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b2a297fa 1/*************************************************************************
2* Copyright(c) 1998-2009, ALICE Experiment at CERN, All rights reserved. *
3* *
4* Author: The ALICE Off-line Project. *
5* Contributors are mentioned in the code where appropriate. *
6* *
7* Permission to use, copy, modify and distribute this software and its *
8* documentation strictly for non-commercial purposes is hereby granted *
9* without fee, provided that the above copyright notice appears in all *
10* copies and that both the copyright notice and this permission notice *
11* appear in the supporting documentation. The authors make no claims *
12* about the suitability of this software for any purpose. It is *
13* provided "as is" without express or implied warranty. *
14**************************************************************************/
15
16///////////////////////////////////////////////////////////////////////////
17// //
18// Dielectron Pair class. Internally it makes use of AliKFParticle. //
19// //
20///////////////////////////////////////////////////////////////////////////
21
22
ba15fdfb 23#include <TDatabasePDG.h>
24#include <AliVTrack.h>
25#include <AliVVertex.h>
26#include <AliPID.h>
236e1bda 27#include <AliExternalTrackParam.h>
1750c463 28#include <AliESDEvent.h>
ba15fdfb 29
b2a297fa 30#include "AliDielectronPair.h"
b2a297fa 31
32ClassImp(AliDielectronPair)
33
1750c463 34Double_t AliDielectronPair::fBeamEnergy=-1.;
35
b2a297fa 36AliDielectronPair::AliDielectronPair() :
b2a297fa 37 fType(-1),
a655b716 38 fLabel(-1),
e4339752 39 fPdgCode(0),
b2a297fa 40 fPair(),
572b0139 41 fD1(),
42 fD2(),
b2a297fa 43 fRefD1(),
08b801a6 44 fRefD2(),
45 fKFUsage(kTRUE)
b2a297fa 46{
47 //
48 // Default Constructor
49 //
50
51}
52
53//______________________________________________
54AliDielectronPair::AliDielectronPair(AliVTrack * const particle1, Int_t pid1,
55 AliVTrack * const particle2, Int_t pid2, Char_t type) :
b2a297fa 56 fType(type),
a655b716 57 fLabel(-1),
e4339752 58 fPdgCode(0),
b2a297fa 59 fPair(),
572b0139 60 fD1(),
61 fD2(),
b2a297fa 62 fRefD1(),
08b801a6 63 fRefD2(),
64 fKFUsage(kTRUE)
b2a297fa 65{
66 //
67 // Constructor with tracks
68 //
69 SetTracks(particle1, pid1, particle2, pid2);
70}
71
1201a1a9 72//______________________________________________
73AliDielectronPair::AliDielectronPair(const AliKFParticle * const particle1,
74 const AliKFParticle * const particle2,
75 AliVTrack * const refParticle1,
76 AliVTrack * const refParticle2, Char_t type) :
77 fType(type),
78 fLabel(-1),
e4339752 79 fPdgCode(0),
1201a1a9 80 fPair(),
81 fD1(),
82 fD2(),
83 fRefD1(),
08b801a6 84 fRefD2(),
85 fKFUsage(kTRUE)
1201a1a9 86{
87 //
88 // Constructor with tracks
89 //
90 SetTracks(particle1, particle2,refParticle1,refParticle2);
91}
92
b2a297fa 93//______________________________________________
94AliDielectronPair::~AliDielectronPair()
95{
96 //
97 // Default Destructor
98 //
99
100}
101
102//______________________________________________
103void AliDielectronPair::SetTracks(AliVTrack * const particle1, Int_t pid1,
104 AliVTrack * const particle2, Int_t pid2)
105{
106 //
572b0139 107 // Sort particles by pt, first particle larget Pt
