[u/mrichter/AliRoot.git] / PWG3 / AliBtoJPSItoEle.cxx

/**************************************************************************
 * Copyright(c) 1998-1999, ALICE Experiment at CERN, All rights reserved. *
 *                                                                        *
 * Author: The ALICE Off-line Project.                                    *
 * Contributors are mentioned in the code where appropriate.              *
 *                                                                        *
 * Permission to use, copy, modify and distribute this software and its   *
 * documentation strictly for non-commercial purposes is hereby granted   *
 * without fee, provided that the above copyright notice appears in all   *
 * copies and that both the copyright notice and this permission notice   *
 * appear in the supporting documentation. The authors make no claims     *
 * about the suitability of this software for any purpose. It is          *
 * provided "as is" without express or implied warranty.                  *
 **************************************************************************/

//----------------------------------------------------------------------------
//               Implementation of the BtoJPSItoEle class
//                  for pp and PbPb interactions
// Note: the two decay tracks are labelled: 0 (positive electron)
//                                          1 (negative electron)
//            Origin: G.E. Bruno    giuseppe.bruno@ba.infn.it            
//  based on Class for charm golden channel (D0->Kpi)
//----------------------------------------------------------------------------

// #include <Riostream.h> // for debugging

#include <TH1.h>
#include <TH2.h>
#include <TCanvas.h>
#include <TPaveLabel.h>
#include <TVector3.h>

#include "AliBtoJPSItoEle.h"

ClassImp(AliBtoJPSItoEle)

//----------------------------------------------------------------------------
AliBtoJPSItoEle::AliBtoJPSItoEle() {
  // Default constructor
  
  fSignal = kFALSE;
  fJpsiPrimary = kFALSE;

  fEvent = 0;

  fTrkNum[0] = 0;
  fTrkNum[1] = 0;

  fV1x = 0.;
  fV1y = 0.;
  fV1z = 0.;
  fV2x = 0.;
  fV2y = 0.;
  fV2z = 0.;
  fDCA = 0.;

  fPx[0] = 0.;
  fPy[0] = 0.;
  fPz[0] = 0.;
  fPx[1] = 0.;
  fPy[1] = 0.;
  fPz[1] = 0.;

  fd0[0] = 0.;
  fd0[1] = 0.;

  fPdg[0] = 0;
  fPdg[1] = 0;
  fMum[0] = 0;
  fMum[1] = 0;
  fGMum[0] = 0;
  fGMum[1] = 0;

  fTagPi[0] = 0.;
  fTagPi[1] = 0.;
  fTagKa[0] = 0.;
  fTagKa[1] = 0.;
  fTagNid[0] = 0.;
  fTagNid[1] = 0.;

  fWgtJPsi=0;

}
//----------------------------------------------------------------------------
AliBtoJPSItoEle::AliBtoJPSItoEle(Int_t ev,Int_t trkNum[2],
		       Double_t v1[3],Double_t v2[3], 
		       Double_t dca,
		       Double_t mom[6],Double_t d0[2]) {
  // Constructor

  fSignal = kFALSE;
  fJpsiPrimary = kFALSE;

  fEvent = ev;
  fTrkNum[0] = trkNum[0];
  fTrkNum[1] = trkNum[1];

  fV1x = v1[0];
  fV1y = v1[1];
  fV1z = v1[2];
  fV2x = v2[0];
  fV2y = v2[1];
  fV2z = v2[2];
  fDCA = dca;

  fPx[0] = mom[0];
  fPy[0] = mom[1];
  fPz[0] = mom[2];
  fPx[1] = mom[3];
  fPy[1] = mom[4];
  fPz[1] = mom[5];

  fd0[0] = d0[0];
  fd0[1] = d0[1];

  fPdg[0] = 0;
  fPdg[1] = 0;
  fMum[0] = 0;
  fMum[1] = 0;
  fGMum[0] = 0;
  fGMum[1] = 0;

  fTagPi[0]  = 0.;
  fTagPi[1]  = 0.;
  fTagKa[0]  = 0.;
  fTagKa[1]  = 0.;
  fTagNid[0] = 0.;
  fTagNid[1] = 0.;

