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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