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368fc61e | 1 | //#include <TClonesArray.h> |
2 | ||
3 | #include <TDatabasePDG.h> | |
4 | #include <TFile.h> | |
5 | #include "AliConst.h" | |
6 | #include "AliGenMUONLMR.h" | |
7 | #include "AliMC.h" | |
8 | #include "AliRun.h" | |
9 | #include "AliGenEventHeader.h" | |
10 | ||
11 | ClassImp(AliGenMUONLMR) | |
12 | ||
0458f038 | 13 | |
14 | AliGenMUONLMR::AliGenMUONLMR () : AliGenMC(), fNMuMin(2), fGenSingleProc(-1), fCosTheta(0), fRhoLineShape(0), fHMultMu(0), fHNProc(0) { | |
368fc61e | 15 | // |
16 | // default constructor | |
17 | // | |
18 | // initialize pt and y distributions according to a fit to | |
19 | // Pythia simulation at sqrt(s) = 7 TeV | |
20 | printf ("Using AliGenMUONLMR as generator\n"); | |
21 | for (Int_t ipart=0; ipart < fgkNpart; ipart++) fScaleMult[ipart] = 1; | |
22 | fScaleMult[kPionLMR] = 0; // set pion multiplicity to zero | |
23 | fScaleMult[kKaonLMR] = 0; // set kaon multiplicity to zero | |
24 | Int_t pdg[7] = {211, 321, 221, 113, 223, 333, 331}; | |
25 | char* fptname[7] = {"fPtPion","fPtKaon","fPtEta","fPtRho","fPtOmega","fPtPhi","fPtEtaPrime"}; | |
26 | char* fyname[7] = {"fYPion","fYKaon","fYEta","fYRho","fYOmega","fYPhi","fYEtaPrime"}; | |
27 | char* fnname[7] = {"fMultPion","fMultKaon","fMultEta","fMultRho","fMultOmega","fMultPhi","fMultEtaPrime"}; | |
28 | char* fdname[2] = {"fDecPion","fDecKaon"}; | |
29 | Double_t ptparam[7][3] = { {1,0.427,2.52}, // pions from Pythia | |
30 | {1,0.58,2.57}, // kaons from Pythia | |
31 | {1,0.641,2.62}, // eta from Pythia | |
32 | {1,1.2,2.5}, // rho+omega from ALICE muon | |
33 | {1,1.2,2.5}, // rho+omega from ALICE muon | |
34 | {1,1.03,2.5}, // phi from ALICE muon | |
35 | {1,0.72,2.5}}; // etaPrime from Pythia | |
36 | ||
37 | Double_t yparam[7][3] = { {1, 0.8251, 3.657}, // pions from pythia | |
38 | {1, 1.83, 2.698}, // kaons from pythia | |
39 | {1, 1.169, 3.282}, // eta from pythia | |
40 | {1, 1.234, 3.264}, // rho from pythia | |
41 | {1, 1.311, 3.223}, // omega from pythia | |
42 | {1, 2.388, 2.129}, // phi from pythia | |
43 | {1, 1.13,3.3}}; // eta prime from pythia | |
44 | ||
45 | // multiplicity parameters from pythia | |
46 | Double_t nparam[7][9] = { {353.582, 6.76263, 1.66979, 998.445, 9.73281, 12.6704, 175.187, 29.08, 40.2531}, | |
47 | {1.e4, 0.2841, 0,0,0,0,0,0,0}, | |
48 | {1.e4, 0.2647, 0,0,0,0,0,0,0}, | |
49 | {7055, 0.1786, 0,0,0,0,0,0,0}, | |
50 | {7500, 0.1896, 0,0,0,0,0,0,0}, | |
51 | {5.e04, 1.167, 0,0,0,0,0,0,0}, | |
52 | {2.9e04,0.714, 0,0,0,0,0,0,0}}; | |
53 | ||
54 | Double_t ctau[2] = {7.8045, 3.712}; | |
55 | ||
56 | for (Int_t i=0; i<fgkNpart; i++) { | |
57 | fPDG[i] = pdg[i]; | |
58 | if (i!=0) { | |
59 | fMult[i] = new TF1(fnname[i],"[0]*exp(-[1]*x)",0,30); | |
60 | fMult[i]->SetParameters(nparam[i][0],nparam[i][1]); | |
61 | } | |
62 | else { | |
63 | fMult[i] = new TF1(fnname[i],"gaus(0)+gaus(3)+gaus(6)",0,150); | |
64 | for (Int_t j=0; j<9; j++) fMult[i]->SetParameter(j,nparam[i][j]); | |
65 | } | |
66 | ||
67 | fPt[i] = new TF1(fptname[i],AliGenMUONLMR::PtDistr,0,20,3); | |
68 | fPt[i]->SetParameters(ptparam[i][0], ptparam[i][1], ptparam[i][2]); | |
69 | fY[i] = new TF1(fyname[i],AliGenMUONLMR::YDistr,-10,10,3); | |
70 | fY[i]->SetParameters(yparam[i][0], yparam[i][1], yparam[i][2]); | |
71 | } | |
72 | ||
73 | for(Int_t i = 0; i<2; i++){ | |
74 | fDecay[i] = new TF1(fdname[i],"exp(-x/[0])",0,150); | |
75 | fDecay[i]->SetParameter(0,ctau[i]); | |
76 | } | |
77 | ||
78 | for (Int_t ipart = 0; ipart < fgkNpart; ipart++) { | |
