CMSSW_4_4_3_patch1/src/RecoMET/METAlgorithms/src/CSCHaloAlgo.cc

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#include "RecoMET/METAlgorithms/interface/CSCHaloAlgo.h"
#include "FWCore/Common/interface/TriggerNames.h"
/*
  [class]:  CSCHaloAlgo
  [authors]: R. Remington, The University of Florida
  [description]: See CSCHaloAlgo.h
  [date]: October 15, 2009
*/
using namespace reco;
using namespace std;
using namespace edm;
#include "TMath.h"

CSCHaloAlgo::CSCHaloAlgo()
{
  deta_threshold = 0.;
  min_inner_radius = 0.;
  max_inner_radius = 9999.;
  min_outer_radius = 0.;
  max_outer_radius = 9999.;
  dphi_threshold = 999.;
  norm_chi2_threshold = 999.;
  recHit_t0=0.;
  recHit_twindow=25.;
  expected_BX=3;
  max_dt_muon_segment=-10.0;
  max_free_inverse_beta=0.0;
  
  min_outer_theta = 0.;
  max_outer_theta = TMath::Pi();
  
  matching_dphi_threshold = 0.18; //radians
  matching_deta_threshold = 0.4;
  matching_dwire_threshold = 5.;
}

reco::CSCHaloData CSCHaloAlgo::Calculate(const CSCGeometry& TheCSCGeometry,
                                         edm::Handle<reco::MuonCollection>& TheCosmicMuons,  
                                         const edm::Handle<reco::MuonTimeExtraMap> TheCSCTimeMap,
                                         edm::Handle<reco::MuonCollection>& TheMuons,
                                         edm::Handle<CSCSegmentCollection>& TheCSCSegments, 
                                         edm::Handle<CSCRecHit2DCollection>& TheCSCRecHits,
                                         edm::Handle < L1MuGMTReadoutCollection >& TheL1GMTReadout,
                                         edm::Handle<edm::TriggerResults>& TheHLTResults,
                                         const edm::TriggerNames * triggerNames, 
                                         const edm::Handle<CSCALCTDigiCollection>& TheALCTs,
                                         MuonSegmentMatcher *TheMatcher,  
                                         const edm::Event& TheEvent)
{
  reco::CSCHaloData TheCSCHaloData;
  int imucount=0;
  if( TheCosmicMuons.isValid() )
    {
      short int n_tracks_small_beta=0;
      short int n_tracks_small_dT=0;
      short int n_tracks_small_dT_and_beta=0;
      for( reco::MuonCollection::const_iterator iMuon = TheCosmicMuons->begin() ; iMuon != TheCosmicMuons->end() ; iMuon++, imucount++ )
        {
          reco::TrackRef Track = iMuon->outerTrack();
          if(!Track) continue;

          bool StoreTrack = false;
          // Calculate global phi coordinate for central most rechit in the track
          float innermost_global_z = 1500.;
          float outermost_global_z = 0.;
          GlobalPoint InnerMostGlobalPosition(0.,0.,0.);  // smallest abs(z)
          GlobalPoint OuterMostGlobalPosition(0.,0.,0.);  // largest abs(z)
          int nCSCHits = 0;
          for(unsigned int j = 0 ; j < Track->extra()->recHits().size(); j++ )
            {
              edm::Ref<TrackingRecHitCollection> hit( Track->extra()->recHits(), j );
              if( !hit->isValid() ) continue;
              DetId TheDetUnitId(hit->geographicalId());
              if( TheDetUnitId.det() != DetId::Muon ) continue;
              if( TheDetUnitId.subdetId() != MuonSubdetId::CSC ) continue;

              const GeomDetUnit *TheUnit = TheCSCGeometry.idToDetUnit(TheDetUnitId);
              LocalPoint TheLocalPosition = hit->localPosition();  
              const BoundPlane& TheSurface = TheUnit->surface();
              const GlobalPoint TheGlobalPosition = TheSurface.toGlobal(TheLocalPosition);

