]> git.uio.no Git - u/mrichter/AliRoot.git/blame - MUON/AliMUONTrackParam.cxx
git://git.uio.no / u / mrichter / AliRoot.git / blame
? search:
summary | shortlog | log | commit | commitdiff | tree
blob | blame (incremental) | history | HEAD
Removing extrap.F (Christian)
[u/mrichter/AliRoot.git] / MUON / AliMUONTrackParam.cxx
CommitLineData
a9e2aefa 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
88cb7938 16/* $Id$ */
a9e2aefa 17
3831f268 18///////////////////////////////////////////////////
19//
20// Track parameters
21// in
22// ALICE
23// dimuon
24// spectrometer
a9e2aefa 25//
3831f268 26///////////////////////////////////////////////////
a9e2aefa 27
58443fe3 28//#include <Riostream.h>
3831f268 29#include "AliMUON.h"
a9e2aefa 30#include "AliMUONTrackParam.h"
58443fe3 31//#include "AliMUONChamber.h"
a9e2aefa 32#include "AliRun.h"
94de3818 33#include "AliMagF.h"
8c343c7c 34#include "AliLog.h"
a9e2aefa 35
36ClassImp(AliMUONTrackParam) // Class implementation in ROOT context
37
61adb9bd 38 //_________________________________________________________________________
30178c30 39AliMUONTrackParam::AliMUONTrackParam()
40 : TObject()
41{
42// Constructor
43
44 fInverseBendingMomentum = 0;
45 fBendingSlope = 0;
46 fNonBendingSlope = 0;
47 fZ = 0;
48 fBendingCoor = 0;
49 fNonBendingCoor = 0;
50}
61adb9bd 51
30178c30 52 //_________________________________________________________________________
53AliMUONTrackParam&
54AliMUONTrackParam::operator=(const AliMUONTrackParam& theMUONTrackParam)
61adb9bd 55{
58443fe3 56 // Asignment operator
30178c30 57 if (this == &theMUONTrackParam)
61adb9bd 58 return *this;
59
30178c30 60 // base class assignement
61 TObject::operator=(theMUONTrackParam);
62
63 fInverseBendingMomentum = theMUONTrackParam.fInverseBendingMomentum;
64 fBendingSlope = theMUONTrackParam.fBendingSlope;
65 fNonBendingSlope = theMUONTrackParam.fNonBendingSlope;
66 fZ = theMUONTrackParam.fZ;
67 fBendingCoor = theMUONTrackParam.fBendingCoor;
68 fNonBendingCoor = theMUONTrackParam.fNonBendingCoor;
61adb9bd 69
70 return *this;
71}
72 //_________________________________________________________________________
30178c30 73AliMUONTrackParam::AliMUONTrackParam(const AliMUONTrackParam& theMUONTrackParam)
74 : TObject(theMUONTrackParam)
61adb9bd 75{
58443fe3 76 // Copy constructor
30178c30 77 fInverseBendingMomentum = theMUONTrackParam.fInverseBendingMomentum;
78 fBendingSlope = theMUONTrackParam.fBendingSlope;
79 fNonBendingSlope = theMUONTrackParam.fNonBendingSlope;
80 fZ = theMUONTrackParam.fZ;
81 fBendingCoor = theMUONTrackParam.fBendingCoor;
82 fNonBendingCoor = theMUONTrackParam.fNonBendingCoor;
61adb9bd 83}
a9e2aefa 84
a9e2aefa 85 //__________________________________________________________________________
86void AliMUONTrackParam::ExtrapToZ(Double_t Z)
87{
88 // Track parameter extrapolation to the plane at "Z".
89 // On return, the track parameters resulting from the extrapolation
90 // replace the current track parameters.
a9e2aefa 91 if (this->fZ == Z) return; // nothing to be done if same Z
92 Double_t forwardBackward; // +1 if forward, -1 if backward
5b64e914 93 if (Z < this->fZ) forwardBackward = 1.0; // spectro. z<0
a9e2aefa 94 else forwardBackward = -1.0;
a6f03ddb 95 Double_t vGeant3[7], vGeant3New[7]; // 7 in parameter ????
a9e2aefa 96 Int_t iGeant3, stepNumber;
97 Int_t maxStepNumber = 5000; // in parameter ????
98 // For safety: return kTRUE or kFALSE ????
a6f03ddb 99 // Parameter vector for calling EXTRAP_ONESTEP
a9e2aefa 100 SetGeant3Parameters(vGeant3, forwardBackward);
956019b6 101 // sign of charge (sign of fInverseBendingMomentum if forward motion)
a6f03ddb 102 // must be changed if backward extrapolation
956019b6 103 Double_t chargeExtrap = forwardBackward *
104 TMath::Sign(Double_t(1.0), this->fInverseBendingMomentum);
a9e2aefa 105 Double_t stepLength = 6.0; // in parameter ????
106 // Extrapolation loop
107 stepNumber = 0;
5b64e914 108 while (((-forwardBackward * (vGeant3[2] - Z)) <= 0.0) && // spectro. z<0
a9e2aefa 109 (stepNumber < maxStepNumber)) {
110 stepNumber++;
a6f03ddb 111 // Option for switching between helix and Runge-Kutta ????
4d03a78e 112 //ExtrapOneStepRungekutta(chargeExtrap, stepLength, vGeant3, vGeant3New);
113 ExtrapOneStepHelix(chargeExtrap, stepLength, vGeant3, vGeant3New);
5b64e914 114 if ((-forwardBackward * (vGeant3New[2] - Z)) > 0.0) break; // one is beyond Z spectro. z<0
a9e2aefa 115 // better use TArray ????
116 for (iGeant3 = 0; iGeant3 < 7; iGeant3++)
117 {vGeant3[iGeant3] = vGeant3New[iGeant3];}
118 }
119 // check maxStepNumber ????
a9e2aefa 120 // Interpolation back to exact Z (2nd order)
121 // should be in function ???? using TArray ????
