[SBS_sim] Abstract for APS April Meeting 2013

[Vahe Mamyan]

Dear all,

Below is an abstract for APS April Meeting.
Comments are welcome.

Thank you,
Vahe


  Simulation of a hadron calorimeter for Jefferson Lab Hall-A Super Bigbite
Spectrometer

A “shashlik” hadron calorimeter is being designed for the new Super Bigbite
Spectrometer in
Jefferson Lab Hall-A. The calorimeter will be used in coincidence-nucleon
form-factor experiments
after Jefferson Lab's 12 GeV upgrade. It is being optimized to detect
hadrons in a momentum range of
2-10 GeV/c and provide high hadron-detection efficiency with excellent time
and spatial resolution.
Ongoing work is focused on optimizing time response by exploring
unconventional scintillator and
wavelength shifter (WLS) materials.
 A Geant4 simulation has been developed to optimize energy, position and
time-resolution and hadron
detection efficiency of the calorimeter. Significant efforts were made to
implement the simulation as
realistically as possible. Optical properties, decay times and light yield
of the scintillator and the
wavelength shifter were included in the simulation. Optical photons were
tracked inside the WLS-lightguides
taking into account surface properties of the light guide. Quantum
efficiency of the PMT was
also included. In order to correctly simulate the response of the PMT,
actual single photo-electron
(SPE) waveforms were measured and used to form the cumulative response of
the PMT. The simulated
signal is a sum of all waveforms with corresponding arrival times. The
response of the PMT is saved in
a ROOT file and analyzed to extract detector-response time resolution.
Simulation has been validated by measuring detector-response time
resolution for cosmic ray muons in
hadron calorimeter blocks of a similar design used in the COMPASS
experiment. It was found that the
simulation was able to predict response time resolution for the cosmic ray
muons with 5% precision.
Another test with ELJEN 232 scintillator and ELJEN 299-27 WLS combination
was conducted to
study their suitability for use in the hadron calorimeter as well as to
validate the simulation. The results
of that test indicate that this combination is suitable for the hadron
calorimeter and the simulation is
able to predict time resolution with better than 5% precision.
 In conclusion, simulation predicts ~1.5 ns FWHM time resolution, 5-3 cm
spatial resolution and more
than 90% hadron detection efficiency.
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