              float z = TheGlobalPosition.z();
              if( TMath::Abs(z) < innermost_global_z )
                {
                  innermost_global_z = TMath::Abs(z);
                  InnerMostGlobalPosition = GlobalPoint( TheGlobalPosition);
                }
              if( TMath::Abs(z) > outermost_global_z )
                {
                  outermost_global_z = TMath::Abs(z);
                  OuterMostGlobalPosition = GlobalPoint( TheGlobalPosition );
                }
              nCSCHits ++;
            }

          std::vector<const CSCSegment*> MatchedSegments = TheMatcher->matchCSC(*Track,TheEvent);
          // Find the inner and outer segments separately in case they don't agree completely with recHits
          // Plan for the possibility segments in both endcaps
          float InnerSegmentTime[2] = {0,0};
          float OuterSegmentTime[2] = {0,0};
          float innermost_seg_z[2] = {1500,1500};
          float outermost_seg_z[2] = {0,0};
          for (std::vector<const CSCSegment*>::const_iterator segment =MatchedSegments.begin();
               segment != MatchedSegments.end(); ++segment)
            {
              CSCDetId TheCSCDetId((*segment)->cscDetId());
              const CSCChamber* TheCSCChamber = TheCSCGeometry.chamber(TheCSCDetId);
              LocalPoint TheLocalPosition = (*segment)->localPosition();
              const GlobalPoint TheGlobalPosition = TheCSCChamber->toGlobal(TheLocalPosition);
              float z = TheGlobalPosition.z();
              int TheEndcap = TheCSCDetId.endcap();
              if( TMath::Abs(z) < innermost_seg_z[TheEndcap-1] )
                {
                  innermost_seg_z[TheEndcap-1] = TMath::Abs(z);
                  InnerSegmentTime[TheEndcap-1] = (*segment)->time();
                }
              if( TMath::Abs(z) > outermost_seg_z[TheEndcap-1] )
                {
                  outermost_seg_z[TheEndcap-1] = TMath::Abs(z);
                  OuterSegmentTime[TheEndcap-1] = (*segment)->time();
                }
            }

          if( nCSCHits < 3 ) continue; // This needs to be optimized, but is the minimum 

          float dT_Segment = 0; // default safe value, looks like collision muon
         
          if( innermost_seg_z[0] < outermost_seg_z[0]) // two segments in ME+
            dT_Segment =  OuterSegmentTime[0]-InnerSegmentTime[0];
          if( innermost_seg_z[1] < outermost_seg_z[1]) // two segments in ME-
            {
              // replace the measurement if there weren't segments in ME+ or
              // if the track in ME- has timing more consistent with an incoming particle
              if (dT_Segment == 0.0 ||  OuterSegmentTime[1]-InnerSegmentTime[1] < dT_Segment)
                dT_Segment = OuterSegmentTime[1]-InnerSegmentTime[1] ;
            }

          if( OuterMostGlobalPosition.x() == 0. || OuterMostGlobalPosition.y() == 0. || OuterMostGlobalPosition.z() == 0. ) 
            continue;
          if( InnerMostGlobalPosition.x() == 0. || InnerMostGlobalPosition.y() == 0. || InnerMostGlobalPosition.z() == 0. )
            continue;
          
          //Its a CSC Track,store it if it passes halo selection 
          StoreTrack = true;      

          float deta = TMath::Abs( OuterMostGlobalPosition.eta() - InnerMostGlobalPosition.eta() );
          float dphi = TMath::ACos( TMath::Cos( OuterMostGlobalPosition.phi() - InnerMostGlobalPosition.phi() ) ) ;
          float theta = Track->outerMomentum().theta();
          float innermost_x = InnerMostGlobalPosition.x() ;
          float innermost_y = InnerMostGlobalPosition.y();
          float outermost_x = OuterMostGlobalPosition.x();
          float outermost_y = OuterMostGlobalPosition.y();
          float innermost_r = TMath::Sqrt(innermost_x *innermost_x + innermost_y * innermost_y );
          float outermost_r = TMath::Sqrt(outermost_x *outermost_x + outermost_y * outermost_y );
          
          if( deta < deta_threshold )
            StoreTrack = false;
          if( theta > min_outer_theta && theta < max_outer_theta )
            StoreTrack = false;
          if( dphi > dphi_threshold )
            StoreTrack = false;
          if( innermost_r < min_inner_radius )
            StoreTrack = false;
          if( innermost_r > max_inner_radius )
            StoreTrack = false;
          if( outermost_r < min_outer_radius )
            StoreTrack = false;
          if( outermost_r > max_outer_radius )
            StoreTrack  = false;
          if( Track->normalizedChi2() > norm_chi2_threshold )
            StoreTrack = false;

          if( StoreTrack )
            {
              TheCSCHaloData.GetCSCTrackImpactPositions().push_back( InnerMostGlobalPosition );
              TheCSCHaloData.GetTracks().push_back( Track );
            }

