A Classic Thesis Style - Johannes Gutenberg-Universität Mainz

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3.4 collected data and runs selection 65
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Figure 39: Trajectories simulated by Geant, only limited by the geometrical
acceptance of the magnet window, are tracked till the planes
defined by F and G. Horizontal lines show actual wall sizes (F
in black and G in blue). It is clear that large inefficiencies results
from the limited vertical dimensions of the Walls.
been employed in a first hypernuclear experiment, where only Kaon
tagging at low momentum resolution was needed.
3.4 collected data and runs selection
Kaos experimental program started with two kaon electroproduction
campaigns in the years 2008 and 2009. The detailed knowledge of
the spectrometer performance and operation acquired during several
previous characterization beam times allowed an almost failure free
data taking. Altought most of the runs were taken at 2 µA, data was
also taken at 4 µA and 1 µA 5 . Kinematics was chosen so that Λ an Σ 0
reaction channels falled within the acceptance (this excludes the first
half of the 2008 data where only Λ production was studied).
The data collected in 2008 corresponds to effectively 6 days of beam
time with a total integrated luminosity of 284 fbarn −1 . The main
kaon electroproduction campaign carried out in 2009 accumulated 244
hours of beam time at 2 µA (14 % dead time), and 38 hours at 4 µA
(45 % dead time). This resulted in a total luminosity-after correctionsof
aproximately 2300 fbarn − 1.
A slightly reduced set of physical runs was obtained after several
diagnostic tests to exclude possible undetected problems during data
taking. Coincidence rate, kaon production rate, luminosity, beam
current and data acquisition system dead time where monitored for
this purpose (see Fig. 41).
5 Tracking efficiency was well under control at these other currents, as it was explained
above.