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. *
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 *
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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 **************************************************************************/
18 ///////////////////////////////////////////////////////////////////////////////
20 // Transition Radiation Detector version 1 -- slow simulator //
24 <img src="picts/AliTRDfullClass.gif">
29 ///////////////////////////////////////////////////////////////////////////////
34 #include <TLorentzVector.h>
38 #include <TVirtualMC.h>
42 #include "AliTRDgeometry.h"
43 #include "AliTRDhit.h"
44 #include "AliTRDmatrix.h"
45 #include "AliTRDsim.h"
51 //_____________________________________________________________________________
52 AliTRDv1::AliTRDv1():AliTRD()
55 // Default constructor
69 //_____________________________________________________________________________
70 AliTRDv1::AliTRDv1(const char *name, const char *title)
74 // Standard constructor for Transition Radiation Detector version 1
86 SetBufferSize(128000);
90 //_____________________________________________________________________________
91 AliTRDv1::AliTRDv1(const AliTRDv1 &trd):AliTRD(trd)
97 ((AliTRDv1 &) trd).Copy(*this);
101 //_____________________________________________________________________________
102 AliTRDv1::~AliTRDv1()
105 // AliTRDv1 destructor
108 if (fDeltaE) delete fDeltaE;
113 //_____________________________________________________________________________
114 AliTRDv1 &AliTRDv1::operator=(const AliTRDv1 &trd)
117 // Assignment operator
120 if (this != &trd) ((AliTRDv1 &) trd).Copy(*this);
125 //_____________________________________________________________________________
126 void AliTRDv1::Copy(TObject &trd)
132 ((AliTRDv1 &) trd).fSensSelect = fSensSelect;
133 ((AliTRDv1 &) trd).fSensPlane = fSensPlane;
134 ((AliTRDv1 &) trd).fSensChamber = fSensChamber;
135 ((AliTRDv1 &) trd).fSensSector = fSensSector;
136 ((AliTRDv1 &) trd).fSensSectorRange = fSensSectorRange;
138 fDeltaE->Copy(*((AliTRDv1 &) trd).fDeltaE);
139 fTR->Copy(*((AliTRDv1 &) trd).fTR);
143 //_____________________________________________________________________________
144 void AliTRDv1::CreateGeometry()
147 // Create the GEANT geometry for the Transition Radiation Detector - Version 1
148 // This version covers the full azimuth.
151 // Check that FRAME is there otherwise we have no place where to put the TRD
152 AliModule* frame = gAlice->GetModule("FRAME");
155 // Define the chambers
156 AliTRD::CreateGeometry();
160 //_____________________________________________________________________________
161 void AliTRDv1::CreateMaterials()
164 // Create materials for the Transition Radiation Detector version 1
167 AliTRD::CreateMaterials();
171 //_____________________________________________________________________________
172 void AliTRDv1::CreateTRhit(Int_t det)
175 // Creates an electron cluster from a TR photon.
176 // The photon is assumed to be created a the end of the radiator. The
177 // distance after which it deposits its energy takes into account the
178 // absorbtion of the entrance window and of the gas mixture in drift
183 const Int_t kPdgElectron = 11;
186 const Float_t kWion = 22.04;
188 // Maximum number of TR photons per track
189 const Int_t kNTR = 50;
191 TLorentzVector mom, pos;
193 // Create TR at the entrance of the chamber
194 if (gMC->IsTrackEntering()) {
196 // Create TR only for electrons
197 Int_t iPdg = gMC->TrackPid();
198 if (TMath::Abs(iPdg) != kPdgElectron) return;
204 gMC->TrackMomentum(mom);
205 Float_t pTot = mom.Rho();
206 fTR->CreatePhotons(iPdg,pTot,nTR,eTR);
208 printf("AliTRDv1::CreateTRhit -- ");
209 printf("Boundary error: nTR = %d, kNTR = %d\n",nTR,kNTR);
213 // Loop through the TR photons
214 for (Int_t iTR = 0; iTR < nTR; iTR++) {
216 Float_t energyMeV = eTR[iTR] * 0.001;
217 Float_t energyeV = eTR[iTR] * 1000.0;
218 Float_t absLength = 0;
221 // Take the absorbtion in the entrance window into account
222 Double_t muMy = fTR->GetMuMy(energyMeV);
223 sigma = muMy * fFoilDensity;
225 absLength = gRandom->Exp(1.0/sigma);
226 if (absLength < AliTRDgeometry::MyThick()) continue;
232 // The absorbtion cross sections in the drift gas
234 // Gas-mixture (Xe/CO2)