          // Analyze the MuonTimeExtra information
          if( TheCSCTimeMap.isValid() ) 
            {
              reco::MuonRef muonR(TheCosmicMuons,imucount);
              const reco::MuonTimeExtraMap & timeMapCSC = *TheCSCTimeMap;
              reco::MuonTimeExtra timecsc = timeMapCSC[muonR];
              float freeInverseBeta = timecsc.freeInverseBeta();
              
              if (dT_Segment < max_dt_muon_segment )
                n_tracks_small_dT++;
              if (freeInverseBeta < max_free_inverse_beta)
                n_tracks_small_beta++;
              if ((dT_Segment < max_dt_muon_segment) &&  (freeInverseBeta < max_free_inverse_beta))
                n_tracks_small_dT_and_beta++;
            }
          else 
            {
              static bool MuonTimeFail = false;
              if( !MuonTimeFail ) 
                {
                  edm::LogWarning  ("InvalidInputTag") <<  "The MuonTimeExtraMap does not appear to be in the event. Some beam halo "
                                                       << " identification variables will be empty" ;
                  MuonTimeFail = true;
                }
            }
        }
      TheCSCHaloData.SetNIncomingTracks(n_tracks_small_dT,n_tracks_small_beta,n_tracks_small_dT_and_beta);
    }
  else // collection is invalid
    {
      static bool CosmicFail = false;
      if( !CosmicFail ) 
        {
          edm::LogWarning  ("InvalidInputTag") << " The Cosmic Muon collection does not appear to be in the event. These beam halo "
                                               << " identification variables will be empty" ;
          CosmicFail = true;
        }
    }

  if( TheHLTResults.isValid() )
    {
      bool EventPasses = false;
       for( unsigned int index = 0 ; index < vIT_HLTBit.size(); index++)
         {
           if( vIT_HLTBit[index].label().size() )
             {
               //Get the HLT bit and check to make sure it is valid 
               unsigned int bit = triggerNames->triggerIndex( vIT_HLTBit[index].label().c_str());
               if( bit < TheHLTResults->size() )
                 {
                   //If any of the HLT names given by the user accept, then the event passes
                   if( TheHLTResults->accept( bit ) && !TheHLTResults->error( bit ) )
                     {
                       EventPasses = true;
                     }
                 }
             }
         }
       if( EventPasses )
         TheCSCHaloData.SetHLTBit(true);
       else
         TheCSCHaloData.SetHLTBit(false);
     }
  else //  HLT results are not valid
    {
      static bool HLTFail = false;
      if( !HLTFail ) 
        {
          edm::LogWarning  ("InvalidInputTag") << "The HLT results do not appear to be in the event. The beam halo HLT trigger "
                                               << "decision will not be used in the halo identification"; 
          HLTFail = true;
        }
    }

   if( TheL1GMTReadout.isValid() )
     {
       L1MuGMTReadoutCollection const *gmtrc = TheL1GMTReadout.product ();
       std::vector < L1MuGMTReadoutRecord > gmt_records = gmtrc->getRecords ();
       std::vector < L1MuGMTReadoutRecord >::const_iterator igmtrr;
       
