Understanding Photons in the CLEOc Detector

David Cinabro and Mikhail Dubrovin, mentors

	Electrons are a vital tool in the study of the
charm quark.  The largest background to electrons in CLEOc
is the conversion of a photon into an electron-positron
pair in the material of the detector.  Fortunately photon
conversions leave a distinctive geometric pattern in the
detector.  The photons are produced at the interaction point,
fly away straight without leaving any track, and materialize
as an electron-positron pair traveling parallel which then
leaves tracks that curve away from each other in the magnetic
field of the tracking system.  By searching for this distinctive
pattern and identifying electrons from photon conversions
this background can be reduced and calibrated improving the
quality of CLEOc's electron sample improving the measurement
of charm decays to electrons and enabling the search for
rare charm decays to electrons.  The project involves developing
the photon conversion finding algorithm in C++, running it
on CLEOc simulated and real data, and comparing the results.