122 Double_t dZ12 = vGeant3New[2] - vGeant3[2]; // 1->2
123 Double_t dZ1i = Z - vGeant3[2]; // 1-i
124 Double_t dZi2 = vGeant3New[2] - Z; // i->2
125 Double_t xPrime = (vGeant3New[0] - vGeant3[0]) / dZ12;
126 Double_t xSecond =
127 ((vGeant3New[3] / vGeant3New[5]) - (vGeant3[3] / vGeant3[5])) / dZ12;
128 Double_t yPrime = (vGeant3New[1] - vGeant3[1]) / dZ12;
129 Double_t ySecond =
130 ((vGeant3New[4] / vGeant3New[5]) - (vGeant3[4] / vGeant3[5])) / dZ12;
131 vGeant3[0] = vGeant3[0] + xPrime * dZ1i - 0.5 * xSecond * dZ1i * dZi2; // X
132 vGeant3[1] = vGeant3[1] + yPrime * dZ1i - 0.5 * ySecond * dZ1i * dZi2; // Y
133 vGeant3[2] = Z; // Z
134 Double_t xPrimeI = xPrime - 0.5 * xSecond * (dZi2 - dZ1i);
135 Double_t yPrimeI = yPrime - 0.5 * ySecond * (dZi2 - dZ1i);
956019b6 136 // (PX, PY, PZ)/PTOT assuming forward motion
a9e2aefa 137 vGeant3[5] =
138 1.0 / TMath::Sqrt(1.0 + xPrimeI * xPrimeI + yPrimeI * yPrimeI); // PZ/PTOT
139 vGeant3[3] = xPrimeI * vGeant3[5]; // PX/PTOT
140 vGeant3[4] = yPrimeI * vGeant3[5]; // PY/PTOT
956019b6 141 // Track parameters from Geant3 parameters,
142 // with charge back for forward motion
143 GetFromGeant3Parameters(vGeant3, chargeExtrap * forwardBackward);
a9e2aefa 144}
145
146 //__________________________________________________________________________
147void AliMUONTrackParam::SetGeant3Parameters(Double_t *VGeant3, Double_t ForwardBackward)
148{
149 // Set vector of Geant3 parameters pointed to by "VGeant3"
150 // from track parameters in current AliMUONTrackParam.
151 // Since AliMUONTrackParam is only geometry, one uses "ForwardBackward"
152 // to know whether the particle is going forward (+1) or backward (-1).
153 VGeant3[0] = this->fNonBendingCoor; // X
154 VGeant3[1] = this->fBendingCoor; // Y
155 VGeant3[2] = this->fZ; // Z
156 Double_t pYZ = TMath::Abs(1.0 / this->fInverseBendingMomentum);
157 Double_t pZ =
158 pYZ / TMath::Sqrt(1.0 + this->fBendingSlope * this->fBendingSlope);
159 VGeant3[6] =
160 TMath::Sqrt(pYZ * pYZ +
161 pZ * pZ * this->fNonBendingSlope * this->fNonBendingSlope); // PTOT
5b64e914 162 VGeant3[5] = -ForwardBackward * pZ / VGeant3[6]; // PZ/PTOT spectro. z<0
a9e2aefa 163 VGeant3[3] = this->fNonBendingSlope * VGeant3[5]; // PX/PTOT
164 VGeant3[4] = this->fBendingSlope * VGeant3[5]; // PY/PTOT
165}
166
167 //__________________________________________________________________________
168void AliMUONTrackParam::GetFromGeant3Parameters(Double_t *VGeant3, Double_t Charge)
169{
170 // Get track parameters in current AliMUONTrackParam
956019b6 171 // from Geant3 parameters pointed to by "VGeant3",
172 // assumed to be calculated for forward motion in Z.
a9e2aefa 173 // "InverseBendingMomentum" is signed with "Charge".
174 this->fNonBendingCoor = VGeant3[0]; // X
175 this->fBendingCoor = VGeant3[1]; // Y
176 this->fZ = VGeant3[2]; // Z
177 Double_t pYZ = VGeant3[6] * TMath::Sqrt(1.0 - VGeant3[3] * VGeant3[3]);
178 this->fInverseBendingMomentum = Charge / pYZ;
179 this->fBendingSlope = VGeant3[4] / VGeant3[5];
180 this->fNonBendingSlope = VGeant3[3] / VGeant3[5];
181}
182
183 //__________________________________________________________________________
184void AliMUONTrackParam::ExtrapToStation(Int_t Station, AliMUONTrackParam *TrackParam)
185{
186 // Track parameters extrapolated from current track parameters ("this")
187 // to both chambers of the station(0..) "Station"
188 // are returned in the array (dimension 2) of track parameters
189 // pointed to by "TrackParam" (index 0 and 1 for first and second chambers).
190 Double_t extZ[2], z1, z2;
ecfa008b 191 Int_t i1 = -1, i2 = -1; // = -1 to avoid compilation warnings
a9e2aefa 192 AliMUON *pMUON = (AliMUON*) gAlice->GetModule("MUON"); // necessary ????
193 // range of Station to be checked ????
194 z1 = (&(pMUON->Chamber(2 * Station)))->Z(); // Z of first chamber
195 z2 = (&(pMUON->Chamber(2 * Station + 1)))->Z(); // Z of second chamber
196 // First and second Z to extrapolate at
197 if ((z1 > this->fZ) && (z2 > this->fZ)) {i1 = 0; i2 = 1;}
198 else if ((z1 < this->fZ) && (z2 < this->fZ)) {i1 = 1; i2 = 0;}
199 else {
8c343c7c 200 AliError(Form("Starting Z (%f) in between z1 (%f) and z2 (%f) of station(0..)%d",this->fZ,z1,z2,Station));
201// cout << "ERROR in AliMUONTrackParam::CreateExtrapSegmentInStation" << endl;
202// cout << "Starting Z (" << this->fZ << ") in between z1 (" << z1 <<
203// ") and z2 (" << z2 << ") of station(0..) " << Station << endl;
a9e2aefa 204 }
205 extZ[i1] = z1;
206 extZ[i2] = z2;
207 // copy of track parameters
208 TrackParam[i1] = *this;
209 // first extrapolation
210 (&(TrackParam[i1]))->ExtrapToZ(extZ[0]);
211 TrackParam[i2] = TrackParam[i1];
212 // second extrapolation
213 (&(TrackParam[i2]))->ExtrapToZ(extZ[1]);
214 return;
215}
216
04b5ea16 217 //__________________________________________________________________________
889a0215 218void AliMUONTrackParam::ExtrapToVertex(Double_t xVtx, Double_t yVtx, Double_t zVtx)
04b5ea16 219{
220 // Extrapolation to the vertex.
