ITS/AliITSsegmentationSSD.cxx

   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   *
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   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
  16 /* $Id$ */
  17
  18 #include <Riostream.h>
  19 #include <TMath.h>
  20 #include "AliITSsegmentationSSD.h"
  21
  22 //////////////////////////////////////////////////////
  23 // Segmentation class for                           //
  24 // silicon strips                                   //
  25 //                                                  //
  26 //////////////////////////////////////////////////////
  27 const Float_t AliITSsegmentationSSD::fgkDxDefault = 72960.;
  28 const Float_t AliITSsegmentationSSD::fgkDzDefault = 40000.;
  29 const Float_t AliITSsegmentationSSD::fgkDyDefault = 300.;
  30 const Float_t AliITSsegmentationSSD::fgkPitchDefault = 95.;
  31 const Int_t AliITSsegmentationSSD::fgkNstripsDefault = 768;
  32
  33 ClassImp(AliITSsegmentationSSD)
  34 AliITSsegmentationSSD::AliITSsegmentationSSD(): AliITSsegmentation(),
  35 fNstrips(0),
  36 fStereoP(0),
  37 fStereoN(0),
  38 fPitch(0),
  39 fStereoPl5(0),
  40 fStereoNl5(0),
  41 fStereoPl6(0),
  42 fStereoNl6(0),
  43 fLayer(0){
  44     // default constructor
  45 }
  46 //----------------------------------------------------------------------
  47 AliITSsegmentationSSD::AliITSsegmentationSSD(AliITSgeom *geom):
  48 fNstrips(0),
  49 fStereoP(0),
  50 fStereoN(0),
  51 fPitch(0),
  52 fStereoPl5(0),
  53 fStereoNl5(0),
  54 fStereoPl6(0),
  55 fStereoNl6(0),
  56 fLayer(0){
  57     // constuctor
  58     fGeom = geom;
  59     fCorr = 0;
  60     SetDetSize(fgkDxDefault,fgkDzDefault,fgkDyDefault);
  61     SetPadSize(fgkPitchDefault,0.);
  62     SetNPads(fgkNstripsDefault,0);
  63     SetAngles();
  64     fLayer = 0;
  65 }
  66
  67 //______________________________________________________________________
  68 void AliITSsegmentationSSD::Copy(TObject &obj) const {
  69   // protected method. copy this to obj
  70   AliITSsegmentation::Copy(obj);
  71   ((AliITSsegmentationSSD& ) obj).Clear();
  72   ((AliITSsegmentationSSD& ) obj).fNstrips = fNstrips;
  73   ((AliITSsegmentationSSD& ) obj).fStereoP = fStereoP;
  74   ((AliITSsegmentationSSD& ) obj).fStereoN = fStereoN;
  75   ((AliITSsegmentationSSD& ) obj).fStereoPl5 = fStereoPl5;
  76   ((AliITSsegmentationSSD& ) obj).fStereoNl5 = fStereoNl5;
  77   ((AliITSsegmentationSSD& ) obj).fStereoPl6 = fStereoPl6;
  78   ((AliITSsegmentationSSD& ) obj).fStereoNl6 = fStereoNl6;
  79   ((AliITSsegmentationSSD& ) obj).fLayer   = fLayer;
  80   ((AliITSsegmentationSSD& ) obj).fPitch   = fPitch;
  81   ((AliITSsegmentationSSD& ) obj).fLayer   = fLayer;
  82
  83 }
  84
  85 //______________________________________________________________________
  86 AliITSsegmentationSSD& AliITSsegmentationSSD::operator=(
  87                         const AliITSsegmentationSSD &source){
  88 // Operator =
  89   if(this != &source){
  90     source.Copy(*this);
  91   }
  92   return *this;
  93 }
  94 //______________________________________________________________________
  95 AliITSsegmentationSSD::AliITSsegmentationSSD(const AliITSsegmentationSSD &source):
