1 /**************************************************************************
2 * Copyright(c) 1998-1999, ALICE Experiment at CERN, All rights reserved. *
4 * Author: The ALICE Off-line Project. *
5 * Contributors are mentioned in the code where appropriate. *
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 **************************************************************************/
18 //-------------------------------------------------------------------------
19 // Implementation of the ESD V0 vertex class
20 // This class is part of the Event Data Summary
21 // set of classes and contains information about
22 // V0 kind vertexes generated by a neutral particle
23 // Origin: Iouri Belikov, IReS, Strasbourg, Jouri.Belikov@cern.ch
24 // Modified by: Marian Ivanov, CERN, Marian.Ivanov@cern.ch
25 // and Boris Hippolyte,IPHC, hippolyt@in2p3.fr
26 //-------------------------------------------------------------------------
28 #include <Riostream.h>
30 #include <TDatabasePDG.h>
32 #include <TParticlePDG.h>
36 #include "AliExternalTrackParam.h"
40 const AliESDV0Params AliESDv0::fgkParams;
42 AliESDv0::AliESDv0() :
46 fEffMass(TDatabasePDG::Instance()->GetParticle(kK0Short)->Mass()),
64 //--------------------------------------------------------------------
65 // Default constructor (K0s)
66 //--------------------------------------------------------------------
68 for (Int_t i=0; i<3; i++) {
74 for (Int_t i=0; i<6; i++) {
78 for (Int_t i=0;i<6;i++){fClusters[0][i]=0; fClusters[1][i]=0;}
79 fNormDCAPrim[0]=fNormDCAPrim[1]=0;
80 for (Int_t i=0;i<3;i++){fAngle[i]=0;}
81 for (Int_t i=0;i<4;i++){fCausality[i]=0;}
84 AliESDv0::AliESDv0(const AliESDv0& v0) :
88 fEffMass(v0.fEffMass),
89 fDcaV0Daughters(v0.fDcaV0Daughters),
92 fDistSigma(v0.fDistSigma),
93 fChi2Before(v0.fChi2Before),
94 fChi2After(v0.fChi2After),
95 fPointAngleFi(v0.fPointAngleFi),
96 fPointAngleTh(v0.fPointAngleTh),
97 fPointAngle(v0.fPointAngle),
98 fPdgCode(v0.fPdgCode),
102 fNBefore(v0.fNBefore),
104 fOnFlyStatus(v0.fOnFlyStatus)
106 //--------------------------------------------------------------------
107 // The copy constructor
108 //--------------------------------------------------------------------
110 for (int i=0; i<3; i++) {
111 fPos[i] = v0.fPos[i];
112 fNmom[i] = v0.fNmom[i];
113 fPmom[i] = v0.fPmom[i];
115 for (int i=0; i<6; i++) {
116 fPosCov[i] = v0.fPosCov[i];
119 for (Int_t i=0; i<2; i++) {
120 fNormDCAPrim[i]=v0.fNormDCAPrim[i];
122 for (Int_t i=0;i<6;i++){
123 fClusters[0][i]=v0.fClusters[0][i];
124 fClusters[1][i]=v0.fClusters[1][i];
126 for (Int_t i=0;i<3;i++){
127 fAngle[i]=v0.fAngle[i];
129 for (Int_t i=0;i<4;i++){fCausality[i]=v0.fCausality[i];}
133 AliESDv0::AliESDv0(const AliExternalTrackParam &t1, Int_t i1,
134 const AliExternalTrackParam &t2, Int_t i2) :
138 fEffMass(TDatabasePDG::Instance()->GetParticle(kK0Short)->Mass()),
156 //--------------------------------------------------------------------
157 // Main constructor (K0s)
158 //--------------------------------------------------------------------