108 // set AliKF daughters and pair
1201a1a9 109 // refParticle1 and 2 are the original tracks. In the case of track rotation
110 // they are needed in the framework
b2a297fa 111 //
112 fPair.Initialize();
572b0139 113 fD1.Initialize();
114 fD2.Initialize();
8df8e382 115
b2a297fa 116 AliKFParticle kf1(*particle1,pid1);
117 AliKFParticle kf2(*particle2,pid2);
572b0139 118
b2a297fa 119 fPair.AddDaughter(kf1);
120 fPair.AddDaughter(kf2);
8df8e382 121
4fae8ef9 122 if (particle1->Pt()>particle2->Pt()){
123 fRefD1 = particle1;
124 fRefD2 = particle2;
125 fD1+=kf1;
126 fD2+=kf2;
127 } else {
128 fRefD1 = particle2;
129 fRefD2 = particle1;
130 fD1+=kf2;
131 fD2+=kf1;
132 }
133}
134//______________________________________________
135void AliDielectronPair::SetGammaTracks(AliVTrack * const particle1, Int_t pid1,
136 AliVTrack * const particle2, Int_t pid2)
137{
138 //
139 // Sort particles by pt, first particle larget Pt
140 // set AliKF daughters and a GAMMA pair
141 // refParticle1 and 2 are the original tracks. In the case of track rotation
142 // they are needed in the framework
143 //
144 fD1.Initialize();
145 fD2.Initialize();
146
147 AliKFParticle kf1(*particle1,pid1);
148 AliKFParticle kf2(*particle2,pid2);
149 fPair.ConstructGamma(kf1,kf2);
150
a655b716 151 if (particle1->Pt()>particle2->Pt()){
152 fRefD1 = particle1;
153 fRefD2 = particle2;
572b0139 154 fD1+=kf1;
155 fD2+=kf2;
a655b716 156 } else {
157 fRefD1 = particle2;
158 fRefD2 = particle1;
572b0139 159 fD1+=kf2;
160 fD2+=kf1;
a655b716 161 }
b2a297fa 162}
163
1201a1a9 164//______________________________________________
165void AliDielectronPair::SetTracks(const AliKFParticle * const particle1,
166 const AliKFParticle * const particle2,
167 AliVTrack * const refParticle1,
168 AliVTrack * const refParticle2)
169{
170 //
171 // Sort particles by pt, first particle larget Pt
172 // set AliKF daughters and pair
173 // refParticle1 and 2 are the original tracks. In the case of track rotation
174 // they are needed in the framework
175 //
176 fPair.Initialize();
177 fD1.Initialize();
178 fD2.Initialize();
179
180 AliKFParticle kf1(*particle1);
181 AliKFParticle kf2(*particle2);
182
183 fPair.AddDaughter(kf1);
184 fPair.AddDaughter(kf2);
185
186 if (kf1.GetPt()>kf2.GetPt()){
187 fRefD1 = refParticle1;
188 fRefD2 = refParticle2;
189 fD1+=kf1;
190 fD2+=kf2;
191 } else {
192 fRefD1 = refParticle2;
193 fRefD2 = refParticle1;
194 fD1+=kf2;
195 fD2+=kf1;
196 }
197}
198
61d106d3 199//______________________________________________
200void AliDielectronPair::GetThetaPhiCM(Double_t &thetaHE, Double_t &phiHE, Double_t &thetaCS, Double_t &phiCS) const
201{
202 //
203 // Calculate theta and phi in helicity and Collins-Soper coordinate frame
204 //
1201a1a9 205 Double_t pxyz1[3]={fD1.GetPx(),fD1.GetPy(),fD1.GetPz()};
206 Double_t pxyz2[3]={fD2.GetPx(),fD2.GetPy(),fD2.GetPz()};
61d106d3 207 Double_t eleMass=AliPID::ParticleMass(AliPID::kElectron);
208 Double_t proMass=AliPID::ParticleMass(AliPID::kProton);
209
1201a1a9 210// AliVParticle *d1 = static_cast<AliVParticle*>(fRefD1.GetObject());
211// AliVParticle *d2 = static_cast<AliVParticle*>(fRefD2.GetObject());
61d106d3 212
1201a1a9 213// d1->PxPyPz(pxyz1);