  fWgtJPsi=0;
}
//----------------------------------------------------------------------------
AliBtoJPSItoEle::~AliBtoJPSItoEle() {}
//____________________________________________________________________________
AliBtoJPSItoEle::AliBtoJPSItoEle( const AliBtoJPSItoEle& btoJpsi):TObject(btoJpsi) {
  // dummy copy constructor
}
//----------------------------------------------------------------------------
void AliBtoJPSItoEle::ApplyPID(TString pidScheme) {
  // Applies particle identification

  if(!pidScheme.CompareTo("TRDTPCparam")  && fPdg[0]==0) {
    printf("AliBtoJPSItoEle::ApplyPID :\n Warning: TRD-TPC parameterized PID can be used only for simulation!\n"); 
    return;
  }

  if(!pidScheme.CompareTo("TRDTPCparam")) {
    // tagging of the positive track
    if(TMath::Abs(fPdg[0])==11) { // electron
      fTagEl[0] = 0.81;
      fTagNid[0] = 1.-fTagEl[0];
    }
    else if(TMath::Abs(fPdg[0])==211) { // pion
      fTagEl[0]   = TRDTPCCombinedPIDParametrization(PChild(0));
      fTagNid[0] = 1.-fTagEl[0];
    } 
    else { // all the others 
      fTagEl[0]  = 0.;
      fTagNid[0] = 1.;
    } 
    // tagging of the negative track
    if(TMath::Abs(fPdg[1])==11) { // electron
      fTagEl[1] = 0.81;
      fTagNid[1] = 1.-fTagEl[1];
    }
    else if(TMath::Abs(fPdg[1])==211) { // pion
      fTagEl[1]   = TRDTPCCombinedPIDParametrization(PChild(1));
      fTagNid[1] = 1.-fTagEl[1];
    }
    else { // all the others
      fTagEl[1]  = 0.;
      fTagNid[1] = 1.;
    }
  }

  if(!pidScheme.CompareTo("ESDCombinedPID")) {
    fTagEl[0]=fPIDrespEl[0];
    fTagEl[1]=fPIDrespEl[1];
    fTagNid[0] = 1.-fTagEl[0];
    fTagNid[1] = 1.-fTagEl[1];
  }
  return;
}
//----------------------------------------------------------------------------
Double_t AliBtoJPSItoEle::ChildrenRelAngle() const {
  // relative angle between K and pi

  TVector3 mom0(fPx[0],fPy[0],fPz[0]);
  TVector3 mom1(fPx[1],fPy[1],fPz[1]);

  Double_t angle = mom0.Angle(mom1);

  return angle; 
}
//----------------------------------------------------------------------------
void AliBtoJPSItoEle::ComputeWgts() {
  // calculate the weights for PID


  // assignement of the weights from PID
  fWgtJPsi    = fTagEl[0]*fTagEl[1]; // both assumed to be electrons 

  
  // if(fWgtJPsi<0.) cerr<<"AliBtoJPSItoEle::ComputeWgts()  Negative weight!!!\n";
  

  return;
}
//----------------------------------------------------------------------------
void AliBtoJPSItoEle::CorrectWgt4BR(Double_t factor) {
  // correct weights of background from charm 

  fWgtJPsi    *= factor;

  return;
}
//----------------------------------------------------------------------------
Double_t AliBtoJPSItoEle::CosPointing() const {
  // cosine of pointing angle in space

  TVector3 mom(Px(),Py(),Pz());
  TVector3 flight(fV2x-fV1x,fV2y-fV1y,fV2z-fV1z);

  Double_t pta = mom.Angle(flight);

  return TMath::Cos(pta); 
}
//----------------------------------------------------------------------------
Double_t AliBtoJPSItoEle::CosPointingXY() const {
  // cosine of pointing angle in transverse plane

  TVector3 momXY(Px(),Py(),0.);
  TVector3 flightXY(fV2x-fV1x,fV2y-fV1y,0.);

  Double_t ptaXY = momXY.Angle(flightXY);

  return TMath::Cos(ptaXY); 
}
//----------------------------------------------------------------------------
void AliBtoJPSItoEle::CosThetaStar(Double_t &ctsJPsi) const {
  // cosine of decay angle in the J/Psi rest frame (of the negative electron)

