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    User name R. Michaels

    Log entry time 21:36:19 on October14,2010

    Entry number 334919

    keyword=study to analyze trigger efficiency

    There is a question: why such a low proton rate on L-HRS ?

    We'll study the trigger efficiency roughly.
    This was done with thin C12 target for runs 7367 and 7368.

    The relevant triggers are

    T1 = S2m (i.e. the "or" of 16 PMTs on Left side)
    T2 = S0 (just one PMT, the "A")
    T3 = S1.and.S2 (the usual definition)

    Cosmic rates are
    T1 = 560 ... so clearly a lot of junk (can clean up with tracks ?)
    T2 = 320
    T3 = 3.5

    With 5 uA the rates are roughly
    T1 = 1 kHz
    T2 = 550 Hz
    T3 = 10 Hz

    Go to 20 uA
    T1 = 2200 Hz
    T2 = 1200 Hz
    T3 = 28 Hz
    (WRONG ! see below)

    Decide on PS factors
    ps1 = 20, ps2 = 12, ps3 = 1

    Start run 7367 for trigger efficiency study.
    I = 20 uA initially

    Start another run (7368) because I was clearing scalers
    during the previous run

    Noticed that the 1024 Hz clock is double-pulsing.
    Switched xscaler scaler.map file to normalize to channel 24
    (the 25th chan) which is the 103.7 kHz. This doubles the
    observed rates, and makes them correct.

    Started run 7368 at 20 uA
    Then at event 104K we ask for 10 uA.
    At event 138K we as for beam off (measure baseline)
    Some rates vs current
    current .... 20 uA ... 10 uA .... beam off
    T1 ........ 4600 Hz ... 3000 Hz .... 1150
    T2 ........ 2500 ...... 1600 .... 650
    T3 ........ 55 ....... 32 ..... 7

    The number of events with zero versus 1 track (50K events
    ........ n=0 .... n=1
    T1 .... 24279 ... 51
    T2 .... 19978 ... 232
    T3 .... 766 ..... 4500

    Let TN0 = num event with 0 tracks and TN1 = same for 1 track
    To get the "true" rate R of charged particles we
    correct the 20 uA rate according to a formula
    R = K * (R_20 - R_off)
    where R_off = rate with beam off
    R_20 = rate at 20 uA
    x = R_off / (R_20 + R_off)
    K = TN1 / ((1-x)*TN0 + TN1)

    ...... x ..... K ......... R
    T1 ... 0.20 ... 0.0026 ... 9 Hz
    T2 ... 0.21 ... 0.015 .... 28 Hz
    T3 ... 0.11 ... 0.87 .... 42 Hz

    The rates R are inconsistent, but I suppose T1 and T2 are
    very dirty and my crude analysis didn't clean them up well.
    Not sure what we can conclude online. Perhaps offline.