Fix for event mixing, when it was selecting events out of range of multiplicity cut
[u/mrichter/AliRoot.git] / EVGEN / AliGenMUONLMR.cxx
CommitLineData
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
11ClassImp(AliGenMUONLMR)
12
0458f038 13
14AliGenMUONLMR::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
151AliGenMUONLMR::~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
176void 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
189Double_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
204Double_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
213void 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
363void 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
406void 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
449void 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
584Double_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 629Double_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