  Double_t pStar = TMath::Sqrt(TMath::Power(kMJPsi*kMJPsi-2.*kMe*kMe,2.)-4.*kMe*kMe*kMe*kMe)/(2.*kMJPsi);

  Double_t beta = P()/Energy();
  Double_t gamma = Energy()/kMJPsi;

  ctsJPsi = (Ql(1)/gamma-beta*TMath::Sqrt(pStar*pStar+kMe*kMe))/pStar;
  // if(ctsJPsi > 1.)  { cerr<<"AliBtoJPSItoEle::CosThetaStar: > 1 "<<ctsJPsi<<"!\n"; }
  // if(ctsJPsi < -1.) { cerr<<"AliBtoJPSItoEle::CosThetaStar: < -1 "<<ctsJPsi<<"!\n"; }

  return;
}
//----------------------------------------------------------------------------
Double_t AliBtoJPSItoEle::Eta() const {
  // pseudorapidity of the J/Psi

  Double_t theta = TMath::Pi()/2.-TMath::ATan2(Pz(),Pt());
  Double_t eta = -TMath::Log(TMath::Tan(theta/2.));
  return eta;
}
//----------------------------------------------------------------------------
Double_t AliBtoJPSItoEle::EtaChild(Int_t child) const {
  // pseudorapidity of the decay tracks

  Double_t theta = TMath::Pi()/2.-TMath::ATan2(fPz[child],PtChild(child));
  Double_t eta = -TMath::Log(TMath::Tan(theta/2.));
  return eta;
}
//----------------------------------------------------------------------------
void AliBtoJPSItoEle::GetWgts(Double_t &WgtJPsi) 
  const {
  // returns the weights for pid

    WgtJPsi    = fWgtJPsi; 

  return;
}
//----------------------------------------------------------------------------
Double_t AliBtoJPSItoEle::ImpPar() const {
  // J/Psi impact parameter in the bending plane
  
    Double_t k = -(fV2x-fV1x)*Px()-(fV2y-fV1y)*Py();
    k /= Pt()*Pt();
    Double_t dx = fV2x-fV1x+k*Px();
    Double_t dy = fV2y-fV1y+k*Py();
    Double_t absDD = TMath::Sqrt(dx*dx+dy*dy);
    TVector3 mom(Px(),Py(),Pz());
    TVector3 flight(fV2x-fV1x,fV2y-fV1y,fV2z-fV1z);
    TVector3 cross = mom.Cross(flight);
    return (cross.Z()>0. ? absDD : -absDD);
}
//----------------------------------------------------------------------------
void AliBtoJPSItoEle::InvMass(Double_t &mJPsi) const {
  // invariant mass as J/Psi

  Double_t energy[2];

  // J/psi -> e- e+
  energy[1] = TMath::Sqrt(kMe*kMe+PChild(1)*PChild(1));
  energy[0] = TMath::Sqrt(kMe*kMe+PChild(0)*PChild(0));

  mJPsi = TMath::Sqrt((energy[0]+energy[1])*(energy[0]+energy[1])-P()*P());
    
  return;

}
//----------------------------------------------------------------------------
Double_t AliBtoJPSItoEle::Ql(Int_t child) const {
  // longitudinal momentum of decay tracks w.r.t. to J/Psi momentum

  Double_t qL;
  TVector3 mom(fPx[child],fPy[child],fPz[child]);
  TVector3 momJPsi(Px(),Py(),Pz());

  qL = mom.Dot(momJPsi)/momJPsi.Mag();

  return qL ;
}
//----------------------------------------------------------------------------
Double_t AliBtoJPSItoEle::Qt() const {
  // transverse momentum of decay tracks w.r.t. to JPsi momentum  

