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"
106 #include "Riostream.h"
108 ClassImp(AliInvmass) // Class implementation to enable ROOT I/O
110 AliInvmass::AliInvmass()
112 // Creation of an AliInvmass object and initialisation of parameters
121 ////////////////////////////////////////////////////////////////////////////////
122 AliInvmass::~AliInvmass()
124 // Destructor to delete dynamically allocated memory
137 ////////////////////////////////////////////////////////////////////////////////
138 void AliInvmass::SetStorageMode(Int_t m)
140 // Set storage mode for the result arrays for inv. mass and comb. background
144 ////////////////////////////////////////////////////////////////////////////////
145 void AliInvmass::SetThetaSwitch(Int_t i)
147 // Enable/Disable (1/0) switching of theta angle in comb. bkg. reconstruction.
148 // Default : Switching of theta is enabled.
150 if (i==0) fNewtheta=0;
152 ////////////////////////////////////////////////////////////////////////////////
153 void AliInvmass::SetPhiSwitch(Int_t i)
155 // Enable/Disable (1/0) switching of phi angle in comb. bkg. reconstruction.
156 // Default : Switching of phi is enabled.
160 ////////////////////////////////////////////////////////////////////////////////
161 Int_t AliInvmass::GetStorageMode() const
163 // Provide mode of storage for the result arrays for inv. mass and comb. background
166 ////////////////////////////////////////////////////////////////////////////////
167 Int_t AliInvmass::GetThetaSwitch() const
169 // Provide the theta switching flag
172 ////////////////////////////////////////////////////////////////////////////////
173 Int_t AliInvmass::GetPhiSwitch() const
175 // Provide the phi switching flag
178 ////////////////////////////////////////////////////////////////////////////////
179 TObjArray* AliInvmass::Invmass(TObjArray* a1,TObjArray* a2)
181 // Perform two-particle invariant mass reconstruction
186 ////////////////////////////////////////////////////////////////////////////////
187 TObjArray* AliInvmass::CombBkg(TObjArray* a1,TObjArray* a2)
189 // Perform two-particle combinatorial background reconstruction
201 ////////////////////////////////////////////////////////////////////////////////
202 void AliInvmass::Combine(TObjArray* a1,TObjArray* a2)
204 // Perform two-particle invariant mass reconstruction
206 if ((!fBkg || fMode==1) && fMinv)
212 if (fBkg && (fMode !=1) && fMbkg)
218 Int_t isame; // Indicates whether both lists are identical
222 // Index i must loop over the shortest of a1 and a2
225 Int_t ni=a1->GetEntries();
226 Int_t nj=a2->GetEntries();
240 Double_t v2[4],vx[4];
243 Int_t jmin; // Start index for list j
244 Int_t jx; // Index for randomly picked particle for comb. bkg. reconstruction
246 for (Int_t i=0; i<ni; i++) // Select first a particle from list i
248 p1=(AliTrack*)listi->At(i);
255 for (Int_t j=jmin; j<nj; j++) // Select also a particle from list j
257 p2=(AliTrack*)listj->At(j);
258 if (p1==p2) p2=0; // Don't combine particle with itself
262 p2->GetVector(v2,"sph");
264 // Take theta and phi from randomly chosen other list j particle for bkg. reconstr.
268 if ((!isame && nj>1) || (isame && nj>2))
270 jx=int(fRndm.Uniform(0,float(nj)));
271 px=(AliTrack*)listj->At(jx);
273 while (!px || px==p2 || px==p1)
277 px=(AliTrack*)listj->At(jx);
280 px->GetVector(vx,"sph");
281 if (fNewtheta) v2[2]=vx[2]; // Replace the theta angle in the v2 vector
282 if (fNewphi) v2[3]=vx[3]; // Replace the phi angle in the v2 vector
286 if ((!fBkg && p2) || (fBkg && px))
288 // Store the data of this two-particle combination
289 ptot.SetVector(v2,"sph");
290 ptot=(Ali4Vector)(ptot+(*p1));
294 t->Set4Momentum(ptot);
296 if (!fBkg || fMode==1)
300 fMinv=new TObjArray();
309 fMbkg=new TObjArray();
316 } // End of second particle loop
318 } // End of first particle loop
320 ////////////////////////////////////////////////////////////////////////////////