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2 | // Class AliRsnCutBetheBloch | |
3 | // | |
4 | // General implementation of a single cut strategy, which can be: | |
5 | // - a value contained in a given interval [--> IsBetween() ] | |
6 | // - a value equal to a given reference [--> MatchesValue()] | |
7 | // | |
8 | // In all cases, the reference value(s) is (are) given as data members | |
9 | // and each kind of cut requires a given value type (Int, UInt, Double), | |
10 | // but the cut check procedure is then automatized and chosen thanks to | |
11 | // an enumeration of the implemented cut types. | |
12 | // At the end, the user (or any other point which uses this object) has | |
13 | // to use the method IsSelected() to check if this cut has been passed. | |
14 | // | |
15 | // authors: Martin Vala (martin.vala@cern.ch) | |
16 | // Alberto Pulvirenti (alberto.pulvirenti@ct.infn.it) | |
17 | // | |
18 | #include "TMath.h" | |
19 | ||
20 | #include "AliLog.h" | |
21 | #include "AliESDtrack.h" | |
22 | ||
23 | #include "AliRsnDaughter.h" | |
24 | #include "AliRsnCutBetheBloch.h" | |
25 | ||
26 | ClassImp(AliRsnCutBetheBloch) | |
27 | ||
28 | //_________________________________________________________________________________________________ | |
29 | AliRsnCutBetheBloch::AliRsnCutBetheBloch() : | |
30 | AliRsnCut(), | |
31 | fCorrect(kTRUE), | |
32 | fMass(1.0), | |
33 | fMIP(50.0) | |
34 | { | |
35 | // | |
36 | // Default constructor. | |
37 | // | |
38 | ||
39 | fConst[0] = fConst[1] = fConst[2] = fConst[3] = fConst[4] = 0.0; | |
40 | } | |
41 | ||
42 | //_________________________________________________________________________________________________ | |
43 | AliRsnCutBetheBloch::AliRsnCutBetheBloch | |
44 | (const char *name, Double_t fractionRange, Double_t mass, Double_t mip, Bool_t correct) : | |
45 | AliRsnCut(name, -fractionRange, fractionRange), | |
46 | fCorrect(correct), | |
47 | fMass(mass), | |
48 | fMIP(mip) | |
49 | { | |
50 | // | |
51 | // Main constructor. | |
52 | // the cut range is the relative fraction of the value: | |
53 | // BB*(1-fraction) < TPC < BB*(1+fraction) | |
54 | // which means: | |
55 | // -fraction < (TPC - BB)/BB < fraction | |
56 | // | |
57 | ||
58 | fConst[0] = fConst[1] = fConst[2] = fConst[3] = fConst[4] = 0.0; | |
59 | } | |
60 | ||
61 | //_________________________________________________________________________________________________ | |
62 | AliRsnCutBetheBloch::AliRsnCutBetheBloch | |
63 | (const char *name, Double_t fractionRange, AliPID::EParticleType type, Double_t mip, Bool_t correct) : | |
64 | AliRsnCut(name, -fractionRange, fractionRange), | |
65 | fCorrect(correct), | |
66 | fMass(0.0), | |
67 | fMIP(mip) | |
68 | { | |
69 | // | |
70 | // Main constructor. | |
71 | // the cut range is the relative fraction of the value: | |
72 | // BB*(1-fraction) < TPC < BB*(1+fraction) | |
73 | // which means: | |
74 | // -fraction < (TPC - BB)/BB < fraction | |
75 | // | |
76 | ||
77 | SetMass(type); | |
78 | fConst[0] = fConst[1] = fConst[2] = fConst[3] = fConst[4] = 0.0; | |
79 | } | |
80 | ||
81 | //_____________________________________________________________________________ | |
82 | Double_t AliRsnCutBetheBloch::BetheBloch(AliRsnDaughter *track) | |
83 | { | |
84 | // | |
85 | // Computes the theoretical dE/dx according to | |