  TVector3 mom0(fPx[0],fPy[0],fPz[0]);
  TVector3 momJPsi(Px(),Py(),Pz());

  return mom0.Perp(momJPsi);
}
//----------------------------------------------------------------------------
Bool_t AliBtoJPSItoEle::Select(const Double_t* cuts,Int_t& okB) 
  const {
//
// This function compares the B candidates with a set of cuts:
//
// cuts[0] = inv. mass half width [GeV]   
// cuts[1] = dca [micron]
// cuts[2] = cosThetaStar 
// cuts[3] = pTP [GeV/c]
// cuts[4] = pTN [GeV/c]
// cuts[5] = d0P [micron]   upper limit!
// cuts[6] = d0N [micron]  upper limit!
// cuts[7] = d0d0 [micron^2]
// cuts[8] = cosThetaPoint
//
// If the candidate doesn't pass the cuts it sets the weight to 0
// and return kFALSE
//
  Double_t mJPsi,ctsJPsi;
  okB=1; 

  if(PtChild(1) < cuts[3] || PtChild(0) < cuts[4]) okB = 0;
  if(!okB) return kFALSE;

  if(TMath::Abs(Getd0Child(1)) > cuts[5] || 
     TMath::Abs(Getd0Child(0)) > cuts[6]) okB = 0;
  if(!okB) return kFALSE;

  if(GetDCA() > cuts[1]) { okB = 0; return kFALSE; }

  InvMass(mJPsi);
  if(TMath::Abs(mJPsi-kMJPsi)    > cuts[0]) okB = 0;
  if(!okB) return kFALSE;

  CosThetaStar(ctsJPsi);
  if(TMath::Abs(ctsJPsi)    > cuts[2]) okB = 0;
  if(!okB) return kFALSE;

  if(ProdImpParams() > cuts[7]) { okB = 0; return kFALSE; }

  if(CosPointing()   < cuts[8]) { okB = 0; return kFALSE; }

  return kTRUE;
}
//-----------------------------------------------------------------------------
void AliBtoJPSItoEle::SetPIDresponse(Double_t resp0[5],Double_t resp1[5]) {
  // Set combined PID detector response probabilities

  fPIDrespEl[0] = resp0[0];
  fPIDrespEl[1] = resp1[0];
  fPIDrespMu[0] = resp0[1];
  fPIDrespMu[1] = resp1[1];
  fPIDrespPi[0] = resp0[2];
  fPIDrespPi[1] = resp1[2];
  fPIDrespKa[0] = resp0[3];
  fPIDrespKa[1] = resp1[3];
  fPIDrespPr[0] = resp0[4];
  fPIDrespPr[1] = resp1[4];

  return;
} 
//-----------------------------------------------------------------------------
void AliBtoJPSItoEle::GetPIDresponse(Double_t resp0[5],Double_t resp1[5]) const {
  // Get combined PID detector response probabilities
                                                                                                                          
  resp0[0] = fPIDrespEl[0];
  resp1[0] = fPIDrespEl[1]; 
  resp0[1] = fPIDrespMu[0];
  resp1[1] = fPIDrespMu[1];
  resp0[2] = fPIDrespPi[0];
  resp1[2] = fPIDrespPi[1];
  resp0[3] = fPIDrespKa[0];
  resp1[3] = fPIDrespKa[1];
  resp0[4] = fPIDrespPr[0];
  resp1[4] = fPIDrespPr[1];
                                                                                                                          
  return;
}
//----------------------------------------------------------------------------
Double_t AliBtoJPSItoEle::TRDTPCCombinedPIDParametrization(Double_t p) const {


  // a first raw parametrization of the probability to misidentify a charged pion as electron as a 
  // function of the momentum, as given by the combined TPC and TRD response. 
  //  PID cuts are set such that the probability for correct electron id is 90% in each of the two 
  //    detectors
  
// first estimate based on parameterization in the B-> single electron analysis
  Double_t value=0;
  Double_t p1 =11.;
  Double_t p2=0.00007;
  Double_t p3=0.007;
  value=p2+p3*(1.-exp(-TMath::Power(p/p1,4.)));

// Better estimation based on TRD test beam (as presented by Andrea at Munster)
  value/=0.01; // here remove from TPC+TRD the TRD contribution estimated to be 0.01
  if (p<10.) value*=(1.32-0.18*p+0.076*p*p-0.0037*p*p*p)/100.;
  if (p>10.) value*=(0.48+0.287*p)/100.;

