A Classic Thesis Style - Johannes Gutenberg-Universität Mainz

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20 introduction 1.6 previous experiments Kaon electroproduction experiments started in the early 70s, when the scaling behavior of deep inelastic electron scattering was well documented but almost no data was available for exclusive channels. The experimental activity was concentrated in Cambridge Electron Accelerator (CEA), the Wilson Synchrotron Laboratory (Harvard-Cornell) and the Deutsches Elektronen-Synchrotron (DESY), being mainly focused on the differences in the production dynamics between Λ and Σ 0 [38, 39, 40, 41]. The experimental arrangements consisted on dualarm spectrometers (as in the case of the measurement presented in this thesis. See chapter 2) with limited kinematic coverage across the center-of-momentum angles. Interestingly, these experiments were designed to collect data at very forward angles (note half-quadrupoles completed with mirror iron plates in Fig. 8). As we shall see in the next sections, this region is of crucial importance since theoretical models widely disagree there. Unfortunately, the data quality was in general poor and this issue remains as one of the most important open ploblems in the field [37]. Despite their limited angular coverage, [nb/sr] cm K /dΩ v dσ 700 600 500 400 300 200 100 Λ 0 Σ W= 2.15 GeV, θcm= 0 deg 0 0 0.5 1 1.5 2 2.5 3 3.5 2 Q 4 (GeV Figure 7: Q 2 dependence of the K + Λ and K + Σ 0 electroproduction crosssection at center of mass energy W=2.15 GeV. Data is from Cambridge Electron Accelerator (CEA), the Wilson Synchrotron Laboratory (Harvard-Cornell) and the Deutsches Elektronen-Synchrotron (DESY), and has been scaled in the hadronic energy W to 2.16 GeV and in the polar kaon center of mass angle to zero when necessary. Dipole fits to the data are also shown by dashed lines. clear differences between Λ and Σ 0 production mechanisms could be observed. Fig. 7 shows the collected data scaled to zero degrees in kaon polar angle and to W = 2.15 GeV as in [39, 42]. It can be seen that 2 )
1.6 previous experiments 21 Σ 0 cross-section falls much faster than Λ with Q 2 . A rough Rosenbluth separation performed by Bebek et al. [39] allowed to conclude that only the transversal component of the cross-section (σT ) contributed for Σ 0 , but both transversal and longitudinal (σL) were relevant for Λ production. Figure 8: Spectrometer tandem at DESY showing standard arrangement of kaon electroproduction experiments during the 70s. The electron beam hits a 10 cm long hydrogen target. Similar spectrometers detect the scattered electron and produced kaon in coincidence. Trajectories through the dipole are reconstructed with the help of four multiwire proportional chambers for momentum determination and tracked back to the target for angular reconstruction. PID was based on time of flight and Cherenkov signals. The new era of kaon electro and photo-production experiments started in the 90s. High duty electron accelerators allowed drastic reduction in statistical errors what allowed an identification of resonance structures especially in the Λ channel [43]. From 1993 up to 1998, SAPHIR collaboration in Bonn delivered several high quality data sets for kaon photoproduction with energies up to 2.6 GeV [44, 45, 46, 47, 48]. The data analyzed in [45] showed for the first time a resonance structure at W ≈ 1900 MeV. It was claimed [49] that this structure could be explained by D13(1895 MeV), one of the missing resonances (see Fig. 9) predicted by quark models. LEPS at SPRING8 in Japan and GRAAL at the European Synchrotron Radiation Facility in France have also contributed to a rich set of photoproduction data in several isospin channels, including single and double polarization observables [50, 51, 52, 53]. The most ambitious experimental program covering both photo and eletro-production is being carried out at Jefferson Laboratory (Thomas Jefferson National Accelerator Facility) since 1996. Man power and experimental facilities are sufficient to
Page 1: M E A S U R E M E N T O F T H E U N
Page 5: A B S T R A C T The new stage of th
Page 9 and 10: C O N T E N T S i kaon electroprodu
Page 11: Part I K A O N E L E C T R O P R O
Page 14 and 15: 4 introduction Lorentz invariance.
Page 16 and 17: 6 introduction appear in the K + Λ
Page 18 and 19: 8 introduction there was almost no
Page 20 and 21: 10 introduction This allows us to w
Page 22 and 23: 12 introduction K ¡p γ ∗ Λ(Σ
Page 24 and 25: 14 introduction means of the isobar
Page 26 and 27: 16 introduction amount of resonance
Page 28 and 29: 18 introduction photo and electropr
Page 32 and 33: 22 introduction Figure 9: Total cro
Page 35 and 36: E X P E R I M E N TA L S E T U P A
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70 detection efficiencies and data
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C O N C L U S I O N S The effort to
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cm [nb/sr] dσ v / dΩ K 1500 1000
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cm [nb/sr] dσ / dΩ K 500 400 300
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Part II F E A S I B I L I T Y S T U
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90 conclusions Figure 55: Emission
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92 prototyping and efficiency measu
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100 prototyping and efficiency meas
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102 prototyping and efficiency meas
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104 noise and radiation damage Figu
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106 noise and radiation damage Prob
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110 noise and radiation damage Figu
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112 noise and radiation damage Puls
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114 noise and radiation damage Tabl
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118 conclusions been tested and fou
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120 theoretical background photopro
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122 theoretical background effect o
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124 theoretical background A physic
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126 theoretical background taken in
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128 theoretical background for the
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130 theoretical background a.8 φ d
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132 theoretical background where σ
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134 theoretical background by showi
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136 theoretical background With thi
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138 bibliography [16] J. C. David,
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140 bibliography [44] M. Bockhorst
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142 bibliography [71] P. Achenbach
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144 bibliography [98] S. Nozawa and
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146 bibliography Figure 24 Spek B d
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Figure 73 Annealing at 80° of the
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A Classic Thesis Style - Johannes Gutenberg-Universität Mainz

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