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56b1929b | 1 | /************************************************************************** |
2 | * Copyright(c) 1998-1999, ALICE Experiment at CERN, All rights reserved. * | |
3 | * * | |
4 | * Author: The ALICE Off-line Project. * | |
5 | * Contributors are mentioned in the code where appropriate. * | |
6 | * * | |
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 | **************************************************************************/ | |
15 | ||
16 | /* $Id$ */ | |
17 | ||
18 | //____________________________________________________________________ | |
19 | // | |
7684b53c | 20 | // Reconstruct charged particle multiplicity in the FMD |
21 | // | |
22 | // [See also the AliFMDReconstructor class] | |
23 | // | |
24 | // This class reconstructs the multiplicity based on the assumption | |
088f8e79 | 25 | // that all particles are minimum ionizing. |
26 | // Hence, the name `naiive' | |
56b1929b | 27 | // |
28 | #include "AliFMD.h" // ALIFMD_H | |
29 | #include "AliFMDMultNaiive.h" // ALIFMDMULTNAIIVE_H | |
1a1fdef7 | 30 | #include "AliFMDParameters.h" // ALIFMDPARAMETERS_H |
56b1929b | 31 | #include "AliFMDMultStrip.h" // ALIFMDMULTNAIIVE_H |
32 | #include "AliFMDDigit.h" // ALIFMDDIGIT_H | |
33 | #include <TClonesArray.h> // ROOT_TClonesArray | |
34 | #include <TTree.h> // ROOT_TTree | |
35 | ||
36 | //____________________________________________________________________ | |
925e6570 | 37 | ClassImp(AliFMDMultNaiive) |
1a1fdef7 | 38 | #if 0 |
39 | ; // This is here to keep Emacs for indenting the next line | |
40 | #endif | |
56b1929b | 41 | |
42 | //____________________________________________________________________ | |
43 | AliFMDMultNaiive::AliFMDMultNaiive() | |
44 | : AliFMDMultAlgorithm("Naiive", "Naiive") | |
45 | { | |
46 | // Default CTOR | |
47 | fMult = new TClonesArray("AliFMDMultStrip", 1000); | |
48 | } | |
49 | ||
50 | //____________________________________________________________________ | |
51 | void | |
52 | AliFMDMultNaiive::PreRun(AliFMD* fmd) | |
53 | { | |
54 | // Initialise before a run | |
55 | AliFMDMultAlgorithm::PreRun(fmd); | |
1a1fdef7 | 56 | AliFMDParameters* pars = AliFMDParameters::Instance(); |
57 | fEdepMip = pars->GetEdepMip(); | |
58 | fGain = (Float_t(pars->GetVA1MipRange()) / pars->GetAltroChannelSize() | |
56b1929b | 59 | * fEdepMip); |
60 | } | |
61 | ||
62 | //____________________________________________________________________ | |
63 | void | |
64 | AliFMDMultNaiive::PreEvent(TTree* treeR, Float_t ipZ) | |
65 | { | |
66 | // Reset internal data | |
67 | AliFMDMultAlgorithm::PreEvent(treeR, ipZ); | |
68 | fTreeR->Branch("FMDNaiive", &fMult); | |
69 | } | |
70 | ||
71 | //____________________________________________________________________ | |
72 | void | |
73 | AliFMDMultNaiive::ProcessDigit(AliFMDDigit* digit, | |
74 | Float_t eta, | |
75 | Float_t phi, | |
76 | UShort_t count) | |
77 | { | |
78 | // Process one digit. | |
79 | // | |
80 | // Parameters: | |
81 | // | |
82 | // digit Digit to process | |
83 | // eta Pseudo-rapidity of digit | |
84 | // phi Azimuthal angle of digit | |
85 | // count ADC (corrected for the pedestal) | |
86 | // | |
87 | // This calculates the energy deposited and the number of MIPs that | |
88 | // this energy deposition corresponds to | |
89 | // | |
90 | // EnergyDeposited = cos(theta) * gain * count | |
91 | // Multiplicity = EnergyDeposited / EnergyDepositedPerMIP | |
92 | // | |
93 | // where gain is a conversion factor from number of counts to an | |
94 | // energy: | |
95 | // Pre_Amp_MIP_Range 1 | |
96 | // gain = ----------------- * --------------------- | |
97 | // ADC_channel_size EnergyDepositedPerMip | |
98 | // | |
99 | // and theta is the particles incident angle on the strip, given by | |
100 | // | |
101 | // theta = 2 * atan(exp(-eta)) | |
102 | // | |
103 | // The cos(theta) factor corrects for the fact that the particle may | |
104 | // traverse the strip at an angle, and therefor have a longer flight | |
105 | // length, leading to a larger energy deposition. | |
106 | // | |
107 | if (!digit) return; | |
108 | Double_t edep = Adc2Energy(digit, eta, count); | |
109 | Double_t mult = Energy2Multiplicity(digit, edep); | |
7684b53c | 110 | |
111 | AliFMDMultStrip* m = | |
112 | new ((*fMult)[fNMult]) AliFMDMultStrip(digit->Detector(), | |
113 | digit->Ring(), | |
114 | digit->Sector(), | |
115 | digit->Strip(), | |
116 | eta, phi, | |
117 | edep, mult, | |
118 | AliFMDMult::kNaiive); | |
119 | (void)m; | |
56b1929b | 120 | fNMult++; |
121 | } | |
122 | //____________________________________________________________________ | |
123 | Float_t | |
124 | AliFMDMultNaiive::Adc2Energy(AliFMDDigit* /* digit */, | |
125 | Float_t eta, | |
126 | UShort_t count) | |
127 | { | |
128 | // Converts number of ADC counts to energy deposited. | |
129 | // Note, that this member function can be overloaded by derived | |
130 | // classes to do strip-specific look-ups in databases or the like, | |
131 | // to find the proper gain for a strip. | |
132 | // | |
133 | // In this simple version, we calculate the energy deposited as | |
134 | // | |
135 | // EnergyDeposited = cos(theta) * gain * count | |
136 | // | |
137 | // where | |
138 | // | |
139 | // Pre_amp_MIP_Range | |
140 | // gain = ----------------- * Energy_deposited_per_MIP | |
141 | // ADC_channel_size | |
142 | // | |
143 | // is constant and the same for all strips. | |
21888c5f | 144 | Double_t theta = 2 * TMath::ATan(TMath::Exp(-eta)); |
c263f0ab | 145 | Double_t edep = TMath::Abs(TMath::Cos(theta)) * fGain * count; |
56b1929b | 146 | return edep; |
147 | } | |
148 | ||
149 | //____________________________________________________________________ | |
150 | Float_t | |
151 | AliFMDMultNaiive::Energy2Multiplicity(AliFMDDigit* /* digit */, | |
152 | Float_t edep) | |
153 | { | |
154 | // Converts an energy signal to number of particles. | |
155 | // Note, that this member function can be overloaded by derived | |
156 | // classes to do strip-specific look-ups in databases or the like, | |
157 | // to find the proper gain for a strip. | |
158 | // | |
159 | // In this simple version, we calculate the multiplicity as | |
160 | // | |
161 | // multiplicity = Energy_deposited / Energy_deposited_per_MIP | |
162 | // | |
163 | // where | |
164 | // | |
165 | // Energy_deposited_per_MIP = 1.664 * SI_density * SI_thickness | |
166 | // | |
167 | // is constant and the same for all strips | |
168 | return edep / fEdepMip; | |
169 | } | |
170 | ||
171 | ||
172 | ||
173 | //____________________________________________________________________ | |
174 | // | |
175 | // EOF | |
176 | // |