Further progress for a fast scanning of nuclear emulsions
with Large Angle Scanning System
A.Alexandrovab, V.Tioukova, M.Vladymirovb
aINFN
sezione di Napoli, I-80125 Napoli, Italy
bLPI - Lebedev Physical Institute of the Russian Academy of Sciences, RUS-119991 Moscow, Russia
In the large-scale emulsion experiment OPERA, dedicated to direct observation of
the νµ-ντ oscillations in the appearance mode, several (about 5) candidate events are
expected. The only way to increase the statistical significance of the final result is
reduction of the physical background. Dedicated Monte-Carlo study demonstrated
that it is possible to increase detection efficiency and significantly reduce physical
background by increasing both angular acceptance of track reconstruction in
emulsion and scanned volume by including in processing not only vertex brick but
also neighboring ones to perform the full reconstruction of not only the vertex
region but all event products.
Here we report about a newly developed Large Angle Scanning System (LASSO) that
uses innovative techniques and algorithms developed in past two years in a series of
R&Ds aimed at improvements in scanning speed, angular acceptance and efficiency
of microtrack reconstruction, and overall performance of the European Scanning
System (ESS). The ESS, used for OPERA data processing since 2007, had nominal
scanning speed of 20 cm2/h and typical angular acceptance of 0.57 rad. A novel
approach for fast scanning of nuclear emulsions with continuous motion of the
microscope stage was developed and reported last year. With the LASSO’s
Continuous Motion technique, it is possible to double the scanning speed of the ESS,
bringing it to 40 cm2/hour, without any changes in the standard hardware. With the
novel microtrack reconstruction algorithm, developed for LASSO, the ESS becomes
capable of effectively reconstructing microtracks without any angular limits. To
achieve maximal performance both image processing and microtrack reconstruction
algorithms extensively use GPU processing. Apart from OPERA, LASSO is now actively
used for muon radiography data processing.