79 | fParticle[ipart] = new TParticle(); | |
80 | fParticle[ipart]->SetPdgCode(fPDG[ipart]); | |
81 | } | |
82 | ||
83 | TDatabasePDG *pdgdb = TDatabasePDG::Instance(); | |
84 | Double_t mumass = pdgdb->GetParticle(13)->Mass(); | |
85 | fMu[0] = new TParticle(); | |
86 | fMu[0]->SetPdgCode(-13); | |
87 | fMu[0]->SetCalcMass(mumass); | |
88 | fMu[1] = new TParticle(); | |
89 | fMu[1]->SetPdgCode(13); | |
90 | fMu[1]->SetCalcMass(mumass); | |
91 | ||
92 | // function for polarized theta distributions | |
93 | fCosTheta = new TF1 ("fCosTheta","1+[0]*x*x",-1,1); | |
94 | fCosTheta->SetParameter(0,1); | |
95 | ||
96 | // Dalitz decays | |
97 | Int_t nbins = 1000; | |
98 | Double_t xmin = 0, xmax = 2; | |
99 | fDalitz[0] = new TH1F("hDalitzEta","",nbins,xmin,xmax); | |
100 | fDalitz[1] = new TH1F("hDalitzOmega","",nbins,xmin,xmax); | |
101 | fDalitz[2] = new TH1F("hDalitzEtaPrime","",nbins,xmin,xmax); | |
102 | ||
103 | Double_t meta = pdgdb->GetParticle("eta")->Mass(); | |
104 | Double_t momega = pdgdb->GetParticle("omega")->Mass(); | |
105 | Double_t metaPrime = pdgdb->GetParticle("eta'")->Mass(); | |
106 | Double_t mpi0 = pdgdb->GetParticle("pi0")->Mass(); | |
107 | Double_t md3 = 0, mres = 0; | |
108 | ||
109 | for (Int_t index = 0; index < 3; index++) { | |
110 | if (index == 0) { | |
111 | mres = meta; | |
112 | md3 = 0; | |
113 | } | |
114 | else if (index == 1) { | |
115 | mres = momega; | |
116 | md3 = mpi0; | |
117 | } | |
118 | else if (index == 2) { | |
119 | mres = metaPrime; | |
120 | md3 = 0; | |
121 | } | |
122 | Double_t delta = md3 * md3 / (mres * mres); | |
123 | Double_t epsilon = mumass * mumass / (mres * mres); | |
0458f038 | 124 | Int_t nbins0 = fDalitz[index]->GetNbinsX(); |
125 | Double_t xmin0 = fDalitz[index]->GetXaxis()->GetXmin(); | |
368fc61e | 126 | Double_t deltax = fDalitz[index]->GetBinWidth(1); |
0458f038 | 127 | Double_t xd = xmin0 - deltax/2.; |
128 | for (Int_t ibin = 0; ibin< nbins0; ibin++) { | |
368fc61e | 129 | Double_t dalval = 0; |
130 | xd += deltax; | |
131 | if (xd > 4. *epsilon) { | |
132 | Double_t bracket = TMath::Power(1. + xd/(1. - delta),2) | |
133 | - 4. * xd / ((1. - delta) * (1. - delta)); | |
134 | if (bracket > 0) { | |
135 | dalval = TMath::Power(bracket,1.5) /xd * | |
136 | TMath::Sqrt(1 - 4 * epsilon / xd) * (1 + 2 * epsilon / xd) * | |
137 | FormFactor(xd * mres * mres, index); | |
138 | fDalitz[index]->Fill(xd,dalval); | |
139 | } | |
140 | } | |
141 | } | |
142 | } | |
143 | ||
144 | fRhoLineShape = new TF1("fRhoLineShape",RhoLineShapeNew,0,2,2); | |
145 | fHMultMu = new TH1D("fHMultMu","Muon multiplicity",20,-0.5,19.5); | |
146 | fHNProc = new TH1D("fHNProc","Number of gen. evts. per process in 4 pi",9,-0.5,8.5); | |
147 | } | |
148 | ||
149 | //----------------------------------------------------------- | |
150 | ||
151 | AliGenMUONLMR::~AliGenMUONLMR() | |
152 | { | |
153 | // Default destructor | |
154 | for (Int_t i=0; i<7; i++) { | |
155 | delete fPt[i]; | |
156 | delete fY[i]; | |
157 | delete fMult[i]; | |
158 | delete fParticle[i]; | |
159 | } | |
160 | ||
161 | for (Int_t i=0; i<2; i++) { | |
162 | delete fDecay[i]; | |
163 | delete fMu[i]; | |
164 | } | |
165 | ||
166 | for (Int_t i=0; i<3; i++) delete fDalitz[i]; | |
167 | ||
168 | delete fCosTheta; fCosTheta = 0; | |
169 | delete fRhoLineShape; fRhoLineShape = 0; | |
170 | delete fHMultMu; fHMultMu = 0; | |
171 | delete fHNProc; fHNProc = 0; | |
172 | } | |
173 | ||
174 | //----------------------------------------------------------- | |
175 | ||
