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 *
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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 "AliTRDsim.h"
50 //_____________________________________________________________________________
51 AliTRDv1::AliTRDv1():AliTRD()
54 // Default constructor
68 //_____________________________________________________________________________
69 AliTRDv1::AliTRDv1(const char *name, const char *title)
73 // Standard constructor for Transition Radiation Detector version 1
85 SetBufferSize(128000);
89 //_____________________________________________________________________________
90 AliTRDv1::AliTRDv1(const AliTRDv1 &trd):AliTRD(trd)
96 ((AliTRDv1 &) trd).Copy(*this);
100 //_____________________________________________________________________________
101 AliTRDv1::~AliTRDv1()
104 // AliTRDv1 destructor
107 if (fDeltaE) delete fDeltaE;
112 //_____________________________________________________________________________
113 AliTRDv1 &AliTRDv1::operator=(const AliTRDv1 &trd)
116 // Assignment operator
119 if (this != &trd) ((AliTRDv1 &) trd).Copy(*this);
124 //_____________________________________________________________________________
125 void AliTRDv1::Copy(TObject &trd)
131 ((AliTRDv1 &) trd).fSensSelect = fSensSelect;
132 ((AliTRDv1 &) trd).fSensPlane = fSensPlane;
133 ((AliTRDv1 &) trd).fSensChamber = fSensChamber;
134 ((AliTRDv1 &) trd).fSensSector = fSensSector;
135 ((AliTRDv1 &) trd).fSensSectorRange = fSensSectorRange;
137 fDeltaE->Copy(*((AliTRDv1 &) trd).fDeltaE);
138 fTR->Copy(*((AliTRDv1 &) trd).fTR);
142 //_____________________________________________________________________________
143 void AliTRDv1::CreateGeometry()
146 // Create the GEANT geometry for the Transition Radiation Detector - Version 1
147 // This version covers the full azimuth.
150 // Check that FRAME is there otherwise we have no place where to put the TRD
151 AliModule* frame = gAlice->GetModule("FRAME");
154 // Define the chambers
155 AliTRD::CreateGeometry();
159 //_____________________________________________________________________________
160 void AliTRDv1::CreateMaterials()
163 // Create materials for the Transition Radiation Detector version 1
166 AliTRD::CreateMaterials();
170 //_____________________________________________________________________________
171 void AliTRDv1::CreateTRhit(Int_t det)
174 // Creates an electron cluster from a TR photon.
175 // The photon is assumed to be created a the end of the radiator. The
176 // distance after which it deposits its energy takes into account the
177 // absorbtion of the entrance window and of the gas mixture in drift
182 const Int_t kPdgElectron = 11;
185 const Float_t kWion = 22.04;
187 // Maximum number of TR photons per track
188 const Int_t kNTR = 50;
190 TLorentzVector mom, pos;
192 // Create TR at the entrance of the chamber
193 if (gMC->IsTrackEntering()) {
195 // Create TR only for electrons
196 Int_t iPdg = gMC->TrackPid();
197 if (TMath::Abs(iPdg) != kPdgElectron) return;
203 gMC->TrackMomentum(mom);
204 Float_t pTot = mom.Rho();
205 fTR->CreatePhotons(iPdg,pTot,nTR,eTR);
207 printf("AliTRDv1::CreateTRhit -- ");
208 printf("Boundary error: nTR = %d, kNTR = %d\n",nTR,kNTR);
212 // Loop through the TR photons
213 for (Int_t iTR = 0; iTR < nTR; iTR++) {
215 Float_t energyMeV = eTR[iTR] * 0.001;
216 Float_t energyeV = eTR[iTR] * 1000.0;
217 Float_t absLength = 0;
220 // Take the absorbtion in the entrance window into account
221 Double_t muMy = fTR->GetMuMy(energyMeV);
222 sigma = muMy * fFoilDensity;
224 absLength = gRandom->Exp(1.0/sigma);
225 if (absLength < AliTRDgeometry::MyThick()) continue;
231 // The absorbtion cross sections in the drift gas
233 // Gas-mixture (Xe/CO2)
234 Double_t muXe = fTR->GetMuXe(energyMeV);
235 Double_t muCO = fTR->GetMuCO(energyMeV);
236 sigma = (0.85 * muXe + 0.15 * muCO) * fGasDensity * fTR->GetTemp();
239 // Gas-mixture (Xe/Isobutane)
240 Double_t muXe = fTR->GetMuXe(energyMeV);
241 Double_t muBu = fTR->GetMuBu(energyMeV);
242 sigma = (0.97 * muXe + 0.03 * muBu) * fGasDensity * fTR->GetTemp();
245 // The distance after which the energy of the TR photon
248 absLength = gRandom->Exp(1.0/sigma);
249 if (absLength > AliTRDgeometry::DrThick()) continue;
255 // The position of the absorbtion
257 gMC->TrackPosition(pos);
258 posHit[0] = pos[0] + mom[0] / pTot * absLength;
259 posHit[1] = pos[1] + mom[1] / pTot * absLength;
260 posHit[2] = pos[2] + mom[2] / pTot * absLength;
263 Int_t q = ((Int_t) (energyeV / kWion));
265 // Add the hit to the array. TR photon hits are marked
266 // by negative charge
267 AddHit(gAlice->GetMCApp()->GetCurrentTrackNumber(),det,posHit,-q,kTRUE);
275 //_____________________________________________________________________________
276 void AliTRDv1::Init()
279 // Initialise Transition Radiation Detector after geometry has been built.
