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