176 | void AliGenMUONLMR::FinishRun(){ | |
177 | // save some histograms to an output file | |
178 | Int_t nbins = fHNProc->GetNbinsX(); | |
179 | for (Int_t ibin=1; ibin <= nbins; ibin++) printf ("ibin = %d nEvProc = %g\n", | |
180 | ibin,fHNProc->GetBinContent(ibin)); | |
181 | TFile *fout = new TFile("AliGenMUONLMR_histos.root","recreate"); | |
182 | fHMultMu->Write(); | |
183 | fHNProc->Write(); | |
184 | fout->Close(); | |
185 | } | |
186 | ||
187 | //----------------------------------------------------------- | |
188 | ||
189 | Double_t AliGenMUONLMR::YDistr(Double_t *px, Double_t *par){ | |
190 | // function for rapidity distribution: plateau at par[0] + | |
191 | // gaussian tails centered at par[1] and with par[2]=sigma | |
192 | Double_t x = TMath::Abs(px[0]); | |
193 | Double_t func = 0; | |
194 | if (x<par[1]) func = par[0]; | |
195 | else { | |
196 | Double_t z = (x-par[1])/(par[2]); | |
197 | func = par[0] * TMath::Exp(-0.5 * z * z); | |
198 | } | |
199 | return func; | |
200 | } | |
201 | ||
202 | //----------------------------------------------------------- | |
203 | ||
204 | Double_t AliGenMUONLMR::PtDistr(Double_t *px, Double_t *par){ | |
205 | // pt distribution: power law | |
206 | Double_t x = px[0]; | |
207 | Double_t func = par[0] * x / TMath::Power((1+(x/par[1])*(x/par[1])),par[2]); | |
208 | return func; | |
209 | } | |
210 | ||
211 | //----------------------------------------------------------- | |
212 | ||
213 | void AliGenMUONLMR::Generate() { | |
214 | // | |
215 | // generate the low mass resonances and their decays according to | |
216 | // the multiplicity parameterized by pythia and BR from PDG | |
217 | // rapidity distributions parametrized from pythia | |
218 | // pt distributions from data (or pythia for etaprime) | |
219 | // | |
220 | Double_t pxPushed[100], pyPushed[100], pzPushed[100], ePushed[100]; | |
221 | Int_t nmuons = -1, npartPushed = 0, pdgPushed[100]; | |
222 | Double_t polar[3]= {0,0,0}; // Polarisation of the parent particle (for GEANT tracking) | |
223 | Double_t origin0[3]; // Origin of the generated parent particle (for GEANT tracking) | |
224 | // Calculating vertex position per event | |
225 | for (Int_t j=0;j<3;j++) origin0[j]=fOrigin[j]; | |
226 | if(fVertexSmear==kPerEvent) { | |
227 | Vertex(); | |
228 | for (Int_t j=0;j<3;j++) origin0[j]=fVertex[j]; | |
229 | } | |
230 | ||
231 | printf ("In Generate()\n"); | |
232 | TParticle *mother; | |
233 | TDatabasePDG* pdg = TDatabasePDG::Instance(); | |
234 | ||
235 | Double_t pt, y, phi, mass, px, py, pz, ene, mt; | |
236 | ||
237 | const Int_t nproc = 9; | |
238 | Int_t idRes[nproc] = {kEtaLMR, kEtaLMR, kRhoLMR, kOmegaLMR, kOmegaLMR, kPhiLMR, kEtaPrimeLMR, kPionLMR, kKaonLMR}; | |
239 | Double_t BR[nproc] = {5.8e-6, 3.1e-4, 4.55e-5, 7.28e-4, 1.3e-4, 2.86e-4, 1.04e-4, 1, 0.6344}; | |
240 | // Double_t BR[nproc] = {1, 1, 1, 1, 1, 1, 1, 1, 1}; | |
241 | Int_t idDec[nproc] = {0, 1, 0, 0, 1, 0, 1, 2, 2}; // 0:2body, 1:Dalitz, 2:pi/K | |
242 | Int_t mult[nproc] = {0,0,0,0,0,0,0,0,0}; | |
243 | ||
244 | while (nmuons < fNMuMin) { | |
245 | ||
246 | nmuons = 0; | |
247 | npartPushed = 0; | |
248 | for (Int_t iproc=0; iproc<nproc; iproc++) { | |
249 | if (fGenSingleProc == -1) { | |
250 | mult[iproc] = Int_t(fMult[idRes[iproc]]->GetRandom()*fScaleMult[idRes[iproc]]); | |
251 | } | |
252 | else { | |
253 | if (iproc==fGenSingleProc) { | |
254 | mult[iproc] = 1; | |
255 | BR[iproc] = 1; | |
256 | } | |
257 | else { | |
258 | mult[iproc] = 0; | |
259 | BR[iproc] = 0; | |
260 | } | |
261 | } | |
262 | } | |