214// d2->PxPyPz(pxyz2);
61d106d3 215
1750c463 216 TLorentzVector projMom(0.,0.,-fBeamEnergy,TMath::Sqrt(fBeamEnergy*fBeamEnergy+proMass*proMass));
217 TLorentzVector targMom(0.,0., fBeamEnergy,TMath::Sqrt(fBeamEnergy*fBeamEnergy+proMass*proMass));
61d106d3 218
219 // first & second daughter 4-mom
220 TLorentzVector p1Mom(pxyz1[0],pxyz1[1],pxyz1[2],
221 TMath::Sqrt(pxyz1[0]*pxyz1[0]+pxyz1[1]*pxyz1[1]+pxyz1[2]*pxyz1[2]+eleMass*eleMass));
222 TLorentzVector p2Mom(pxyz2[0],pxyz2[1],pxyz2[2],
223 TMath::Sqrt(pxyz2[0]*pxyz2[0]+pxyz2[1]*pxyz2[1]+pxyz2[2]*pxyz2[2]+eleMass*eleMass));
224 // J/Psi 4-momentum vector
225 TLorentzVector motherMom=p1Mom+p2Mom;
226
227 // boost all the 4-mom vectors to the mother rest frame
228 TVector3 beta = (-1.0/motherMom.E())*motherMom.Vect();
229 p1Mom.Boost(beta);
230 p2Mom.Boost(beta);
231 projMom.Boost(beta);
232 targMom.Boost(beta);
233
234 // x,y,z axes
235 TVector3 zAxisHE = (motherMom.Vect()).Unit();
236 TVector3 zAxisCS = ((projMom.Vect()).Unit()-(targMom.Vect()).Unit()).Unit();
237 TVector3 yAxis = ((projMom.Vect()).Cross(targMom.Vect())).Unit();
238 TVector3 xAxisHE = (yAxis.Cross(zAxisHE)).Unit();
239 TVector3 xAxisCS = (yAxis.Cross(zAxisCS)).Unit();
240
241 // fill theta and phi
1201a1a9 242 if(fD1.GetQ()>0){
61d106d3 243 thetaHE = zAxisHE.Dot((p1Mom.Vect()).Unit());
244 thetaCS = zAxisCS.Dot((p1Mom.Vect()).Unit());
245 phiHE = TMath::ATan2((p1Mom.Vect()).Dot(yAxis), (p1Mom.Vect()).Dot(xAxisHE));
246 phiCS = TMath::ATan2((p1Mom.Vect()).Dot(yAxis), (p1Mom.Vect()).Dot(xAxisCS));
247 } else {
248 thetaHE = zAxisHE.Dot((p2Mom.Vect()).Unit());
249 thetaCS = zAxisCS.Dot((p2Mom.Vect()).Unit());
250 phiHE = TMath::ATan2((p2Mom.Vect()).Dot(yAxis), (p2Mom.Vect()).Dot(xAxisHE));
251 phiCS = TMath::ATan2((p2Mom.Vect()).Dot(yAxis), (p2Mom.Vect()).Dot(xAxisCS));
252 }
253}
254
151ddcbc 255//______________________________________________
256void AliDielectronPair::GetRotPair(Double_t &RotPairx, Double_t &RotPairy, Double_t &RotPairz) const
257{
258 // calculation of rotation p1 p2
259 Double_t px1=-9999.,py1=-9999.,pz1=-9999.;
260 Double_t px2=-9999.,py2=-9999.,pz2=-9999.;
261
262 px1 = fD1.GetPx();
263 py1 = fD1.GetPy();
264 pz1 = fD1.GetPz();
265
266 px2 = fD2.GetPx();
267 py2 = fD2.GetPy();
268 pz2 = fD2.GetPz();
269
270 // normal vector of ee plane
271 Double_t pnorx = py1*pz2 - pz1*py2;
272 Double_t pnory = pz1*px2 - px1*pz2;
273 Double_t pnorz = px1*py2 - py1*px2;
274 Double_t pnor = TMath::Sqrt( pnorx*pnorx + pnory*pnory + pnorz*pnorz );
275
276 //unit vector
277 Double_t upnx = -9999.;
278 Double_t upny = -9999.;
279 Double_t upnz = -9999.;
280 if (pnor !=0)
281 {
282 upnx= pnorx/pnor;
283 upny= pnory/pnor;
284 upnz= pnorz/pnor;
285 }
286
287
288 RotPairx = upnx;
289 RotPairy = upny;
290 RotPairz = upnz;
291
292}
293
294
236e1bda 295//______________________________________________
296Double_t AliDielectronPair::PsiPair(Double_t MagField) const
297{
298 //Following idea to use opening of colinear pairs in magnetic field from e.g. PHENIX
299 //to ID conversions. Adapted from AliTRDv0Info class
99345a64 300 Double_t x, y;//, z;
236e1bda 301 x = fPair.GetX();
302 y = fPair.GetY();
99345a64 303 // z = fPair.GetZ();
236e1bda 304