221 // Returns the track parameters resulting from the extrapolation,
222 // in the current TrackParam.
956019b6 223 // Changes parameters according to Branson correction through the absorber
04b5ea16 224
5b64e914 225 Double_t zAbsorber = -503.0; // to be coherent with the Geant absorber geometry !!!!
226 // spectro. (z<0)
04b5ea16 227 // Extrapolates track parameters upstream to the "Z" end of the front absorber
b45fd22b 228 ExtrapToZ(zAbsorber); // !!!
5b64e914 229 // Makes Branson correction (multiple scattering + energy loss)
889a0215 230 BransonCorrection(xVtx,yVtx,zVtx);
5b64e914 231 // Makes a simple magnetic field correction through the absorber
b45fd22b 232 FieldCorrection(zAbsorber);
04b5ea16 233}
234
43af2cb6 235
236// Keep this version for future developments
04b5ea16 237 //__________________________________________________________________________
43af2cb6 238// void AliMUONTrackParam::BransonCorrection()
239// {
240// // Branson correction of track parameters
241// // the entry parameters have to be calculated at the end of the absorber
242// Double_t zEndAbsorber, zBP, xBP, yBP;
243// Double_t pYZ, pX, pY, pZ, pTotal, xEndAbsorber, yEndAbsorber, radiusEndAbsorber2, pT, theta;
244// Int_t sign;
245// // Would it be possible to calculate all that from Geant configuration ????
246// // and to get the Branson parameters from a function in ABSO module ????
247// // with an eventual contribution from other detectors like START ????
248// // Radiation lengths outer part theta > 3 degres
249// static Double_t x01[9] = { 18.8, // C (cm)
250// 10.397, // Concrete (cm)
251// 0.56, // Plomb (cm)
252// 47.26, // Polyethylene (cm)
253// 0.56, // Plomb (cm)
254// 47.26, // Polyethylene (cm)
255// 0.56, // Plomb (cm)
256// 47.26, // Polyethylene (cm)
257// 0.56 }; // Plomb (cm)
258// // inner part theta < 3 degres
259// static Double_t x02[3] = { 18.8, // C (cm)
260// 10.397, // Concrete (cm)
261// 0.35 }; // W (cm)
262// // z positions of the materials inside the absober outer part theta > 3 degres
263// static Double_t z1[10] = { 90, 315, 467, 472, 477, 482, 487, 492, 497, 502 };
264// // inner part theta < 3 degres
265// static Double_t z2[4] = { 90, 315, 467, 503 };
266// static Bool_t first = kTRUE;
267// static Double_t zBP1, zBP2, rLimit;
268// // Calculates z positions of the Branson's planes: zBP1 for outer part and zBP2 for inner part (only at the first call)
269// if (first) {
270// first = kFALSE;
271// Double_t aNBP = 0.0;
272// Double_t aDBP = 0.0;
273// Int_t iBound;
274
275// for (iBound = 0; iBound < 9; iBound++) {
276// aNBP = aNBP +
277// (z1[iBound+1] * z1[iBound+1] * z1[iBound+1] -
278// z1[iBound] * z1[iBound] * z1[iBound] ) / x01[iBound];
279// aDBP = aDBP +
280// (z1[iBound+1] * z1[iBound+1] - z1[iBound] * z1[iBound] ) / x01[iBound];
281// }
282// zBP1 = (2.0 * aNBP) / (3.0 * aDBP);
283// aNBP = 0.0;
284// aDBP = 0.0;
285// for (iBound = 0; iBound < 3; iBound++) {
286// aNBP = aNBP +
287// (z2[iBound+1] * z2[iBound+1] * z2[iBound+1] -
288// z2[iBound] * z2[iBound ] * z2[iBound] ) / x02[iBound];
289// aDBP = aDBP +
290// (z2[iBound+1] * z2[iBound+1] - z2[iBound] * z2[iBound]) / x02[iBound];
291// }
292// zBP2 = (2.0 * aNBP) / (3.0 * aDBP);
293// rLimit = z2[3] * TMath::Tan(3.0 * (TMath::Pi()) / 180.);
294// }
295
296// pYZ = TMath::Abs(1.0 / fInverseBendingMomentum);
297// sign = 1;
298// if (fInverseBendingMomentum < 0) sign = -1;
299// pZ = pYZ / (TMath::Sqrt(1.0 + fBendingSlope * fBendingSlope));
300// pX = pZ * fNonBendingSlope;
301// pY = pZ * fBendingSlope;
302// pTotal = TMath::Sqrt(pYZ *pYZ + pX * pX);
303// xEndAbsorber = fNonBendingCoor;
304// yEndAbsorber = fBendingCoor;
305// radiusEndAbsorber2 = xEndAbsorber * xEndAbsorber + yEndAbsorber * yEndAbsorber;
306
307// if (radiusEndAbsorber2 > rLimit*rLimit) {
308// zEndAbsorber = z1[9];
309// zBP = zBP1;
310// } else {
311// zEndAbsorber = z2[3];
312// zBP = zBP2;
313// }
314
315// xBP = xEndAbsorber - (pX / pZ) * (zEndAbsorber - zBP);
316// yBP = yEndAbsorber - (pY / pZ) * (zEndAbsorber - zBP);
317
318// // new parameters after Branson and energy loss corrections
319// pZ = pTotal * zBP / TMath::Sqrt(xBP * xBP + yBP * yBP + zBP * zBP);
320// pX = pZ * xBP / zBP;
321// pY = pZ * yBP / zBP;
322// fBendingSlope = pY / pZ;
323// fNonBendingSlope = pX / pZ;
324
325// pT = TMath::Sqrt(pX * pX + pY * pY);
326// theta = TMath::ATan2(pT, pZ);
327// pTotal =
328// TotalMomentumEnergyLoss(rLimit, pTotal, theta, xEndAbsorber, yEndAbsorber);
329
330// fInverseBendingMomentum = (sign / pTotal) *
331// TMath::Sqrt(1.0 +
332// fBendingSlope * fBendingSlope +
333// fNonBendingSlope * fNonBendingSlope) /
334// TMath::Sqrt(1.0 + fBendingSlope * fBendingSlope);
335
336// // vertex position at (0,0,0)
337// // should be taken from vertex measurement ???