263 | ||
264 | if (fGenSingleProc == -1) { | |
265 | mult[1] = mult[0]; | |
266 | mult[4] = mult[3]; | |
267 | } | |
268 | ||
269 | for (Int_t iproc = 0; iproc < nproc; iproc++) { | |
270 | // printf ("Multiplicity for process %d is %d\n",iproc,mult[iproc]); | |
271 | for (Int_t imult=0; imult<mult[iproc]; imult++) { | |
272 | if (gRandom->Rndm() < BR[iproc]) { | |
273 | fHNProc->Fill(iproc); | |
274 | Int_t ipart = idRes[iproc]; | |
275 | pt = fPt[ipart]->GetRandom(); | |
276 | y = fY[ipart]->GetRandom(); | |
277 | phi = gRandom->Rndm() * 2 * TMath::Pi(); | |
278 | mass = pdg->GetParticle(fPDG[ipart])->Mass(); | |
279 | px = pt * TMath::Cos(phi); | |
280 | py = pt * TMath::Sin(phi); | |
281 | mt = TMath::Sqrt(pt * pt + mass * mass); | |
282 | pz = mt * TMath::SinH(y); | |
283 | ene = mt * TMath::CosH(y); | |
284 | ||
285 | mother = fParticle[ipart]; | |
286 | mother->SetMomentum(px,py,pz,ene); | |
287 | mother->SetCalcMass(mass); | |
288 | if (!KinematicSelection(mother,0)) continue; | |
289 | ||
290 | Bool_t hasDecayed = kTRUE; | |
291 | if (idDec[iproc] == 0) Decay2Body(mother); | |
292 | else if (idDec[iproc] == 1) DalitzDecay(mother); | |
293 | else DecayPiK(mother,hasDecayed); | |
294 | if (!hasDecayed) continue; | |
295 | Bool_t isMu0Acc = KinematicSelection(fMu[0],1); | |
296 | Bool_t isMu1Acc = KinematicSelection(fMu[1],1); | |
297 | Bool_t isMuFromPiKAcc = kTRUE; | |
298 | ||
299 | if (idDec[iproc] == 2) isMuFromPiKAcc = (mother->GetPdgCode()>0) ? isMu0Acc : isMu1Acc; | |
300 | // mother | |
301 | if ((idDec[iproc] < 2 && (isMu0Acc || isMu1Acc)) || | |
302 | (idDec[iproc] == 2 && isMuFromPiKAcc)) { | |
303 | pdgPushed[npartPushed] = mother->GetPdgCode(); | |
304 | pxPushed[npartPushed] = mother->Px(); | |
305 | pyPushed[npartPushed] = mother->Py(); | |
306 | pzPushed[npartPushed] = mother->Pz(); | |
307 | ePushed[npartPushed] = mother->Energy(); | |
308 | npartPushed++; | |
309 | if (isMu0Acc && (idDec[iproc] < 2 || mother->GetPdgCode() > 0)) { | |
310 | pdgPushed[npartPushed] = fMu[0]->GetPdgCode(); | |
311 | pxPushed[npartPushed] = fMu[0]->Px(); | |
312 | pyPushed[npartPushed] = fMu[0]->Py(); | |
313 | pzPushed[npartPushed] = fMu[0]->Pz(); | |
314 | ePushed[npartPushed] = fMu[0]->Energy(); | |
315 | npartPushed++; | |
316 | nmuons++; | |
317 | } | |
318 | ||
319 | if (isMu1Acc && (idDec[iproc] < 2 || mother->GetPdgCode() < 0)) { | |
320 | pdgPushed[npartPushed] = fMu[1]->GetPdgCode(); | |
321 | pxPushed[npartPushed] = fMu[1]->Px(); | |
322 | pyPushed[npartPushed] = fMu[1]->Py(); | |
323 | pzPushed[npartPushed] = fMu[1]->Pz(); | |
324 | ePushed[npartPushed] = fMu[1]->Energy(); | |
325 | npartPushed++; | |
326 | nmuons++; | |
327 | } | |
328 | } | |
329 | } // end if BR | |
330 | } // end loop on multiplicity | |
331 | } // end loop on process | |
332 | fHMultMu->Fill(nmuons); | |
333 | } // keep on generating until at least a muon is created in the event | |
334 | ||
335 | Int_t ntmother = 0, ntchild =0; | |
336 | for (Int_t ipart = 0; ipart < npartPushed; ipart++) { | |
337 | if (TMath::Abs(pdgPushed[ipart]) != 13) { // particle is not a muon, hence it's a mother | |
338 | PushTrack(0,-1,pdgPushed[ipart], | |
339 | pxPushed[ipart],pyPushed[ipart],pzPushed[ipart],ePushed[ipart], | |
340 | origin0[0],origin0[1],origin0[2],0., | |
341 | polar[0],polar[1],polar[2], | |
342 | kPPrimary,ntmother,1,11); | |
343 | KeepTrack(ntmother); | |
344 | } | |
345 | else { | |
346 | PushTrack(1,ntmother,pdgPushed[ipart], | |
347 | pxPushed[ipart],pyPushed[ipart],pzPushed[ipart],ePushed[ipart], | |
