Relationships between objects in different subdetectors

The JULIA program provides relationships between objects reconstructed in the various detector components if they are topologically associated to each other. These relations are available in ALPHA and can be used for charged tracks, ECAL objects, HCAL objects, and composite calorimeter objects. (Below, IOBJ is any ALPHA ``track'' number referring to a charged track, cal. object, ECAL object, or HCAL object.)

KNCHGD (IOBJ)

Number of charged tracks associated to IOBJ.

KCHGD (IOBJ, N)

The Nth charged track associated to IOBJ.

For example,

            IOBJ = ... any calorimeter object ...
            DO 10 N = 1, KNCHGD (IOBJ)
            ICHGD = KCHGD (IOBJ, N)
      C ...   analysis of a charged track ICHGD associated to IOBJ ...
         10 CONTINUE

Note: If IOBJ in the example above is a charged track itself, then KNCHGD (IOBJ) is 1 and KCHGD (IOBJ,1) gives IOBJ. Similarly:

KNECAL (IOBJ)

Number of ECAL objects associated to IOBJ.

KECAL (IOBJ, N)

The Nth ECAL object associated to IOBJ.

KNHCAL (IOBJ)

Number of HCAL objects associated to IOBJ.

KHCAL (IOBJ, N)

The Nth HCAL object associated to IOBJ.

The relation from a composite calorimeter object ICOMP to each of its contributing ECAL and HCAL object is provided by the relations described above: KECAL (ICOMP,N) and KHCAL (ICOMP,N). In addition, the composite object is treated as ``mother'' of the contributing ECAL and HCAL objects, so the mother-daughter or daughter-mother relation described in 7.5 can be used for all calorimeter objects.

Note that the composite calorimeter objects in ALPHA are not identical to those in the PCRL bank. ALPHA composite calorimeter objects include at most one HCAL object, while the PCRL objects may include many HCAL objects. ALPHA starts with each HCAL object and adds the ECAL objects that are associated to it. If an ECAL object is associated to more than one HCAL object, its energy is divided equally among the HCAL objects.