MiniballGeometry.cc

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#include "MiniballGeometry.hh"
 
ClassImp(MiniballGeometry)
 
void MiniballGeometry::SetupCluster( double user_theta, double user_phi, double user_alpha, double user_r, double user_z ) {
 
    // Set the user value
    theta = user_theta * TMath::DegToRad();
    phi = user_phi * TMath::DegToRad();
    alpha = user_alpha * TMath::DegToRad();
    r = user_r;
    z = user_z;
    
    // Resize arrays
    seg_offset.resize( ncry );
    for( unsigned int i = 0; i < ncry; ++i )
        seg_offset[i].resize( nseg );
 
    // Set individual values
    SetupCluster();
 
    return;
 
}
 
 
void MiniballGeometry::SetupCluster() {
 
    // Some constants
    double root32 = TMath::Sqrt(3.0) / 2.0;
 
    // Parameters determined by Hannah Kleis for new cryostats
    double interaction_depth = 18.0;                
    double inter_crystal_gap = 1.0;                 
    double dist_cap_crystal = 0.55;                 
    double cap_thickness = 0.70;                    
    double alpha_taper = 4.125 * TMath::DegToRad(); 
    double dist_flat_to_flat = 61.35;               
    double dist_core_corner = dist_flat_to_flat / TMath::Sqrt(3.0); 
    double R = 0.5 * dist_core_corner - dist_cap_crystal - cap_thickness;
    double focal_length = ( dist_core_corner + inter_crystal_gap * 0.5 );
    focal_length /= TMath::Tan( alpha_taper );      
 
    // Old parameters to which the online angles were optimised
    if( type == 0 ) {
        
        interaction_depth = 0.0;
        dist_core_corner = 34.0;
        focal_length = 400.0;
        R = dist_core_corner * 0.5;
        alpha_taper = TMath::ATan( dist_core_corner / focal_length );
        
    }
    
    // These values assume we are going to rotate the crystals to make a cluster
    // The real life clock positions will be 4 hours earlier after rotation
    // Therefore we need to start 4 hours later, then we rotate to the right position
    // Z is beam direction
    // Y is out to the right (horizontal)
    // X is directly upwards (vertical)
    // Offset from centre of a detector to centre of a segment
    for( unsigned char i = 0; i < ncry; i++ ) {
 
        seg_offset[i][0].SetXYZ(  0.0  ,  0.0,        0.0 ); // core in centre
        seg_offset[i][1].SetXYZ(  R / 2, -R * root32, 0.0 ); // 10 o'clock
        seg_offset[i][2].SetXYZ( -R / 2, -R * root32, 0.0 ); // 8 o'clock
        seg_offset[i][3].SetXYZ(  R    ,  0.0,        0.0 ); // 12 o'clock
        seg_offset[i][4].SetXYZ(  R / 2,  R * root32, 0.0 ); // 2 o'clock
        seg_offset[i][5].SetXYZ( -R    ,  0.0,        0.0 ); // 6 o'clock
        seg_offset[i][6].SetXYZ( -R / 2,  R * root32, 0.0 ); // 4 o'clock
    
    }
    
    // Nominal distance for the Miniball clusters is at some larger distance
    // So we push the crystal out there, shift it out a bit
    // then rotate it around.
    for( unsigned char i = 0; i < ncry; i++ ) {
        
        for( unsigned char j = 0; j < nseg; j++ ) {
        
            // out to nominal distance in beam direction
            seg_offset[i][j].SetZ( focal_length );
 
            // Rotate out to focal point of crystal (goes up in MB frame)
            seg_offset[i][j].RotateY( alpha_taper );
 
            // rotate around the appropriate angle for each crystal
            seg_offset[i][j].RotateZ( -TMath::TwoPi() * i / 3.0 );
            
            // Now bring it all back to the correct distance and shift to the interaction depth
            seg_offset[i][j].SetZ( seg_offset[i][j].Z() - focal_length + interaction_depth + r );
 
        }
    
    }
 
    //std::cout << "X = " << seg_offset[0][0].X() << ", ";
    //std::cout << "Y = " << seg_offset[0][0].Y() << ", ";
    //std::cout << "Z = " << seg_offset[0][0].Z() << std::endl;
    
    // Offsets - We start now with the crystal in beam direction (X)
    double myalpha, myphi, mytheta;
    
    if( phi > TMath::Pi() || phi < 0 ) {
        myalpha = alpha;
        myphi = TMath::PiOver2() + phi;
        mytheta = theta;
    }
    else {
        myalpha = alpha;
        myphi = TMath::PiOver2() - phi;
        mytheta = -theta;
    }
 
    // Rotate segments to appropriate angle
    for( unsigned char i = 0; i < ncry; i++ ) {
        for( unsigned char j = 0; j < nseg; j++ ) {
            seg_offset[i][j].RotateZ( -myalpha ); // anti-clockwise to agree with old convention
            seg_offset[i][j].RotateY( myphi );
            seg_offset[i][j].RotateX( mytheta );
        }
    }
  
    // Shift Miniball so that target it as origin
    mbzoffset.SetXYZ( 0.0, 0.0, -z );
    for( unsigned char i = 0; i < ncry; i++ ) {
        for( unsigned char j = 0; j < nseg; j++ ) {
             seg_offset[i][j] += mbzoffset;
         }
     }
 
    return;
    
}