348 | origin0[0],origin0[1],origin0[2],0., | |
349 | polar[0],polar[1],polar[2], | |
350 | kPDecay,ntchild,1,1); | |
351 | KeepTrack(ntchild); | |
352 | } | |
353 | } | |
354 | SetHighWaterMark(ntchild); | |
355 | AliGenEventHeader* header = new AliGenEventHeader("LMR"); | |
356 | header->SetPrimaryVertex(fVertex); | |
357 | header->SetNProduced(fNprimaries); | |
358 | AddHeader(header); | |
359 | } | |
360 | ||
361 | //------------------------------------------------------------------ | |
362 | ||
363 | void AliGenMUONLMR::Decay2Body(TParticle *mother){ | |
364 | // performs decay in two muons of the low mass resonances | |
365 | Double_t md1 = fMu[0]->GetMass(); | |
366 | Int_t pdg = mother->GetPdgCode(); | |
367 | Double_t mres =0; | |
368 | // if mother is a rho, extract the mass from its line shape | |
369 | // otherwise consider the resonance mass | |
370 | if (pdg == 113) mres = fRhoLineShape->GetRandom(); | |
371 | else mres = mother->GetCalcMass(); | |
372 | // while (mres < md1 + md2) mres = fDsigmaDm[res]->GetRandom(); | |
373 | // energies and momenta in rest frame | |
374 | Double_t e1 = mres / 2.; | |
375 | Double_t p1 = TMath::Sqrt((e1 + md1)*(e1 - md1)); | |
376 | // orientation in decaying particle rest frame | |
377 | Double_t costheta = gRandom->Rndm() * 2 - 1; | |
378 | Double_t sintheta = TMath::Sqrt((1. + costheta)*(1. - costheta)); | |
379 | Double_t phi = 2. * TMath::Pi() * gRandom->Rndm(); | |
380 | Double_t px1 = p1 * sintheta * TMath::Cos(phi); | |
381 | Double_t py1 = p1 * sintheta * TMath::Sin(phi); | |
382 | Double_t pz1 = p1 * costheta; | |
383 | ||
384 | // boost muons into lab frame | |
385 | ||
386 | TLorentzVector vmother, v1, v2; | |
387 | // TLorentzVector boosted1, boosted2; | |
388 | vmother.SetPxPyPzE(mother->Px(),mother->Py(),mother->Pz(),mother->Energy()); | |
389 | v1.SetPxPyPzE(px1,py1,pz1,e1); | |
390 | v2.SetPxPyPzE(-px1,-py1,-pz1,e1); | |
391 | ||
392 | TVector3 betaParent = (1./vmother.E())*vmother.Vect(); // beta = p/E | |
393 | v1.Boost(betaParent); | |
394 | v2.Boost(betaParent); | |
395 | ||
396 | // TLorentzVector vtot = v1 + v2; | |
397 | // printf ("mother: %g %g %g %g\n",vmother.Px(), vmother.Py(), vmother.Pz(), vmother.E()); | |
398 | // printf ("vtot : %g %g %g %g\n",vtot.Px(), vtot.Py(), vtot.Pz(), vtot.E()); | |
399 | ||
400 | fMu[0]->SetMomentum(v1.Px(),v1.Py(),v1.Pz(),v1.E()); | |
401 | fMu[1]->SetMomentum(v2.Px(),v2.Py(),v2.Pz(),v2.E()); | |
402 | } | |
403 | ||
404 | //------------------------------------------------------------------ | |
405 | ||
406 | void AliGenMUONLMR::DecayPiK(TParticle *mother, Bool_t &hasDecayed){ | |
407 | // performs decays of pions and kaons | |
408 | Double_t md1 = fMu[0]->GetMass(); | |
409 | // extract the mass from the resonance's line shape | |
410 | Double_t mres = mother->GetMass(); | |
411 | // choose the pi/k sign, assuming 50% probabilities for both signs | |
412 | Int_t sign = (gRandom->Rndm() > 0.5) ? 1 : -1; | |
413 | mother->SetPdgCode(sign * TMath::Abs(mother->GetPdgCode())); | |
414 | ||
415 | // energies and momenta in rest frame | |
416 | Double_t e1 = (mres*mres + md1*md1)/(2*mres); | |
417 | Double_t p1 = TMath::Sqrt((e1 + md1)*(e1 - md1)); | |
418 | // orientation in decaying particle rest frame | |
419 | Double_t costheta = gRandom->Rndm() * 2 - 1; | |
420 | Double_t sintheta = TMath::Sqrt((1. + costheta)*(1. - costheta)); | |
421 | Double_t phi = 2. * TMath::Pi() * gRandom->Rndm(); | |
422 | Double_t px1 = p1 * sintheta * TMath::Cos(phi); | |