284 if(fDebug) printf("%s: Slow simulator\n",ClassName());
287 printf(" Only plane %d is sensitive\n",fSensPlane);
288 if (fSensChamber >= 0)
289 printf(" Only chamber %d is sensitive\n",fSensChamber);
290 if (fSensSector >= 0) {
291 Int_t sens1 = fSensSector;
292 Int_t sens2 = fSensSector + fSensSectorRange;
293 sens2 -= ((Int_t) (sens2 / AliTRDgeometry::Nsect()))
294 * AliTRDgeometry::Nsect();
295 printf(" Only sectors %d - %d are sensitive\n",sens1,sens2-1);
299 printf("%s: TR simulation on\n",ClassName());
301 printf("%s: TR simulation off\n",ClassName());
304 // First ionization potential (eV) for the gas mixture (90% Xe + 10% CO2)
305 const Float_t kPoti = 12.1;
306 // Maximum energy (50 keV);
307 const Float_t kEend = 50000.0;
308 // Ermilova distribution for the delta-ray spectrum
309 Float_t poti = TMath::Log(kPoti);
310 Float_t eEnd = TMath::Log(kEend);
311 fDeltaE = new TF1("deltae",Ermilova,poti,eEnd,0);
314 printf("%s: ",ClassName());
315 for (Int_t i = 0; i < 80; i++) printf("*");
321 //_____________________________________________________________________________
322 AliTRDsim *AliTRDv1::CreateTR()
325 // Enables the simulation of TR
328 fTR = new AliTRDsim();
333 //_____________________________________________________________________________
334 void AliTRDv1::SetSensPlane(Int_t iplane)
337 // Defines the hit-sensitive plane (0-5)
340 if ((iplane < 0) || (iplane > 5)) {
341 printf("Wrong input value: %d\n",iplane);
342 printf("Use standard setting\n");
353 //_____________________________________________________________________________
354 void AliTRDv1::SetSensChamber(Int_t ichamber)
357 // Defines the hit-sensitive chamber (0-4)
360 if ((ichamber < 0) || (ichamber > 4)) {
361 printf("Wrong input value: %d\n",ichamber);
362 printf("Use standard setting\n");
369 fSensChamber = ichamber;
373 //_____________________________________________________________________________
374 void AliTRDv1::SetSensSector(Int_t isector)
377 // Defines the hit-sensitive sector (0-17)
380 SetSensSector(isector,1);
384 //_____________________________________________________________________________
385 void AliTRDv1::SetSensSector(Int_t isector, Int_t nsector)
388 // Defines a range of hit-sensitive sectors. The range is defined by
389 // <isector> (0-17) as the starting point and <nsector> as the number
390 // of sectors to be included.
393 if ((isector < 0) || (isector > 17)) {
394 printf("Wrong input value <isector>: %d\n",isector);
395 printf("Use standard setting\n");
397 fSensSectorRange = 0;
402 if ((nsector < 1) || (nsector > 18)) {
403 printf("Wrong input value <nsector>: %d\n",nsector);
404 printf("Use standard setting\n");
406 fSensSectorRange = 0;
412 fSensSector = isector;
413 fSensSectorRange = nsector;
417 //_____________________________________________________________________________
418 void AliTRDv1::StepManager()
421 // Slow simulator. Every charged track produces electron cluster as hits
422 // along its path across the drift volume. The step size is set acording
423 // to Bethe-Bloch. The energy distribution of the delta electrons follows
424 // a spectrum taken from Ermilova et al.