       int icsc = 0;
       int PlusZ = 0 ;
       int MinusZ = 0 ;
       // Check to see if CSC BeamHalo trigger is tripped
       for (igmtrr = gmt_records.begin (); igmtrr != gmt_records.end (); igmtrr++)
         {
           std::vector < L1MuRegionalCand >::const_iterator iter1;
           std::vector < L1MuRegionalCand > rmc;
           rmc = igmtrr->getCSCCands ();
           for (iter1 = rmc.begin (); iter1 != rmc.end (); iter1++)
             {
              if (!(*iter1).empty ())
                {
                  if ((*iter1).isFineHalo ())
                    {
                      float halophi = iter1->phiValue();
                      halophi = halophi > TMath::Pi() ? halophi - 2.*TMath::Pi() : halophi;
                      float haloeta = iter1->etaValue();
                      bool HaloIsGood = true;
                      // Check if halo trigger is faked by any collision muons
                      if( TheMuons.isValid() )
                        {
                          float dphi = 9999.;
                          float deta = 9999.;
                          for( reco::MuonCollection::const_iterator mu = TheMuons->begin(); mu != TheMuons->end() && HaloIsGood ; mu++ )
                            {
                              // Don't match with SA-only muons
                              if( mu->isStandAloneMuon() && !mu->isTrackerMuon() && !mu->isGlobalMuon() )  continue;
                              
                              /*
                              if(!mu->isTrackerMuon())
                                {
                                  if( mu->isStandAloneMuon() )
                                    {
                                      //make sure that this SA muon is not actually a halo-like muon
                                      float theta =  mu->outerTrack()->outerMomentum().theta();
                                      float deta = TMath::Abs(mu->outerTrack()->outerPosition().eta() - mu->outerTrack()->innerPosition().eta());
                                      if( theta < min_outer_theta || theta > max_outer_theta )  //halo-like
                                        continue;
                                      else if ( deta > deta_threshold ) //halo-like
                                        continue;
                                    }
                                }
                              */
                            
                              const std::vector<MuonChamberMatch> chambers = mu->matches();
                              for(std::vector<MuonChamberMatch>::const_iterator iChamber = chambers.begin();
                                  iChamber != chambers.end() ; iChamber ++ )
                                {
                                  if( iChamber->detector() != MuonSubdetId::CSC ) continue;
                                  for( std::vector<reco::MuonSegmentMatch>::const_iterator iSegment = iChamber->segmentMatches.begin() ; 
                                       iSegment != iChamber->segmentMatches.end(); ++iSegment )
                                    {
                                      edm::Ref<CSCSegmentCollection> cscSegment = iSegment->cscSegmentRef;
                                      std::vector<CSCRecHit2D> hits = cscSegment -> specificRecHits();
                                      for( std::vector<CSCRecHit2D>::iterator iHit = hits.begin();
                                           iHit != hits.end() ; iHit++ )
                                        {
                                          DetId TheDetUnitId(iHit->cscDetId());
                                          const GeomDetUnit *TheUnit = TheCSCGeometry.idToDetUnit(TheDetUnitId);
                                          LocalPoint TheLocalPosition = iHit->localPosition();
                                          const BoundPlane& TheSurface = TheUnit->surface();
                                          GlobalPoint TheGlobalPosition = TheSurface.toGlobal(TheLocalPosition);
                                          
                                          float phi_ = TheGlobalPosition.phi();
                                          float eta_ = TheGlobalPosition.eta();
                                          
                                          deta = deta < TMath::Abs( eta_ - haloeta ) ? deta : TMath::Abs( eta_ - haloeta );
                                          dphi = dphi < TMath::ACos(TMath::Cos(phi_ - halophi)) ? dphi : TMath::ACos(TMath::Cos(phi_ - halophi));
                                        }
                                    }
                                }
                              if ( dphi < matching_dphi_threshold && deta < matching_deta_threshold) 
                                HaloIsGood = false; // i.e., collision muon likely faked halo trigger
                            }
                        }
                      if( !HaloIsGood ) 
                        continue;
                      if( (*iter1).etaValue() > 0 )
                        PlusZ++;
                      else
                        MinusZ++;
                    }
                  else
                    icsc++;
                }
             }
         }
       TheCSCHaloData.SetNumberOfHaloTriggers(PlusZ, MinusZ);
     }
   else
     {
       static bool L1Fail = false;
       if( !L1Fail ) 
         {
           edm::LogWarning  ("InvalidInputTag") << "The L1MuGMTReadoutCollection does not appear to be in the event. The L1 beam halo trigger "
                                                << "decision will not be used in the halo identification"; 
           L1Fail = true;
         }
     }