338// fBendingCoor = 0.0;
339// fNonBendingCoor = 0;
340// fZ= 0;
341// }
342
889a0215 343void AliMUONTrackParam::BransonCorrection(Double_t xVtx,Double_t yVtx,Double_t zVtx)
04b5ea16 344{
345 // Branson correction of track parameters
346 // the entry parameters have to be calculated at the end of the absorber
43af2cb6 347 // simplified version: the z positions of Branson's planes are no longer calculated
348 // but are given as inputs. One can use the macros MUONTestAbso.C and DrawTestAbso.C
349 // to test this correction.
04b5ea16 350 // Would it be possible to calculate all that from Geant configuration ????
956019b6 351 // and to get the Branson parameters from a function in ABSO module ????
352 // with an eventual contribution from other detectors like START ????
889a0215 353 //change to take into account the vertex postition (real, reconstruct,....)
354
43af2cb6 355 Double_t zBP, xBP, yBP;
356 Double_t pYZ, pX, pY, pZ, pTotal, xEndAbsorber, yEndAbsorber, radiusEndAbsorber2, pT, theta;
357 Int_t sign;
04b5ea16 358 static Bool_t first = kTRUE;
b45fd22b 359 static Double_t zBP1, zBP2, rLimit, thetaLimit, zEndAbsorber;
43af2cb6 360 // zBP1 for outer part and zBP2 for inner part (only at the first call)
04b5ea16 361 if (first) {
362 first = kFALSE;
43af2cb6 363
5b64e914 364 zEndAbsorber = -503; // spectro (z<0)
b45fd22b 365 thetaLimit = 3.0 * (TMath::Pi()) / 180.;
5b64e914 366 rLimit = TMath::Abs(zEndAbsorber) * TMath::Tan(thetaLimit);
367 zBP1 = -450; // values close to those calculated with EvalAbso.C
368 zBP2 = -480;
04b5ea16 369 }
370
371 pYZ = TMath::Abs(1.0 / fInverseBendingMomentum);
372 sign = 1;
b8dc484b 373 if (fInverseBendingMomentum < 0) sign = -1;
374 pZ = Pz();
375 pX = Px();
376 pY = Py();
04b5ea16 377 pTotal = TMath::Sqrt(pYZ *pYZ + pX * pX);
378 xEndAbsorber = fNonBendingCoor;
379 yEndAbsorber = fBendingCoor;
380 radiusEndAbsorber2 = xEndAbsorber * xEndAbsorber + yEndAbsorber * yEndAbsorber;
381
382 if (radiusEndAbsorber2 > rLimit*rLimit) {
04b5ea16 383 zBP = zBP1;
384 } else {
04b5ea16 385 zBP = zBP2;
386 }
387
388 xBP = xEndAbsorber - (pX / pZ) * (zEndAbsorber - zBP);
389 yBP = yEndAbsorber - (pY / pZ) * (zEndAbsorber - zBP);
390
391 // new parameters after Branson and energy loss corrections
b45fd22b 392// Float_t zSmear = zBP - gRandom->Gaus(0.,2.); // !!! possible smearing of Z vertex position
889a0215 393
394 Float_t zSmear = zBP ;
b45fd22b 395
889a0215 396 pZ = pTotal * (zSmear-zVtx) / TMath::Sqrt((xBP-xVtx) * (xBP-xVtx) + (yBP-yVtx) * (yBP-yVtx) +( zSmear-zVtx) * (zSmear-zVtx) );
397 pX = pZ * (xBP - xVtx)/ (zSmear-zVtx);
398 pY = pZ * (yBP - yVtx) / (zSmear-zVtx);
04b5ea16 399 fBendingSlope = pY / pZ;
400 fNonBendingSlope = pX / pZ;
5b64e914 401
04b5ea16 402
403 pT = TMath::Sqrt(pX * pX + pY * pY);
5b64e914 404 theta = TMath::ATan2(pT, TMath::Abs(pZ));
b45fd22b 405 pTotal = TotalMomentumEnergyLoss(thetaLimit, pTotal, theta);
04b5ea16 406
407 fInverseBendingMomentum = (sign / pTotal) *
408 TMath::Sqrt(1.0 +
409 fBendingSlope * fBendingSlope +
410 fNonBendingSlope * fNonBendingSlope) /
411 TMath::Sqrt(1.0 + fBendingSlope * fBendingSlope);
412
413 // vertex position at (0,0,0)
414 // should be taken from vertex measurement ???
889a0215 415
416 fBendingCoor = xVtx;
417 fNonBendingCoor = yVtx;
418 fZ= zVtx;
419
04b5ea16 420}
b45fd22b 421
04b5ea16 422 //__________________________________________________________________________
b45fd22b 423Double_t AliMUONTrackParam::TotalMomentumEnergyLoss(Double_t thetaLimit, Double_t pTotal, Double_t theta)
04b5ea16 424{
425 // Returns the total momentum corrected from energy loss in the front absorber
43af2cb6 426 // One can use the macros MUONTestAbso.C and DrawTestAbso.C
427 // to test this correction.
b45fd22b 428 // Momentum energy loss behaviour evaluated with the simulation of single muons (april 2002)
04b5ea16 429 Double_t deltaP, pTotalCorrected;
430
b45fd22b 431 // Parametrization to be redone according to change of absorber material ????
956019b6 432 // See remark in function BransonCorrection !!!!