  return value;
}
//----------------------------------------------------------------------------
Commit	Line	Data
27e190fb	1	/**************************************************************************
	2	* Copyright(c) 1998-1999, 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	// Implementation of the BtoJPSItoEle class
	18	// for pp and PbPb interactions
	19	// Note: the two decay tracks are labelled: 0 (positive electron)
	20	// 1 (negative electron)
	21	// Origin: G.E. Bruno giuseppe.bruno@ba.infn.it
	22	// based on Class for charm golden channel (D0->Kpi)
	23	//----------------------------------------------------------------------------
	24
	25	// #include <Riostream.h> // for debugging
	26
	27	#include <TH1.h>
	28	#include <TH2.h>
	29	#include <TCanvas.h>
	30	#include <TPaveLabel.h>
	31	#include <TVector3.h>
	32
	33	#include "AliBtoJPSItoEle.h"
	34
	35	ClassImp(AliBtoJPSItoEle)
	36
	37	//----------------------------------------------------------------------------
	38	AliBtoJPSItoEle::AliBtoJPSItoEle() {
	39	// Default constructor
	40
	41	fSignal = kFALSE;
	42	fJpsiPrimary = kFALSE;
	43
	44	fEvent = 0;
	45
	46	fTrkNum[0] = 0;
	47	fTrkNum[1] = 0;
	48
	49	fV1x = 0.;
	50	fV1y = 0.;
	51	fV1z = 0.;
	52	fV2x = 0.;
	53	fV2y = 0.;
	54	fV2z = 0.;
	55	fDCA = 0.;
	56
	57	fPx[0] = 0.;
	58	fPy[0] = 0.;
	59	fPz[0] = 0.;
	60	fPx[1] = 0.;
	61	fPy[1] = 0.;
	62	fPz[1] = 0.;
	63
	64	fd0[0] = 0.;
65	fd0[1] = 0.;
66
67	fPdg[0] = 0;
68	fPdg[1] = 0;
69	fMum[0] = 0;
70	fMum[1] = 0;
71	fGMum[0] = 0;
72	fGMum[1] = 0;
73
74	fTagPi[0] = 0.;
75	fTagPi[1] = 0.;
76	fTagKa[0] = 0.;
77	fTagKa[1] = 0.;
78	fTagNid[0] = 0.;
79	fTagNid[1] = 0.;
80
81	fWgtJPsi=0;
82
83	}
84	//----------------------------------------------------------------------------
85	AliBtoJPSItoEle::AliBtoJPSItoEle(Int_t ev,Int_t trkNum[2],
86	Double_t v1[3],Double_t v2[3],
87	Double_t dca,
88	Double_t mom[6],Double_t d0[2]) {
89	// Constructor
90
91	fSignal = kFALSE;
92	fJpsiPrimary = kFALSE;
93
94	fEvent = ev;
95	fTrkNum[0] = trkNum[0];
96	fTrkNum[1] = trkNum[1];
97
98	fV1x = v1[0];
99	fV1y = v1[1];
100	fV1z = v1[2];
101	fV2x = v2[0];
102	fV2y = v2[1];
103	fV2z = v2[2];
104	fDCA = dca;
105
106	fPx[0] = mom[0];
107	fPy[0] = mom[1];
108	fPz[0] = mom[2];
109	fPx[1] = mom[3];
110	fPy[1] = mom[4];
111	fPz[1] = mom[5];
112
113	fd0[0] = d0[0];
114	fd0[1] = d0[1];
115
116	fPdg[0] = 0;
117	fPdg[1] = 0;
118	fMum[0] = 0;
119	fMum[1] = 0;
120	fGMum[0] = 0;
121	fGMum[1] = 0;
122
123	fTagPi[0] = 0.;
124	fTagPi[1] = 0.;
125	fTagKa[0] = 0.;
126	fTagKa[1] = 0.;
127	fTagNid[0] = 0.;
128	fTagNid[1] = 0.;
129
130	fWgtJPsi=0;
131	}
132	//----------------------------------------------------------------------------
133	AliBtoJPSItoEle::~AliBtoJPSItoEle() {}
134	//____________________________________________________________________________
135	AliBtoJPSItoEle::AliBtoJPSItoEle( const AliBtoJPSItoEle& btoJpsi):TObject(btoJpsi) {
136	// dummy copy constructor
137	}
138	//----------------------------------------------------------------------------
139	void AliBtoJPSItoEle::ApplyPID(TString pidScheme) {
140	// Applies particle identification
141
142	if(!pidScheme.CompareTo("TRDTPCparam") && fPdg[0]==0) {