   // Loop over CSCALCTDigi collection to look for out-of-time chamber triggers 
   // A collision muon in real data should only have ALCTDigi::getBX() = 3 ( in MC, it will be 6 )
   // Note that there could be two ALCTs per chamber 
   short int n_alctsP=0;
   short int n_alctsM=0;
   if(TheALCTs.isValid())
     {
       for (CSCALCTDigiCollection::DigiRangeIterator j=TheALCTs->begin(); j!=TheALCTs->end(); j++) 
         {
           const CSCALCTDigiCollection::Range& range =(*j).second;
           CSCDetId detId((*j).first.rawId());
           for (CSCALCTDigiCollection::const_iterator digiIt = range.first; digiIt!=range.second; ++digiIt)
             {
               if( (*digiIt).isValid() && ( (*digiIt).getBX() < expected_BX ) )
                 {
                   int digi_endcap  = detId.endcap();
                   int digi_station = detId.station();
                   int digi_ring    = detId.ring();
                   int digi_chamber = detId.chamber();
                   int digi_wire    = digiIt->getKeyWG();
                   if( digi_station == 1 && digi_ring == 4 )   //hack
                     digi_ring = 1;
                   
                   bool DigiIsGood = true;
                   int dwire = 999.;
                   if( TheMuons.isValid() ) 
                     {
                       //Check if there are any collision muons with hits in the vicinity of the digi
                       for(reco::MuonCollection::const_iterator mu = TheMuons->begin(); mu!= TheMuons->end() && DigiIsGood ; mu++ )
                         {
                           if( !mu->isTrackerMuon() && !mu->isGlobalMuon() && mu->isStandAloneMuon() ) continue;

                           const std::vector<MuonChamberMatch> chambers = mu->matches();
                           for(std::vector<MuonChamberMatch>::const_iterator iChamber = chambers.begin();
                               iChamber != chambers.end(); iChamber ++ )
                             {
                               if( iChamber->detector() != MuonSubdetId::CSC ) continue;
                               for( std::vector<reco::MuonSegmentMatch>::const_iterator iSegment = iChamber->segmentMatches.begin();
                                    iSegment != iChamber->segmentMatches.end(); iSegment++ )
                                 {
                                   edm::Ref<CSCSegmentCollection> cscSegRef = iSegment->cscSegmentRef;
                                   std::vector<CSCRecHit2D> hits = cscSegRef->specificRecHits();
                                   for( std::vector<CSCRecHit2D>::iterator iHit = hits.begin();
                                        iHit != hits.end(); iHit++ )
                                     {
                                       if( iHit->cscDetId().endcap() != digi_endcap ) continue;
                                       if( iHit->cscDetId().station() != digi_station ) continue;
                                       if( iHit->cscDetId().ring() != digi_ring ) continue;
                                       if( iHit->cscDetId().chamber() != digi_chamber ) continue;
                                       CSCRecHit2D::ChannelContainer hitwires = iHit->wgroups();
                                       int nwires = hitwires.size();
                                       int center_id = nwires/2 + 1;
                                       int hit_wire = hitwires[center_id -1 ];
                                       dwire = dwire < TMath::Abs(hit_wire - digi_wire)? dwire : TMath::Abs(hit_wire - digi_wire );
                                     }
                                 }
                             }
                           if( dwire <= matching_dwire_threshold ) 
                             DigiIsGood = false;  // collision-like muon is close to this digi
                         }
                     }
                   // only count out of time digis if they are not matched to collision muons
                   if( DigiIsGood ) 
                     {
                       if( detId.endcap() == 1 ) 
                         n_alctsP++;
                       else if ( detId.endcap() ==  2) 
                         n_alctsM++;
                     }
                 }
             }
         }
     }
   else
     {
       static bool DigiFail=false;
       if (!DigiFail){
         edm::LogWarning  ("InvalidInputTag") << "The CSCALCTDigiCollection does not appear to be in the event. The ALCT Digis will "
                                              << " not be used in the halo identification"; 
         DigiFail=true;
       }
     }
   TheCSCHaloData.SetNOutOfTimeTriggers(n_alctsP,n_alctsM);

