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 ////////////////////////////////////////////////////////////////////////////////
20 // Construction of invariant mass and combinatorial background.
25 // TObjArray* photons=new TObjArray(); // Array with photon tracks for pi0 rec.
27 // // Code to create some photon tracks from pi0 decays
29 // for (Int_t i=0; i<ntracks; i++)
31 // photons->Add(new Alitrack);
37 // // Perform the invariant mass and comb. bkg. reconstruction
39 // TObjArray* allm=q.Invmass(photons,photons); // All reconstructed invariant masses
41 // TH1F* hall=new TH1F("hall","hall",200,0,2); // Histo with M_inv of all combinations
44 // if (allm) nall=allm->GetEntries();
48 // for (Int_t j=0; j<nall; j++)
50 // t=(AliTrack*)allm->At(j);
58 // TObjArray* bkgm=q.CombBkg(photons,photons); // Reconstructed comb. background
60 // TH1F* hbkg=new TH1F("hbkg","hbkg",200,0,2); // Histo with M_inv. of comb. background
63 // if (bkgm) nbkg=bkgm->GetEntries();
65 // for (Int_t j=0; j<nbkg; j++)
67 // t=(AliTrack*)bkgm->At(j);
75 // TH1F* hsig=new TH1F("sig","sig",200,0,2); // Histo with the bkg. subtracted signal
77 // hsig->Add(hall,hbkg,1,-1);
80 // Note : By default the storage of the reconstructed information is performed
81 // in separate TObjArrays for the signal and comb. background resp.
82 // In order to limit the memory usage, AliInvmass::SetStorageMode(1) may be
83 // used to activate only a single TObjArray to store the reconstructed information.
84 // Consequently, the following statements
86 // TObjArray* allm=q.Invmass(photons,photons);
87 // TObjArray* bkgm=q.CombBkg(photons,photons);
89 // will result in the fact that after he invokation of CombBkg
90 // the information of "allm" is lost due to the fact that the storage is
91 // is re-used for "bkgm" in case the "single storage" option has been selected.
92 // Usage of the, in that case invalid, pointer "allm" may cause your
95 // * Thus : In case of single storage usage, all invokations of the returned
96 // array pointer have to be completed before invoking any memberfunction
97 // of the same AliInvmass object again.
101 //--- Author: Nick van Eijndhoven 12-apr-1999 UU-SAP Utrecht
102 //- Modified: NvE $Date$ UU-SAP Utrecht
103 ////////////////////////////////////////////////////////////////////////////////
105 #include "AliInvmass.h"
107 ClassImp(AliInvmass) // Class implementation to enable ROOT I/O
109 AliInvmass::AliInvmass()
111 // Creation of an AliInvmass object and initialisation of parameters
120 ////////////////////////////////////////////////////////////////////////////////
121 AliInvmass::~AliInvmass()
123 // Destructor to delete dynamically allocated memory
136 ////////////////////////////////////////////////////////////////////////////////
137 void AliInvmass::SetStorageMode(Int_t m)
139 // Set storage mode for the result arrays for inv. mass and comb. background
143 ////////////////////////////////////////////////////////////////////////////////
144 void AliInvmass::SetThetaSwitch(Int_t i)
146 // Enable/Disable (1/0) switching of theta angle in comb. bkg. reconstruction.
147 // Default : Switching of theta is enabled.
149 if (i==0) fNewtheta=0;
151 ////////////////////////////////////////////////////////////////////////////////
152 void AliInvmass::SetPhiSwitch(Int_t i)
154 // Enable/Disable (1/0) switching of phi angle in comb. bkg. reconstruction.
155 // Default : Switching of phi is enabled.
159 ////////////////////////////////////////////////////////////////////////////////
160 Int_t AliInvmass::GetStorageMode()
162 // Provide mode of storage for the result arrays for inv. mass and comb. background
165 ////////////////////////////////////////////////////////////////////////////////
166 Int_t AliInvmass::GetThetaSwitch()
168 // Provide the theta switching flag
171 ////////////////////////////////////////////////////////////////////////////////
172 Int_t AliInvmass::GetPhiSwitch()
174 // Provide the phi switching flag
177 ////////////////////////////////////////////////////////////////////////////////
178 TObjArray* AliInvmass::Invmass(TObjArray* a1,TObjArray* a2)
180 // Perform two-particle invariant mass reconstruction
185 ////////////////////////////////////////////////////////////////////////////////
186 TObjArray* AliInvmass::CombBkg(TObjArray* a1,TObjArray* a2)
188 // Perform two-particle combinatorial background reconstruction
200 ////////////////////////////////////////////////////////////////////////////////
201 void AliInvmass::Combine(TObjArray* a1,TObjArray* a2)
203 // Perform two-particle invariant mass reconstruction
205 if ((!fBkg || fMode==1) && fMinv)
211 if (fBkg && (fMode !=1) && fMbkg)
217 Int_t isame; // Indicates whether both lists are identical
221 // Index i must loop over the shortest of a1 and a2
224 Int_t ni=a1->GetEntries();
225 Int_t nj=a2->GetEntries();
239 Double_t v2[4],vx[4];
242 Int_t jmin; // Start index for list j
243 Int_t jx; // Index for randomly picked particle for comb. bkg. reconstruction
245 for (Int_t i=0; i<ni; i++) // Select first a particle from list i
247 p1=(AliTrack*)listi->At(i);
254 for (Int_t j=jmin; j<nj; j++) // Select also a particle from list j
256 p2=(AliTrack*)listj->At(j);
257 if (p1==p2) p2=0; // Don't combine particle with itself
261 p2->GetVector(v2,"sph");
263 // Take theta and phi from randomly chosen other list j particle for bkg. reconstr.
267 if ((!isame && nj>1) || (isame && nj>2))
269 jx=int(fRndm.Uniform(0,float(nj)));
270 px=(AliTrack*)listj->At(jx);
272 while (!px || px==p2 || px==p1)
276 px=(AliTrack*)listj->At(jx);
279 px->GetVector(vx,"sph");
280 if (fNewtheta) v2[2]=vx[2]; // Replace the theta angle in the v2 vector
281 if (fNewphi) v2[3]=vx[3]; // Replace the phi angle in the v2 vector
285 if ((!fBkg && p2) || (fBkg && px))
287 // Store the data of this two-particle combination
288 ptot.SetVector(v2,"sph");
289 ptot=(Ali4Vector)(ptot+(*p1));
293 t->Set4Momentum(ptot);
295 if (!fBkg || fMode==1)
299 fMinv=new TObjArray();
308 fMbkg=new TObjArray();
315 } // End of second particle loop
317 } // End of first particle loop
319 ////////////////////////////////////////////////////////////////////////////////