1 /**************************************************************************
2 * Copyright(c) 2004, ALICE Experiment at CERN, All rights reserved. *
4 * Author: The ALICE Off-line Project. *
5 * Contributors are mentioned in the code where appropriate. *
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14 **************************************************************************/
16 /** @file AliFMDSDigitizer.cxx
17 @author Christian Holm Christensen <cholm@nbi.dk>
18 @date Mon Mar 27 12:38:26 2006
19 @brief FMD Digitizers implementation
22 //////////////////////////////////////////////////////////////////////////////
24 // This class contains the procedures simulation ADC signal for the
25 // Forward Multiplicity detector : Hits->Digits and Hits->SDigits
32 // - ADC count in this channel
39 // - Total energy deposited in the strip
40 // - ADC count in this channel
42 // As the Digits and SDigits have so much in common, the classes
43 // AliFMDDigitizer and AliFMDSDigitizer are implemented via a base
44 // class AliFMDBaseDigitizer.
46 // +---------------------+
47 // | AliFMDBaseDigitizer |
48 // +---------------------+
51 // +----------+---------+
53 // +-----------------+ +------------------+
54 // | AliFMDDigitizer | | AliFMDSDigitizer |
55 // +-----------------+ +------------------+
57 // These classes has several paramters:
61 // (Only AliFMDDigitizer)
62 // Mean and width of the pedestal. The pedestal is simulated
63 // by a Guassian, but derived classes my override MakePedestal
64 // to simulate it differently (or pick it up from a database).
67 // The dymamic MIP range of the VA1_ALICE pre-amplifier chip
70 // The largest number plus one that can be stored in one
71 // channel in one time step in the ALTRO ADC chip.
74 // How many times the ALTRO ADC chip samples the VA1_ALICE
75 // pre-amplifier signal. The VA1_ALICE chip is read-out at
76 // 10MHz, while it's possible to drive the ALTRO chip at
77 // 25MHz. That means, that the ALTRO chip can have time to
78 // sample each VA1_ALICE signal up to 2 times. Although it's
79 // not certain this feature will be used in the production,
80 // we'd like have the option, and so it should be reflected in
84 // The shaping function of the VA1_ALICE is generally given by
86 // f(x) = A(1 - exp(-Bx))
88 // where A is the total charge collected in the pre-amp., and B is a
89 // paramter that depends on the shaping time of the VA1_ALICE circut.
91 // When simulating the shaping function of the VA1_ALICe
92 // pre-amp. chip, we have to take into account, that the shaping
93 // function depends on the previous value of read from the pre-amp.
95 // That results in the following algorithm:
98 // FOR charge IN pre-amp. charge train DO
99 // IF last < charge THEN
100 // f(t) = (charge - last) * (1 - exp(-B * t)) + last
102 // f(t) = (last - charge) * exp(-B * t) + charge)
104 // FOR i IN # samples DO
105 // adc_i = f(i / (# samples))
112 // pre-amp. charge train
113 // is a series of 128 charges read from the VA1_ALICE chip
116 // is the number of times the ALTRO ADC samples each of the 128
117 // charges from the pre-amp.
119 // Where Q is the total charge collected by the VA1_ALICE
120 // pre-amplifier. Q is then given by
126 // where E is the total energy deposited in a silicon strip, R is the
127 // dynamic range of the VA1_ALICE pre-amp (fVA1MipRange), e is the
128 // energy deposited by a single MIP, and S ALTRO channel size in each
129 // time step (fAltroChannelSize).
131 // The energy deposited per MIP is given by
135 // where M is the universal number 1.664, rho is the density of
136 // silicon, and w is the depth of the silicon sensor.
138 // The final ADC count is given by
142 // where P is the (randomized) pedestal (see MakePedestal)
144 // This class uses the class template AliFMDMap<Type> to make an
145 // internal cache of the energy deposted of the hits. The class
146 // template is instantasized as
148 // typedef AliFMDMap<std::pair<Float_t, UShort_t> > AliFMDEdepMap;
150 // The first member of the values is the summed energy deposition in a
151 // given strip, while the second member of the values is the number of
152 // hits in a given strip. Using the second member, it's possible to
153 // do some checks on just how many times a strip got hit, and what
154 // kind of error we get in our reconstructed hits. Note, that this
155 // information is currently not written to the digits tree. I think a
156 // QA (Quality Assurance) digit tree is better suited for that task.
157 // However, the information is there to be used in the future.
160 // Latest changes by Christian Holm Christensen
162 //////////////////////////////////////////////////////////////////////////////
165 // | A(-1 + B + exp(-B))
166 // | f(x) dx = ------------------- = 1
170 // and B is the a parameter defined by the shaping time (fShapingTime).
