1 /**************************************************************************
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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 *
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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 **************************************************************************/
16 //-------------------------------------------------------------------------
18 // This is a generator of beam-beam pileup.
19 // It generates interactions within 3 orbits (+-1) around
20 // the trigger event. The trigger event itself is chosen
21 // randomly among the bunch crossings within the central orbit.
22 // The user can decide whenever to include in the simulation the
23 // "trigger" interaction or not. This is handled by the
24 // GenerateTrigInteraction(Bool_t flag) method.
25 // In the case the trigger interaction is included, it is
26 // generated using the same settings (vertex smear for example) as
28 // In case the trigger simulation is not included, the user can make
29 // a cocktail of generator used to produce the trigger interaction and
30 // AliGenPileup. In this case in order to avoid a fake increase of the rate around the
31 // trigger, the number of background events within the bunch
32 // crossing of the trigger is readuced by one.
33 // The beam profile (the list of the active bunch crossings) can be
34 // controlled via the SetBCMask(const char *mask) method. The syntax
35 // follows the one in AliTriggerBCMask class. For example:
36 // "3564H" would mean that all the bunch corssings within the orbit
37 // are aloowed (which is of course unphysical). In case one wants to simulate
38 // one-bunch-crossing-per-orbit scenario, the way to do it is to put something like:
39 // "1H3563L" or similar.
40 // The SetGenerator(AliGenerator *generator, Float_t rate) method is
41 // used in order to define the generator to be used. The second argument is the pileup
42 // rate in terms of #_of_interactions/bunch-crossing = sigma_tot * luminosity.
43 // The pileup generation time window can be set via
44 // AliGenerator::SetPileUpTimeWindow(Float_t pileUpTimeW) method. By the default the
45 // window is set to 88micros (= TPC readout window).
47 // cvetan.cheshkov@cern.ch 9/12/2008
48 //-------------------------------------------------------------------------
50 #include <TParticle.h>
52 #include "AliGenPileup.h"
54 #include "AliGenCocktailEventHeader.h"
55 #include "AliGenCocktailEntry.h"
59 ClassImp(AliGenPileup)
61 AliGenPileup::AliGenPileup():
63 fBCMask("bcm","3564H"),
67 // The pileup time window is by default
68 // set to the TPC readout one
70 fTitle= "Beam-beam pileup";
72 fPileUpTimeWindow = 88e-6;
75 AliGenPileup::~AliGenPileup()
80 void AliGenPileup::SetGenerator(AliGenerator *generator, Float_t rate)
82 // The method sets the geenrator to be used
83 // for pileup simulation.
84 // The second argument is the pileup rate in terms of
85 // #_of_interactions/bunch-crossing = sigma_tot * luminosity.
86 // There is a protection in case the generator was already set.
88 if (FirstGenerator()) {
89 AliError("Pileup generator has been already set! Nothing done");
93 AddGenerator(generator,"pileup generator",rate);
96 void AliGenPileup::AddGenerator(AliGenerator *Generator,
100 // The method used to add the pileup generator
101 // in the cocktail list.