235 Double_t muXe = fTR->GetMuXe(energyMeV);
236 Double_t muCO = fTR->GetMuCO(energyMeV);
237 sigma = (0.85 * muXe + 0.15 * muCO) * fGasDensity * fTR->GetTemp();
240 // Gas-mixture (Xe/Isobutane)
241 Double_t muXe = fTR->GetMuXe(energyMeV);
242 Double_t muBu = fTR->GetMuBu(energyMeV);
243 sigma = (0.97 * muXe + 0.03 * muBu) * fGasDensity * fTR->GetTemp();
246 // The distance after which the energy of the TR photon
249 absLength = gRandom->Exp(1.0/sigma);
250 if (absLength > AliTRDgeometry::DrThick()) continue;
256 // The position of the absorbtion
258 gMC->TrackPosition(pos);
259 posHit[0] = pos[0] + mom[0] / pTot * absLength;
260 posHit[1] = pos[1] + mom[1] / pTot * absLength;
261 posHit[2] = pos[2] + mom[2] / pTot * absLength;
264 Int_t q = ((Int_t) (energyeV / kWion));
266 // Add the hit to the array. TR photon hits are marked
267 // by negative charge
268 AddHit(gAlice->GetMCApp()->GetCurrentTrackNumber(),det,posHit,-q,kTRUE);
276 //_____________________________________________________________________________
277 void AliTRDv1::Init()
280 // Initialise Transition Radiation Detector after geometry has been built.
285 if(fDebug) printf("%s: Slow simulator\n",ClassName());
288 printf(" Only plane %d is sensitive\n",fSensPlane);
289 if (fSensChamber >= 0)
290 printf(" Only chamber %d is sensitive\n",fSensChamber);
291 if (fSensSector >= 0) {
292 Int_t sens1 = fSensSector;
293 Int_t sens2 = fSensSector + fSensSectorRange;
294 sens2 -= ((Int_t) (sens2 / AliTRDgeometry::Nsect()))
295 * AliTRDgeometry::Nsect();
296 printf(" Only sectors %d - %d are sensitive\n",sens1,sens2-1);
300 printf("%s: TR simulation on\n",ClassName());
302 printf("%s: TR simulation off\n",ClassName());
305 // First ionization potential (eV) for the gas mixture (90% Xe + 10% CO2)
306 const Float_t kPoti = 12.1;
307 // Maximum energy (50 keV);
308 const Float_t kEend = 50000.0;
309 // Ermilova distribution for the delta-ray spectrum
310 Float_t poti = TMath::Log(kPoti);
311 Float_t eEnd = TMath::Log(kEend);
312 fDeltaE = new TF1("deltae",Ermilova,poti,eEnd,0);
315 printf("%s: ",ClassName());
316 for (Int_t i = 0; i < 80; i++) printf("*");
322 //_____________________________________________________________________________
323 AliTRDsim *AliTRDv1::CreateTR()
326 // Enables the simulation of TR
329 fTR = new AliTRDsim();
334 //_____________________________________________________________________________
335 void AliTRDv1::SetSensPlane(Int_t iplane)
338 // Defines the hit-sensitive plane (0-5)
341 if ((iplane < 0) || (iplane > 5)) {
342 printf("Wrong input value: %d\n",iplane);
343 printf("Use standard setting\n");
354 //_____________________________________________________________________________
355 void AliTRDv1::SetSensChamber(Int_t ichamber)
358 // Defines the hit-sensitive chamber (0-4)
361 if ((ichamber < 0) || (ichamber > 4)) {
362 printf("Wrong input value: %d\n",ichamber);
363 printf("Use standard setting\n");
370 fSensChamber = ichamber;
374 //_____________________________________________________________________________
375 void AliTRDv1::SetSensSector(Int_t isector)
378 // Defines the hit-sensitive sector (0-17)
381 SetSensSector(isector,1);
385 //_____________________________________________________________________________
386 void AliTRDv1::SetSensSector(Int_t isector, Int_t nsector)
389 // Defines a range of hit-sensitive sectors. The range is defined by
390 // <isector> (0-17) as the starting point and <nsector> as the number
391 // of sectors to be included.
394 if ((isector < 0) || (isector > 17)) {
395 printf("Wrong input value <isector>: %d\n",isector);
396 printf("Use standard setting\n");
398 fSensSectorRange = 0;
403 if ((nsector < 1) || (nsector > 18)) {
404 printf("Wrong input value <nsector>: %d\n",nsector);
405 printf("Use standard setting\n");
407 fSensSectorRange = 0;
413 fSensSector = isector;
414 fSensSectorRange = nsector;
418 //_____________________________________________________________________________
419 void AliTRDv1::StepManager()
422 // Slow simulator. Every charged track produces electron cluster as hits
423 // along its path across the drift volume. The step size is set acording
424 // to Bethe-Bloch. The energy distribution of the delta electrons follows
425 // a spectrum taken from Ermilova et al.
