bst_strip.cc

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// %%%%%%%%%%%%%
// gemc headers
// %%%%%%%%%%%%%
#include "bst_strip.h"

#include <iostream>
#include <cmath>
#include <cstdlib>

void bst_strip::fill_infos()
{
    
    intersensors = (0.11 + 0.002)*mm;  // gap between sensors + microgap
    alpha        = 3.0*deg;            // max angle of the strips
    pitch        = 0.156*mm;           // pitch of the strips
    
    // number of cards by sector for each layer
    NSensors.push_back(3);   NSensors.push_back(3);
    NSensors.push_back(3);   NSensors.push_back(3);
    NSensors.push_back(3);   NSensors.push_back(3);
    NSensors.push_back(3);   NSensors.push_back(3);
    
    DZ_inLength  = 0.984*mm;   // size of the band of dead zones all around in the length of the card
    DZ_inWidth   = 0.835*mm;   // size of the band of dead zones all around in the width of the card
    SensorLength = 111.625*mm; // length of 1 Sensor
    SensorWidth  = 42.02*mm;  // width 1 Sensor
    
    // Number of strips
    Nstrips  = (int) floor((SensorWidth-2.0*DZ_inLength)/pitch) - 1;
    
}


vector<double> bst_strip::FindStrip(int layer, int sector, int isens, G4ThreeVector Lxyz)
{
    
    // the return vector is always in pairs.
    // The first number is the ID,
    // the second number is the sharing percentage
    // layer and sector are the indexes (i.e. layer is the actual layern-1)
    vector<double> strip_id;
    
    int StripHit = -1;
    double minDist = 999;  // distance between actual x and x of the k-strip at the actual z
    double dalpha = alpha/((float)Nstrips);
    
    // local x position in the sensor: need to add 1/2 active area
    double lx = Lxyz.x() + SensorWidth/2.0 - DZ_inLength;
    
    // local z position in the module: need to add 1/2 active area + 1(2) full sensor lengths if on sensor 2(3)
    double lz = Lxyz.z() + SensorLength/2.0 - DZ_inWidth + (isens-1)*(SensorLength + intersensors) ;
    
    // particle must be in the z active area of the sensor
    if( fabs(Lxyz.z()) < (SensorLength/2.0 - DZ_inWidth))
    {
        
        
        // looping over all strips to find the closest
        // to the point
        for(int k=0; k<Nstrips; k++)
        {
            // angle of the k-strip
            double alpha_k = k*dalpha;
            
            // strip equation is z = mz + intcp
            double intcp = 0;
            double     m = 0;
            
            if(layer%2 == 0)
            {
                // intercept: for layer A it starts from the top of the active area of the sensor in sector 1
                // which is at positive local x
                intcp = SensorWidth - 2*DZ_inLength - (k+1)*pitch ;
                m     = -tan(alpha_k/rad);
            }
            
            if(layer%2 == 1)
            {
                // intercept: for layer B it starts from the bottom of the active area of the sensor in sector 1
                // which is at negative local x
                intcp = (k+1)*pitch ;
                m     = tan(alpha_k/rad);
            }
            
            // x position of the strip according to the active local z position
            double stripx = intcp + m*lz;
            
            if(fabs(lx - stripx) < minDist)
            {
                minDist = fabs(lx - stripx);
                StripHit = k+1;
            }
            
        }
    }
    
    if(StripHit != -1)
    {
        // correcting for z positioning inside the module
        double dpitch = pitch + lz*tan(dalpha/rad);
        
        // one strip only, all energy to it
        if(fabs(minDist)<=dpitch/4.0)
        {
            strip_id.push_back(StripHit);
            strip_id.push_back(1);
        }
        // two hits, on the right of the strip
        // 10% loss due to capacitance between strip and backplane
        if(minDist>dpitch/4.0)
        {
            strip_id.push_back(StripHit);
            strip_id.push_back(0.45);
            strip_id.push_back(StripHit+1);
            strip_id.push_back(0.45);
        }
        // two hits, on the left of the strip
        // 10% loss due to capacitance between strip and backplane
        if(minDist<-dpitch/4.0)
        {
            strip_id.push_back(StripHit);
            strip_id.push_back(0.45);
            strip_id.push_back(StripHit-1);
            strip_id.push_back(0.45);
        }
    }
    else
    {
        strip_id.push_back(-1);
        strip_id.push_back(1);
    }
    return strip_id;
    
    
}