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

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counts/days*4 hitsDay (Red) and Night (Blue) spectrum21.81.61.41.210.80.60.40.2200 300 400 500 600nhitsFigure 4.8: Day and night spectra for the energy region outside the 210 Po peak. Nosignificant difference between the spectra is observed. Figure from [73].4.4.2 8 B NeutrinosSpectroscopic measurements of solar 8 B neutrinos have been done previously byKamiokande [11] and Super-Kamiokande [31] using a water Čerenkov detector andSNO [74] using deuterium as a target, all with an energy threshold of ∼ 5MeV orhigher. Recently, the SNO collaboration published an analysis with a threshold of3.5 MeV [29].Borexino is the first experiment succeeding in spectroscopic measurements ofthe 8 B neutrino flux using liquid scintillator. All major backgrounds above the2.614 MeV gamma from the decay of 208 Tl could be reduced sufficiently allowingto set the energy threshold for the 8 B neutrinos as low as 3MeV [75]. Taking intoaccount the 7 Be neutrino measurements described in the previous section, Borexinois the first experiment where neutrinos from both pp-chain reactions have beeninvestigated simultaneously. Very interestingly, the energy region of those neutrinoscovers the transition region from vacuum to matter dominated oscillations inthe LMA solution of the MSW effect described in Section 2.2.2, thus providing anexcellent method to experimentally challenge this prediction.Two different analyses were done for the 8 B neutrinos, one with a threshold of3MeV and another one with a higher threshold at 5 MeV to be able to compare theresults with earlier measurements from Super-Kamiokande and SNO. Recent resultsare based on 488 days of data taking, with a total exposure time after cuts of 345.3days in a fiducial target volume of 100 tons.8 B neutrinos were selected from data through the application of a set of cutsdescribed in [75]. An interaction rate of 0.217 ± 0.038 stat ± 0.008 syst counts per dayand 100 tons was found for an energy threshold of 3 MeV. Raising this threshold to+0.0085MeV, 0.134 ±0.022 stat counts per day and 100 tons remain. Fig. 4.9 shows−0.007systthe 8 B neutrino energy spectrum for the selected data. It is consistent with thehigh metallicity SSM BPS09(GS98) model presented in Section 2.3 in combination64
Counts / 2 MeV / 345.3 days45403530252015DataBPS09(GS98)+LMA−MSWBPS09(AGS05)+LMA−MSW10504 6 8 10 12 14Energy [MeV]Figure 4.9: 8 B neutrino spectrum measured by Borexino. The red dots show thespectrum after data selection and background subtraction. Also shown are the expectedvalues from current SSMs with high (BPS09(GS98)) and low (BPS09(AGS05))metallicity under the assumption of LMA-MSW oscillations. Figure from [75].with the prediction of LMA-MSW oscillations assuming ∆m 2 = 7.69 ×10 −5 eV 2 andtan 2 θ = 0.45 also included in the plot.The 8 B neutrino flux derived from the data is found to be (2.7±0.4 stat ±0.2 syst )×10 6 cm −2 s −1 above 5 MeV and (2.4±0.4 stat ±0.1 syst )×10 6 cm −2 s −1 above 3 MeV. Thiscompares to an expected flux predicted by the SSM of (5.88 ± 0.65) × 10 6 cm −2 s −1with no oscillation, thus confirming solar ν e disappearance. The average ν e survivalprobability ¯P ee has been calculated for both energy regions. For a mean energy of8.9 MeV a value of P ee = 0.29 ± 0.10 for 8 B neutrinos is obtained. Comparing thisresult with the survival probability of the mono energetic 0.862 MeV 7 Be neutrinospresented in the previous section allows again to test the matter enhanced oscillationmechanisms of solar neutrinos. Both probabilities are shown in Fig. 4.10 among theearlier results from SNO and the radio chemical experiments. The data confirm theMSW-LMA solution for matter enhanced oscillations of solar neutrinos. However,whereas the MSW-LMA model seems to be favored also in combination with theother solar oscillation experiments, recent analyses including also the KamLANDdata see hints for possible non standard interactions [76].4.4.3 Anti Electron Neutrinos – Geo-NeutrinosThe observation of geo-neutrinos has been first reported by KamLAND in 2005 [49].Although Borexino is smaller than the KamLAND detector it has the advantage ofa significantly lower anti neutrino background from nuclear power plants. Also, theintrinsic radioactive background is much lower and thus a successful observation ofgeo-neutrinos was reported in 2010 [50].The results are based on a 252.6 ton year fiducial exposure. Altogether 21 ¯ν ecandidate events could be identified. Anti electron neutrinos have two main sourceson Earth: they are produced at nuclear reactors and they are emitted in β − decays.65
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Setup of a Drift Tube Muon Trackera
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AbstractIn this work the setup and
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3.5.5 Pattern Recognition . . . . .
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viii
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essential for vetoing these events.
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Chapter 2NeutrinosThe standard mode
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However, it did not yet deliver an
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Table 2.1: Neutrino oscillation par
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this assumption, the Standard Solar
Page 21 and 22: Figure 2.1: Neutrino flux at Earth
Page 23 and 24: asymmetry between neutrino and anti
Page 25 and 26: Figure 2.3: Expected ¯ν e energy
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 74 and 75: eeSurvival probability for ν e, P0
Page 76 and 77: the CMT to the Borexino tracking, t
Page 78 and 79: P C P DSCINT C SCINT DySCINT BSCINT
Page 80 and 81: Figure 5.2: The CMT setup on top of
Page 82 and 83: Angular AcceptanceAngular Acceptanc
Page 84 and 85: Comparison nhits=3 vs nhits=4N [a.u
Page 86 and 87: Table 5.3: Overview of all muon run
Page 88 and 89: N/dayAll Triggers vs Time12000h_tim
Page 90 and 91: Reco Hits in Scintillatory [mm]1000
Page 92 and 93: PMTPMTScintillatorPMTPMTFigure 5.16
Page 94 and 95: the CMT data file and the Borexino
Page 96 and 97: Zenith Angle CMT and BX-GL Tracks h
Page 98 and 99: Lateral x Resolution CMT - IDhlatx_
Page 100 and 101: Distance d between CMT and BX-GL Tr
Page 102 and 103: Angular difference αN [arbitrary u
Page 104 and 105: [m]z bxTrack Position in BX x=0 Pla
Page 106 and 107: N [arbitrary units]∆y all data200
Page 108 and 109: To determine the Borexino tracking
Page 110 and 111: Table A.1: Variables that can be se
Page 112 and 113: espectively. The channel numbers ar
Page 114 and 115: xyϕϕ ′βx ′µFigure C.2: Rela
Page 116 and 117: the z-coordinate z op,0 of the firs
Page 118 and 119: xyEvent: 470, Entry: 470, Time Tue
Page 120 and 121: [14] Ch. Kraus et al. Final Results
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[49] T. Araki et al. Experimental i
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Jan Lenkeit und Björn Wonsak sowie
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