442 Double_t betaGamma, pp;
445 Bool_t drRegion = kFALSE;
446 Bool_t amRegion = kFALSE;
449 TString cIdSensDr = "J";
450 TString cIdSensAm = "K";
451 Char_t cIdChamber[3];
454 TLorentzVector pos, mom;
456 const Int_t kNplan = AliTRDgeometry::Nplan();
457 const Int_t kNcham = AliTRDgeometry::Ncham();
458 const Int_t kNdetsec = kNplan * kNcham;
460 const Double_t kBig = 1.0E+12;
463 const Float_t kWion = 22.04;
464 // Maximum momentum for e+ e- g
465 const Float_t kPTotMaxEl = 0.002;
466 // Minimum energy for the step size adjustment
467 const Float_t kEkinMinStep = 1.0e-5;
468 // Plateau value of the energy-loss for electron in xenon
469 // taken from: Allison + Comb, Ann. Rev. Nucl. Sci. (1980), 30, 253
470 //const Double_t kPlateau = 1.70;
471 // the averaged value (26/3/99)
472 const Float_t kPlateau = 1.55;
473 // dN1/dx|min for the gas mixture (90% Xe + 10% CO2)
474 const Float_t kPrim = 48.0;
475 // First ionization potential (eV) for the gas mixture (90% Xe + 10% CO2)
476 const Float_t kPoti = 12.1;
479 const Int_t kPdgElectron = 11;
481 // Set the maximum step size to a very large number for all
482 // neutral particles and those outside the driftvolume
483 gMC->SetMaxStep(kBig);
485 // Use only charged tracks
486 if (( gMC->TrackCharge() ) &&
487 (!gMC->IsTrackStop() ) &&
488 (!gMC->IsTrackDisappeared())) {
490 // Inside a sensitive volume?
493 cIdCurrent = gMC->CurrentVolName();
494 if (cIdSensDr == cIdCurrent[1]) {
497 if (cIdSensAm == cIdCurrent[1]) {
500 if (drRegion || amRegion) {
502 // The hit coordinates and charge
503 gMC->TrackPosition(pos);
508 // The sector number (0 - 17)
509 // The numbering goes clockwise and starts at y = 0
510 // Not fully consistent to new corrdinate schema!!!
511 Float_t phi = kRaddeg*TMath::ATan2(pos[0],pos[1]);
516 sec = ((Int_t) (phi / 20));
518 // The plane and chamber number
519 cIdChamber[0] = cIdCurrent[2];
520 cIdChamber[1] = cIdCurrent[3];
521 Int_t idChamber = (atoi(cIdChamber) % kNdetsec);
522 cha = ((Int_t) idChamber / kNplan);
523 pla = ((Int_t) idChamber % kNplan);
525 // Check on selected volumes
526 Int_t addthishit = 1;
528 if ((fSensPlane >= 0) && (pla != fSensPlane )) addthishit = 0;
529 if ((fSensChamber >= 0) && (cha != fSensChamber)) addthishit = 0;
530 if (fSensSector >= 0) {
531 Int_t sens1 = fSensSector;
532 Int_t sens2 = fSensSector + fSensSectorRange;
533 sens2 -= ((Int_t) (sens2 / AliTRDgeometry::Nsect()))
534 * AliTRDgeometry::Nsect();
536 if ((sec < sens1) || (sec >= sens2)) addthishit = 0;
539 if ((sec < sens1) && (sec >= sens2)) addthishit = 0;
547 // The detector number
548 det = fGeometry->GetDetector(pla,cha,sec);
550 // Special hits and TR photons only in the drift region
553 // Create a track reference at the entrance and
554 // exit of each chamber that contain the
555 // momentum components of the particle
556 if (gMC->IsTrackEntering() || gMC->IsTrackExiting()) {
557 gMC->TrackMomentum(mom);
558 AddTrackReference(gAlice->GetMCApp()->GetCurrentTrackNumber());
561 // Create the hits from TR photons
562 if (fTR) CreateTRhit(det);
566 // Calculate the energy of the delta-electrons
567 eDelta = TMath::Exp(fDeltaE->GetRandom()) - kPoti;
568 eDelta = TMath::Max(eDelta,0.0);
570 // The number of secondary electrons created
571 qTot = ((Int_t) (eDelta / kWion) + 1);