305 Double_t m1[3] = {0,0,0};
306 Double_t m2[3] = {0,0,0};
307
308 m1[0] = fD1.GetPx();
309 m1[1] = fD1.GetPy();
310 m1[2] = fD1.GetPz();
311
312 m2[0] = fD2.GetPx();
313 m2[1] = fD2.GetPy();
314 m2[2] = fD2.GetPz();
315
316 Double_t deltat = 1.;
317 deltat = TMath::ATan(m2[2]/(TMath::Sqrt(m2[0]*m2[0] + m2[1]*m2[1])+1.e-13))-
318 TMath::ATan(m1[2]/(TMath::Sqrt(m1[0]*m1[0] + m1[1]*m1[1])+1.e-13));//difference of angles of the two daughter tracks with z-axis
319
320 Double_t radiussum = TMath::Sqrt(x*x + y*y) + 50;//radius to which tracks shall be propagated
321
322 Double_t mom1Prop[3];
323 Double_t mom2Prop[3];
324
325 AliExternalTrackParam *d1 = static_cast<AliExternalTrackParam*>(fRefD1.GetObject());
326 AliExternalTrackParam *d2 = static_cast<AliExternalTrackParam*>(fRefD2.GetObject());
327
328 AliExternalTrackParam nt(*d1), pt(*d2);
236e1bda 329
330 Double_t fPsiPair = 4.;
331 if(nt.PropagateTo(radiussum,MagField) == 0)//propagate tracks to the outside
332 fPsiPair = -5.;
333 if(pt.PropagateTo(radiussum,MagField) == 0)
334 fPsiPair = -5.;
335 pt.GetPxPyPz(mom1Prop);//Get momentum vectors of tracks after propagation
336 nt.GetPxPyPz(mom2Prop);
337
338
339
340 Double_t pEle =
341 TMath::Sqrt(mom2Prop[0]*mom2Prop[0]+mom2Prop[1]*mom2Prop[1]+mom2Prop[2]*mom2Prop[2]);//absolute momentum val
342 Double_t pPos =
343 TMath::Sqrt(mom1Prop[0]*mom1Prop[0]+mom1Prop[1]*mom1Prop[1]+mom1Prop[2]*mom1Prop[2]);//absolute momentum val
344
345 Double_t scalarproduct =
346 mom1Prop[0]*mom2Prop[0]+mom1Prop[1]*mom2Prop[1]+mom1Prop[2]*mom2Prop[2];//scalar product of propagated posit
347
348 Double_t chipair = TMath::ACos(scalarproduct/(pEle*pPos));//Angle between propagated daughter tracks
349
350 fPsiPair = TMath::Abs(TMath::ASin(deltat/chipair));
351
352 return fPsiPair;
353
354}
355
8df8e382 356//______________________________________________
357Double_t AliDielectronPair::ThetaPhiCM(const AliVParticle* d1, const AliVParticle* d2,
61d106d3 358 const Bool_t isHE, const Bool_t isTheta)
359{
360 // The function calculates theta and phi in the mother rest frame with
8df8e382 361 // respect to the helicity coordinate system and Collins-Soper coordinate system
362 // TO DO: generalize for different decays (only J/Psi->e+e- now)
363
364 // Laboratory frame 4-vectors:
365 // projectile beam & target beam 4-mom
61d106d3 366 Double_t px1=d1->Px();
367 Double_t py1=d1->Py();
368 Double_t pz1=d1->Pz();
369 Double_t px2=d2->Px();
370 Double_t py2=d2->Py();
371 Double_t pz2=d2->Pz();
372 Double_t eleMass=AliPID::ParticleMass(AliPID::kElectron);
373 Double_t proMass=AliPID::ParticleMass(AliPID::kProton);
b2ad74d0 374// printf(" beam energy %f \n ", fBeamEnergy);
1750c463 375 TLorentzVector projMom(0.,0.,-fBeamEnergy,TMath::Sqrt(fBeamEnergy*fBeamEnergy+proMass*proMass));
376 TLorentzVector targMom(0.,0., fBeamEnergy,TMath::Sqrt(fBeamEnergy*fBeamEnergy+proMass*proMass));
8df8e382 377
378 // first & second daughter 4-mom
61d106d3 379 TLorentzVector p1Mom(px1,py1,pz1,TMath::Sqrt(px1*px1+py1*py1+pz1*pz1+eleMass*eleMass));
380 TLorentzVector p2Mom(px2,py2,pz2,TMath::Sqrt(px2*px2+py2*py2+pz2*pz2+eleMass*eleMass));
8df8e382 381 // J/Psi 4-momentum vector
382 TLorentzVector motherMom=p1Mom+p2Mom;