  96     AliITSsegmentation(source),
  97 fNstrips(0),
  98 fStereoP(0),
  99 fStereoN(0),
 100 fPitch(0),
 101 fStereoPl5(0),
 102 fStereoNl5(0),
 103 fStereoPl6(0),
 104 fStereoNl6(0),
 105 fLayer(0){
 106     // copy constructor
 107   source.Copy(*this);
 108 }
 109 //----------------------------------------------------------------------
 110 void AliITSsegmentationSSD::Init(){
 111     // standard initalizer
 112
 113     SetPadSize(fgkPitchDefault,0.);
 114     SetNPads(fgkNstripsDefault,0);
 115     SetAngles();
 116 }
 117 //----------------------------------------------------------------------
 118 void AliITSsegmentationSSD::Angles(Float_t &aP,Float_t &aN) const{
 119   // P and N side stereo angles
 120     if (fLayer == 5){
 121         aP = fStereoPl5;
 122         aN = fStereoNl5;
 123     } // end if
 124     if (fLayer == 6){
 125         aP = fStereoPl6;
 126         aN = fStereoNl6;
 127     } // end if
 128 }
 129 //----------------------------------------------------------------------
 130 void AliITSsegmentationSSD::SetLayer(Int_t l){
 131   //set fLayer data member (only 5 or 6 are allowed)
 132     if (l==5) fLayer =5;
 133     if (l==6) fLayer =6;
 134     if((l!=5) && (l!=6))Error("SetLayer","Layer can be 5 or 6, not %d",l);
 135 }
 136 //----------------------------------------------------------------------
 137 void AliITSsegmentationSSD::GetPadTxz(Float_t &x,Float_t &z) const{
 138     // returns P and N sided strip numbers for a given location.
 139     // Transformation from microns detector center local coordinates
 140     // to detector P and N side strip numbers..
 141     /*                       _-  Z
 142                     + angle /    ^
 143         fNstrips           v     |   N-Side        ...0
 144             \-------/------------|-----------\--------\
 145             |\\\\\\/////////////.|\\\\\\\\\\\\\\\\\\\\|
 146             |0\\\\/////////////..|.\\\\\\\\\\\\\\\\\\\|
 147             |00\\/////////////...|..\\\\\\\\\\\\\\\\\\|
 148        X <--|000/////////////... |...\\\\\\\\\\\\\\\\\|
 149             |00/////////////...  | ...\\\\\\\\\\\\\\\\|
 150             |0/////////////...   |  ...\\\\\\\\\\\\\\\|
 151             |//////////////...   |  ...\\\\\\\\\\\\\\\|
 152             /-----\--------------|--------------------/
 153         fNstrips-1             P-Side              ...0
 154                      |0\
 155                      |00\
 156         Dead region: |000/
 157                      |00/
 158                      |0/
 159     // expects x, z in microns
 160     */
 161     Float_t stereoP, stereoN;
 162     Angles(stereoP,stereoN);
 163     Float_t tanP = TMath::Tan(stereoP);
 164     Float_t tanN = TMath::Tan(-stereoN);
 165     Float_t x1 = x;
 166     Float_t z1 = z;
 167     x1 += fDx/2;
 168     z1 += fDz/2;
 169     x   = (x1 - z1*tanP)/fPitch;
 170     z   = (x1 - tanN*(z1 - fDz))/fPitch;
 171 }
 172 //----------------------------------------------------------------------
 173 void AliITSsegmentationSSD::GetPadIxz(Float_t x,Float_t z,Int_t &iP,Int_t &iN) const {
 174   // returns P and N sided strip numbers for a given location.
