L3Dch and L3Emc (May 1997)

  The Packages L3Dch and L3Emc are intended for the development
of algorithms for doing the event rejection in the level 3 trigger.

  The Main developers of this are:

    L3Dch : Anders Ryd       ryd@cithe502.cithep.caltech.edu
    L3Emc : Songhoon Yang    songhoon@cithe502.cithep.caltech.edu

  This BaBar CVS software is not released for regular builds.

 Brief status:

  L3Dch 
    The approach here is to use the segments found in the L1 trigger
    and perform a fast pattern recognition in 3-D to obtain the impact
    parameters in both r-phi and z. Events that has tracks originating 
    from the IP are accepted. This is efficient at rejecting production
    of tracks in the magnets and masking near the IP. However, the 
    algorithm has to be highly efficient on signal, so it is important
    that it is efficient at finding tracks in the signal events. Currently
    the focus is on how to achieve a high efficiency in a fast algorithm.
    With a requirement of handling 2 kHz input the algorithms running in
    L3 have to be fast. 
    An initial implementation suggested that the approach of using the
    L1 segments is feasible; rejection of background and efficiency for
    signal events were close to what was required while the algorithm
    was fast enough to useful in L3.


  L3Emc
    The idea is similar to what is used in L3Dch, tower energies from 
    L1 are used to try to separate signal events from backgrounds. This
    project is just started and we anticipate results over the next few 
    months.