track finding : fgmakesftrk

In the Sci-Fi detector, track finding means the finding of the good combination of X and Y fragments.

The procedure is as follows :

Case 1 : ${\mathbf FLAG \; of \; {\it Track} : fgflagtrksci = 0}$

For all the combinations of X and Y fragments, compare the most upstream and the most downstream position of X and Y fragments. If both sides matches within one scifi layer, these two fragments make one 3D track.

Example of tracks :

                                        1 1 1 1 1
        Scifi layer : 1 2 3 4 5 6 7 8 9 0 1 2 3 4 : : : : :
        X fragment  :   o o o o o o o o o 
        Y fragment  :     o o o o o o o 

or      X fragment  :  	o o o o o o o o o o o
        Y fragment  :     o o o o o o o o o o o

Case 2 : ${\mathbf FLAG \; of \; {\it Track} : fgflagtrksci = 0}$

For all the combinations of X and Y fragments, Compare the most upstream and the most downstream position of X and Y fragments. If one side matches within one scifi layer and the other side matches within two scifi layers, these two fragments make one 3D track.

Example of tracks :

                                        1 1 1 1 1
        Scifi layer : 1 2 3 4 5 6 7 8 9 0 1 2 3 4 : : : : :
        X fragment  :  	    o o o o o o o o 
        Y fragment  :     o o o o o o o o o o o

or      X fragment  :  	o o o o o o o o o o o
        Y fragment  :       o o o o o o o o o o

Case 3 : ${\mathbf FLAG \; of \; {\it Track} : fgflagtrksci = 3}$

For X(or Y) fragments which are not used in the above procedures(Case 1 or 2), if there is any Y(or X) fragment whose end point matches within two scifi layers, and if the fragment escapes to the scifi boundary or dead area, then after check the possibility that the track can pass the light guide part, make one 3D track.

Example of tracks :

                                        1 1 1 1 1
        Scifi layer : 1 2 3 4 5 6 7 8 9 0 1 2 3 4 .....

                      |~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~|
        X fragment  : |       o o o o o o o o o o o      |   Top View
                      |                                  |   (Z-X plane)
                      |__________________________________|

                      |~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~|
        Y fragment  : |         o                        |   Side View
                      |           o                      |   (Z-Y plane)
                      |_____________o____________________|

                           Light guide for X plane is
                           located this side!!!

   In this case, the most upstream hits matches in 1 scifi layer each other
   and the Y fragment escapes from the SCIFI volume to the Light guide side
   of X plane. So, there is some possibility that the hits in the later part
   (from 9th layer) of X fragment are made from the light guide.
   So, this case, these two fragments make one 3D track.

Case 4 : ${\mathbf FLAG \; of \; {\it Track} : fgflagtrksci = 1}$

For all X and Y fragments which are not used in the above procedures(Case 1-3), if the overlap length of any combination of fragments exceeds 0.5 of the track length, these two fragments make one 3D track.

Example of tracks :

                                        1 1 1 1 1
        Scifi layer : 1 2 3 4 5 6 7 8 9 0 1 2 3 4 : : : : :
        X fragment  :  	    o o o o o o o o 
        Y fragment  :     o o o o o o 

        overlap length = 5 layers
        track length   = 9 layers  ==> 5 > 0.5*9
        So, this case, one 3D track are made.

or      X fragment  :  	o o o o o o
        Y fragment  :       o o o o o o o o

        overlap length = 4 layers
        track   length = 10 layers ==> 4 < 0.5*10
        So, this case, 3D track will not be made.

Case 5 : ${\mathbf FLAG \; of \; {\it Track} : fgflagtrksci = 2}$

For all the X(or Y) fragments which are not used in Case 1 and 2, find the pair Y(or X) fragment which has maximum number of overlapping layers among the fragments not used in Case 1,2,3,4. If the overlap length of this pair exceeds 0.5 of track length and if the number of overlapping layers exceeds 1/3 of number of hits in one fragment, these pair makes one 3D track.

Example of tracks :

                                        1 1 1 1 1
        Scifi layer : 1 2 3 4 5 6 7 8 9 0 1 2 3 4 .....
        X fragment  :  	    o o o o o o o o     (not used in Case 1 and 2)
       Y1 fragment  :     o o x o o o           (not used in Case 1-4)
       Y2 fragment  :   o o o x o x o           (not used in Case 1-4)
	
       # of overlapping layer of X and Y1 = 4 layers
       # of overlapping layer of X and Y2 = 3 layers
       ===> Y1 is selected.
       For Y1 fragment,
         # of overlapping layer of Y1 = 4 layers
         Number of hits = max(nhit of X and Y) = 8 hits ==>  4 > 1/3*8 (OK)
         overlap length = 5 layers(from layer 4 to layer 8)
         track length   = 9 layers(from layer 2 to layer 11) ==> 5 > 0.5*9 (OK)
       So, this case, X and Y1 make 3D track.