143	printf("AliBtoJPSItoEle::ApplyPID :\n Warning: TRD-TPC parameterized PID can be used only for simulation!\n");
144	return;
145	}
146
147	if(!pidScheme.CompareTo("TRDTPCparam")) {
148	// tagging of the positive track
149	if(TMath::Abs(fPdg[0])==11) { // electron
150	fTagEl[0] = 0.81;
151	fTagNid[0] = 1.-fTagEl[0];
152	}
153	else if(TMath::Abs(fPdg[0])==211) { // pion
154	fTagEl[0] = TRDTPCCombinedPIDParametrization(PChild(0));
155	fTagNid[0] = 1.-fTagEl[0];
156	}
157	else { // all the others
158	fTagEl[0] = 0.;
159	fTagNid[0] = 1.;
160	}
161	// tagging of the negative track
162	if(TMath::Abs(fPdg[1])==11) { // electron
163	fTagEl[1] = 0.81;
164	fTagNid[1] = 1.-fTagEl[1];
165	}
166	else if(TMath::Abs(fPdg[1])==211) { // pion
167	fTagEl[1] = TRDTPCCombinedPIDParametrization(PChild(1));
168	fTagNid[1] = 1.-fTagEl[1];
169	}
170	else { // all the others
171	fTagEl[1] = 0.;
172	fTagNid[1] = 1.;
173	}
174	}
175
176	if(!pidScheme.CompareTo("ESDCombinedPID")) {
177	fTagEl[0]=fPIDrespEl[0];
178	fTagEl[1]=fPIDrespEl[1];
179	fTagNid[0] = 1.-fTagEl[0];
180	fTagNid[1] = 1.-fTagEl[1];
181	}
182	return;
183	}
184	//----------------------------------------------------------------------------
185	Double_t AliBtoJPSItoEle::ChildrenRelAngle() const {
186	// relative angle between K and pi
187
188	TVector3 mom0(fPx[0],fPy[0],fPz[0]);
189	TVector3 mom1(fPx[1],fPy[1],fPz[1]);
190
191	Double_t angle = mom0.Angle(mom1);
192
193	return angle;
194	}
195	//----------------------------------------------------------------------------
196	void AliBtoJPSItoEle::ComputeWgts() {
197	// calculate the weights for PID
198
199
200	// assignement of the weights from PID
201	fWgtJPsi = fTagEl[0]*fTagEl[1]; // both assumed to be electrons
202
203
204	// if(fWgtJPsi<0.) cerr<<"AliBtoJPSItoEle::ComputeWgts() Negative weight!!!\n";
205
206
207	return;
208	}
209	//----------------------------------------------------------------------------
210	void AliBtoJPSItoEle::CorrectWgt4BR(Double_t factor) {
211	// correct weights of background from charm
212
213	fWgtJPsi *= factor;
214
215	return;
216	}
217	//----------------------------------------------------------------------------
218	Double_t AliBtoJPSItoEle::CosPointing() const {
219	// cosine of pointing angle in space
220
221	TVector3 mom(Px(),Py(),Pz());
222	TVector3 flight(fV2x-fV1x,fV2y-fV1y,fV2z-fV1z);
223
224	Double_t pta = mom.Angle(flight);
225
226	return TMath::Cos(pta);
227	}
228	//----------------------------------------------------------------------------
229	Double_t AliBtoJPSItoEle::CosPointingXY() const {
230	// cosine of pointing angle in transverse plane
231
232	TVector3 momXY(Px(),Py(),0.);
233	TVector3 flightXY(fV2x-fV1x,fV2y-fV1y,0.);
234
235	Double_t ptaXY = momXY.Angle(flightXY);
236
237	return TMath::Cos(ptaXY);
238	}
239	//----------------------------------------------------------------------------
240	void AliBtoJPSItoEle::CosThetaStar(Double_t &ctsJPsi) const {
241	// cosine of decay angle in the J/Psi rest frame (of the negative electron)
242
243	Double_t pStar = TMath::Sqrt(TMath::Power(kMJPsikMJPsi-2.kMekMe,2.)-4.kMekMekMekMe)/(2.kMJPsi);
244
245	Double_t beta = P()/Energy();
246	Double_t gamma = Energy()/kMJPsi;
247