423 | Double_t py1 = p1 * sintheta * TMath::Sin(phi); | |
424 | Double_t pz1 = p1 * costheta; | |
425 | ||
426 | // boost muons into lab frame | |
427 | TLorentzVector vmother, v1; | |
428 | vmother.SetPxPyPzE(mother->Px(),mother->Py(),mother->Pz(),mother->Energy()); | |
429 | v1.SetPxPyPzE(px1,py1,pz1,e1); | |
430 | ||
431 | TVector3 betaParent = (1./vmother.E())*vmother.Vect(); // beta = p/E | |
432 | v1.Boost(betaParent); | |
433 | if (mother->GetPdgCode()>0) fMu[0]->SetMomentum(v1.Px(),v1.Py(),v1.Pz(),v1.E()); | |
434 | else fMu[1]->SetMomentum(v1.Px(),v1.Py(),v1.Pz(),v1.E()); | |
435 | ||
436 | Int_t idmother = -1; | |
437 | if (TMath::Abs(mother->GetPdgCode())== 211) idmother = 0; | |
438 | if (TMath::Abs(mother->GetPdgCode())== 321) idmother = 1; | |
439 | Double_t gammaRes = mother->Energy()/mres; | |
440 | Double_t zResCM = fDecay[idmother]->GetRandom(); | |
441 | Double_t zResLab = gammaRes*zResCM; | |
442 | if(zResLab > 0.938) hasDecayed = 0; // 0.938: distance from IP to absorber + lambda_i | |
443 | else hasDecayed = 1; | |
444 | ||
445 | } | |
446 | ||
447 | //------------------------------------------------------------------- | |
448 | ||
449 | void AliGenMUONLMR::DalitzDecay(TParticle *mother){ | |
450 | // | |
451 | // perform dalitz decays of eta, omega and etaprime | |
452 | // | |
453 | //in the rest frame of the virtual photon: | |
454 | Double_t mres = mother->GetCalcMass(); | |
455 | Double_t mumass = fMu[0]->GetMass(); | |
456 | Double_t md3 = 0; // unless differently specified, third particle is a photon | |
457 | if (mother->GetPdgCode() == 223) md3 = 0.134977; // if mother is an omega, third particle is a pi0 | |
458 | Int_t index = -1; | |
459 | if (mother->GetPdgCode() == 221) index = 0; // eta | |
460 | else if (mother->GetPdgCode() == 223) index = 1; // omega | |
461 | else if (mother->GetPdgCode() == 331) index = 2; // etaPrime | |
462 | Int_t flag = 0; | |
463 | Double_t xd=0, mvirt2=0; | |
464 | Double_t countIt = 0; | |
465 | while (flag==0) { | |
466 | xd = fDalitz[index]->GetRandom(); | |
467 | mvirt2 = xd * mres * mres; // mass of virtual photon | |
468 | // check kinematics | |
469 | if (mres - md3 > TMath::Sqrt(mvirt2) && TMath::Sqrt(mvirt2)/2. > mumass) flag=1; | |
470 | if (++countIt>1E11) { | |
471 | mvirt2 = mres * mres * 0.998; | |
472 | break; | |
473 | } | |
474 | } | |
475 | ||
476 | // | |
477 | // Generate muons in virtual photon rest frame. | |
478 | // z axis is the virt. photon direction (before boost) | |
479 | // | |
480 | ||
481 | Double_t e1 = TMath::Sqrt(mvirt2)/2.; // energy of mu1 in the virtual photon frame | |
482 | Double_t psquare = (e1 + mumass)*(e1 - mumass); | |
483 | if (psquare<0) { | |
484 | printf("Error in AliGenMUONLMR::DalitzDecay: sqrt of psquare = %f put to 0\n",psquare); | |
485 | psquare = 0; | |
486 | } | |
487 | Double_t p1 = TMath::Sqrt(psquare); | |
488 | //theta angle between the pos. muon and the virtual photon | |
489 | Double_t costheta = fCosTheta->GetRandom(); | |
490 | if (costheta>1) costheta = 1; | |
491 | if (costheta<-1) costheta = -1; | |
492 | Double_t sintheta = TMath::Sqrt((1. + costheta)*(1. - costheta)); | |
493 | Double_t phi = 2 * TMath::Pi() * gRandom->Rndm(); | |
494 | Double_t sinphi = TMath::Sin(phi); | |
495 | Double_t cosphi = TMath::Cos(phi); | |
496 | ||
497 | // fill 4-vectors of leptons in the virtual photon frame | |
498 | ||
499 | Double_t px1 = p1*sintheta*cosphi; | |
500 | Double_t py1 = p1*sintheta*sinphi; | |
501 | Double_t pz1 = p1*costheta; | |
502 | Double_t px2 = -p1*sintheta*cosphi; | |