160 for (Int_t i=0; i<6; i++) {
164 //Trivial estimation of the vertex parameters
165 Double_t alpha=t1.GetAlpha(), cs=TMath::Cos(alpha), sn=TMath::Sin(alpha);
168 Double_t px1=tmp[0], py1=tmp[1], pz1=tmp[2];
170 Double_t x1=tmp[0], y1=tmp[1], z1=tmp[2];
171 const Double_t ss=0.0005*0.0005;//a kind of a residual misalignment precision
172 Double_t sx1=sn*sn*t1.GetSigmaY2()+ss, sy1=cs*cs*t1.GetSigmaY2()+ss;
175 alpha=t2.GetAlpha(); cs=TMath::Cos(alpha); sn=TMath::Sin(alpha);
177 Double_t px2=tmp[0], py2=tmp[1], pz2=tmp[2];
179 Double_t x2=tmp[0], y2=tmp[1], z2=tmp[2];
180 Double_t sx2=sn*sn*t2.GetSigmaY2()+ss, sy2=cs*cs*t2.GetSigmaY2()+ss;
182 Double_t sz1=t1.GetSigmaZ2(), sz2=t2.GetSigmaZ2();
183 Double_t wx1=sx2/(sx1+sx2), wx2=1.- wx1;
184 Double_t wy1=sy2/(sy1+sy2), wy2=1.- wy1;
185 Double_t wz1=sz2/(sz1+sz2), wz2=1.- wz1;
186 fPos[0]=wx1*x1 + wx2*x2; fPos[1]=wy1*y1 + wy2*y2; fPos[2]=wz1*z1 + wz2*z2;
188 //fPos[0]=0.5*(x1+x2); fPos[1]=0.5*(y1+y2); fPos[2]=0.5*(z1+z2);
189 fNmom[0]=px1; fNmom[1]=py1; fNmom[2]=pz1;
190 fPmom[0]=px2; fPmom[1]=py2; fPmom[2]=pz2;
192 for (Int_t i=0;i<6;i++){fClusters[0][i]=0; fClusters[1][i]=0;}
193 fNormDCAPrim[0]=fNormDCAPrim[1]=0;
194 for (Int_t i=0;i<3;i++){fAngle[i]=0;}
195 for (Int_t i=0;i<4;i++){fCausality[i]=0;}
198 AliESDv0& AliESDv0::operator=(const AliESDv0 &v0){
201 //--------------------------------------------------------------------
202 // The assingment operator
203 //--------------------------------------------------------------------
205 if(this==&v0)return *this;
206 TObject::operator=(v0);
207 fParamN = v0.fParamN;
208 fParamP = v0.fParamP;
209 fEffMass = v0.fEffMass;
210 fDcaV0Daughters = v0.fDcaV0Daughters;
211 fChi2V0 = v0.fChi2V0;
213 fDistSigma = v0.fDistSigma;
214 fChi2Before = v0.fChi2Before;
215 fChi2After = v0.fChi2After;
216 fPointAngleFi = v0.fPointAngleFi;
217 fPointAngleTh = v0.fPointAngleTh;
218 fPointAngle = v0.fPointAngle;
219 fPdgCode = v0.fPdgCode;
222 fStatus = v0.fStatus;
223 fNBefore = v0.fNBefore;
224 fNAfter = v0.fNAfter;
225 fOnFlyStatus = v0.fOnFlyStatus;
227 for (int i=0; i<3; i++) {
228 fPos[i] = v0.fPos[i];
229 fNmom[i] = v0.fNmom[i];
230 fPmom[i] = v0.fPmom[i];
232 for (int i=0; i<6; i++) {
233 fPosCov[i] = v0.fPosCov[i];
235 for (Int_t i=0; i<2; i++) {
236 fNormDCAPrim[i]=v0.fNormDCAPrim[i];
238 for (Int_t i=0;i<6;i++){
239 fClusters[0][i]=v0.fClusters[0][i];
240 fClusters[1][i]=v0.fClusters[1][i];
242 for (Int_t i=0;i<3;i++){
243 fAngle[i]=v0.fAngle[i];
245 for (Int_t i=0;i<4;i++){fCausality[i]=v0.fCausality[i];}
250 void AliESDv0::Copy(TObject& obj) const {
252 // this overwrites the virtual TOBject::Copy()
253 // to allow run time copying without casting
256 if(this==&obj)return;
257 AliESDv0 *robj = dynamic_cast<AliESDv0*>(&obj);
258 if(!robj)return; // not an aliesesv0
263 AliESDv0::~AliESDv0(){
264 //--------------------------------------------------------------------
266 //--------------------------------------------------------------------