441 Double_t betaGamma, pp;
444 Bool_t drRegion = kFALSE;
445 Bool_t amRegion = kFALSE;
448 TString cIdSensDr = "J";
449 TString cIdSensAm = "K";
450 Char_t cIdChamber[3];
453 TLorentzVector pos, mom;
455 const Int_t kNplan = AliTRDgeometry::Nplan();
456 const Int_t kNcham = AliTRDgeometry::Ncham();
457 const Int_t kNdetsec = kNplan * kNcham;
459 const Double_t kBig = 1.0E+12;
462 const Float_t kWion = 22.04;
463 // Maximum momentum for e+ e- g
464 const Float_t kPTotMaxEl = 0.002;
465 // Minimum energy for the step size adjustment
466 const Float_t kEkinMinStep = 1.0e-5;
467 // Plateau value of the energy-loss for electron in xenon
468 // taken from: Allison + Comb, Ann. Rev. Nucl. Sci. (1980), 30, 253
469 //const Double_t kPlateau = 1.70;
470 // the averaged value (26/3/99)
471 const Float_t kPlateau = 1.55;
472 // dN1/dx|min for the gas mixture (90% Xe + 10% CO2)
473 const Float_t kPrim = 48.0;
474 // First ionization potential (eV) for the gas mixture (90% Xe + 10% CO2)
475 const Float_t kPoti = 12.1;
478 const Int_t kPdgElectron = 11;
480 // Set the maximum step size to a very large number for all
481 // neutral particles and those outside the driftvolume
482 gMC->SetMaxStep(kBig);
484 // Use only charged tracks
485 if (( gMC->TrackCharge() ) &&
486 (!gMC->IsTrackStop() ) &&
487 (!gMC->IsTrackDisappeared())) {
489 // Inside a sensitive volume?
492 cIdCurrent = gMC->CurrentVolName();
493 if (cIdSensDr == cIdCurrent[1]) {
496 if (cIdSensAm == cIdCurrent[1]) {
499 if (drRegion || amRegion) {
501 // The hit coordinates and charge
502 gMC->TrackPosition(pos);
507 // The sector number (0 - 17)
508 // The numbering goes clockwise and starts at y = 0
509 // Not fully consistent to new corrdinate schema!!!
510 Float_t phi = kRaddeg*TMath::ATan2(pos[0],pos[1]);
515 sec = ((Int_t) (phi / 20));
517 // The plane and chamber number
518 cIdChamber[0] = cIdCurrent[2];
519 cIdChamber[1] = cIdCurrent[3];
520 Int_t idChamber = (atoi(cIdChamber) % kNdetsec);
521 cha = ((Int_t) idChamber / kNplan);
522 pla = ((Int_t) idChamber % kNplan);
524 // Check on selected volumes
525 Int_t addthishit = 1;
527 if ((fSensPlane >= 0) && (pla != fSensPlane )) addthishit = 0;
528 if ((fSensChamber >= 0) && (cha != fSensChamber)) addthishit = 0;
529 if (fSensSector >= 0) {
530 Int_t sens1 = fSensSector;
531 Int_t sens2 = fSensSector + fSensSectorRange;
532 sens2 -= ((Int_t) (sens2 / AliTRDgeometry::Nsect()))
533 * AliTRDgeometry::Nsect();
535 if ((sec < sens1) || (sec >= sens2)) addthishit = 0;
538 if ((sec < sens1) && (sec >= sens2)) addthishit = 0;
546 // The detector number
547 det = fGeometry->GetDetector(pla,cha,sec);
549 // Special hits and TR photons only in the drift region
552 // Create a track reference at the entrance and
553 // exit of each chamber that contain the
554 // momentum components of the particle
555 if (gMC->IsTrackEntering() || gMC->IsTrackExiting()) {
556 gMC->TrackMomentum(mom);
557 AddTrackReference(gAlice->GetMCApp()->GetCurrentTrackNumber());
560 // Create the hits from TR photons
561 if (fTR) CreateTRhit(det);
565 // Calculate the energy of the delta-electrons
566 eDelta = TMath::Exp(fDeltaE->GetRandom()) - kPoti;
567 eDelta = TMath::Max(eDelta,0.0);
569 // The number of secondary electrons created
570 qTot = ((Int_t) (eDelta / kWion) + 1);