 175     /*                       _-  Z
 176                     + angle /    ^
 177         fNstrips           v     |   N-Side        ...0
 178             \-------/------------|-----------\--------\
 179             |\\\\\\/////////////.|\\\\\\\\\\\\\\\\\\\\|
 180             |0\\\\/////////////..|.\\\\\\\\\\\\\\\\\\\|
 181             |00\\/////////////...|..\\\\\\\\\\\\\\\\\\|
 182        X <--|000/////////////... |...\\\\\\\\\\\\\\\\\|
 183             |00/////////////...  | ...\\\\\\\\\\\\\\\\|
 184             |0/////////////...   |  ...\\\\\\\\\\\\\\\|
 185             |//////////////...   |  ...\\\\\\\\\\\\\\\|
 186             /-----\--------------|--------------------/
 187         fNstrips-1             P-Side              ...0
 188                      |0\
 189                      |00\
 190         Dead region: |000/
 191                      |00/
 192                      |0/
 193
 194     // expects x, z in microns
 195   */
 196
 197     Float_t stereoP, stereoN;
 198     Angles(stereoP,stereoN);
 199     Float_t tanP=TMath::Tan(stereoP);
 200     Float_t tanN=TMath::Tan(stereoN);
 201     Float_t x1=x,z1=z;
 202     x1 += fDx/2;
 203     z1 += fDz/2;
 204     Float_t  ldX = x1 - z1*tanP;          // distance from left-down edge
 205     iP = (Int_t)(ldX/fPitch);
 206     iP = (iP<0)? -1: iP;
 207     iP = (iP>fNstrips)? -1: iP;
 208
 209     ldX = x1 - tanN*(fDz - z1);
 210     iN = (Int_t)(ldX/fPitch);
 211     iN = (iN<0)? -1: iN;
 212     iN = (iN>fNstrips)? -1: iN;
 213
 214 }
 215 //-------------------------------------------------------
 216 void AliITSsegmentationSSD::GetPadCxz(Int_t iP,Int_t iN,Float_t &x,Float_t &z) const {
 217     // actually this is the GetCrossing(Float_t &,Float_t &)
 218     // returns local x, z  in microns !
 219
 220     Float_t lDx = fDx; // detector size in x direction, microns
 221     Float_t lDz = fDz; // detector size in z direction, microns
 222     Float_t xP; // x coordinate in the P side from the first P strip
 223     Float_t xN; // x coordinate in the N side from the first N strip
 224     Float_t stereoP, stereoN;
 225     Angles(stereoP,stereoN);
 226     Float_t kP=TMath::Tan(stereoP);
 227     Float_t kN=TMath::Tan(stereoN);
 228
 229     xP=iP*fPitch;
 230     xN=iN*fPitch;
 231     x = xP + kP*(lDz*kN-xP+xN)/(kP+kN);
 232     z = (lDz*kN-xP+xN)/(kP+kN);
 233     x -= lDx/2;
 234     z -= lDz/2;
 235     //if(TMath::Abs(z) > Dz/2) cout<<"Warning, wrong z local ="<<z<<endl;
 236     // Check that zL is inside the detector for the
 237     // correspondent xP and xN coordinates
 238
 239     return;
 240 }
 241 //______________________________________________________________________
 242 Bool_t AliITSsegmentationSSD::LocalToDet(Float_t x,Float_t z,
 243                                        Int_t &iP,Int_t &iN) const {
 244     // Transformation from Geant cm detector center local coordinates
 245     // to detector P and N side strip numbers..
 246     /*                       _-  Z
 247                     + angle /    ^
 248         fNstrips           v     |   N-Side        ...0
 249             \-------/------------|-----------\--------\
 250             |\\\\\\/////////////.|\\\\\\\\\\\\\\\\\\\\|
 251             |0\\\\/////////////..|.\\\\\\\\\\\\\\\\\\\|
 252             |00\\/////////////...|..\\\\\\\\\\\\\\\\\\|
 253        X <--|000/////////////... |...\\\\\\\\\\\\\\\\\|
 254             |00/////////////...  | ...\\\\\\\\\\\\\\\\|
 255             |0/////////////...   |  ...\\\\\\\\\\\\\\\|
 256             |//////////////...   |  ...\\\\\\\\\\\\\\\|
 257             /-----\--------------|--------------------/
 258         fNstrips-1             P-Side              ...0
 259                      |0\
 260                      |00\
 261         Dead region: |000/
 262                      |00/
 263                      |0/
 264     */
 265     const Double_t kconst = 1.0E-04; // convert microns to cm.
 266
 267     x /= kconst;  // convert to microns
 268     z /= kconst;  // convert to microns
 269     this->GetPadTxz(x,z);
 270
 271     // first for P side
 272     iP = (Int_t) x;
 273     if(iP<0 || iP>=fNstrips) iP=-1; // strip number must be in range.
