Setup of a Drift Tube Muon Tracker and Calibration of Muon ...

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2.4.2 Cosmic NeutrinosThe sources of the cosmic radiation causing the atmospheric neutrinos describedin the previous section are still not fully explored. Apart from particles associatedwith solar flares, the cosmic radiation comes from outside the solar system [33]. Itreaches energies exceeding 10 20 eV, leading to the expectation of also finding ultrahigh energy neutrinos among it. Neutrinos are not affected by absorption or electromagneticforces, so they reach the Earth on a direct path from their source. Thismakes them unique and offers a great opportunity to use them as messenger particles,helping to find any point sources that could be identified as an origin of cosmicrays. Experiments like Antares [45] or IceCube [46] detect these neutrinos using theEarth as a target. Placed deep inside the water (ice), they look for the Čerenkovlight produced by high energetic muons or electrons produced in neutrino interactionwith the Earth. Ultra high energetic neutrinos are even capable of producingτs with energies high enough to propagate over a distance of the order of 100 m,before decaying and thus leaving a signature of two Čerenkov cones. Hence theseneutrino telescopes are sensitive to all neutrino flavors.2.4.3 Supernova NeutrinosThe hydrogen burning as a source of the energy released by starts as describedin Section 2.3 has a limited lifetime, depending mainly on the size of the star.During hydrogen burning, stars are in a hydrostatic equilibrium, meaning that itsgravitational forces are counterparted by its radiative pressure. Once the hydrogenis mostly burned up, the core of the star becomes more dense and the temperaturerises thus allowing fusion processes of heavier elements, again creating a hydrostaticequilibrium. This process continues for more and more heavy elements, leading toconcentric shells that are relics of the previous burning phases. However it has anend once the core contains mainly iron (Fe burning), since at this point no energycan be gained from fusion anymore.If, at this point, the core of the star exceeds the Chandrasekhar mass limitof approximately 1.4M ⊙ , the core collapses due to the gravitational pressure toa neutron star. This is the case for stars more massive than 8M ⊙ and results inan optically very bright so-called core-collapse supernova. During the collapse, theso-called neutronization or deleptonization takes place converting large amountsof protons into neutrons by electron capture, thus emitting a vast number of ν e .The collapse is stopped when the core reaches densities ρ > 3 × 10 14 g cm −3 , avalue normally found for atomic nuclei. The nuclear forces now start to becomerepulsive, the core is no further compressible and matter bounces back. ν¯ν pairs ofall flavors are produced and the core cools down by their emission. This simplifiedpicture shows that a supernova leaves a distinct signature in the neutrino spectrum:First the emission of ν e lasting a few milliseconds followed by the emission of allneutrino types for about 10 s. In these processes, neutrinos carry away 99% ofthe energy released in the supernova with typical energies of 10 MeV per neutrino.Again, the neutrinos involved can be used as messenger particles giving an earlywarning of an upcoming (visible) supernova in the electromagnetic spectrum. Mostcurrent neutrino experiments capable of detecting supernova neutrinos are thereforeconnected to the socalled SuperNova Early Warning System SNEWS. In the event16
Figure 2.3: Expected ¯ν e energy distribution for geo-neutrinos from the 238 U, 232 Thand 40 K chain. The dashed line indicated the sensitivity limit for detection via inverseβ decay. Figure from [49].of a galactic supernova at a distance of approximately 8kpc, about 100 neutrinointeraction within a few seconds would be expected in the Borexino experiment.2.4.4 Geo-NeutrinosGeo-neutrinos (¯ν e ) are produced in β decays of radionuclides inside the Earth. Theywere originally proposed bye G. Eder [47] and G. Marx [48] in the 1960s.The processes inside the Earth are to a large extent still unknown. Seismologistsare able to reconstruct the density profile of the Earth but not its composition. Andsamples taken from holes dig in the upper crust of the Earth’s outer mantle can onlytell about the geochemical properties up to depth in the order of a few kilometers.Questions about the influence of radionuclides to the terrestrial heat productionor the composition of the Earth’s core remain unanswered. The investigation ofgeo-neutrinos can give an answer to the abundance of radioactive elements insidethe Earth. The hypothesis of a natural fission reactor in the Earth’s core can beaddressed.Neutrino sources inside the Earth are radioactive nuclear isotopes with half-livesof the order of the Earth’s age or longer. These are mainly 238 U, 232 Th and 40 K. Theresulting energy spectrum from their decay chains is depicted in Fig. 2.3. The picturealso marks the sensitivity limit for the detection of geo-neutrinos via the inverseβ decay, which has a threshold energy of 1.806 MeV. This way only selected geoneutrinosfrom the 238 U and 232 Th chains can be detected. The relative abundancesof the different sources can then be identified by comparing the measurements tothe different distinct energy spectra. The existence of geo-neutrinos was first shownby KamLAND in 2005 [49] and recently confirmed by the Borexino experiment [50].Measurements in different locations can give new constraints on the thorium anduranium abundances in the Earth’s crust and mantle. The study of geo-neutrinoscan also help to understand the terrestrial heat production, that is a tiny heatflux of approximately 60 to 90 mW/m 2 emitted by the Earth. Although this is a17
Page 1 and 2: Setup of a Drift Tube Muon Trackera
Page 3: AbstractIn this work the setup and
Page 6 and 7: 3.5.5 Pattern Recognition . . . . .