383
384 // boost all the 4-mom vectors to the mother rest frame
385 TVector3 beta = (-1.0/motherMom.E())*motherMom.Vect();
386 p1Mom.Boost(beta);
387 p2Mom.Boost(beta);
388 projMom.Boost(beta);
389 targMom.Boost(beta);
390
391 // x,y,z axes
392 TVector3 zAxis;
393 if(isHE) zAxis = (motherMom.Vect()).Unit();
394 else zAxis = ((projMom.Vect()).Unit()-(targMom.Vect()).Unit()).Unit();
395 TVector3 yAxis = ((projMom.Vect()).Cross(targMom.Vect())).Unit();
396 TVector3 xAxis = (yAxis.Cross(zAxis)).Unit();
397
398 // return either theta or phi
399 if(isTheta) {
400 if(d1->Charge()>0)
401 return zAxis.Dot((p1Mom.Vect()).Unit());
402 else
403 return zAxis.Dot((p2Mom.Vect()).Unit());
404
405 }
406 else {
407 if(d1->Charge()>0)
408 return TMath::ATan2((p1Mom.Vect()).Dot(yAxis), (p1Mom.Vect()).Dot(xAxis));
409 else
410 return TMath::ATan2((p2Mom.Vect()).Dot(yAxis), (p2Mom.Vect()).Dot(xAxis));
411 }
412}
413
414//______________________________________________
415Double_t AliDielectronPair::ThetaPhiCM(const Bool_t isHE, const Bool_t isTheta) const {
416 // The function calculates theta and phi in the mother rest frame with
417 // respect to the helicity coordinate system and Collins-Soper coordinate system
418 // TO DO: generalize for different decays (only J/Psi->e+e- now)
419
420 // Laboratory frame 4-vectors:
421 // projectile beam & target beam 4-mom
45b2b1b8 422 AliVParticle *d1 = static_cast<AliVParticle*>(fRefD1.GetObject());
423 AliVParticle *d2 = static_cast<AliVParticle*>(fRefD2.GetObject());
61d106d3 424
61d106d3 425 Double_t px1=d1->Px();
426 Double_t py1=d1->Py();
427 Double_t pz1=d1->Pz();
428 Double_t px2=d2->Px();
429 Double_t py2=d2->Py();
430 Double_t pz2=d2->Pz();
431 Double_t eleMass=AliPID::ParticleMass(AliPID::kElectron);
432 Double_t proMass=AliPID::ParticleMass(AliPID::kProton);
433
1750c463 434 TLorentzVector projMom(0.,0.,-fBeamEnergy,TMath::Sqrt(fBeamEnergy*fBeamEnergy+proMass*proMass));
435 TLorentzVector targMom(0.,0., fBeamEnergy,TMath::Sqrt(fBeamEnergy*fBeamEnergy+proMass*proMass));
61d106d3 436
437 // first & second daughter 4-mom
438 // first & second daughter 4-mom
439 TLorentzVector p1Mom(px1,py1,pz1,TMath::Sqrt(px1*px1+py1*py1+pz1*pz1+eleMass*eleMass));
440 TLorentzVector p2Mom(px2,py2,pz2,TMath::Sqrt(px2*px2+py2*py2+pz2*pz2+eleMass*eleMass));
8df8e382 441 // J/Psi 4-momentum vector
442 TLorentzVector motherMom=p1Mom+p2Mom;
443
444 // boost all the 4-mom vectors to the mother rest frame
445 TVector3 beta = (-1.0/motherMom.E())*motherMom.Vect();
446 p1Mom.Boost(beta);
447 p2Mom.Boost(beta);
448 projMom.Boost(beta);
449 targMom.Boost(beta);
450
451 // x,y,z axes
452 TVector3 zAxis;
453 if(isHE) zAxis = (motherMom.Vect()).Unit();
454 else zAxis = ((projMom.Vect()).Unit()-(targMom.Vect()).Unit()).Unit();
455 TVector3 yAxis = ((projMom.Vect()).Cross(targMom.Vect())).Unit();
456 TVector3 xAxis = (yAxis.Cross(zAxis)).Unit();
457
458 // return either theta or phi
459 if(isTheta) {
460 if(fD1.GetQ()>0)
461 return zAxis.Dot((p1Mom.Vect()).Unit());
462 else
463 return zAxis.Dot((p2Mom.Vect()).Unit());
464 }
465 else {
466 if(fD1.GetQ()>0)
467 return TMath::ATan2((p1Mom.Vect()).Dot(yAxis), (p1Mom.Vect()).Dot(xAxis));
468 else
