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    User name Eugene

    Log entry time 17:01:32 on February 3,2002

    Entry number 81656

    keyword=DVCS tests with RCS calorimeter


    DVCS Test

    Goal: measure the rates and backgrounds to DVCS using HRSL (for e-),
    and the RCS LG calorimeter. The proton recoil is not detected.

    Kinematics:

    E0 Q2 th_e- P_e- th_g* q E_g th_g
    5.784 1.3 -14.6 3.500 20.2 2.55 2.23 20.0

    The beam appeared for very short periods. We took about an 1h
    run at about 4:00-5:00 3 Feb. At about 12:00 the beam came back
    but VDC died and the test was terminated.

    beam run length(min) thresh magnet veto target
    1uA 2009 20 1500 off off 15cm LH
    2010 25 1500 off on
    10uA 2011 4 1500 on off
    1uA 2012 15 1500 on off VDC dead
    3uA 2013 15 1000 on off VDC dead

    The trigger rates looks as follows:

    beam threshold Tr1 Tr3 Tr5 Tr7
    1uA 1000 9.0E3 1.5E3 2 1.5E3
    1500 2.6E3
    2000 0.9E3
    2600 0.3E3
    10uA 1500 ? 1.1E4 30 1.5E4

    Preliminary results are:
    a) At 1uA the accidental coincidence make about 1/6 of the
    coincidence rate.
    b) The coincidence rate is about 20 times higher than the expected
    DVCS rate, which is about 15 per 20 min run at 1uA.
    c) No clear DVCS kinematical signature was visible in the missing
    mass spectrum or energies correlarion plot. The statistics
    was too low to hope to see anything.





    FIGURE 1

    FIGURE 2