503 | Double_t py2 = -p1*sintheta*sinphi; | |
504 | Double_t pz2 = -p1*costheta; | |
505 | Double_t e2 = e1; | |
506 | ||
507 | fMu[0]->SetMomentum(px1,py1,pz1,e1); | |
508 | fMu[1]->SetMomentum(px2,py2,pz2,e2); | |
509 | ||
510 | // calculate components of non-dilepton in CMS of parent resonance | |
511 | ||
512 | Double_t e3 = (mres * mres + md3 * md3 - mvirt2) / (2.*mres); | |
513 | Double_t psquare3 = (e3 + md3)*(e3 - md3); | |
514 | if (psquare3<0) { | |
515 | printf("Error in AliGenMUONLMR::DalitzDecay: sqrt of psquare3 = %f put to 0\n",psquare3); | |
516 | psquare3 = 0; | |
517 | } | |
518 | Double_t p3 = TMath::Sqrt(psquare3); | |
519 | Double_t costheta2 = 2.* gRandom->Rndm() - 1.; // angle between virtual photon and resonance | |
520 | if (costheta2>1) costheta2 = 1; | |
521 | if (costheta2<-1) costheta2 = -1; | |
522 | Double_t sintheta2 = TMath::Sqrt((1. + costheta2)*(1. - costheta2)); | |
523 | Double_t phi2 = 2 * TMath::Pi() * gRandom->Rndm(); | |
524 | Double_t sinphi2 = TMath::Sin(phi2); | |
525 | Double_t cosphi2 = TMath::Cos(phi2); | |
526 | Double_t px3 = p3*sintheta2*cosphi2; | |
527 | Double_t py3 = p3*sintheta2*sinphi2; | |
528 | Double_t pz3 = p3*costheta2; | |
529 | TLorentzVector v3(px3,py3,pz3,e3); | |
530 | ||
531 | sintheta2 = -sintheta2; | |
532 | cosphi2 = -cosphi2; | |
533 | sinphi2 = -sinphi2; | |
534 | ||
535 | Double_t px1new = px1*costheta2*cosphi2 - py1*sinphi2 + pz1*sintheta2*cosphi2; | |
536 | Double_t py1new = px1*costheta2*sinphi2 + py1*cosphi2 + pz1*sintheta2*sinphi2; | |
537 | Double_t pz1new =-px1*sintheta2 + pz1*costheta2; | |
538 | Double_t px2new = px2*costheta2*cosphi2 - py2*sinphi2 + pz2*sintheta2*cosphi2; | |
539 | Double_t py2new = px2*costheta2*sinphi2 + py2*cosphi2 + pz2*sintheta2*sinphi2; | |
540 | Double_t pz2new =-px2*sintheta2 + pz2*costheta2; | |
541 | ||
542 | fMu[0]->SetMomentum(px1new,py1new,pz1new,e1); | |
543 | fMu[1]->SetMomentum(px2new,py2new,pz2new,e2); | |
544 | ||
545 | Double_t evirt = mres - e3; | |
546 | Double_t pxvirt = -px3; | |
547 | Double_t pyvirt = -py3; | |
548 | Double_t pzvirt = -pz3; | |
549 | TLorentzVector vvirt(pxvirt,pyvirt,pzvirt,evirt); | |
550 | TVector3 betaVirt = (1./evirt) * vvirt.Vect(); // virtual photon beta in res frame | |
551 | ||
552 | TLorentzVector v1(px1,py1,pz1,e1); | |
553 | TLorentzVector v2(px2,py2,pz2,e2); | |
554 | ||
555 | // boost the muons in the frame where the resonance is at rest | |
556 | ||
557 | v1.Boost(betaVirt); | |
558 | v2.Boost(betaVirt); | |
559 | ||
560 | // boost muons and third particle in lab frame | |
561 | ||
562 | TLorentzVector vmother(mother->Px(), mother->Py(), mother->Pz(), mother->Energy()); | |
563 | TVector3 resBetaLab = (1./vmother.E())*vmother.Vect(); // eta beta in lab frame | |
564 | v1.Boost(resBetaLab); | |
565 | v2.Boost(resBetaLab); | |
566 | v3.Boost(resBetaLab); | |
567 | vvirt.Boost(resBetaLab); | |
568 | ||
569 | fMu[0]->SetMomentum(v1.Px(),v1.Py(),v1.Pz(),v1.E()); | |
570 | fMu[1]->SetMomentum(v2.Px(),v2.Py(),v2.Pz(),v2.E()); | |
571 | // part3->SetMomentum(v3.Px(),v3.Py(),v3.Pz(),v3.E()); | |
572 | ||
573 | // TLorentzVector vtot = v1 + v2 + v3; | |
574 | // TLorentzVector vdimu = v1 + v2; | |
575 | // printf ("mother: %g %g %g %g\n",vmother.Px(), vmother.Py(), vmother.Pz(), vmother.E()); | |
576 | // printf ("vtot : %g %g %g %g\n",vtot.Px(), vtot.Py(), vtot.Pz(), vtot.E()); | |
577 | // printf ("vvirt : %g %g %g %g\n",vvirt.Px(), vvirt.Py(), vvirt.Pz(), vvirt.E()); | |
578 | // printf ("vdimu : %g %g %g %g\n",vdimu.Px(), vdimu.Py(), vdimu.Pz(), vdimu.E()); | |