Page 8 and 9: viii
Page 10 and 11: essential for vetoing these events.
Page 13 and 14: Chapter 2NeutrinosThe standard mode
Page 15 and 16: However, it did not yet deliver an
Page 17 and 18: Table 2.1: Neutrino oscillation par
Page 19 and 20: this assumption, the Standard Solar
Page 21 and 22: Figure 2.1: Neutrino flux at Earth
Page 23: asymmetry between neutrino and anti
Page 27: Nb neutrino/fission-11010-2Neutrino
Page 30 and 31: 108−dE/dx (MeV g −1 cm 2 )65432
Page 32 and 33: Figure 3.3: Setup of the muon track
Page 34 and 35: zyxModule b.0Module a.0Module b.1Mo
Page 36 and 37: Figure 3.6: Display of the slow con
Page 38 and 39: plastic scintillators. To avoid all
Page 40 and 41: N hitsHitmap Plane 06000h_hitmap0En
Page 42 and 43: Table 3.4: Data structure for calib
Page 44 and 45: TDC SpectrumN/[2 Channels]1000800H_
Page 46 and 47: Table 3.5: List of variables calcul
Page 48 and 49: with ∆⃗q = ⃗q n − ⃗q n−
Page 50 and 51: N [a.u.]∆ α (x)2200020000da0Entr
Page 52 and 53: d[mm]Reco Drift Distances201816H_RE
Page 54 and 55: N [a.u.]Real DataReal data0.06MCh1E
Page 56 and 57: χ 2N [a.u.]Probability103×10hc2p0
Page 58 and 59: N [a.u]Residuals20001800h0Entries 3
Page 60 and 61: Counts/(10 keV × day × 100 tons)1
Page 62 and 63: 4.1.3 Čerenkov LightČerenkov dete
Page 64 and 65: 4.2 The Borexino DetectorThe Borexi
Page 66 and 67: muons, is reduced by going deep und
Page 68 and 69: (typically below 50 cm), the locati
Page 70 and 71: 510Counts/(10 keV x day x 100 tons)
Page 72 and 73: counts/days*4 hitsDay (Red) and Nig
Page 74 and 75:
eeSurvival probability for ν e, P0
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the CMT to the Borexino tracking, t
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P C P DSCINT C SCINT DySCINT BSCINT
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Figure 5.2: The CMT setup on top of
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Angular AcceptanceAngular Acceptanc
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Comparison nhits=3 vs nhits=4N [a.u
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Table 5.3: Overview of all muon run
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N/dayAll Triggers vs Time12000h_tim
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Reco Hits in Scintillatory [mm]1000
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PMTPMTScintillatorPMTPMTFigure 5.16
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the CMT data file and the Borexino
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Zenith Angle CMT and BX-GL Tracks h
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Lateral x Resolution CMT - IDhlatx_
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Distance d between CMT and BX-GL Tr
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Angular difference αN [arbitrary u
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[m]z bxTrack Position in BX x=0 Pla
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N [arbitrary units]∆y all data200
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To determine the Borexino tracking
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Table A.1: Variables that can be se
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espectively. The channel numbers ar
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xyϕϕ ′βx ′µFigure C.2: Rela
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the z-coordinate z op,0 of the firs
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xyEvent: 470, Entry: 470, Time Tue
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[14] Ch. Kraus et al. Final Results
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[49] T. Araki et al. Experimental i
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116
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Jan Lenkeit und Björn Wonsak sowie
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