469 return TMath::ATan2((p2Mom.Vect()).Dot(yAxis), (p2Mom.Vect()).Dot(xAxis));
470 }
471}
2e02dba4 472//______________________________________________
473Double_t AliDielectronPair::GetCosPointingAngle(const AliVVertex *primVtx) const
474{
475 //
476 // Calculate the poiting angle of the pair to the primary vertex and take the cosine
477 //
478 if(!primVtx) return -1.;
479
480 Double_t deltaPos[3]; //vector between the reference point and the V0 vertex
481 deltaPos[0] = fPair.GetX() - primVtx->GetX();
482 deltaPos[1] = fPair.GetY() - primVtx->GetY();
483 deltaPos[2] = fPair.GetZ() - primVtx->GetZ();
484
485 Double_t momV02 = fPair.GetPx()*fPair.GetPx() + fPair.GetPy()*fPair.GetPy() + fPair.GetPz()*fPair.GetPz();
486 Double_t deltaPos2 = deltaPos[0]*deltaPos[0] + deltaPos[1]*deltaPos[1] + deltaPos[2]*deltaPos[2];
487
488 Double_t cosinePointingAngle = (deltaPos[0]*fPair.GetPx() + deltaPos[1]*fPair.GetPy() + deltaPos[2]*fPair.GetPz()) / TMath::Sqrt(momV02 * deltaPos2);
489
490 return TMath::Abs(cosinePointingAngle);
491
492}
ba15fdfb 493
99345a64 494//______________________________________________
495Double_t AliDielectronPair::GetArmAlpha() const
496{
497 //
498 // Calculate the Armenteros-Podolanski Alpha
499 //
500 Int_t qD1 = fD1.GetQ();
501
502 TVector3 momNeg( (qD1<0?fD1.GetPx():fD2.GetPx()),
503 (qD1<0?fD1.GetPy():fD2.GetPy()),
504 (qD1<0?fD1.GetPz():fD2.GetPz()) );
505 TVector3 momPos( (qD1<0?fD2.GetPx():fD1.GetPx()),
506 (qD1<0?fD2.GetPy():fD1.GetPy()),
507 (qD1<0?fD2.GetPz():fD1.GetPz()) );
508 TVector3 momTot(Px(),Py(),Pz());
509
510 Double_t lQlNeg = momNeg.Dot(momTot)/momTot.Mag();
511 Double_t lQlPos = momPos.Dot(momTot)/momTot.Mag();
512
513 return ((lQlPos - lQlNeg)/(lQlPos + lQlNeg));
514}
515
516//______________________________________________
517Double_t AliDielectronPair::GetArmPt() const
518{
519 //
520 // Calculate the Armenteros-Podolanski Pt
521 //
522 Int_t qD1 = fD1.GetQ();
523
524 TVector3 momNeg( (qD1<0?fD1.GetPx():fD2.GetPx()),
525 (qD1<0?fD1.GetPy():fD2.GetPy()),
526 (qD1<0?fD1.GetPz():fD2.GetPz()) );
527 TVector3 momTot(Px(),Py(),Pz());
528
529 return (momNeg.Perp(momTot));
530}
531
5720c765 532// //______________________________________________
533// Double_t AliDielectronPair::GetLXY(const AliVVertex * const vtx) const
534// {
535// //
536// // Calculate the decay length in XY taking into account the primary vertex position
537// //
538// if(!vtx) return 0;
539// return ( (Xv()-vtx->GetX()) * Px() + (Yv()-vtx->GetY()) * Py() )/Pt() ;
540// }
ba15fdfb 541
5720c765 542// //______________________________________________
543// Double_t AliDielectronPair::GetPseudoProperTime(const AliVVertex * const vtx) const
544// {
545// //
546// // Calculate the pseudo proper time
547// //
548// Double_t lxy=GetLXY(vtx);
549// Double_t psProperDecayLength = lxy*(TDatabasePDG::Instance()->GetParticle(443)->Mass())/Pt();
550// return psProperDecayLength;
551// }
805bd069 552
553
554//______________________________________________
555Double_t AliDielectronPair::PhivPair(Double_t MagField) const
556{
557 //Following idea to use opening of colinear pairs in magnetic field from e.g. PHENIX
558 //to ID conversions. Angle between ee plane and magnetic field is calculated.