579 | ||
580 | } | |
581 | ||
582 | //------------------------------------------------------------------ | |
583 | ||
584 | Double_t AliGenMUONLMR::FormFactor(Double_t q2, Int_t decay){ | |
585 | // Calculates the form factor for Dalitz decays A->B+l+l | |
586 | // Returns: |F(q^2)|^2 | |
587 | // | |
588 | // References: L.G. Landsberg, Physics Reports 128 No.6 (1985) 301-376. | |
589 | ||
590 | Double_t ff2, mass2; | |
591 | Double_t n2, n4, m2; | |
592 | // Lepton-G | |
593 | ||
594 | Double_t lambda2inv = 0; | |
595 | switch (decay) { | |
596 | case 0: // eta -> mu mu gamma | |
597 | // eta -> l+ l- gamma: pole approximation | |
598 | lambda2inv = 1.95; | |
599 | mass2 = fParticle[kEtaLMR]->GetMass() * fParticle[kEtaLMR]->GetMass(); | |
600 | if (q2 < mass2) ff2 = TMath::Power(1./(1.-lambda2inv*q2),2); | |
601 | else ff2 = 0; | |
602 | break; | |
603 | case 1: // omega -> mu mu pi0 | |
604 | // omega -> l+ l- pi0: pole approximation | |
605 | mass2 = fParticle[kOmegaLMR]->GetMass() * fParticle[kOmegaLMR]->GetMass(); | |
606 | lambda2inv = 2.26; | |
607 | if (q2 < mass2) ff2 = TMath::Power(1./(1.-lambda2inv*q2),2); | |
608 | else ff2 = 0; | |
609 | break; | |
610 | case 2: // etaPrime -> mu mu gamma | |
611 | mass2 = fParticle[kEtaPrimeLMR]->GetMass() * fParticle[kEtaPrimeLMR]->GetMass(); | |
612 | // eta' -> l+ l- gamma: Breit-Wigner fitted to data | |
613 | n2 = 0.764 * 0.764; | |
614 | n4 = n2 * n2; | |
615 | m2 = 0.1020 * 0.1020; | |
616 | if (q2 < mass2) ff2 = n4 / (TMath::Power(n2-q2,2) + m2 * n2); | |
617 | else ff2 = 0; | |
618 | break; | |
619 | default: | |
620 | printf ("FormFactor: Decay not found\n"); | |
621 | return 0; | |
622 | break; | |
623 | } | |
624 | return ff2; | |
625 | } | |
626 | ||
627 | //____________________________________________________________ | |
628 | ||
0458f038 | 629 | Double_t AliGenMUONLMR::RhoLineShapeNew(Double_t *x, Double_t* /*para*/){ |
368fc61e | 630 | //new parameterization implemented by Hiroyuki Sako (GSI) |
631 | Double_t mass = *x; | |
632 | double r, GammaTot; | |
633 | Double_t mRho = TDatabasePDG::Instance()->GetParticle("rho0")->Mass(); | |
634 | Double_t mPi = TDatabasePDG::Instance()->GetParticle("pi0")->Mass(); | |
635 | Double_t mMu = TDatabasePDG::Instance()->GetParticle("mu-")->Mass(); | |
636 | Double_t Gamma0 = TDatabasePDG::Instance()->GetParticle("rho0")->Width(); | |
637 | ||
638 | const double Norm = 0.0744416*1.01; | |
639 | // 0.0744416 at m = 0.72297 | |
640 | // is the max number with Norm=1 (for rho) | |
641 | ||
642 | double mThreshold = 2.*mPi; | |
643 | ||
644 | const double T = 0.170; // Assumption of pi+ temperature [GeV/c^2] | |
645 | //const double T = 0.11; // Taken from fit to pi+ temperature [GeV/c^2] | |
646 | // with Reference: LEBC-EHS collab., Z. Phys. C 50 (1991) 405 | |
647 | ||
648 | if (mass < mThreshold) { | |
649 | r = 0.; | |
650 | return r; | |
651 | } | |
652 | ||
653 | double k = sqrt(0.25*mass*mass-(mThreshold/2)*(mThreshold/2)); | |
654 | double k0 = sqrt(0.25*mRho*mRho-(mThreshold/2)*(mThreshold/2)); | |
655 | ||
656 | GammaTot = (k/k0)*(k/k0)*(k/k0)*(mRho/mass)*(mRho/mass)*Gamma0; | |
657 | ||
658 | double FormFactor2 = 1/((mass*mass-mRho*mRho)*(mass*mass-mRho*mRho)+ | |
659 | mass*mass*GammaTot*GammaTot); | |
660 | ||
661 | r = pow(mass,1.5)*pow((1-mThreshold*mThreshold/(mass*mass)),1.5)* | |
662 | ((mass*mass+2*mMu*mMu)/(mass*mass))*(pow((mass*mass-4*mMu*mMu),0.5)/mass)*FormFactor2 | |
663 | *exp(-mass/T)/Norm; | |
664 | ||
665 | return r; | |
666 | } | |
667 | ||
668 |