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    Log entry time 04:53:23 on February 17, 2011

    Entry number 347290

    keyword=Neutron efficiency calibration at x<1 - preliminary analysis summery

    For now, we have two types of efficiency measurements with : 1) Mixed thresholds of 30mv(veto, N1, half of N2) and 50mv(half of N2, N3-6) 2) All thresholds are at 30mv.

    The different measurements gave the following resultst: 1) Total number on neutrons: 5000 Efficiency for bars with 50mv: 10%

    2) Total number on neutrons: 10000 Efficiency for bars with 50mv: 15%

    The ratio of BG/(e,e'p)[30mv] / BG/(e,e'p)[50mv] = 1.6

    The main conclusion is that we have a ~40% difference in the efficiency and 60% difference in the BG when going from 30mv to 50mv.

    NOTE: These numbers are cut dependent. All runs are using a 6uA, pass 2, beam except for 1422 with had 12uA.

    For those who are interestead in the details of the analysis here is a short summery.

    A) The runs for setting 1 are 1398-1427 (Note 1422 is with 12uA) The runs for setting 2 are 1431-1460 (for now - we are still taking data!)

    B) The cuts we used to identefy neutrons are: abs(SK.emiss - 0.0055)<0.0035 abs(SK.Mrecoil-0.942)<0.008 abs(atan(SK.Prec_y/SK.Prec_x)*180/3.14)<15 abs(atan2(SK.Prec_x,SK.Prec_z)*180/3.14+97)<5

    For the efficiency determination we changed the angular cuts to +/-10 and +/-3 degrees instead of the normal 15 and 5.

    A copy of this log entry has been emailed to: rshneor@jlab.org , igor.korover@gmail.com , eip@tauphy.tau.ac.il , vasulk@jlab.org , kelleher@jlab.org , sgilad@mit.edu , n.muangma@gmail.com , doug@jlab.org