04b5ea16 433 // The name is not so good, and there are many arguments !!!!
b45fd22b 434 if (theta < thetaLimit ) {
435 if (pTotal < 20) {
436 deltaP = 2.5938 + 0.0570 * pTotal - 0.001151 * pTotal * pTotal;
04b5ea16 437 } else {
b45fd22b 438 deltaP = 3.0714 + 0.011767 *pTotal;
04b5ea16 439 }
440 } else {
b45fd22b 441 if (pTotal < 20) {
442 deltaP = 2.1207 + 0.05478 * pTotal - 0.00145079 * pTotal * pTotal;
04b5ea16 443 } else {
b45fd22b 444 deltaP = 2.6069 + 0.0051705 * pTotal;
04b5ea16 445 }
446 }
447 pTotalCorrected = pTotal + deltaP / TMath::Cos(theta);
448 return pTotalCorrected;
449}
450
b45fd22b 451 //__________________________________________________________________________
452void AliMUONTrackParam::FieldCorrection(Double_t Z)
453{
454 //
455 // Correction of the effect of the magnetic field in the absorber
456 // Assume a constant field along Z axis.
457
458 Float_t b[3],x[3];
459 Double_t bZ;
460 Double_t pYZ,pX,pY,pZ,pT;
461 Double_t pXNew,pYNew;
462 Double_t c;
463
464 pYZ = TMath::Abs(1.0 / fInverseBendingMomentum);
465 c = TMath::Sign(1.0,fInverseBendingMomentum); // particle charge
466
b8dc484b 467 pZ = Pz();
468 pX = Px();
469 pY = Py();
b45fd22b 470 pT = TMath::Sqrt(pX*pX+pY*pY);
471
5b64e914 472 if (TMath::Abs(pZ) <= 0) return;
b45fd22b 473 x[2] = Z/2;
474 x[0] = x[2]*fNonBendingSlope;
475 x[1] = x[2]*fBendingSlope;
476
477 // Take magn. field value at position x.
478 gAlice->Field()->Field(x, b);
479 bZ = b[2];
480
481 // Transverse momentum rotation
482 // Parameterized with the study of DeltaPhi = phiReco - phiGen as a function of pZ.
5b64e914 483 Double_t phiShift = c*0.436*0.0003*bZ*Z/pZ;
b45fd22b 484 // Rotate momentum around Z axis.
485 pXNew = pX*TMath::Cos(phiShift) - pY*TMath::Sin(phiShift);
486 pYNew = pX*TMath::Sin(phiShift) + pY*TMath::Cos(phiShift);
487
488 fBendingSlope = pYNew / pZ;
489 fNonBendingSlope = pXNew / pZ;
490
491 fInverseBendingMomentum = c / TMath::Sqrt(pYNew*pYNew+pZ*pZ);
492
b8dc484b 493}
494 //__________________________________________________________________________
495Double_t AliMUONTrackParam::Px()
496{
497 // return px from track paramaters
498 Double_t pYZ, pZ, pX;
499 pYZ = 0;
500 if ( TMath::Abs(fInverseBendingMomentum) > 0 )
501 pYZ = TMath::Abs(1.0 / fInverseBendingMomentum);
502 pZ = -pYZ / (TMath::Sqrt(1.0 + fBendingSlope * fBendingSlope)); // spectro. (z<0)
503 pX = pZ * fNonBendingSlope;
504 return pX;
505}
506 //__________________________________________________________________________
507Double_t AliMUONTrackParam::Py()
508{
509 // return px from track paramaters
510 Double_t pYZ, pZ, pY;
511 pYZ = 0;
512 if ( TMath::Abs(fInverseBendingMomentum) > 0 )
513 pYZ = TMath::Abs(1.0 / fInverseBendingMomentum);
514 pZ = -pYZ / (TMath::Sqrt(1.0 + fBendingSlope * fBendingSlope)); // spectro. (z<0)
515 pY = pZ * fBendingSlope;
516 return pY;
517}
518 //__________________________________________________________________________
519Double_t AliMUONTrackParam::Pz()
520{
521 // return px from track paramaters
522 Double_t pYZ, pZ;
523 pYZ = 0;
524 if ( TMath::Abs(fInverseBendingMomentum) > 0 )
525 pYZ = TMath::Abs(1.0 / fInverseBendingMomentum);
526 pZ = -pYZ / (TMath::Sqrt(1.0 + fBendingSlope * fBendingSlope)); // spectro. (z<0)
527 return pZ;
528}
529 //__________________________________________________________________________
530Double_t AliMUONTrackParam::P()
531{
532 // return p from track paramaters
533 Double_t pYZ, pZ, p;
534 pYZ = 0;
535 if ( TMath::Abs(fInverseBendingMomentum) > 0 )
536 pYZ = TMath::Abs(1.0 / fInverseBendingMomentum);
537 pZ = -pYZ / (TMath::Sqrt(1.0 + fBendingSlope * fBendingSlope)); // spectro. (z<0)
538 p = TMath::Abs(pZ) *
539 TMath::Sqrt(1.0 + fBendingSlope * fBendingSlope + fNonBendingSlope * fNonBendingSlope);
540 return p;
541
b45fd22b 542}
4d03a78e 543 //__________________________________________________________________________
544void AliMUONTrackParam::ExtrapOneStepHelix(Double_t charge, Double_t step,
f161a467 545 Double_t *vect, Double_t *vout) const
4d03a78e 546{
547// ******************************************************************
548// * *
549// * Performs the tracking of one step in a magnetic field *
550// * The trajectory is assumed to be a helix in a constant field *
551// * taken at the mid point of the step. *
552// * Parameters: *