271 Double_t AliESDv0::ChangeMassHypothesis(Int_t code) {
272 //--------------------------------------------------------------------
273 // This function changes the mass hypothesis for this V0
274 // and returns the "kinematical quality" of this hypothesis
275 //--------------------------------------------------------------------
277 Double_t piMass=TDatabasePDG::Instance()->GetParticle(kPiPlus)->Mass();
279 Double_t prMass=TDatabasePDG::Instance()->GetParticle(kProton)->Mass();
281 Double_t k0Mass=TDatabasePDG::Instance()->GetParticle(kK0Short)->Mass();
283 Double_t l0Mass=TDatabasePDG::Instance()->GetParticle(kLambda0)->Mass();
285 Double_t nmass=piMass, pmass=piMass, mass=k0Mass, ps=0.206;
291 nmass=piMass; pmass=prMass; mass=l0Mass; ps=0.101; break;
293 pmass=piMass; nmass=prMass; mass=l0Mass; ps=0.101; break;
297 AliError("invalide PDG code ! Assuming K0s...");
302 Double_t pxn=fNmom[0], pyn=fNmom[1], pzn=fNmom[2];
303 Double_t pxp=fPmom[0], pyp=fPmom[1], pzp=fPmom[2];
305 Double_t en=TMath::Sqrt(nmass*nmass + pxn*pxn + pyn*pyn + pzn*pzn);
306 Double_t ep=TMath::Sqrt(pmass*pmass + pxp*pxp + pyp*pyp + pzp*pzp);
307 Double_t pxl=pxn+pxp, pyl=pyn+pyp, pzl=pzn+pzp;
308 Double_t pl=TMath::Sqrt(pxl*pxl + pyl*pyl + pzl*pzl);
310 fEffMass=TMath::Sqrt((en+ep)*(en+ep)-pl*pl);
312 Double_t beta=pl/(en+ep);
313 Double_t pln=(pxn*pxl + pyn*pyl + pzn*pzl)/pl;
314 Double_t plp=(pxp*pxl + pyp*pyl + pzp*pzl)/pl;
316 Double_t pt2=pxp*pxp + pyp*pyp + pzp*pzp - plp*plp;
318 Double_t a=(plp-pln)/(plp+pln);
319 a -= (pmass*pmass-nmass*nmass)/(mass*mass);
320 a = 0.25*beta*beta*mass*mass*a*a + pt2;
326 void AliESDv0::GetPxPyPz(Double_t &px, Double_t &py, Double_t &pz) const {
327 //--------------------------------------------------------------------
328 // This function returns V0's momentum (global)
329 //--------------------------------------------------------------------
330 px=fNmom[0]+fPmom[0];
331 py=fNmom[1]+fPmom[1];
332 pz=fNmom[2]+fPmom[2];
335 void AliESDv0::GetXYZ(Double_t &x, Double_t &y, Double_t &z) const {
336 //--------------------------------------------------------------------
337 // This function returns V0's position (global)
338 //--------------------------------------------------------------------
344 Float_t AliESDv0::GetD(Double_t x0, Double_t y0, Double_t z0) const {
345 //--------------------------------------------------------------------
346 // This function returns V0's impact parameter
347 //--------------------------------------------------------------------
348 Double_t x=fPos[0],y=fPos[1],z=fPos[2];
349 Double_t px=fNmom[0]+fPmom[0];
350 Double_t py=fNmom[1]+fPmom[1];
351 Double_t pz=fNmom[2]+fPmom[2];
353 Double_t dx=(y0-y)*pz - (z0-z)*py;
354 Double_t dy=(x0-x)*pz - (z0-z)*px;
355 Double_t dz=(x0-x)*py - (y0-y)*px;
356 Double_t d=TMath::Sqrt((dx*dx+dy*dy+dz*dz)/(px*px+py*py+pz*pz));
361 Float_t AliESDv0::GetV0CosineOfPointingAngle(Double_t& refPointX, Double_t& refPointY, Double_t& refPointZ) const {
362 // calculates the pointing angle of the V0 wrt a reference point
