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. *
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12 * about the suitability of this software for any purpose. It is *
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14 **************************************************************************/
16 /// \class AliTPCExBEffective
17 /// \brief Correct for the rest of ExB effect which are not covered by physical models
21 /// dr = c0* integral(Er/Ez) + c1* integral(Erphi/Ez)
22 /// drphi = -c1* integral(Er/Ez) + c0* integral(Erphi/Ez)
24 /// wt = Bz*(k*vdrift/E) ~ 0.3 at B=0.5 T
25 /// c0 = 1/(1+T2*T2*wt*wt)
26 /// c1 = T1*wt/(1+T1*T1*wt*wt)
28 /// Residual integral(Er/Ez,Erphi/Ez) obtained comparing the B field 0 and B field +-0.5 T setting
29 /// minimizing track matching residuals
30 /// delta(Er/Ez) ~ sum[ poln(r) * polm(z) * cos(n,phi)]
33 #include "TGeoGlobalMagField.h"
34 #include "AliTPCcalibDB.h"
35 #include "AliTPCParam.h"
39 #include "AliTPCROC.h"
40 #include "AliTPCExBEffective.h"
42 ClassImp(AliTPCExBEffective)
45 AliTPCExBEffective::AliTPCExBEffective()
46 : AliTPCCorrection("ExB_effective","ExB effective"),
54 // default constructor
58 AliTPCExBEffective::~AliTPCExBEffective() {
59 /// default destructor
65 void AliTPCExBEffective::Init() {
66 /// Initialization funtion
68 AliMagF* magF= (AliMagF*)TGeoGlobalMagField::Instance()->GetField();
69 if (!magF) AliError("Magneticd field - not initialized");
70 Double_t bzField = magF->SolenoidField()/10.; //field in T
71 AliTPCParam *param= AliTPCcalibDB::Instance()->GetParameters();
72 if (!param) AliError("Parameters - not initialized");
73 Double_t vdrift = param->GetDriftV()/1000000.; // [cm/us] // From dataBase: to be updated: per second (ideally)
74 Double_t ezField = 400; // [V/cm] // to be updated: never (hopefully)
75 Double_t wt = -10.0 * (bzField*10) * vdrift / ezField ;
76 // Correction Terms for effective omegaTau; obtained by a laser calibration run
77 SetOmegaTauT1T2(wt,fT1,fT2);
82 void AliTPCExBEffective::Update(const TTimeStamp &/*timeStamp*/) {
85 AliMagF* magF= (AliMagF*)TGeoGlobalMagField::Instance()->GetField();
86 if (!magF) AliError("Magneticd field - not initialized");
87 Double_t bzField = magF->SolenoidField()/10.; //field in T
88 AliTPCParam *param= AliTPCcalibDB::Instance()->GetParameters();
89 if (!param) AliError("Parameters - not initialized");
90 Double_t vdrift = param->GetDriftV()/1000000.; // [cm/us] // From dataBase: to be updated: per second (ideally)
91 Double_t ezField = 400; // [V/cm] // to be updated: never (hopefully)
92 Double_t wt = -10.0 * (bzField*10) * vdrift / ezField ;
93 // Correction Terms for effective omegaTau; obtained by a laser calibration run
94 SetOmegaTauT1T2(wt,fT1,fT2);
101 void AliTPCExBEffective::GetCorrection(const Float_t x[],const Short_t roc,Float_t dx[]) {
102 /// Calculates the correction due conical shape
104 if (!fPolynomA) return;
105 AliTPCROC * calROC = AliTPCROC::Instance();
106 const Double_t kRTPC0 =calROC->GetPadRowRadii(0,0);
107 const Double_t kRTPC1 =calROC->GetPadRowRadii(36,calROC->GetNRows(36)-1);
108 Float_t rmiddle=(kRTPC0+kRTPC1)/2.;
110 Double_t phi = TMath::ATan2(x[1],x[0]);
111 Double_t r = TMath::Sqrt(x[1]*x[1]+x[0]*x[0]);
112 Double_t driftN = 1.-TMath::Abs(x[2])/calROC->GetZLength(0); // drift from 0 to 1
113 Double_t localxN = 2*(r-rmiddle)/(kRTPC1-kRTPC0); // normalize local x position
116 Double_t erphiez = 0;
117 if (roc%36<18) erez= GetSum(*fPolynomA, *fPolynomValA, localxN, driftN, phi,0);
118 if (roc%36>=18) erez= GetSum(*fPolynomC, *fPolynomValC, localxN, driftN, phi,0);
119 if (roc%36<18) erphiez= GetSum(*fPolynomA, *fPolynomValA, localxN, driftN, phi,1);
120 if (roc%36>=18) erphiez= GetSum(*fPolynomC, *fPolynomValC, localxN, driftN, phi,1);
122 Double_t dr = fC0 * erez + fC1 * erphiez;
123 Double_t drphi = -fC1 * erez + fC0 * erphiez;
125 // Calculate distorted position
130 // Calculate correction in cartesian coordinates
131 dx[0] = r * TMath::Cos(phi) - x[0];
132 dx[1] = r * TMath::Sin(phi) - x[1];
133 dx[2] = 0.; // z distortion not implemented (1st order distortions)
139 Double_t AliTPCExBEffective::GetSum(const TMatrixD& mpol, const TMatrixD&mcoef, Double_t r, Double_t drift, Double_t phi, Int_t coord) const {
140 /// Summation of the polynomials
142 Int_t npols=mpol.GetNrows();
144 for (Int_t ipol=0;ipol<npols; ipol++){
145 Double_t pR = 1, pD=1, pPhi=1;
146 Int_t icoord = TMath::Nint(mpol(ipol,0));
147 if (icoord!=coord) continue;
148 Int_t npolR = TMath::Nint(mpol(ipol,1));
149 Int_t npolD = TMath::Nint(mpol(ipol,2));
150 Int_t npolPhi = TMath::Nint(mpol(ipol,3));
151 Double_t coef=mcoef(ipol,0);
153 for (Int_t ipolR=1; ipolR<=npolR; ipolR++) pR*=r; // use simple polynoms
154 for (Int_t ipolD=1; ipolD<=npolD; ipolD++) pD*=drift; // use simple polynoms
155 pPhi=TMath::Cos(npolPhi*phi);
156 sum+= pR*pD*pPhi*coef;
162 void AliTPCExBEffective::SetPolynoms(const TMatrixD *polA,const TMatrixD *polC){
163 /// Set correction polynom - coefficients
165 fPolynomA = new TMatrixD(*polA);
166 fPolynomC = new TMatrixD(*polC);
169 void AliTPCExBEffective::SetCoeficients(const TMatrixD *valA,const TMatrixD *valC){
170 /// Set correction polynom - coefficients
172 fPolynomValA = new TMatrixD(*valA);
173 fPolynomValC = new TMatrixD(*valC);
179 void AliTPCExBEffective::Print(const Option_t* option) const {
180 /// Print function to check the settings (e.g. the twist in the X direction)
181 /// option=="a" prints the C0 and C1 coefficents for calibration purposes
183 TString opt = option; opt.ToLower();
184 printf("%s\t%s\n",GetName(),GetTitle());
186 if (opt.Contains("a")) { // Print all details
187 printf(" - T1: %1.4f, T2: %1.4f \n",fT1,fT2);
188 printf(" - C0: %1.4f, C1: %1.4f \n",fC0,fC1);
189 fPolynomValA->Print();
190 fPolynomValC->Print();