248	ctsJPsi = (Ql(1)/gamma-betaTMath::Sqrt(pStarpStar+kMe*kMe))/pStar;
249	// if(ctsJPsi > 1.) { cerr<<"AliBtoJPSItoEle::CosThetaStar: > 1 "<<ctsJPsi<<"!\n"; }
250	// if(ctsJPsi < -1.) { cerr<<"AliBtoJPSItoEle::CosThetaStar: < -1 "<<ctsJPsi<<"!\n"; }
251
252	return;
253	}
254	//----------------------------------------------------------------------------
255	Double_t AliBtoJPSItoEle::Eta() const {
256	// pseudorapidity of the J/Psi
257
258	Double_t theta = TMath::Pi()/2.-TMath::ATan2(Pz(),Pt());
259	Double_t eta = -TMath::Log(TMath::Tan(theta/2.));
260	return eta;
261	}
262	//----------------------------------------------------------------------------
263	Double_t AliBtoJPSItoEle::EtaChild(Int_t child) const {
264	// pseudorapidity of the decay tracks
265
266	Double_t theta = TMath::Pi()/2.-TMath::ATan2(fPz[child],PtChild(child));
267	Double_t eta = -TMath::Log(TMath::Tan(theta/2.));
268	return eta;
269	}
270	//----------------------------------------------------------------------------
271	void AliBtoJPSItoEle::GetWgts(Double_t &WgtJPsi)
272	const {
273	// returns the weights for pid
274
275	WgtJPsi = fWgtJPsi;
276
277	return;
278	}
279	//----------------------------------------------------------------------------
280	Double_t AliBtoJPSItoEle::ImpPar() const {
281	// J/Psi impact parameter in the bending plane
282
283	Double_t k = -(fV2x-fV1x)Px()-(fV2y-fV1y)Py();
284	k /= Pt()*Pt();
285	Double_t dx = fV2x-fV1x+k*Px();
286	Double_t dy = fV2y-fV1y+k*Py();
287	Double_t absDD = TMath::Sqrt(dxdx+dydy);
288	TVector3 mom(Px(),Py(),Pz());
289	TVector3 flight(fV2x-fV1x,fV2y-fV1y,fV2z-fV1z);
290	TVector3 cross = mom.Cross(flight);
291	return (cross.Z()>0. ? absDD : -absDD);
292	}
293	//----------------------------------------------------------------------------
294	void AliBtoJPSItoEle::InvMass(Double_t &mJPsi) const {
295	// invariant mass as J/Psi
296
297	Double_t energy[2];
298
299	// J/psi -> e- e+
300	energy[1] = TMath::Sqrt(kMekMe+PChild(1)PChild(1));
301	energy[0] = TMath::Sqrt(kMekMe+PChild(0)PChild(0));
302
303	mJPsi = TMath::Sqrt((energy[0]+energy[1])(energy[0]+energy[1])-P()P());
304
305	return;
306
307	}
308	//----------------------------------------------------------------------------
309	Double_t AliBtoJPSItoEle::Ql(Int_t child) const {
310	// longitudinal momentum of decay tracks w.r.t. to J/Psi momentum
311
312	Double_t qL;
313	TVector3 mom(fPx[child],fPy[child],fPz[child]);
314	TVector3 momJPsi(Px(),Py(),Pz());
315
316	qL = mom.Dot(momJPsi)/momJPsi.Mag();
317
318	return qL ;
319	}
320	//----------------------------------------------------------------------------
321	Double_t AliBtoJPSItoEle::Qt() const {
322	// transverse momentum of decay tracks w.r.t. to JPsi momentum
323
324	TVector3 mom0(fPx[0],fPy[0],fPz[0]);
325	TVector3 momJPsi(Px(),Py(),Pz());
326
327	return mom0.Perp(momJPsi);
328	}
329	//----------------------------------------------------------------------------
330	Bool_t AliBtoJPSItoEle::Select(const Double_t* cuts,Int_t& okB)
331	const {
332	//
333	// This function compares the B candidates with a set of cuts:
334	//
335	// cuts[0] = inv. mass half width [GeV]
336	// cuts[1] = dca [micron]
337	// cuts[2] = cosThetaStar
338	// cuts[3] = pTP [GeV/c]
339	// cuts[4] = pTN [GeV/c]
