A Classic Thesis Style - Johannes Gutenberg-Universität Mainz

48 experimental setup and data acquisition
Once all the data for a trigger event has been digitalized, a home
made dedicated software called Aqua++ running on Linux based VME
front-end computers (located in the spectrometer platform), loads it
on Aqua-defined structures. Kaos front-end CPUs are called spekk
and spekkt and read the data of the MWPCs and scintillator walls
respectively. The structured data from the different detectors is sent
via a TCP/IP protocol through the ethernet to the online1 machine
in the control room. The data goes trough a joining process first, and
then is dispatched to the event-builder, where it is merged according
to the information from modules that label the events of each detector,
indicating event number and type. Run files with the information of
positive and negative arm detectors are finally generated. This files
are analyzed with another component of the A1 software package
(COLA++) for event reconstruction. The final goal of this analysis is the
determination of the detected particles four momenta at the target. For
this purpose corrections based on energy loss on known structures and
detectors are applied and track reconstruction is performed according
to wire chambers information.
2.9 kinematical setting
For the kaon electroproduction runs, the maximum achievable energy
was used. 1507 MeV electrons accelerated through the four stages
explained in section 2.2 collided with a liquid-hydrogen target. Co-
Table 4: Laboratory kinematics of the kaon electroproduction campaigns of
2008 and 2009. Most of the data was taken at setting II with Λ and
Σ 0 hyperons within the spectrometer acceptance.
Setting Q 2 W ɛ qe ′ θe ′ pK θK
−− (GeV/c) 2 GeV (trans.) GeV/c deg GeV/c deg
I 0.050 1.67 0.54 0.455 15.8 Λ: 0.466 -31.5
II 0.036 1.75 0.39 0.318 15.5 Λ: 0.642 -31.5
Σ 0 : 0.466
incidence data was taken at two different settings with kaons in a
large in-plane angular range, θK =21-43 deg, and in the momentum
range of 400-700MeV/c. Scattered electrons were detected at a central
spectrometer B angle of 15 ◦ .
Most of the data was taken in a configuration with both Λ and
Σ 0 within the spectrometer acceptance. This setting with a central
momentum in Kaos of 530 MeV/c and a central momentum in spectrometer
B of 327 MeV/c was used during part of the 2008 beam
time and continued by a longer data-taking campaign in 2009. The
mean four-momentum transfer squared in this setting was Q 2 = 0.036