559
560 //Define local buffer variables for leg properties
561 Double_t px1=-9999.,py1=-9999.,pz1=-9999.;
562 Double_t px2=-9999.,py2=-9999.,pz2=-9999.;
563
564 if(MagField>0){
565 if(fD1.GetQ()>0){
566 px1 = fD1.GetPx();
567 py1 = fD1.GetPy();
568 pz1 = fD1.GetPz();
569
570 px2 = fD2.GetPx();
571 py2 = fD2.GetPy();
572 pz2 = fD2.GetPz();
573 }else{
574 px1 = fD2.GetPx();
575 py1 = fD2.GetPy();
576 pz1 = fD2.GetPz();
577
578 px2 = fD1.GetPx();
579 py2 = fD1.GetPy();
580 pz2 = fD1.GetPz();
581 }
582 }else{
583 if(fD1.GetQ()>0){
584 px1 = fD2.GetPx();
585 py1 = fD2.GetPy();
586 pz1 = fD2.GetPz();
587
588 px2 = fD1.GetPx();
589 py2 = fD1.GetPy();
590 pz2 = fD1.GetPz();
591 }else{
592 px1 = fD1.GetPx();
593 py1 = fD1.GetPy();
594 pz1 = fD1.GetPz();
595
596 px2 = fD2.GetPx();
597 py2 = fD2.GetPy();
598 pz2 = fD2.GetPz();
599 }
600 }
601
602 Double_t px = px1+px2;
603 Double_t py = py1+py2;
604 Double_t pz = pz1+pz2;
605 Double_t dppair = TMath::Sqrt(px*px+py*py+pz*pz);
606
607 //unit vector of (pep+pem)
608 Double_t pl = dppair;
609 Double_t ux = px/pl;
610 Double_t uy = py/pl;
611 Double_t uz = pz/pl;
612 Double_t ax = uy/TMath::Sqrt(ux*ux+uy*uy);
613 Double_t ay = -ux/TMath::Sqrt(ux*ux+uy*uy);
614
615 //momentum of e+ and e- in (ax,ay,az) axis. Note that az=0 by
616 //definition.
617 //Double_t ptep = iep->Px()*ax + iep->Py()*ay;
618 //Double_t ptem = iem->Px()*ax + iem->Py()*ay;
619
620 Double_t pxep = px1;
621 Double_t pyep = py1;
622 Double_t pzep = pz1;
623 Double_t pxem = px2;
624 Double_t pyem = py2;
625 Double_t pzem = pz2;
626
627 //vector product of pep X pem
628 Double_t vpx = pyep*pzem - pzep*pyem;
629 Double_t vpy = pzep*pxem - pxep*pzem;
630 Double_t vpz = pxep*pyem - pyep*pxem;
631 Double_t vp = sqrt(vpx*vpx+vpy*vpy+vpz*vpz);
632 //Double_t thev = acos(vpz/vp);
633
634 //unit vector of pep X pem
635 Double_t vx = vpx/vp;
636 Double_t vy = vpy/vp;
637 Double_t vz = vpz/vp;
638
639 //The third axis defined by vector product (ux,uy,uz)X(vx,vy,vz)
640 Double_t wx = uy*vz - uz*vy;
641 Double_t wy = uz*vx - ux*vz;
642 //Double_t wz = ux*vy - uy*vx;
643 //Double_t wl = sqrt(wx*wx+wy*wy+wz*wz);
644 // by construction, (wx,wy,wz) must be a unit vector.
