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 **************************************************************************/
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"),
68 // The pileup time window is by default
69 // set to the TPC readout one
71 fTitle= "Beam-beam pileup";
73 fPileUpTimeWindow = 88e-6;
76 AliGenPileup::~AliGenPileup()
81 void AliGenPileup::SetGenerator(AliGenerator *generator, Float_t rate, Bool_t flag)
83 // The method sets the geenrator to be used
84 // for pileup simulation.
85 // The second argument is the pileup rate in terms of
86 // #_of_interactions/bunch-crossing = sigma_tot * luminosity.
87 // There is a protection in case the generator was already set.
89 if (FirstGenerator()) {
90 AliError("Pileup generator has been already set! Nothing done");
94 AddGenerator(generator,"pileup generator",rate);
98 void AliGenPileup::AddGenerator(AliGenerator *Generator,
102 // The method used to add the pileup generator
103 // in the cocktail list.
104 // The method is protected in order to avoid
106 AliGenCocktail::AddGenerator(Generator,Name,RateExp);
109 Bool_t AliGenPileup::SetBCMask(const char *mask)
111 // Set the active bunch-crossings that
112 // will be included in the pileup
113 // simulation. For more details on the
114 // syntax of the mask - see
115 // STEER/AliTriggerBCMask.* and the comments
116 // in the header of this file
117 return fBCMask.SetMask(mask);
120 void AliGenPileup::Generate()
123 // Generate pileup event
124 // For details see the coments inline
126 // Check that the pileup generator is correctly set
127 AliGenCocktailEntry *entry = FirstGenerator();
129 AliFatal("No pileup generator entry is found!");
132 AliGenerator *gen = entry->Generator();
134 AliFatal("No pileup generator specified!");
136 else if (gen->NeedsCollisionGeometry()) {
137 AliFatal("No Collision Geometry Provided");
140 // Check that the pileup rate is correctly set
141 Float_t rate = entry->Rate();
143 AliFatal(Form("Invalid rate value: %f",rate));
146 // Create cocktail header
147 if (fHeader) delete fHeader;
148 fHeader = new AliGenCocktailEventHeader("Pileup Cocktail Header");
150 // Generate time of all
151 // the collisions within one orbit
152 Int_t *nIntBC = new Int_t[3*AliTriggerBCMask::kNBits];
153 Int_t *indexBC = new Int_t[3*AliTriggerBCMask::kNBits];
155 while (nTotBC == 0) {
156 for(Int_t iBC = 0; iBC < AliTriggerBCMask::kNBits; iBC++) {
158 if (!fBCMask.GetMask(iBC)) continue;
160 // Int_t nInteractions = gRandom->Poisson(rate);
163 nInteractions = gRandom->Poisson(rate);
165 nInteractions = TMath::Nint(rate) + 1;
167 if (nInteractions == 0) continue;
169 nIntBC[nTotBC] = nInteractions;
170 indexBC[nTotBC] = iBC;
175 // Select the bunch crossing for triggered event
176 Int_t iTrgBC = gRandom->Integer(nTotBC);
177 // Subtract one from the number of events
178 // generated within this bc (only in case
179 // the user disabled the generation of the trigger
181 if (!fGenTrig) nIntBC[iTrgBC]--;
183 // Remove bunch crossings outside pileup
185 for(Int_t iBC = 0; iBC < nTotBC; iBC++) {
186 if (TMath::Abs(25e-9*(indexBC[iBC]-indexBC[iTrgBC])) > fPileUpTimeWindow)
190 // Generate the two orbits around the central one
191 // taking into account the pileup time window
192 for(Int_t iBC = 0; iBC < AliTriggerBCMask::kNBits; iBC++) {
194 if (!fBCMask.GetMask(iBC)) continue;
196 if (TMath::Abs(25e-9*(iBC-AliTriggerBCMask::kNBits-indexBC[iTrgBC])) > fPileUpTimeWindow) continue;
198 Int_t nInteractions = gRandom->Poisson(rate);
199 if (nInteractions == 0) continue;
201 nIntBC[nTotBC] = nInteractions;
202 indexBC[nTotBC] = iBC-AliTriggerBCMask::kNBits;
205 for(Int_t iBC = 0; iBC < AliTriggerBCMask::kNBits; iBC++) {
207 if (!fBCMask.GetMask(iBC)) continue;
209 if (TMath::Abs(25e-9*(iBC+AliTriggerBCMask::kNBits-indexBC[iTrgBC])) > fPileUpTimeWindow) continue;
211 Int_t nInteractions = gRandom->Poisson(rate);
212 if (nInteractions == 0) continue;
214 nIntBC[nTotBC] = nInteractions;
215 indexBC[nTotBC] = iBC+AliTriggerBCMask::kNBits;
219 // Loop over the generated collision times, call the generator
220 // and correct the partcile times in the stack
221 AliStack *stack = AliRunLoader::Instance()->Stack();
223 entry->SetFirst(lastpart);
225 for(Int_t iBC = 0; iBC < nTotBC; iBC++) {
226 Float_t deltat = 25e-9*(indexBC[iBC] - indexBC[iTrgBC]);
227 for (Int_t i = 0; i < nIntBC[iBC]; i++) {
228 // Generate the vertex position and time
230 TArrayF eventVertex(3);
231 for (Int_t j=0; j < 3; j++) eventVertex[j] = fVertex[j];
232 Double_t vTime = deltat + gRandom->Gaus(0,fOsigma[2]/TMath::Ccgs());
234 gen->SetVertex(fVertex.At(0), fVertex.At(1), fVertex.At(2));
237 for (Int_t k = lastpart; k < stack->GetNprimary(); k++) {
239 stack->Particle(k)->ProductionVertex(v);
241 stack->Particle(k)->SetProductionVertex(v);
243 lastpart = stack->GetNprimary();
245 // Store the interaction header in the container of the headers
246 ((AliGenEventHeader*) fHeader->GetHeaders()->Last())->SetPrimaryVertex(eventVertex);
252 entry->SetLast(stack->GetNprimary());
254 fHeader->CalcNProduced();
257 fContainer->AddHeader(fHeader);
259 gAlice->SetGenEventHeader(fHeader);
264 void AliGenPileup::SetRandomise(Bool_t /*flag*/)
266 // This setting is not implemented in
267 // case of pileup generation
268 // So the method gives an warning and exits
269 AliWarning("This setting has no effect on the generator!");
272 void AliGenPileup::UsePerEventRates()
274 // This setting is not implemented in
275 // case of pileup generation
276 // So the method gives an warning and exits
277 AliWarning("This setting has no effect on the generator!");