A proposal for TrkDigi's

February 7, 2001 -- LSR

The digis are lists of hit strips which are used to make up clusters (groups of adjacent hit strips).  Hits that are "adjacent" across tower boundaries are not combined into clusters, and hits that are adjacent across ladders are probably not combined (since the dead space between ladders is about 2 mm, which would be a very wide cluster).

This leads me to imagine a structure as follows ("list" could be "vector");:

A TkrDigi contains a list of  TkrLayers.

    A TkrLayer contains a layer Id (layer number and X/Y) and a list of TkrTowers.

        A TkrTower contains a tower Id, 2-length list of TOT's and a list of TkrLadders.

            A TkrLadder contains a ladder Id and a list of hit Idents.

                An hit Ident contains the info about a hit strip: layer, tower, controller, strip#, etc.

In principle, the ladder information is redundant, since the strip number identifies the ladder. But since it is relevant for clustering, it needs to be supplied somewhere. In this scheme, the converter would supply the ladder number based on the geometry (which makes it a bit of an algorithm, albeit completely determined).

This structure automatically encodes the rule for not continuing clusters over ladders and towers:

    Iterate over layers {
        Iterate over towers {
            Iterate over ladders {
                Sort the hits in this ladder;
                Cluster the hits;
                Add the clusters to the list of clusters for this layer;
            }
        }
    }

The towers are grouped under the layers, because this is more natural for the PatRec, the next step in the reconstruction, which, to first order, doesn't care about towers.

I'm a bit confused about whether tower and ladder Id's are real Id's (that is, uniquely determine the element), or just a number.  For example ladder 3 in layer X12 of tower 4 could be just be labeled "3," since we already know what layer and tower it's in, from the hierarchy, or it could contain the full information.