MINUTES of the Two Photon Working Group

Minutes of the Two Photon Meeting
Wednesday 23, June 1999



 Agenda
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(1) Discussion on trigger with        Guillaume Leibenguth, Alois Putzer
(2) Status of current analyses        all
               a) Jets                Paul Hodgson 
               b) Double Tag          Gerrit Prange
(3) A.O.B.

 Minutes
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(1) Guillaume Leibenguth reported about ideas to further harden one of 
    the triggers, which is based on ITC(TPC) information and ECAL energy 
    deposit (DBL_C_E2). This request comes from Olivier Callot, who 
    verified that a large number of events triggered exclusively by this 
    trigger are due to background and that most of those events are 
    rejected by level 2 and level 3. 
    Since this modification may lead to losses in physics potential for 
    the 2-photon group (events with more than ~8-10 ECAL modules fired 
    and only this trigger condition fulfilled) the 2-photon group is 
    asked to study the potential effect of this modification.
    The trigger group will provide some piece of code (based on the con-
    tent of the bank X1RG) which allows to study each event individually.
    The information provided will be
       * event triggered exclusively by the trigger Yes/No
       * number of ECAL modules fired
       * LVL3 decision Yes/No

    => * Everybody should check, whether his analysis is affected.
       * Exclusively with DBL_C_E2 triggered events could be selected 
         and studied.
       * Care should be taken for topics presently no more OR not 
         yet under study.

(2a)Paul Hodgson gave a status report on his jet analysis. He made 
    good progress, e.g. using a new jet-algorithm. Jet-multiplicities 
    (up to five jets, ycut=0.02) were shown. The acceptance is a 
    linear function (allmost constant) as function of pt; unfolding 
    is not needed. More will come soon: next 2-photon meeting.

(2b)Armin Boehrer showed the first steps of the double-tag analysis of 
    Gerrit Prange. He uses LCAL, SiCAL and BCAL. For LCAL and SiCAL 
    it looks promissing; for BCAL problems arise from large background 
    due to off-momentum electrons.

(3) The 2-photon group Web-pages are being updated (analysis topics, 
    minutes/agenda-page, and the mailing list (new)) and should be kept 
    updated...

 !!! Please check the copies of transparencies in Bld.2  as well !!!
                                                                    Armin