   // Loop over the CSCRecHit2D collection to look for out-of-time recHits
   // Out-of-time is defined as tpeak outside [t_0 + TOF - t_window, t_0 + TOF + t_window]
   // where t_0 and t_window are configurable parameters
   short int n_recHitsP = 0;
   short int n_recHitsM = 0;
   if( TheCSCRecHits.isValid() )
     {
       CSCRecHit2DCollection::const_iterator dRHIter;
       for (dRHIter = TheCSCRecHits->begin(); dRHIter != TheCSCRecHits->end(); dRHIter++) 
         {
           if ( !((*dRHIter).isValid()) ) continue;  // only interested in valid hits
           CSCDetId idrec = (CSCDetId)(*dRHIter).cscDetId();
           float RHTime = (*dRHIter).tpeak();
           LocalPoint rhitlocal = (*dRHIter).localPosition();
           const CSCChamber* chamber = TheCSCGeometry.chamber(idrec);
           GlobalPoint globalPosition = chamber->toGlobal(rhitlocal);
           float globZ = globalPosition.z();
           if ( RHTime < (recHit_t0 - recHit_twindow) )
             {
               if( globZ > 0 )
                 n_recHitsP++;
               else
                 n_recHitsM++;
             }
           
           /*

           float globX = globalPosition.x();
           float globY = globalPosition.y();
           float globZ = globalPosition.z();
           float TOF = (sqrt(globX*globX+ globY*globY + globZ*globZ))/29.9792458 ; //cm -> ns
           if ( (RHTime < (recHit_t0 + TOF - recHit_twindow)) || (RHTime > (recHit_t0 + TOF + recHit_twindow)) )
             {
               if( globZ > 0 ) 
                 n_recHitsP++;
               else
                 n_recHitsM++;
             }
           */
         }
     }
   else
     {
       static bool RecHitFail = false;
       if( !RecHitFail ) 
         {
           edm::LogWarning  ("InvalidInputTag") << "The requested CSCRecHit2DCollection does not appear to be in the event. The CSC RecHit "
                                                << " variables used for halo identification will not be calculated or stored";
           RecHitFail = true;
         }       
     }
   TheCSCHaloData.SetNOutOfTimeHits(n_recHitsP+n_recHitsM);
   // MLR
   // Loop through CSCSegments and count the number of "flat" segments with the same (r,phi),
   // saving the value in TheCSCHaloData.
   short int maxNSegments = 0;
   bool plus_endcap = false;
   bool minus_endcap = false;
   bool both_endcaps = false;
   float r = 0., phi = 0.;
   if (TheCSCSegments.isValid()) {
     for(CSCSegmentCollection::const_iterator iSegment = TheCSCSegments->begin();
         iSegment != TheCSCSegments->end();
         iSegment++) {

       CSCDetId iCscDetID = iSegment->cscDetId();
       bool SegmentIsGood=true;
       //avoid segments from collision muons
       if( TheMuons.isValid() )
         {
           for(reco::MuonCollection::const_iterator mu = TheMuons->begin(); mu!= TheMuons->end() && SegmentIsGood ; mu++ )
             {
               if( !mu->isTrackerMuon() && !mu->isGlobalMuon() && mu->isStandAloneMuon() ) continue;
               const std::vector<MuonChamberMatch> chambers = mu->matches();
               for(std::vector<MuonChamberMatch>::const_iterator kChamber = chambers.begin();
                   kChamber != chambers.end(); kChamber ++ )
                 {
                   if( kChamber->detector() != MuonSubdetId::CSC ) continue;
                   for( std::vector<reco::MuonSegmentMatch>::const_iterator kSegment = kChamber->segmentMatches.begin();
                        kSegment != kChamber->segmentMatches.end(); kSegment++ )
                     {
                       edm::Ref<CSCSegmentCollection> cscSegRef = kSegment->cscSegmentRef;
                       CSCDetId kCscDetID = cscSegRef->cscDetId();
                       
                       if( kCscDetID == iCscDetID ) 
                         {
                           SegmentIsGood = false;
                         }
                     }
                 }
             }
         }
       if(!SegmentIsGood) continue;