573 // Create a new dEdx hit
575 AddHit(gAlice->GetMCApp()->GetCurrentTrackNumber(),det,hits,qTot,kTRUE);
578 AddHit(gAlice->GetMCApp()->GetCurrentTrackNumber(),det,hits,qTot,kFALSE);
581 // Calculate the maximum step size for the next tracking step
582 // Produce only one hit if Ekin is below cutoff
583 aMass = gMC->TrackMass();
584 if ((gMC->Etot() - aMass) > kEkinMinStep) {
586 // The energy loss according to Bethe Bloch
587 iPdg = TMath::Abs(gMC->TrackPid());
588 if ( (iPdg != kPdgElectron) ||
589 ((iPdg == kPdgElectron) && (pTot < kPTotMaxEl))) {
590 gMC->TrackMomentum(mom);
592 betaGamma = pTot / aMass;
593 pp = kPrim * BetheBloch(betaGamma);
594 // Take charge > 1 into account
595 charge = gMC->TrackCharge();
596 if (TMath::Abs(charge) > 1) pp = pp * charge*charge;
598 // Electrons above 20 Mev/c are at the plateau
600 pp = kPrim * kPlateau;
605 gMC->GetRandom()->RndmArray(1, random);
606 while ((random[0] == 1.) || (random[0] == 0.));
607 stepSize = - TMath::Log(random[0]) / pp;
608 gMC->SetMaxStep(stepSize);
621 //_____________________________________________________________________________
622 Double_t AliTRDv1::BetheBloch(Double_t bg)
625 // Parametrization of the Bethe-Bloch-curve
626 // The parametrization is the same as for the TPC and is taken from Lehrhaus.
629 // This parameters have been adjusted to averaged values from GEANT
630 const Double_t kP1 = 7.17960e-02;
631 const Double_t kP2 = 8.54196;
632 const Double_t kP3 = 1.38065e-06;
633 const Double_t kP4 = 5.30972;
634 const Double_t kP5 = 2.83798;
636 // This parameters have been adjusted to Xe-data found in:
637 // Allison & Cobb, Ann. Rev. Nucl. Sci. (1980), 30, 253
638 //const Double_t kP1 = 0.76176E-1;
639 //const Double_t kP2 = 10.632;
640 //const Double_t kP3 = 3.17983E-6;
641 //const Double_t kP4 = 1.8631;
642 //const Double_t kP5 = 1.9479;
644 // Lower cutoff of the Bethe-Bloch-curve to limit step sizes
645 const Double_t kBgMin = 0.8;
646 const Double_t kBBMax = 6.83298;
647 //const Double_t kBgMin = 0.6;
648 //const Double_t kBBMax = 17.2809;
649 //const Double_t kBgMin = 0.4;
650 //const Double_t kBBMax = 82.0;
653 Double_t yy = bg / TMath::Sqrt(1. + bg*bg);
654 Double_t aa = TMath::Power(yy,kP4);
655 Double_t bb = TMath::Power((1./bg),kP5);
656 bb = TMath::Log(kP3 + bb);
657 return ((kP2 - aa - bb)*kP1 / aa);
665 //_____________________________________________________________________________
666 Double_t Ermilova(Double_t *x, Double_t *)
669 // Calculates the delta-ray energy distribution according to Ermilova.
670 // Logarithmic scale !
679 const Int_t kNv = 31;
681 Float_t vxe[kNv] = { 2.3026, 2.9957, 3.4012, 3.6889, 3.9120
682 , 4.0943, 4.2485, 4.3820, 4.4998, 4.6052
683 , 4.7005, 5.0752, 5.2983, 5.7038, 5.9915
684 , 6.2146, 6.5221, 6.9078, 7.3132, 7.6009
685 , 8.0064, 8.5172, 8.6995, 8.9872, 9.2103
686 , 9.4727, 9.9035,10.3735,10.5966,10.8198
689 Float_t vye[kNv] = { 80.0 , 31.0 , 23.3 , 21.1 , 21.0
690 , 20.9 , 20.8 , 20.0 , 16.0 , 11.0
691 , 8.0 , 6.0 , 5.2 , 4.6 , 4.0
692 , 3.5 , 3.0 , 1.4 , 0.67 , 0.44
693 , 0.3 , 0.18 , 0.12 , 0.08 , 0.056
694 , 0.04 , 0.023, 0.015, 0.011, 0.01
703 dpos = energy - vxe[pos2++];
707 if (pos2 > kNv) pos2 = kNv - 1;
710 // Differentiate between the sampling points
711 dnde = (vye[pos1] - vye[pos2]) / (vxe[pos2] - vxe[pos1]);