364 Double_t momV0[3]; //momentum of the V0
365 GetPxPyPz(momV0[0],momV0[1],momV0[2]);
367 Double_t deltaPos[3]; //vector between the reference point and the V0 vertex
368 deltaPos[0] = fPos[0] - refPointX;
369 deltaPos[1] = fPos[1] - refPointY;
370 deltaPos[2] = fPos[2] - refPointZ;
372 Double_t momV02 = momV0[0]*momV0[0] + momV0[1]*momV0[1] + momV0[2]*momV0[2];
373 Double_t deltaPos2 = deltaPos[0]*deltaPos[0] + deltaPos[1]*deltaPos[1] + deltaPos[2]*deltaPos[2];
375 Double_t cosinePointingAngle = (deltaPos[0]*momV0[0] +
376 deltaPos[1]*momV0[1] +
377 deltaPos[2]*momV0[2] ) /
378 TMath::Sqrt(momV02 * deltaPos2);
380 return cosinePointingAngle;
384 // **** The following functions need to be revised
386 void AliESDv0::GetPosCov(Double_t cov[6]) const {
388 for (Int_t i=0; i<6; ++i) cov[i] = fPosCov[i];
392 Double_t AliESDv0::GetSigmaY(){
394 // return sigmay in y at vertex position using covariance matrix
396 const Double_t * cp = fParamP.GetCovariance();
397 const Double_t * cm = fParamN.GetCovariance();
398 Double_t sigmay = cp[0]+cm[0]+ cp[5]*(fParamP.GetX()-fRr)*(fParamP.GetX()-fRr)+ cm[5]*(fParamN.GetX()-fRr)*(fParamN.GetX()-fRr);
399 return (sigmay>0) ? TMath::Sqrt(sigmay):100;
402 Double_t AliESDv0::GetSigmaZ(){
404 // return sigmay in y at vertex position using covariance matrix
406 const Double_t * cp = fParamP.GetCovariance();
407 const Double_t * cm = fParamN.GetCovariance();
408 Double_t sigmaz = cp[2]+cm[2]+ cp[9]*(fParamP.GetX()-fRr)*(fParamP.GetX()-fRr)+ cm[9]*(fParamN.GetX()-fRr)*(fParamN.GetX()-fRr);
409 return (sigmaz>0) ? TMath::Sqrt(sigmaz):100;
412 Double_t AliESDv0::GetSigmaD0(){
414 // Sigma parameterization using covariance matrix
416 // sigma of distance between two tracks in vertex position
417 // sigma of DCA is proportianal to sigmaD0
418 // factor 2 difference is explained by the fact that the DCA is calculated at the position
419 // where the tracks as closest together ( not exact position of the vertex)
421 const Double_t * cp = fParamP.GetCovariance();
422 const Double_t * cm = fParamN.GetCovariance();
423 Double_t sigmaD0 = cp[0]+cm[0]+cp[2]+cm[2]+fgkParams.fPSigmaOffsetD0*fgkParams.fPSigmaOffsetD0;
424 sigmaD0 += ((fParamP.GetX()-fRr)*(fParamP.GetX()-fRr))*(cp[5]+cp[9]);
425 sigmaD0 += ((fParamN.GetX()-fRr)*(fParamN.GetX()-fRr))*(cm[5]+cm[9]);
426 return (sigmaD0>0)? TMath::Sqrt(sigmaD0):100;
430 Double_t AliESDv0::GetSigmaAP0(){
432 //Sigma parameterization using covariance matrices
434 Double_t prec = TMath::Sqrt((fNmom[0]+fPmom[0])*(fNmom[0]+fPmom[0])
435 +(fNmom[1]+fPmom[1])*(fNmom[1]+fPmom[1])
436 +(fNmom[2]+fPmom[2])*(fNmom[2]+fPmom[2]));
437 Double_t normp = TMath::Sqrt(fPmom[0]*fPmom[0]+fPmom[1]*fPmom[1]+fPmom[2]*fPmom[2])/prec; // fraction of the momenta
438 Double_t normm = TMath::Sqrt(fNmom[0]*fNmom[0]+fNmom[1]*fNmom[1]+fNmom[2]*fNmom[2])/prec;
439 const Double_t * cp = fParamP.GetCovariance();
440 const Double_t * cm = fParamN.GetCovariance();
441 Double_t sigmaAP0 = fgkParams.fPSigmaOffsetAP0*fgkParams.fPSigmaOffsetAP0; // minimal part
