A Classic Thesis Style - Johannes Gutenberg-Universität Mainz

D E T E C T I O N E F F I C I E N C I E S A N D D ATA A N A LY S I S
3.1 overview
In short, his wits being quite gone, he hit
upon the strangest notion that ever madman
in this world hit upon, and that was that he
fancied it was right and requisite, as well for
the support of his own honour as for the
service of his country, that he should make a
knight-errant of himself, roaming the world
over in full armour and on horseback in quest
of adventures, and putting in practice himself
all that he had read of as being the usual
practices of knights-errant.
— Don Quijote de la Mancha
Miguel de Cervantes
A major task during the setting up and characterization of Kaos
spectrometer was the determination of detection efficiencies for the
multiwire proportional chambers and scintillator walls. As such, small
detection inefficiencies are not problematic as long as they are well
under control. For that purpose studies concerning tracking efficiency
were particularly important since a large electromagnetic background
was expected at the detectors location [63]; making the determination
of kaon tracks difficult, as many spurious signals of similar amplitude
were present in the chambers at any time. Generally speaking, tracks
of heavily ionizing particles in low noise environments had a larger
probability of being properly reconstructed, and tracking efficiency
deteriorated with increasing beam currents.
This chapter begins by presenting the particular signal phenomenology
characteristic of this type of MWPCs and the method developed
to handle the multiple irregular clusters typically encountered during
the spectrometer operation. Track determination was based on a maximum
likelihood method where different quality factors were assigned
to each candidate track considering known correlations between signals
in both chambers and TOF walls. The efficiency of this method
measured with a dedicated set of scintillator counters is discussed in
the following sections. A clear improvement was achieved by including
the vertical coordinate in the TOF paddles calculated by means of
top-bottom time differences. We analyze the implementation of this
additional quality factor and its impact on the tracking performance.
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