553// * input *
554// * STEP =arc length of the step asked *
555// * VECT =input vector (position,direction cos and momentum) *
556// * CHARGE= electric charge of the particle *
557// * output *
558// * VOUT = same as VECT after completion of the step *
559// * *
560// * ==>Called by : <USER>, GUSWIM *
561// * Author m.hansroul ********* *
562// * modified s.egli, s.v.levonian *
563// * modified v.perevoztchikov
564// * *
565// ******************************************************************
566//
567
568// modif: everything in double precision
569
570 Double_t xyz[3], h[4], hxp[3];
571 Double_t h2xy, hp, rho, tet;
572 Double_t sint, sintt, tsint, cos1t;
573 Double_t f1, f2, f3, f4, f5, f6;
574
58443fe3 575 const Int_t kix = 0;
576 const Int_t kiy = 1;
577 const Int_t kiz = 2;
578 const Int_t kipx = 3;
579 const Int_t kipy = 4;
580 const Int_t kipz = 5;
581 const Int_t kipp = 6;
4d03a78e 582
58443fe3 583 const Double_t kec = 2.9979251e-4;
4d03a78e 584 //
585 // ------------------------------------------------------------------
586 //
587 // units are kgauss,centimeters,gev/c
588 //
58443fe3 589 vout[kipp] = vect[kipp];
4d03a78e 590 if (TMath::Abs(charge) < 0.00001) {
591 for (Int_t i = 0; i < 3; i++) {
592 vout[i] = vect[i] + step * vect[i+3];
593 vout[i+3] = vect[i+3];
594 }
595 return;
596 }
58443fe3 597 xyz[0] = vect[kix] + 0.5 * step * vect[kipx];
598 xyz[1] = vect[kiy] + 0.5 * step * vect[kipy];
599 xyz[2] = vect[kiz] + 0.5 * step * vect[kipz];
4d03a78e 600
601 //cmodif: call gufld (xyz, h) changed into:
602 GetField (xyz, h);
603
604 h2xy = h[0]*h[0] + h[1]*h[1];
605 h[3] = h[2]*h[2]+ h2xy;
606 if (h[3] < 1.e-12) {
607 for (Int_t i = 0; i < 3; i++) {
608 vout[i] = vect[i] + step * vect[i+3];
609 vout[i+3] = vect[i+3];
610 }
611 return;
612 }
613 if (h2xy < 1.e-12*h[3]) {
614 ExtrapOneStepHelix3(charge*h[2], step, vect, vout);
615 return;
616 }
617 h[3] = TMath::Sqrt(h[3]);
618 h[0] /= h[3];
619 h[1] /= h[3];
620 h[2] /= h[3];
58443fe3 621 h[3] *= kec;
4d03a78e 622
58443fe3 623 hxp[0] = h[1]*vect[kipz] - h[2]*vect[kipy];
624 hxp[1] = h[2]*vect[kipx] - h[0]*vect[kipz];
625 hxp[2] = h[0]*vect[kipy] - h[1]*vect[kipx];
4d03a78e 626
58443fe3 627 hp = h[0]*vect[kipx] + h[1]*vect[kipy] + h[2]*vect[kipz];
4d03a78e 628
58443fe3 629 rho = -charge*h[3]/vect[kipp];
4d03a78e 630 tet = rho * step;
631
632 if (TMath::Abs(tet) > 0.15) {
633 sint = TMath::Sin(tet);
634 sintt = (sint/tet);
635 tsint = (tet-sint)/tet;
636 cos1t = 2.*(TMath::Sin(0.5*tet))*(TMath::Sin(0.5*tet))/tet;
637 } else {
638 tsint = tet*tet/36.;
639 sintt = (1. - tsint);
640 sint = tet*sintt;
641 cos1t = 0.5*tet;
642 }
643
644 f1 = step * sintt;
645 f2 = step * cos1t;
646 f3 = step * tsint * hp;
647 f4 = -tet*cos1t;
648 f5 = sint;
649 f6 = tet * cos1t * hp;
650
58443fe3 651 vout[kix] = vect[kix] + f1*vect[kipx] + f2*hxp[0] + f3*h[0];
652 vout[kiy] = vect[kiy] + f1*vect[kipy] + f2*hxp[1] + f3*h[1];
653 vout[kiz] = vect[kiz] + f1*vect[kipz] + f2*hxp[2] + f3*h[2];
4d03a78e 654
58443fe3 655 vout[kipx] = vect[kipx] + f4*vect[kipx] + f5*hxp[0] + f6*h[0];
656 vout[kipy] = vect[kipy] + f4*vect[kipy] + f5*hxp[1] + f6*h[1];
657 vout[kipz] = vect[kipz] + f4*vect[kipz] + f5*hxp[2] + f6*h[2];
4d03a78e 658
659 return;
660}
661
662 //__________________________________________________________________________
663void AliMUONTrackParam::ExtrapOneStepHelix3(Double_t field, Double_t step,
f161a467 664 Double_t *vect, Double_t *vout) const
4d03a78e 665{
666//
667// ******************************************************************
668// * *
669// * Tracking routine in a constant field oriented *
670// * along axis 3 *
671// * Tracking is performed with a conventional *
672// * helix step method *
673// * *
674// * ==>Called by : <USER>, GUSWIM *
675// * Authors R.Brun, M.Hansroul ********* *
676// * Rewritten V.Perevoztchikov
677// * *
678// ******************************************************************
679//
680
681 Double_t hxp[3];
682 Double_t h4, hp, rho, tet;
683 Double_t sint, sintt, tsint, cos1t;
684 Double_t f1, f2, f3, f4, f5, f6;
685
58443fe3 686 const Int_t kix = 0;
687 const Int_t kiy = 1;
688 const Int_t kiz = 2;
689 const Int_t kipx = 3;
690 const Int_t kipy = 4;
691 const Int_t kipz = 5;
692 const Int_t kipp = 6;
4d03a78e 693
58443fe3 694 const Double_t kec = 2.9979251e-4;
4d03a78e 695