442 sigmaAP0 += (cp[5]+cp[9])*(normp*normp)+(cm[5]+cm[9])*(normm*normm); // angular resolution part
443 Double_t sigmaAP1 = GetSigmaD0()/(TMath::Abs(fRr)+0.01); // vertex position part
444 sigmaAP0 += 0.5*sigmaAP1*sigmaAP1;
445 return (sigmaAP0>0)? TMath::Sqrt(sigmaAP0):100;
448 Double_t AliESDv0::GetEffectiveSigmaD0(){
450 // minimax - effective Sigma parameterization
451 // p12 effective curvature and v0 radius postion used as parameters
453 Double_t p12 = TMath::Sqrt(fParamP.GetParameter()[4]*fParamP.GetParameter()[4]+
454 fParamN.GetParameter()[4]*fParamN.GetParameter()[4]);
455 Double_t sigmaED0= TMath::Max(TMath::Sqrt(fRr)-fgkParams.fPSigmaRminDE,0.0)*fgkParams.fPSigmaCoefDE*p12*p12;
458 sigmaED0 = TMath::Sqrt(sigmaED0+fgkParams.fPSigmaOffsetDE*fgkParams.fPSigmaOffsetDE);
459 return (sigmaED0<fgkParams.fPSigmaMaxDE) ? sigmaED0: fgkParams.fPSigmaMaxDE;
463 Double_t AliESDv0::GetEffectiveSigmaAP0(){
465 // effective Sigma parameterization of point angle resolution
467 Double_t p12 = TMath::Sqrt(fParamP.GetParameter()[4]*fParamP.GetParameter()[4]+
468 fParamN.GetParameter()[4]*fParamN.GetParameter()[4]);
469 Double_t sigmaAPE= fgkParams.fPSigmaBase0APE;
470 sigmaAPE+= fgkParams.fPSigmaR0APE/(fgkParams.fPSigmaR1APE+fRr);
471 sigmaAPE*= (fgkParams.fPSigmaP0APE+fgkParams.fPSigmaP1APE*p12);
472 sigmaAPE = TMath::Min(sigmaAPE,fgkParams.fPSigmaMaxAPE);
477 Double_t AliESDv0::GetMinimaxSigmaAP0(){
479 // calculate mini-max effective sigma of point angle resolution
481 //compv0->fTree->SetAlias("SigmaAP2","max(min((SigmaAP0+SigmaAPE0)*0.5,1.5*SigmaAPE0),0.5*SigmaAPE0+0.003)");
482 Double_t effectiveSigma = GetEffectiveSigmaAP0();
483 Double_t sigmaMMAP = 0.5*(GetSigmaAP0()+effectiveSigma);
484 sigmaMMAP = TMath::Min(sigmaMMAP, fgkParams.fPMaxFractionAP0*effectiveSigma);
485 sigmaMMAP = TMath::Max(sigmaMMAP, fgkParams.fPMinFractionAP0*effectiveSigma+fgkParams.fPMinAP0);
488 Double_t AliESDv0::GetMinimaxSigmaD0(){
490 // calculate mini-max sigma of dca resolution
492 //compv0->fTree->SetAlias("SigmaD2","max(min((SigmaD0+SigmaDE0)*0.5,1.5*SigmaDE0),0.5*SigmaDE0)");
493 Double_t effectiveSigma = GetEffectiveSigmaD0();
494 Double_t sigmaMMD0 = 0.5*(GetSigmaD0()+effectiveSigma);
495 sigmaMMD0 = TMath::Min(sigmaMMD0, fgkParams.fPMaxFractionD0*effectiveSigma);
496 sigmaMMD0 = TMath::Max(sigmaMMD0, fgkParams.fPMinFractionD0*effectiveSigma+fgkParams.fPMinD0);
501 Double_t AliESDv0::GetLikelihoodAP(Int_t mode0, Int_t mode1){
503 // get likelihood for point angle
505 Double_t sigmaAP = 0.007; //default sigma
508 sigmaAP = GetSigmaAP0(); // mode 0 - covariance matrix estimates used
511 sigmaAP = GetEffectiveSigmaAP0(); // mode 1 - effective sigma used
514 sigmaAP = GetMinimaxSigmaAP0(); // mode 2 - minimax sigma
517 Double_t apNorm = TMath::Min(TMath::ACos(fPointAngle)/sigmaAP,50.);
518 //normalized point angle, restricted - because of overflow problems in Exp
519 Double_t likelihood = 0;
522 likelihood = TMath::Exp(-0.5*apNorm*apNorm);