86 | // a given mass hypothesis, from which betaGamma is computed | |
87 | // | |
88 | // This is the empirical ALEPH parameterization of the Bethe-Bloch formula. | |
89 | // It is normalized to 1 at the minimum. | |
90 | // | |
91 | // The default values for the kp* parameters are for ALICE TPC. | |
92 | // The value is computed in MIP units, multiplied by 50 to have it in energy. | |
93 | // | |
94 | ||
95 | Double_t betaGamma = track->P() / fMass; | |
96 | Double_t beta = betaGamma / TMath::Sqrt(1.0 + betaGamma * betaGamma); | |
97 | Double_t aa = TMath::Power(beta, fConst[3]); | |
98 | Double_t bb = TMath::Power(1.0 / betaGamma, fConst[4]); | |
99 | ||
100 | bb = TMath::Log(fConst[2] + bb); | |
101 | ||
102 | Double_t out = (fConst[1] - aa - bb) * fConst[0] / aa; | |
103 | ||
104 | if (fCorrect) | |
105 | { | |
106 | Double_t kMeanCorr = 0.1; | |
107 | Double_t meanCorr = (1 + (out - 1) * kMeanCorr); | |
108 | out *= meanCorr; | |
109 | } | |
110 | ||
111 | return out * fMIP; | |
112 | } | |
113 | ||
114 | //_________________________________________________________________________________________________ | |
115 | Bool_t AliRsnCutBetheBloch::IsSelected(ETarget tgt, AliRsnDaughter *track) | |
116 | { | |
117 | // | |
118 | // Cut checker. | |
119 | // | |
120 | ||
121 | // coherence check | |
122 | if (tgt != AliRsnCut::kParticle) | |
123 | { | |
124 | AliError(Form("Wrong target. Skipping cut", GetName())); | |
125 | return kTRUE; | |
126 | } | |
127 | ||
128 | // retrieve the TPC signal | |
129 | AliVParticle *vpart = track->GetRef(); | |
130 | AliESDtrack *esd = dynamic_cast<AliESDtrack*>(vpart); | |
131 | if (!esd) { | |
132 | AliError("ESD information unavailable"); | |
133 | return kTRUE; | |
134 | } | |
135 | ||
136 | // compute Bethe-Bloch with the given mass hypothesis | |
137 | Double_t bb = BetheBloch(track); | |
138 | ||
139 | // the cut range is the relative fraction of the value: | |
140 | // BB*(1-fraction) < TPC < BB*(1+fraction) | |
141 | // which means: | |
142 | // -fraction < (TPC - BB)/BB < fraction | |
143 | // so we must compute the cut value accordingly | |
144 | fCutValueD = (esd->GetTPCsignal() - bb) / bb; | |
145 | ||
146 | // then, this cut is checked inside the range | |
147 | return OkRange(); | |
148 | } | |
149 | ||
150 | //_________________________________________________________________________________________________ | |
151 | Bool_t AliRsnCutBetheBloch::IsSelected(ETarget tgt, AliRsnPairParticle *pair) | |
152 | { | |
153 | // | |
154 | // Cut checker | |
155 | // | |
156 | ||
157 | AliWarning("Cannot apply this cut to pairs"); | |
158 | return kTRUE; | |
159 | } | |
160 | ||
161 | //_________________________________________________________________________________________________ | |
162 | Bool_t AliRsnCutBetheBloch::IsSelected(ETarget tgt, AliRsnEvent *event) | |
163 | { | |
164 | // | |
165 | // Cut checker | |
166 | // | |
167 | ||
168 | AliWarning("Cannot apply this cut to events"); | |
169 | return kTRUE; | |
170 | } | |
171 | ||
172 | //_________________________________________________________________________________________________ | |
173 | Bool_t AliRsnCutBetheBloch::IsSelected(ETarget tgt, AliRsnEvent *ev1, AliRsnEvent *ev2) | |
174 | { | |
175 | // | |
176 | // Cut checker | |
177 | // | |
178 | ||
179 | AliWarning("Cannot apply this cut to event mixing"); | |
180 | return kTRUE; | |
181 | } |