 274     // Now for N side)
 275     iN = (Int_t) z;
 276     if(iN<0 || iN>=fNstrips) iN=-1; // strip number must be in range.
 277     return kTRUE;
 278 }
 279 //----------------------------------------------------------------------
 280 void AliITSsegmentationSSD::DetToLocal(Int_t ix,Int_t iPN,
 281                                        Float_t &x,Float_t &z) const{
 282     // Transformation from detector segmentation/cell coordiantes starting
 283     // from 0. iPN=0 for P side and 1 for N side strip. Returned is z=0.0
 284     // and the corresponding x value..
 285     /*                       _-  Z
 286                     + angle /    ^
 287         fNstrips           v     |   N-Side        ...0
 288             \-------/------------|-----------\--------\
 289             |\\\\\\/////////////.|\\\\\\\\\\\\\\\\\\\\|
 290             |0\\\\/////////////..|.\\\\\\\\\\\\\\\\\\\|
 291             |00\\/////////////...|..\\\\\\\\\\\\\\\\\\|
 292        X <--|000/////////////... |...\\\\\\\\\\\\\\\\\|
 293             |00/////////////...  | ...\\\\\\\\\\\\\\\\|
 294             |0/////////////...   |  ...\\\\\\\\\\\\\\\|
 295             |//////////////...   |  ...\\\\\\\\\\\\\\\|
 296             /-----\--------------|--------------------/
 297         fNstrips-1             P-Side              ...0
 298                      |0\
 299                      |00\
 300         Dead region: |000/
 301                      |00/
 302                      |0/
 303     */
 304     // for strips p-side
 305     // x = a + b + z*tan(fStereoP); a = Dpx(iP)*(iP+0.5)-dx; b = dz*th;
 306     // for strips n-side
 307     // x = a + b + z*tan(fStereoP); a = Dpx(iN)*(iN+0.5)-dx; b = -dz*th;
 308     const Double_t kconst = 1.0E-04; // convert microns to cm.
 309     Float_t flag=kconst*Dx(); // error value
 310     Double_t th=0.0,dx,dz,i,a,b=0.0,xb[4],zb[4];
 311     Float_t stereoP, stereoN;
 312     Angles(stereoP,stereoN);
 313
 314     z = 0.0;  // Strip center in z.
 315     if(iPN<0 || iPN>1){// if error return full detector size in x.
 316         x = z = flag;
 317         return;
 318     } // end if
 319     if(ix<0 || ix>=fNstrips) { // if error return full detector size in x.
 320         x = z = flag;
 321         return;
 322     } // end if
 323     i  = (Double_t) ix;      // convert to double
 324     dx = 0.5*kconst*Dx();    // half distance in x in cm
 325     dz = 0.5*kconst*Dz();    // half distance in z in cm
 326     a  = kconst*Dpx(ix)*(i+0.5)-dx; // Min x value.
 327     if(iPN==0){ //P-side angle defined backwards.
 328         th = TMath::Tan(stereoP);
 329         b  = dz*th;
 330     }else if(iPN==1){ // N-side
 331          th = TMath::Tan(-stereoN);
 332          b  = -dz*th;
 333     } // end if
 334     // compute average/center position of the strip.
 335     xb[0] = +dx; if(th!=0.0) zb[0] = (+dx-a-b)/th; else zb[0] = 0.0;
 336     xb[1] = -dx; if(th!=0.0) zb[1] = (-dx-a-b)/th; else zb[1] = 0.0;
 337     xb[2] = a+b+dz*th; zb[2] = +dz;
 338     xb[3] = a+b-dz*th; zb[3] = -dz;
 339     x = 0.0; z = 0.0;
 340     for(Int_t j=0;j<4;j++){
 341         if(xb[j]>=-dx && xb[j]<=dx && zb[j]>=-dz && zb[j]<=dz){
 342             x += xb[j];
 343             z += zb[j];
 344         } // end if
 345     } // end for
 346     x *= 0.5;
 347     z *= 0.5;
 348     return;
 349 }
 350 //----------------------------------------------------------------------
 351 Bool_t AliITSsegmentationSSD::GetCrossing(Int_t iP,Int_t iN,
 352                                           Float_t &x,Float_t &z,
 353                                           Float_t c[2][2]){
 354     // Given one P side strip and one N side strip, Returns kTRUE if they
 355     // cross each other and the location of the two crossing strips and
 356     // their correxlation matrix c[2][2].