526 likelihood = (TMath::Exp(-0.5*apNorm*apNorm)+0.5* TMath::Exp(-0.25*apNorm*apNorm))/1.5;
530 likelihood = (TMath::Exp(-0.5*apNorm*apNorm)+0.5* TMath::Exp(-0.25*apNorm*apNorm)+0.25*TMath::Exp(-0.125*apNorm*apNorm))/1.75;
537 Double_t AliESDv0::GetLikelihoodD(Int_t mode0, Int_t mode1){
539 // get likelihood for DCA
541 Double_t sigmaD = 0.03; //default sigma
544 sigmaD = GetSigmaD0(); // mode 0 - covariance matrix estimates used
547 sigmaD = GetEffectiveSigmaD0(); // mode 1 - effective sigma used
550 sigmaD = GetMinimaxSigmaD0(); // mode 2 - minimax sigma
554 //Bo: Double_t dNorm = TMath::Min(fDist2/sigmaD,50.);
555 Double_t dNorm = TMath::Min(fDcaV0Daughters/sigmaD,50.);//Bo:
556 //normalized point angle, restricted - because of overflow problems in Exp
557 Double_t likelihood = 0;
560 likelihood = TMath::Exp(-2.*dNorm);
564 likelihood = (TMath::Exp(-2.*dNorm)+0.5* TMath::Exp(-dNorm))/1.5;
568 likelihood = (TMath::Exp(-2.*dNorm)+0.5* TMath::Exp(-dNorm)+0.25*TMath::Exp(-0.5*dNorm))/1.75;
576 Double_t AliESDv0::GetLikelihoodC(Int_t mode0, Int_t /*mode1*/){
578 // get likelihood for Causality
579 // !!! Causality variables defined in AliITStrackerMI !!!
580 // when more information was available
582 Double_t likelihood = 0.5;
583 Double_t minCausal = TMath::Min(fCausality[0],fCausality[1]);
584 Double_t maxCausal = TMath::Max(fCausality[0],fCausality[1]);
585 // minCausal = TMath::Max(minCausal,0.5*maxCausal);
586 //compv0->fTree->SetAlias("LCausal","(1.05-(2*(0.8-exp(-max(RC.fV0rec.fCausality[0],RC.fV0rec.fCausality[1])))+2*(0.8-exp(-min(RC.fV0rec.fCausality[0],RC.fV0rec.fCausality[1]))))/2)**4");
591 likelihood = TMath::Power((1.05-2*(0.8-TMath::Exp(-maxCausal))),4.);
594 likelihood = TMath::Power(1.05-(2*(0.8-TMath::Exp(-maxCausal))+(2*(0.8-TMath::Exp(-minCausal))))*0.5,4.);
601 void AliESDv0::SetCausality(Float_t pb0, Float_t pb1, Float_t pa0, Float_t pa1)
606 fCausality[0] = pb0; // probability - track 0 exist before vertex
607 fCausality[1] = pb1; // probability - track 1 exist before vertex
608 fCausality[2] = pa0; // probability - track 0 exist close after vertex
609 fCausality[3] = pa1; // probability - track 1 exist close after vertex
611 void AliESDv0::SetClusters(Int_t *clp, Int_t *clm)
614 // Set its clusters indexes
616 for (Int_t i=0;i<6;i++) fClusters[0][i] = clp[i];
617 for (Int_t i=0;i<6;i++) fClusters[1][i] = clm[i];
620 Float_t AliESDv0::GetEffMass(UInt_t p1, UInt_t p2){
622 // calculate effective mass
624 const Float_t kpmass[5] = {5.10000000000000037e-04,1.05660000000000004e-01,1.39570000000000000e-01,
625 4.93599999999999983e-01, 9.38270000000000048e-01};
628 Float_t mass1 = kpmass[p1];
629 Float_t mass2 = kpmass[p2];
630 Double_t *m1 = fPmom;
631 Double_t *m2 = fNmom;
633 //if (fRP[p1]+fRM[p2]<fRP[p2]+fRM[p1]){
638 Float_t e1 = TMath::Sqrt(mass1*mass1+
642 Float_t e2 = TMath::Sqrt(mass2*mass2+
647 (m2[0]+m1[0])*(m2[0]+m1[0])+
648 (m2[1]+m1[1])*(m2[1]+m1[1])+
649 (m2[2]+m1[2])*(m2[2]+m1[2]);
651 mass = TMath::Sqrt((e1+e2)*(e1+e2)-mass);