696//
697// ------------------------------------------------------------------
698//
699// units are kgauss,centimeters,gev/c
700//
58443fe3 701 vout[kipp] = vect[kipp];
702 h4 = field * kec;
4d03a78e 703
58443fe3 704 hxp[0] = - vect[kipy];
705 hxp[1] = + vect[kipx];
4d03a78e 706
58443fe3 707 hp = vect[kipz];
4d03a78e 708
58443fe3 709 rho = -h4/vect[kipp];
4d03a78e 710 tet = rho * step;
711 if (TMath::Abs(tet) > 0.15) {
712 sint = TMath::Sin(tet);
713 sintt = (sint/tet);
714 tsint = (tet-sint)/tet;
715 cos1t = 2.* TMath::Sin(0.5*tet) * TMath::Sin(0.5*tet)/tet;
716 } else {
717 tsint = tet*tet/36.;
718 sintt = (1. - tsint);
719 sint = tet*sintt;
720 cos1t = 0.5*tet;
721 }
722
723 f1 = step * sintt;
724 f2 = step * cos1t;
725 f3 = step * tsint * hp;
726 f4 = -tet*cos1t;
727 f5 = sint;
728 f6 = tet * cos1t * hp;
729
58443fe3 730 vout[kix] = vect[kix] + f1*vect[kipx] + f2*hxp[0];
731 vout[kiy] = vect[kiy] + f1*vect[kipy] + f2*hxp[1];
732 vout[kiz] = vect[kiz] + f1*vect[kipz] + f3;
4d03a78e 733
58443fe3 734 vout[kipx] = vect[kipx] + f4*vect[kipx] + f5*hxp[0];
735 vout[kipy] = vect[kipy] + f4*vect[kipy] + f5*hxp[1];
736 vout[kipz] = vect[kipz] + f4*vect[kipz] + f6;
4d03a78e 737
738 return;
739}
740 //__________________________________________________________________________
741void AliMUONTrackParam::ExtrapOneStepRungekutta(Double_t charge, Double_t step,
f161a467 742 Double_t* vect, Double_t* vout) const
4d03a78e 743{
744//
745// ******************************************************************
746// * *
747// * Runge-Kutta method for tracking a particle through a magnetic *
748// * field. Uses Nystroem algorithm (See Handbook Nat. Bur. of *
749// * Standards, procedure 25.5.20) *
750// * *
751// * Input parameters *
752// * CHARGE Particle charge *
753// * STEP Step size *
754// * VECT Initial co-ords,direction cosines,momentum *
755// * Output parameters *
756// * VOUT Output co-ords,direction cosines,momentum *
757// * User routine called *
758// * CALL GUFLD(X,F) *
759// * *
760// * ==>Called by : <USER>, GUSWIM *
761// * Authors R.Brun, M.Hansroul ********* *
762// * V.Perevoztchikov (CUT STEP implementation) *
763// * *
764// * *
765// ******************************************************************
766//
767
768 Double_t h2, h4, f[4];
769 Double_t xyzt[3], a, b, c, ph,ph2;
770 Double_t secxs[4],secys[4],seczs[4],hxp[3];
771 Double_t g1, g2, g3, g4, g5, g6, ang2, dxt, dyt, dzt;
772 Double_t est, at, bt, ct, cba;
773 Double_t f1, f2, f3, f4, rho, tet, hnorm, hp, rho1, sint, cost;
774
775 Double_t x;
776 Double_t y;
777 Double_t z;
778
779 Double_t xt;
780 Double_t yt;
781 Double_t zt;
782
783 Double_t maxit = 1992;
784 Double_t maxcut = 11;
785
58443fe3 786 const Double_t kdlt = 1e-4;
787 const Double_t kdlt32 = kdlt/32.;
788 const Double_t kthird = 1./3.;
789 const Double_t khalf = 0.5;
790 const Double_t kec = 2.9979251e-4;
791
792 const Double_t kpisqua = 9.86960440109;
793 const Int_t kix = 0;
794 const Int_t kiy = 1;
795 const Int_t kiz = 2;
796 const Int_t kipx = 3;
797 const Int_t kipy = 4;
798 const Int_t kipz = 5;
4d03a78e 799
800 // *.
801 // *. ------------------------------------------------------------------
802 // *.
803 // * this constant is for units cm,gev/c and kgauss
804 // *
805 Int_t iter = 0;
806 Int_t ncut = 0;
807 for(Int_t j = 0; j < 7; j++)
808 vout[j] = vect[j];
809
58443fe3 810 Double_t pinv = kec * charge / vect[6];
4d03a78e 811 Double_t tl = 0.;
812 Double_t h = step;
813 Double_t rest;
814
815
816 do {
817 rest = step - tl;
818 if (TMath::Abs(h) > TMath::Abs(rest)) h = rest;
819 //cmodif: call gufld(vout,f) changed into:
820
821 GetField(vout,f);
822
823 // *
824 // * start of integration
825 // *
826 x = vout[0];
827 y = vout[1];
828 z = vout[2];
829 a = vout[3];
830 b = vout[4];
831 c = vout[5];
832
58443fe3 833 h2 = khalf * h;
834 h4 = khalf * h2;
4d03a78e 835 ph = pinv * h;
58443fe3 836 ph2 = khalf * ph;
4d03a78e 837 secxs[0] = (b * f[2] - c * f[1]) * ph2;
838 secys[0] = (c * f[0] - a * f[2]) * ph2;
839 seczs[0] = (a * f[1] - b * f[0]) * ph2;
840 ang2 = (secxs[0]*secxs[0] + secys[0]*secys[0] + seczs[0]*seczs[0]);
58443fe3 841 if (ang2 > kpisqua) break;
4d03a78e 842
843 dxt = h2 * a + h4 * secxs[0];
844 dyt = h2 * b + h4 * secys[0];
845 dzt = h2 * c + h4 * seczs[0];
846 xt = x + dxt;
847 yt = y + dyt;