 357     /*                       _-  Z
 358                     + angle /    ^
 359         fNstrips           v     |   N-Side        ...0
 360             \-------/------------|-----------\--------\
 361             |\\\\\\/////////////.|\\\\\\\\\\\\\\\\\\\\|
 362             |0\\\\/////////////..|.\\\\\\\\\\\\\\\\\\\|
 363             |00\\/////////////...|..\\\\\\\\\\\\\\\\\\|
 364        X <--|000/////////////... |...\\\\\\\\\\\\\\\\\|
 365             |00/////////////...  | ...\\\\\\\\\\\\\\\\|
 366             |0/////////////...   |  ...\\\\\\\\\\\\\\\|
 367             |//////////////...   |  ...\\\\\\\\\\\\\\\|
 368             /-----\--------------|--------------------/
 369         fNstrips-1             P-Side              ...0
 370                      |0\
 371                      |00\
 372         Dead region: |000/
 373                      |00/
 374                      |0/
 375        c[2][2] is defined as follows
 376        /c[0][0]  c[0][1]\ /delta iP\ = /delta x\
 377        \c[1][0]  c[1][1]/ \delta iN/ = \delta z/
 378     */
 379     const Double_t kconst = 1.0E-04; // convert microns to cm.
 380     Double_t thp,thn,th,dx,dz,p,ip,in;
 381     Float_t stereoP, stereoN;
 382     Angles(stereoP,stereoN);
 383
 384     thp = TMath::Tan(stereoP);
 385     thn = TMath::Tan(-stereoN);
 386     th  = thp-thn;
 387     if(th==0.0) { // parall strips then never cross.
 388         x = 0.0;
 389         z = 0.0;
 390         c[0][0] = c[1][0] = c[0][1] = c[1][1] = 0.0;
 391         return kFALSE;
 392     } // end if
 393     // The strips must cross some place in space.
 394     ip = (Double_t) iP;       // convert to double now for speed
 395     in = (Double_t) iN;       // convert to double now for speed
 396     dx = 0.5*kconst*Dx();     // half distance in x in cm
 397     dz = 0.5*kconst*Dz();     // half distance in z in cm
 398     p  = kconst*Dpx(iP);      // Get strip spacing/pitch now
 399     x  = 0.5*p+dx + (p*(in*thp-ip*thn)-2.0*dz*thp*thn)/th;
 400     z  =(p*(in-ip)-dz*(thp+thn))/th;
 401     // compute correlations.
 402     c[0][0] = -thn*p/th; // dx/diP
 403     c[1][1] = p/th;      // dz/diN
 404     c[0][1] = p*thp/th;  // dx/diN
 405     c[1][0] = -p/th;     // dz/diP
 406     if(x<-dx || x>dx || z<-dz || z>dz) return kFALSE; // crossing is outside
 407                                                       // of the detector so
 408                                                       // these strips don't
 409                                                       // cross.
 410     return kTRUE;
 411 }
 412
 413 //----------------------------------------------------------------------
 414 void AliITSsegmentationSSD::PrintDefaultParameters() const {
 415 // Print default values for parameters.
 416 // Values specified as static const data members are shown
 417
 418   cout<<"fgkDxDefault = "<<fgkDxDefault<<endl;
 419   cout<<"fgkDzDefault = "<<fgkDzDefault<<endl;
 420   cout<<"fgkDyDefault = "<<fgkDyDefault<<endl;
 421   cout<<"fgkPitchDefault = "<<fgkPitchDefault<<endl;
 422   cout<<"fgkNstripsDefault = "<<fgkNstripsDefault<<endl;
 423 }