 0.5 * (s3 + s4); |
---|
1300 | else Q2RenSave = sH; |
---|
1301 | Q2RenSave *= renormMultFac; |
---|
1302 | if (renormScale2 == 5) Q2RenSave = renormFixScale; |
---|
1303 | if (factorScale2 == 1) Q2FacSave = pT2 + min(s3, s4); |
---|
1304 | else if (factorScale2 == 2) Q2FacSave = sqrt((pT2 + s3) * (pT2 + s4)); |
---|
1305 | else if (factorScale2 == 3) Q2FacSave = pT2 + 0.5 * (s3 + s4); |
---|
1306 | else Q2FacSave = sH; |
---|
1307 | Q2FacSave *= factorMultFac; |
---|
1308 | if (factorScale2 == 5) Q2FacSave = factorFixScale; |
---|
1309 | |
---|
1310 | // If 3 or more final-state particles then use Sigma3Process logic. |
---|
1311 | } else { |
---|
1312 | double mTSlow = sH; |
---|
1313 | double mTSmed = sH; |
---|
1314 | double mTSprod = 1.; |
---|
1315 | double mTSsum = 0.; |
---|
1316 | for (int i = 0; i < nFin; ++i) { |
---|
1317 | double mTSnow = pow2(lhaUpPtr->m(iFin[i])) |
---|
1318 | + pow2(lhaUpPtr->px(iFin[i])) + pow2(lhaUpPtr->py(iFin[i])); |
---|
1319 | if (mTSnow < mTSlow) {mTSmed = mTSlow; mTSlow = mTSnow;} |
---|
1320 | else if (mTSnow < mTSmed) mTSmed = mTSnow; |
---|
1321 | mTSprod *= mTSnow; |
---|
1322 | mTSsum += mTSnow; |
---|
1323 | } |
---|
1324 | if (renormScale3 == 1) Q2RenSave = mTSlow; |
---|
1325 | else if (renormScale3 == 2) Q2RenSave = sqrt(mTSlow * mTSmed); |
---|
1326 | else if (renormScale3 == 3) Q2RenSave = pow(mTSprod, 1. / nFin); |
---|
1327 | else if (renormScale3 == 4) Q2RenSave = mTSsum / nFin; |
---|
1328 | else Q2RenSave = sH; |
---|
1329 | Q2RenSave *= renormMultFac; |
---|
1330 | if (renormScale3 == 6) Q2RenSave = renormFixScale; |
---|
1331 | if (factorScale3 == 1) Q2FacSave = mTSlow; |
---|
1332 | else if (factorScale3 == 2) Q2FacSave = sqrt(mTSlow * mTSmed); |
---|
1333 | else if (factorScale3 == 3) Q2FacSave = pow(mTSprod, 1. / nFin); |
---|
1334 | else if (factorScale3 == 4) Q2FacSave = mTSsum / nFin; |
---|
1335 | else Q2FacSave = sH; |
---|
1336 | Q2FacSave *= factorMultFac; |
---|
1337 | if (factorScale3 == 6) Q2FacSave = factorFixScale; |
---|
1338 | } |
---|
1339 | } |
---|
1340 | |
---|
1341 | // If alpha_strong and alpha_EM have not been set, then set them. |
---|
1342 | if (lhaUpPtr->alphaQCD() < 0.001) { |
---|
1343 | double Q2RenNow = (scaleLHA < 0.) ? Q2RenSave : pow2(scaleLHA); |
---|
1344 | alpS = couplingsPtr->alphaS(Q2RenNow); |
---|
1345 | } |
---|
1346 | if (lhaUpPtr->alphaQED() < 0.001) { |
---|
1347 | double Q2RenNow = (scaleLHA < 0.) ? Q2RenSave : pow2(scaleLHA); |
---|
1348 | alpEM = couplingsPtr->alphaEM(Q2RenNow); |
---|
1349 | } |
---|
1350 | |
---|
1351 | } |
---|
1352 | |
---|
1353 | //-------------------------------------------------------------------------- |
---|
1354 | |
---|
1355 | // Obtain number of final-state partons from LHA object. |
---|
1356 | |
---|
1357 | int SigmaLHAProcess::nFinal() const { |
---|
1358 | |
---|
1359 | // At initialization size unknown, so return 0. |
---|
1360 | if (lhaUpPtr->sizePart() <= 0) return 0; |
---|
1361 | |
---|
1362 | // Sum up all particles that has first mother = 1. |
---|
1363 | int nFin = 0; |
---|
1364 | for (int i = 3; i < lhaUpPtr->sizePart(); ++i) |
---|
1365 | if (lhaUpPtr->mother1(i) == 1) ++nFin; |
---|
1366 | return nFin; |
---|
1367 | |
---|
1368 | } |
---|
1369 | |
---|
1370 | //========================================================================== |
---|
1371 | |
---|
1372 | } // end namespace Pythia8 |
---|