848 zt = z + dzt;
849 // *
850 // * second intermediate point
851 // *
852
853 est = TMath::Abs(dxt) + TMath::Abs(dyt) + TMath::Abs(dzt);
854 if (est > h) {
855 if (ncut++ > maxcut) break;
58443fe3 856 h *= khalf;
4d03a78e 857 continue;
858 }
859
860 xyzt[0] = xt;
861 xyzt[1] = yt;
862 xyzt[2] = zt;
863
864 //cmodif: call gufld(xyzt,f) changed into:
865 GetField(xyzt,f);
866
867 at = a + secxs[0];
868 bt = b + secys[0];
869 ct = c + seczs[0];
870
871 secxs[1] = (bt * f[2] - ct * f[1]) * ph2;
872 secys[1] = (ct * f[0] - at * f[2]) * ph2;
873 seczs[1] = (at * f[1] - bt * f[0]) * ph2;
874 at = a + secxs[1];
875 bt = b + secys[1];
876 ct = c + seczs[1];
877 secxs[2] = (bt * f[2] - ct * f[1]) * ph2;
878 secys[2] = (ct * f[0] - at * f[2]) * ph2;
879 seczs[2] = (at * f[1] - bt * f[0]) * ph2;
880 dxt = h * (a + secxs[2]);
881 dyt = h * (b + secys[2]);
882 dzt = h * (c + seczs[2]);
883 xt = x + dxt;
884 yt = y + dyt;
885 zt = z + dzt;
886 at = a + 2.*secxs[2];
887 bt = b + 2.*secys[2];
888 ct = c + 2.*seczs[2];
889
890 est = TMath::Abs(dxt)+TMath::Abs(dyt)+TMath::Abs(dzt);
891 if (est > 2.*TMath::Abs(h)) {
892 if (ncut++ > maxcut) break;
58443fe3 893 h *= khalf;
4d03a78e 894 continue;
895 }
896
897 xyzt[0] = xt;
898 xyzt[1] = yt;
899 xyzt[2] = zt;
900
901 //cmodif: call gufld(xyzt,f) changed into:
902 GetField(xyzt,f);
903
58443fe3 904 z = z + (c + (seczs[0] + seczs[1] + seczs[2]) * kthird) * h;
905 y = y + (b + (secys[0] + secys[1] + secys[2]) * kthird) * h;
906 x = x + (a + (secxs[0] + secxs[1] + secxs[2]) * kthird) * h;
4d03a78e 907
908 secxs[3] = (bt*f[2] - ct*f[1])* ph2;
909 secys[3] = (ct*f[0] - at*f[2])* ph2;
910 seczs[3] = (at*f[1] - bt*f[0])* ph2;
58443fe3 911 a = a+(secxs[0]+secxs[3]+2. * (secxs[1]+secxs[2])) * kthird;
912 b = b+(secys[0]+secys[3]+2. * (secys[1]+secys[2])) * kthird;
913 c = c+(seczs[0]+seczs[3]+2. * (seczs[1]+seczs[2])) * kthird;
4d03a78e 914
915 est = TMath::Abs(secxs[0]+secxs[3] - (secxs[1]+secxs[2]))
916 + TMath::Abs(secys[0]+secys[3] - (secys[1]+secys[2]))
917 + TMath::Abs(seczs[0]+seczs[3] - (seczs[1]+seczs[2]));
918
58443fe3 919 if (est > kdlt && TMath::Abs(h) > 1.e-4) {
4d03a78e 920 if (ncut++ > maxcut) break;
58443fe3 921 h *= khalf;
4d03a78e 922 continue;
923 }
924
925 ncut = 0;
926 // * if too many iterations, go to helix
927 if (iter++ > maxit) break;
928
929 tl += h;
58443fe3 930 if (est < kdlt32)
4d03a78e 931 h *= 2.;
932 cba = 1./ TMath::Sqrt(a*a + b*b + c*c);
933 vout[0] = x;
934 vout[1] = y;
935 vout[2] = z;
936 vout[3] = cba*a;
937 vout[4] = cba*b;
938 vout[5] = cba*c;
939 rest = step - tl;
940 if (step < 0.) rest = -rest;
941 if (rest < 1.e-5*TMath::Abs(step)) return;
942
943 } while(1);
944
945 // angle too big, use helix
946
947 f1 = f[0];
948 f2 = f[1];
949 f3 = f[2];
950 f4 = TMath::Sqrt(f1*f1+f2*f2+f3*f3);
951 rho = -f4*pinv;
952 tet = rho * step;
953
954 hnorm = 1./f4;
955 f1 = f1*hnorm;
956 f2 = f2*hnorm;
957 f3 = f3*hnorm;
958
58443fe3 959 hxp[0] = f2*vect[kipz] - f3*vect[kipy];
960 hxp[1] = f3*vect[kipx] - f1*vect[kipz];
961 hxp[2] = f1*vect[kipy] - f2*vect[kipx];
4d03a78e 962
58443fe3 963 hp = f1*vect[kipx] + f2*vect[kipy] + f3*vect[kipz];
4d03a78e 964
965 rho1 = 1./rho;
966 sint = TMath::Sin(tet);
58443fe3 967 cost = 2.*TMath::Sin(khalf*tet)*TMath::Sin(khalf*tet);
4d03a78e 968
969 g1 = sint*rho1;
970 g2 = cost*rho1;
971 g3 = (tet-sint) * hp*rho1;
972 g4 = -cost;
973 g5 = sint;
974 g6 = cost * hp;
975
58443fe3 976 vout[kix] = vect[kix] + g1*vect[kipx] + g2*hxp[0] + g3*f1;
977 vout[kiy] = vect[kiy] + g1*vect[kipy] + g2*hxp[1] + g3*f2;
978 vout[kiz] = vect[kiz] + g1*vect[kipz] + g2*hxp[2] + g3*f3;
4d03a78e 979
58443fe3 980 vout[kipx] = vect[kipx] + g4*vect[kipx] + g5*hxp[0] + g6*f1;
981 vout[kipy] = vect[kipy] + g4*vect[kipy] + g5*hxp[1] + g6*f2;
982 vout[kipz] = vect[kipz] + g4*vect[kipz] + g5*hxp[2] + g6*f3;
4d03a78e 983
984 return;
985}
986//___________________________________________________________
f161a467 987 void AliMUONTrackParam::GetField(Double_t *Position, Double_t *Field) const
4d03a78e 988{
989 // interface to "gAlice->Field()->Field" for arguments in double precision
990
991 Float_t x[3], b[3];
992
993 x[0] = Position[0]; x[1] = Position[1]; x[2] = Position[2];
994
995 gAlice->Field()->Field(x, b);
996 Field[0] = b[0]; Field[1] = b[1]; Field[2] = b[2];
997
998 return;
999 }