172 // Solving the above equation, for A gives
175 // A = ----------------
178 // So, if we define the function g: [0,1] -> [0:1] by
181 // | Bu + exp(-Bu) - Bv - exp(-Bv)
182 // g(u,v) = | f(x) dx = -A -----------------------------
186 // we can evaluate the ALTRO sample of the VA1_ALICE pre-amp between
187 // any two times (u, v), by
190 // B Bu + exp(-Bu) - Bv - exp(-Bv)
191 // C = Q g(u,v) = - Q ---------------- -----------------------------
192 // -1 + B + exp(-B) B
194 // Bu + exp(-Bu) - Bv - exp(-Bv)
195 // = - Q -----------------------------
199 // #include <TTree.h> // ROOT_TTree
200 //#include <TRandom.h> // ROOT_TRandom
201 // #include <AliLog.h> // ALILOG_H
202 #include "AliFMDDebug.h" // Better debug macros
203 #include "AliFMDSDigitizer.h" // ALIFMDDIGITIZER_H
204 #include "AliFMD.h" // ALIFMD_H
205 // #include "AliFMDGeometry.h" // ALIFMDGEOMETRY_H
206 // #include "AliFMDDetector.h" // ALIFMDDETECTOR_H
207 // #include "AliFMDRing.h" // ALIFMDRING_H
208 #include "AliFMDHit.h" // ALIFMDHIT_H
209 // #include "AliFMDDigit.h" // ALIFMDDIGIT_H
210 // #include "AliFMDParameters.h" // ALIFMDPARAMETERS_H
211 // #include <AliRunDigitizer.h> // ALIRUNDIGITIZER_H
212 #include <AliRun.h> // ALIRUN_H
213 #include <AliLoader.h> // ALILOADER_H
214 #include <AliRunLoader.h> // ALIRUNLOADER_H
216 //====================================================================
217 ClassImp(AliFMDSDigitizer)
219 //____________________________________________________________________
220 AliFMDSDigitizer::AliFMDSDigitizer()
222 // Default ctor - don't use it
225 //____________________________________________________________________
226 AliFMDSDigitizer::AliFMDSDigitizer(const Char_t* headerFile,
227 const Char_t* /* sdigfile */)
228 : AliFMDBaseDigitizer("FMDSDigitizer", "FMD SDigitizer")
231 AliFMDDebug(1, (" processed"));
233 fRunLoader = AliRunLoader::GetRunLoader(); // Open(headerFile);
235 Fatal("AliFMDSDigitizer", "cannot open session, header file '%s'",
237 AliLoader* loader = fRunLoader->GetLoader("FMDLoader");
239 Fatal("AliFMDSDigitizer", "cannot find FMD loader in specified event");
241 // Add task to tasks folder
242 loader->PostSDigitizer(this);
246 //____________________________________________________________________
247 AliFMDSDigitizer::~AliFMDSDigitizer()
250 AliLoader* loader = fRunLoader->GetLoader("FMDLoader");
251 loader->CleanSDigitizer();
254 //____________________________________________________________________
256 AliFMDSDigitizer::Exec(Option_t*)
258 // Get the output manager
260 Error("Exec", "Run loader is not set");
263 if (!fRunLoader->GetAliRun()) fRunLoader->LoadgAlice();
264 if (!fRunLoader->TreeE()) fRunLoader->LoadHeader();
266 AliLoader* fmdLoader = fRunLoader->GetLoader("FMDLoader");
267 if (!fmdLoader) Fatal("Exec", "no FMD loader");
269 // Get the AliFMD object
271 static_cast<AliFMD*>(fRunLoader->GetAliRun()->GetDetector("FMD"));
273 AliError("Can not get FMD from gAlice");
277 Int_t nEvents = Int_t(fRunLoader->TreeE()->GetEntries());
278 for (Int_t event = 0; event < nEvents; event++) {
279 AliFMDDebug(1, (" Digitizing event number %d", event));
280 // Get the current loader
281 fRunLoader->GetEvent(event);
283 if (!fmdLoader->TreeS()) fmdLoader->MakeTree("S");
285 fmd->MakeBranch("S");
287 // Cache contriutions
288 SumContributions(fmd);
290 // Digitize the event
293 fmdLoader->TreeS()->Reset();
294 fmdLoader->TreeS()->Fill();
295 fmdLoader->WriteSDigits("OVERWRITE");
299 //____________________________________________________________________
301 AliFMDSDigitizer::AddDigit(AliFMD* fmd,
310 Short_t count4) const
312 // Add a summable digit
313 fmd->AddSDigitByFields(detector, ring, sector, strip, edep,
314 count1, count2, count3, count4);
319 //____________________________________________________________________