102 // The method is protected in order to avoid
104 AliGenCocktail::AddGenerator(Generator,Name,RateExp);
107 Bool_t AliGenPileup::SetBCMask(const char *mask)
109 // Set the active bunch-crossings that
110 // will be included in the pileup
111 // simulation. For more details on the
112 // syntax of the mask - see
113 // STEER/AliTriggerBCMask.* and the comments
114 // in the header of this file
115 return fBCMask.SetMask(mask);
118 void AliGenPileup::Generate()
121 // Generate pileup event
122 // For details see the coments inline
124 // Check that the pileup generator is correctly set
125 AliGenCocktailEntry *entry = FirstGenerator();
127 AliFatal("No pileup generator entry is found!");
130 AliGenerator *gen = entry->Generator();
132 AliFatal("No pileup generator specified!");
134 else if (gen->NeedsCollisionGeometry()) {
135 AliFatal("No Collision Geometry Provided");
138 // Check that the pileup rate is correctly set
139 Float_t rate = entry->Rate();
141 AliFatal(Form("Invalid rate value: %f",rate));
144 // Create cocktail header
145 if (fHeader) delete fHeader;
146 fHeader = new AliGenCocktailEventHeader("Pileup Cocktail Header");
148 // Generate time of all
149 // the collisions within one orbit
150 Int_t *nIntBC = new Int_t[3*AliTriggerBCMask::kNBits];
151 Int_t *indexBC = new Int_t[3*AliTriggerBCMask::kNBits];
153 for(Int_t iBC = 0; iBC < AliTriggerBCMask::kNBits; iBC++) {
155 if (!fBCMask.GetMask(iBC)) continue;
157 Int_t nInteractions = gRandom->Poisson(rate);
158 if (nInteractions == 0) continue;
160 nIntBC[nTotBC] = nInteractions;
161 indexBC[nTotBC] = iBC;
165 // Select the bunch crossing for triggered event
166 Int_t iTrgBC = gRandom->Integer(nTotBC);
167 // Subtract one from the number of events
168 // generated within this bc (only in case
169 // the user disabled the generation of the trigger
171 if (!fGenTrig) nIntBC[iTrgBC]--;
173 // Remove bunch crossings outside pileup
175 for(Int_t iBC = 0; iBC < nTotBC; iBC++) {
176 if (TMath::Abs(25e-9*(indexBC[iBC]-indexBC[iTrgBC])) > fPileUpTimeWindow)
180 // Generate the two orbits around the central one
181 // taking into account the pileup time window
182 for(Int_t iBC = 0; iBC < AliTriggerBCMask::kNBits; iBC++) {
184 if (!fBCMask.GetMask(iBC)) continue;
186 if (TMath::Abs(25e-9*(iBC-AliTriggerBCMask::kNBits-indexBC[iTrgBC])) > fPileUpTimeWindow) continue;
188 Int_t nInteractions = gRandom->Poisson(rate);
189 if (nInteractions == 0) continue;
191 nIntBC[nTotBC] = nInteractions;
192 indexBC[nTotBC] = iBC-AliTriggerBCMask::kNBits;
195 for(Int_t iBC = 0; iBC < AliTriggerBCMask::kNBits; iBC++) {
197 if (!fBCMask.GetMask(iBC)) continue;
199 if (TMath::Abs(25e-9*(iBC+AliTriggerBCMask::kNBits-indexBC[iTrgBC])) > fPileUpTimeWindow) continue;
201 Int_t nInteractions = gRandom->Poisson(rate);
202 if (nInteractions == 0) continue;
204 nIntBC[nTotBC] = nInteractions;
205 indexBC[nTotBC] = iBC+AliTriggerBCMask::kNBits;
209 // Loop over the generated collision times, call the generator
210 // and correct the partcile times in the stack
211 AliStack *stack = AliRunLoader::Instance()->Stack();
213 entry->SetFirst(lastpart);
215 for(Int_t iBC = 0; iBC < nTotBC; iBC++) {
216 Float_t deltat = 25e-9*(indexBC[iBC] - indexBC[iTrgBC]);
217 for (Int_t i = 0; i < nIntBC[iBC]; i++) {
218 // Generate the vertex position and time
220 TArrayF eventVertex(3);
221 for (Int_t j=0; j < 3; j++) eventVertex[j] = fVertex[j];
222 Double_t vTime = deltat + gRandom->Gaus(0,fOsigma[2]/TMath::Ccgs());
224 gen->SetVertex(fVertex.At(0), fVertex.At(1), fVertex.At(2));
227 for (Int_t k = lastpart; k < stack->GetNprimary(); k++) {
229 stack->Particle(k)->ProductionVertex(v);
231 stack->Particle(k)->SetProductionVertex(v);
233 lastpart = stack->GetNprimary();
235 // Store the interaction header in the container of the headers
236 ((AliGenEventHeader*) fHeader->GetHeaders()->Last())->SetPrimaryVertex(eventVertex);
242 entry->SetLast(stack->GetNprimary());
244 fHeader->CalcNProduced();
247 fContainer->AddHeader(fHeader);
249 gAlice->SetGenEventHeader(fHeader);
254 void AliGenPileup::SetRandomise(Bool_t /*flag*/)
256 // This setting is not implemented in
257 // case of pileup generation
258 // So the method gives an warning and exits
259 AliWarning("This setting has no effect on the generator!");
262 void AliGenPileup::UsePerEventRates()
264 // This setting is not implemented in
265 // case of pileup generation
266 // So the method gives an warning and exits
267 AliWarning("This setting has no effect on the generator!");