645 // measure angle between (wx,wy,wz) and (ax,ay,0). The angle between them
646 // should be small if the pair is conversion
647 //
648 Double_t cosPhiV = wx*ax + wy*ay;
649 Double_t phiv = TMath::ACos(cosPhiV);
650
651 return phiv;
652
653}
654
151ddcbc 655//______________________________________________
f3f5888a 656Double_t AliDielectronPair::PairPlaneAngle() const
151ddcbc 657{
658
659 // Calculate the angle between electron pair plane and VZERO-C reaction plane for 2nd harmonic
f3f5888a 660
151ddcbc 661
662 Double_t px1=-9999.,py1=-9999.,pz1=-9999.;
663 Double_t px2=-9999.,py2=-9999.,pz2=-9999.;
664
665 px1 = fD1.GetPx();
666 py1 = fD1.GetPy();
667 pz1 = fD1.GetPz();
668
669 px2 = fD2.GetPx();
670 py2 = fD2.GetPy();
671 pz2 = fD2.GetPz();
672
673 //p1+p2
674 Double_t px = px1+px2;
675 Double_t py = py1+py2;
f3f5888a 676 //Double_t pz = pz1+pz2;
151ddcbc 677
678 // normal vector of ee plane
679 Double_t pnorx = py1*pz2 - pz1*py2;
680 Double_t pnory = pz1*px2 - px1*pz2;
681 Double_t pnorz = px1*py2 - py1*px2;
682 Double_t pnor = TMath::Sqrt( pnorx*pnorx + pnory*pnory + pnorz*pnorz );
683
684 //unit vector
685 Double_t upnx = -9999.;
686 Double_t upny = -9999.;
07bc5543 687 Double_t upnz = -9999.;
688
151ddcbc 689 if (pnor !=0)
690 {
691 upnx= pnorx/pnor;
692 upny= pnory/pnor;
07bc5543 693 upnz= pnorz/pnor;
151ddcbc 694 }
151ddcbc 695
696 // normal vector of strong magnetic field plane
697 //rotation coordinates (x,y,z)->(x',y',z')
f3f5888a 698 //(p1+p2),(0,0,1)
699 Double_t ax = py;
700 Double_t ay = -px;
701 Double_t az = 0.0;
702
696b423a 703 Double_t denomHelper = ax*ax + ay*ay +az*az;
704 Double_t uax = -9999.;
705 Double_t uay = -9999.;
07bc5543 706 Double_t uaz = -9999.;
696b423a 707 if (denomHelper !=0) {
708 uax = ax/TMath::Sqrt(denomHelper);
709 uay = ay/TMath::Sqrt(denomHelper);
07bc5543 710 uaz = az/TMath::Sqrt(denomHelper);
696b423a 711 }
151ddcbc 712 //PM is the angle between Pair plane and Magnetic field plane
07bc5543 713 Double_t cosPM = upnx*uax + upny*uay + upnz*uaz;
151ddcbc 714 Double_t PM = TMath::ACos(cosPM);
715
716 //keep interval [0,pi/2]
717 if(PM > TMath::Pi()/2){
718 PM -= TMath::Pi();
719 PM *= -1.0;
720
721 }
722 return PM;
723}
b2ad74d0 724
725
1750c463 726//______________________________________________
727void AliDielectronPair::SetBeamEnergy(AliVEvent *ev, Double_t beamEbyHand)
728{
729 //
730 // set the beam energy (by hand in case of AODs)
731 //
732 if(ev->IsA()==AliESDEvent::Class())
733 fBeamEnergy = ((AliESDEvent*)ev)->GetBeamEnergy();
734 else
735 fBeamEnergy = beamEbyHand;
736}
151ddcbc 737
696b423a 738