       // Get local direction vector; if direction runs parallel to beamline,
       // count this segment as beam halo candidate.
       LocalPoint iLocalPosition = iSegment->localPosition();
       LocalVector iLocalDirection = iSegment->localDirection();

       GlobalPoint iGlobalPosition = TheCSCGeometry.chamber(iCscDetID)->toGlobal(iLocalPosition);
       GlobalVector iGlobalDirection = TheCSCGeometry.chamber(iCscDetID)->toGlobal(iLocalDirection);

       float iTheta = iGlobalDirection.theta();
       if (iTheta > max_segment_theta && iTheta < TMath::Pi() - max_segment_theta) continue;
       
       float iPhi = iGlobalPosition.phi();
       float iR =  TMath::Sqrt(iGlobalPosition.x()*iGlobalPosition.x() + iGlobalPosition.y()*iGlobalPosition.y());
       short int nSegs = 0;

       // Changed to loop over all Segments (so N^2) to catch as many segments as possible.
       for (CSCSegmentCollection::const_iterator jSegment = TheCSCSegments->begin();
         jSegment != TheCSCSegments->end();
         jSegment++) {
         if (jSegment == iSegment) continue;

         LocalPoint jLocalPosition = jSegment->localPosition();
         LocalVector jLocalDirection = jSegment->localDirection();
         CSCDetId jCscDetID = jSegment->cscDetId();
         GlobalPoint jGlobalPosition = TheCSCGeometry.chamber(jCscDetID)->toGlobal(jLocalPosition);
         GlobalVector jGlobalDirection = TheCSCGeometry.chamber(jCscDetID)->toGlobal(jLocalDirection);
         float jTheta = jGlobalDirection.theta();
         float jPhi = jGlobalPosition.phi();
         float jR =  TMath::Sqrt(jGlobalPosition.x()*jGlobalPosition.x() + jGlobalPosition.y()*jGlobalPosition.y());

         if (TMath::ACos(TMath::Cos(jPhi - iPhi)) <= max_segment_phi_diff 
             && TMath::Abs(jR - iR) <= max_segment_r_diff 
             && (jTheta < max_segment_theta || jTheta > TMath::Pi() - max_segment_theta)) {
           if( TheMuons.isValid() ) {
             for(reco::MuonCollection::const_iterator mu = TheMuons->begin(); mu!= TheMuons->end() && SegmentIsGood ; mu++ ) {
               if( !mu->isTrackerMuon() && !mu->isGlobalMuon() && mu->isStandAloneMuon() ) continue;
               const std::vector<MuonChamberMatch> chambers = mu->matches();
               for(std::vector<MuonChamberMatch>::const_iterator kChamber = chambers.begin();
                   kChamber != chambers.end(); kChamber ++ ) {
                 if( kChamber->detector() != MuonSubdetId::CSC ) continue;
                 for( std::vector<reco::MuonSegmentMatch>::const_iterator kSegment = kChamber->segmentMatches.begin();
                      kSegment != kChamber->segmentMatches.end(); kSegment++ ) {
                   edm::Ref<CSCSegmentCollection> cscSegRef = kSegment->cscSegmentRef;
                   CSCDetId kCscDetID = cscSegRef->cscDetId();
                   
                   if( kCscDetID == jCscDetID ) {
                     SegmentIsGood = false;
                   }
                 }
               }
             }
           }   
           if(SegmentIsGood) {
             nSegs++;
             minus_endcap = iGlobalPosition.z() < 0 || jGlobalPosition.z() < 0;
             plus_endcap = iGlobalPosition.z() > 0 || jGlobalPosition.z() > 0;
           }
         }
       }
       // Correct the fact that the way nSegs counts will always be short by 1
       if (nSegs > 0) nSegs++;
       if (nSegs > maxNSegments) {
         // Use value of r, phi to collect halo CSCSegments for examining timing (not coded yet...)
         r = iR;
         phi = iPhi;
         maxNSegments = nSegs;
         both_endcaps = both_endcaps ? both_endcaps : minus_endcap && plus_endcap;
       }
     }
   }
   TheCSCHaloData.SetNFlatHaloSegments(maxNSegments);
   TheCSCHaloData.SetSegmentsBothEndcaps(both_endcaps);
   // End MLR

   return TheCSCHaloData;
}