340	// cuts[5] = d0P [micron] upper limit!
341	// cuts[6] = d0N [micron] upper limit!
342	// cuts[7] = d0d0 [micron^2]
343	// cuts[8] = cosThetaPoint
344	//
345	// If the candidate doesn't pass the cuts it sets the weight to 0
346	// and return kFALSE
347	//
348	Double_t mJPsi,ctsJPsi;
349	okB=1;
350
351	if(PtChild(1) < cuts[3] \|\| PtChild(0) < cuts[4]) okB = 0;
352	if(!okB) return kFALSE;
353
354	if(TMath::Abs(Getd0Child(1)) > cuts[5] \|\|
355	TMath::Abs(Getd0Child(0)) > cuts[6]) okB = 0;
356	if(!okB) return kFALSE;
357
358	if(GetDCA() > cuts[1]) { okB = 0; return kFALSE; }
359
360	InvMass(mJPsi);
361	if(TMath::Abs(mJPsi-kMJPsi) > cuts[0]) okB = 0;
362	if(!okB) return kFALSE;
363
364	CosThetaStar(ctsJPsi);
365	if(TMath::Abs(ctsJPsi) > cuts[2]) okB = 0;
366	if(!okB) return kFALSE;
367
368	if(ProdImpParams() > cuts[7]) { okB = 0; return kFALSE; }
369
370	if(CosPointing() < cuts[8]) { okB = 0; return kFALSE; }
371
372	return kTRUE;
373	}
374	//-----------------------------------------------------------------------------
375	void AliBtoJPSItoEle::SetPIDresponse(Double_t resp0[5],Double_t resp1[5]) {
376	// Set combined PID detector response probabilities
377
378	fPIDrespEl[0] = resp0[0];
379	fPIDrespEl[1] = resp1[0];
380	fPIDrespMu[0] = resp0[1];
381	fPIDrespMu[1] = resp1[1];
382	fPIDrespPi[0] = resp0[2];
383	fPIDrespPi[1] = resp1[2];
384	fPIDrespKa[0] = resp0[3];
385	fPIDrespKa[1] = resp1[3];
386	fPIDrespPr[0] = resp0[4];
387	fPIDrespPr[1] = resp1[4];
388
389	return;
390	}
391	//-----------------------------------------------------------------------------
392	void AliBtoJPSItoEle::GetPIDresponse(Double_t resp0[5],Double_t resp1[5]) const {
393	// Get combined PID detector response probabilities
394
395	resp0[0] = fPIDrespEl[0];
396	resp1[0] = fPIDrespEl[1];
397	resp0[1] = fPIDrespMu[0];
398	resp1[1] = fPIDrespMu[1];
399	resp0[2] = fPIDrespPi[0];
400	resp1[2] = fPIDrespPi[1];
401	resp0[3] = fPIDrespKa[0];
402	resp1[3] = fPIDrespKa[1];
403	resp0[4] = fPIDrespPr[0];
404	resp1[4] = fPIDrespPr[1];
405
406	return;
407	}
408	//----------------------------------------------------------------------------
409	Double_t AliBtoJPSItoEle::TRDTPCCombinedPIDParametrization(Double_t p) const {
410
411
412	// a first raw parametrization of the probability to misidentify a charged pion as electron as a
413	// function of the momentum, as given by the combined TPC and TRD response.
414	// PID cuts are set such that the probability for correct electron id is 90% in each of the two
415	// detectors
416
417	// first estimate based on parameterization in the B-> single electron analysis
418	Double_t value=0;
419	Double_t p1 =11.;
420	Double_t p2=0.00007;
421	Double_t p3=0.007;
422	value=p2+p3*(1.-exp(-TMath::Power(p/p1,4.)));
423
424	// Better estimation based on TRD test beam (as presented by Andrea at Munster)
425	value/=0.01; // here remove from TPC+TRD the TRD contribution estimated to be 0.01
426	if (p<10.) value=(1.32-0.18p+0.076pp-0.0037pp*p)/100.;
427	if (p>10.) value=(0.48+0.287p)/100.;
428
429	return value;
430	}
431	//----------------------------------------------------------------------------
432
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436