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Introduction

Following text introduces a method to define a clump using iterate methods.
the corresponding energy resolutions for positron and photon at 70Mev,
50Mev and 30Mev were calculated and presented using geant-simulate data.

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How To Define A Clump

First find out the crystal with maximum energy. Using a predefined ANGLE_RANGE
to define a cone centered at this crystal. All crystals within this cone
are considered to belong to the same clump.The new center of clump is calculated
with following formulars:
in which crystal *i* is within the cone. Then the cone will be
redefined by the ANGLE_RANGE and new center. The calculation will not stop
until the new center is the same
as the previous one.

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Energy Resolutions with Deferent ANGLE_RANGES

The Energy Resolution FWHM is a function of ANGLE_RANGE, the graphs *FWHM
vs ANGLE_RANGE* are presented with different energies of photons and
positrons respectively. We use *geant* simulation code to generate
events with or without pedestals apart. In each case, monoenergetic particles
are emitted from the center of the target uniformly in all directions. The results
of 70
Mev positrons and 70
Mev photons are presented in which red
lines denote data without pedestals while black lines denote data with
pedestals allowed for.

we also prsent the energy resolution FWHM of photons at 50 Mev, 30 Mev with pedestal and of positrons at 50 Mev, 30 Mev with pedestal.

© composed with care by:*weidong
li*