572 // Create a new dEdx hit
574 AddHit(gAlice->GetMCApp()->GetCurrentTrackNumber(),det,hits,qTot,kTRUE);
577 AddHit(gAlice->GetMCApp()->GetCurrentTrackNumber(),det,hits,qTot,kFALSE);
580 // Calculate the maximum step size for the next tracking step
581 // Produce only one hit if Ekin is below cutoff
582 aMass = gMC->TrackMass();
583 if ((gMC->Etot() - aMass) > kEkinMinStep) {
585 // The energy loss according to Bethe Bloch
586 iPdg = TMath::Abs(gMC->TrackPid());
587 if ( (iPdg != kPdgElectron) ||
588 ((iPdg == kPdgElectron) && (pTot < kPTotMaxEl))) {
589 gMC->TrackMomentum(mom);
591 betaGamma = pTot / aMass;
592 pp = kPrim * BetheBloch(betaGamma);
593 // Take charge > 1 into account
594 charge = gMC->TrackCharge();
595 if (TMath::Abs(charge) > 1) pp = pp * charge*charge;
597 // Electrons above 20 Mev/c are at the plateau
599 pp = kPrim * kPlateau;
604 gMC->GetRandom()->RndmArray(1, random);
605 while ((random[0] == 1.) || (random[0] == 0.));
606 stepSize = - TMath::Log(random[0]) / pp;
607 gMC->SetMaxStep(stepSize);
620 //_____________________________________________________________________________
621 Double_t AliTRDv1::BetheBloch(Double_t bg)
624 // Parametrization of the Bethe-Bloch-curve
625 // The parametrization is the same as for the TPC and is taken from Lehrhaus.
628 // This parameters have been adjusted to averaged values from GEANT
629 const Double_t kP1 = 7.17960e-02;
630 const Double_t kP2 = 8.54196;
631 const Double_t kP3 = 1.38065e-06;
632 const Double_t kP4 = 5.30972;
633 const Double_t kP5 = 2.83798;
635 // This parameters have been adjusted to Xe-data found in:
636 // Allison & Cobb, Ann. Rev. Nucl. Sci. (1980), 30, 253
637 //const Double_t kP1 = 0.76176E-1;
638 //const Double_t kP2 = 10.632;
639 //const Double_t kP3 = 3.17983E-6;
640 //const Double_t kP4 = 1.8631;
641 //const Double_t kP5 = 1.9479;
643 // Lower cutoff of the Bethe-Bloch-curve to limit step sizes
644 const Double_t kBgMin = 0.8;
645 const Double_t kBBMax = 6.83298;
646 //const Double_t kBgMin = 0.6;
647 //const Double_t kBBMax = 17.2809;
648 //const Double_t kBgMin = 0.4;
649 //const Double_t kBBMax = 82.0;
652 Double_t yy = bg / TMath::Sqrt(1. + bg*bg);
653 Double_t aa = TMath::Power(yy,kP4);
654 Double_t bb = TMath::Power((1./bg),kP5);
655 bb = TMath::Log(kP3 + bb);
656 return ((kP2 - aa - bb)*kP1 / aa);
664 //_____________________________________________________________________________
665 Double_t Ermilova(Double_t *x, Double_t *)
668 // Calculates the delta-ray energy distribution according to Ermilova.
669 // Logarithmic scale !
678 const Int_t kNv = 31;
680 Float_t vxe[kNv] = { 2.3026, 2.9957, 3.4012, 3.6889, 3.9120
681 , 4.0943, 4.2485, 4.3820, 4.4998, 4.6052
682 , 4.7005, 5.0752, 5.2983, 5.7038, 5.9915
683 , 6.2146, 6.5221, 6.9078, 7.3132, 7.6009
684 , 8.0064, 8.5172, 8.6995, 8.9872, 9.2103
685 , 9.4727, 9.9035,10.3735,10.5966,10.8198
688 Float_t vye[kNv] = { 80.0 , 31.0 , 23.3 , 21.1 , 21.0
689 , 20.9 , 20.8 , 20.0 , 16.0 , 11.0
690 , 8.0 , 6.0 , 5.2 , 4.6 , 4.0
691 , 3.5 , 3.0 , 1.4 , 0.67 , 0.44
692 , 0.3 , 0.18 , 0.12 , 0.08 , 0.056
693 , 0.04 , 0.023, 0.015, 0.011, 0.01
702 dpos = energy - vxe[pos2++];
706 if (pos2 > kNv) pos2 = kNv - 1;
709 // Differentiate between the sampling points
710 dnde = (vye[pos1] - vye[pos2]) / (vxe[pos2] - vxe[pos1]);