No Subject

[Alexander Somov <somov@jlab.org>]

Dear colleagues,

Following up discussion about orientation of
pair spectrometer positron counters I've prepared
a few slides:

http://www.jlab.org/~somov/pair_spec/tilt_pos_count/

count_orient.gif   orientation/position of positron counters
                   in geant. All counters are tilted by 15 deg.
                   Each counter here is 1 cm long.

----

count_mult_pos.ps  hit multiplicity (basically it's the average number
                   of counters hitted by track)
                   top plot    - counters are not rotated
                   bottom plot - counters are tilted by 15 deg

As expected, the double hit probability is much smaller for
the tilted geometry; it goes down from 32% (not rotated)
to ~3% (rotated by 15 def).

----

count_en_geant.ps  mean reconstructed energy (in geant) for
                   24 positron counters (top) and 6 electron
                   counters (bottom).

----------------------------------------------------

Note: Rotation of counters is important for relatively large
      counter length. If we make counters shorter, rotation
      becomes not an issue


Cheers,
       Sascha