/data/refman/pasoursint/CMSSW_4_4_5_patch3/src/Geometry/CommonTopologies/src/TrapezoidalStripTopology.cc

Go to the documentation of this file.

#include "Geometry/CommonTopologies/interface/TrapezoidalStripTopology.h"

#include <iostream>
#include <cmath>
#include <algorithm>

TrapezoidalStripTopology::TrapezoidalStripTopology(int ns, float p, 
                                                   float l,
                                                   float r0) :
  theNumberOfStrips(ns), thePitch(p),
  theDistToBeam(r0), theDetHeight(l) {
  theOffset = -theNumberOfStrips/2. * thePitch;
  theYAxOr = 1;
#ifdef VERBOSE
  cout<<"Constructing TrapezoidalStripTopology with"
      <<" nstrips = "<<ns
      <<" pitch = "<<p
      <<" length = "<<l
      <<" r0 ="<<r0
      <<endl;
#endif
}

TrapezoidalStripTopology::TrapezoidalStripTopology(int ns, float p, 
                                                   float l,
                                                   float r0, int yAx) :
  theNumberOfStrips(ns), thePitch(p),
  theDistToBeam(r0), theDetHeight(l), theYAxOr(yAx){
  theOffset = -theNumberOfStrips/2. * thePitch;
#ifdef VERBOSE
  cout<<"Constructing TrapezoidalStripTopology with"
      <<" nstrips = "<<ns
      <<" pitch = "<<p
      <<" length = "<<l
      <<" r0 ="<<r0
      <<" yAxOrientation ="<<yAx
      <<endl;
#endif
}

LocalPoint
TrapezoidalStripTopology::localPosition(float strip) const {
  return LocalPoint( strip*thePitch + theOffset, 0.0);
}

LocalPoint
TrapezoidalStripTopology::localPosition(const MeasurementPoint& mp) const {
  float y = mp.y()*theDetHeight;
  float x = (mp.x()*thePitch + 
             theOffset)*(theYAxOr*y+theDistToBeam)/theDistToBeam;
  return LocalPoint(x,y);
}

LocalError
TrapezoidalStripTopology::localError(float strip, float stripErr2) const {
  float lt,lc2,ls2,lslc;
  float localL2,localP2;
  float sl2,sp2;
  // angle from strip to local frame (see CMS TN / 95-170)
  lt = -(strip*thePitch + theOffset)*theYAxOr/theDistToBeam;
  lc2 = 1.f/(1.+lt*lt);
  lslc = lt*lc2;
  ls2 = 1.f-lc2;
  localL2 = theDetHeight*theDetHeight / lc2;
  localP2 = thePitch*thePitch*lc2;
  sl2 = localL2/12.;
  sp2 = stripErr2*localP2;
  return LocalError(lc2*sp2+ls2*sl2,
                    lslc*(sp2-sl2),
                    ls2*sp2+lc2*sl2);
}

LocalError
TrapezoidalStripTopology::localError(const MeasurementPoint& mp,
                                     const MeasurementError& merr) const {
  float lt,lc2,ls2,lslc;
  float localL,localP;
  float sl2,sp2,spl;
  // angle from strip to local frame (see CMS TN / 95-170)
  lt = -(mp.x()*thePitch + theOffset)*theYAxOr/theDistToBeam;
  lc2 = 1./(1.+lt*lt);
  lslc = lt*lc2;
  ls2 = 1.f-lc2;
  localL = theDetHeight / std::sqrt(lc2);
  localP = localPitch(localPosition(mp));
  sp2 = merr.uu() * localP*localP;
  sl2 = merr.vv() * localL*localL;
  spl = merr.uv() * localP*localL;
  return LocalError(lc2*sp2+ls2*sl2-2*lslc*spl,
                    lslc*(sp2-sl2)+(lc2-ls2)*spl,
                    ls2*sp2+lc2*sl2+2*lslc*spl);
}

float
TrapezoidalStripTopology::strip(const LocalPoint& lp) const {
  float aStrip =
     ((lp.x()*theDistToBeam/(theYAxOr*lp.y()+theDistToBeam))-theOffset)/thePitch;
   if (aStrip < 0 ) aStrip = 0;
  else if (aStrip > theNumberOfStrips)  aStrip = theNumberOfStrips;
  return aStrip;
}

MeasurementPoint
TrapezoidalStripTopology::measurementPosition(const LocalPoint& lp) const {
  return 
    MeasurementPoint(((lp.x()*theDistToBeam/(theYAxOr*lp.y()+theDistToBeam))-theOffset)/thePitch,
                     lp.y()/theDetHeight);
}

MeasurementError
TrapezoidalStripTopology::measurementError(const LocalPoint& lp,
                                           const LocalError& lerr) const {
  float lt,lc2,ls2,lslc;
  float localL,localP;
  float sl2,sp2,spl;
  lt = -lp.x()/(theYAxOr*lp.y()+theDistToBeam)*theYAxOr;
  lc2 = 1./(1.+lt*lt);
  lslc = lt*lc2;
  ls2 = 1.-lc2;
  localL = theDetHeight / std::sqrt(lc2);
  localP = localPitch(lp);
  sp2 = lc2*lerr.xx()+ls2*lerr.yy()+2*lslc*lerr.xy();
  sl2 = ls2*lerr.xx()+lc2*lerr.yy()-2*lslc*lerr.xy();
  spl = lslc*(lerr.yy()-lerr.xx())+(lc2-ls2)*lerr.xy();
  return MeasurementError(sp2/(localP*localP),
                          spl/(localP*localL),
                          sl2/(localL*localL));

}

int
TrapezoidalStripTopology::channel(const LocalPoint& lp) const {
  return std::min(int(strip(lp)),theNumberOfStrips-1);
}

float
TrapezoidalStripTopology::pitch() const {
  return thePitch;
}

float
TrapezoidalStripTopology::localPitch(const LocalPoint& lp) const {
  float x=lp.x();
  float y=theYAxOr*lp.y()+theDistToBeam;
  return thePitch*y/(theDistToBeam*std::sqrt(1.f+x*x/(y*y)));
}

float
TrapezoidalStripTopology::stripAngle(float strip) const {
  return std::atan( -(strip*thePitch + theOffset)*theYAxOr/theDistToBeam );
}

int
TrapezoidalStripTopology::nstrips() const {
  return theNumberOfStrips;
}

float TrapezoidalStripTopology::shiftOffset( float pitch_fraction) {
  theOffset += thePitch * pitch_fraction;
  return theOffset;
}

float TrapezoidalStripTopology::localStripLength(const LocalPoint& lp) 
  const {
  float ltan = -lp.x()/(theYAxOr*lp.y()+theDistToBeam)*theYAxOr;
  float localL = theDetHeight * std::sqrt(1.f+ltan*ltan);
  //  float lcos2 = 1.f/(1.f+ltan*ltan);
  //  float localL = theDetHeight / std::sqrt(lcos2);

  return localL;
}