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

Name Reaction Flux [cm −2 s −1 ] E ν,max [MeV ]pp p + p → d + e + + ν e 5.97 × 10 10 0.422pep p + e − + p → d + ν e 1.41 × 10 8 1.442 †hep 3 He + p → 4 He + e + + ν e 7.90 × 10 3 18.87 Be 7 Be + e − → 7 Li + ν e 5.07 × 10 9 0.861 † /0.384 †8 B 8 B → 8 Be + e + + ν e 5.94 × 10 6 16.3413 N 13 N → 13 C + e + + ν e 2.88 × 10 8 1.19915 O 15 O → 15 N + e + + ν e 2.15 × 10 8 1.732Table 2.2: Solar neutrino fluxes on Earth and energies. The fluxes are predictedby the BPS08(GS) SSM [41]. Neutrinos marked † are mono energetic, for all otherneutrinos the maximum energy is given.Solar neutrino experiments set an upper limit of 2.9% to the fraction of energy thatthe Sun produces via the CNO fusion cycle [41]. In principle, reactions includingalso heavier elements are possible. They highly depend on the temperature and theabundances of elements in the star and do not yet contribute to the energy productionin our Sun. To be able to predict the neutrino fluxes from the different processesa variety of input parameters is needed for the solar models. One key parameteris the Sun’s metallicity Z, being the fraction of heavy elements (> He) in the star.The most elaborate calculations have been developed by the late John N Bahcall [42]and are continued by Peña-Garay and Serenelli [41]. There are significant differencesbetween models assuming a high metallicity (GS) or low heavy metal abundances(AGS). High metallicity models are more consistent with helioseismological data andthe predicted neutrino fluxes from this model are presented in Tab. 2.2.For the pp chain and the CNO I cycle, the net process for fusion is always4p → 4 He + 2e + + 2ν e + 26.73MeV.About 2% of the released energy is carried off by the neutrinos. Flux and energy forneutrinos originating from the different processes are shown in Figure 2.1. Neutrinosoriginating from the pep process as well as the fusion of 7 Be and a proton are monoenergetic because the end state only contains two particles thus resembling a twobody decay. Neutrinos from the pp reaction have the highest abundance, but arewith an energy < 422keV hard to detect.2.3.2 Solar Physics – Solar Neutrinos as MessengersUnlike other particles, neutrinos are the only fusion products in the center of the Sunthat have the ability to penetrate to the surface and escape into space immediately.Studying the properties of solar neutrinos thus makes it possible to study the processesin the core of our Sun. Measuring the individual fluxes of solar neutrinos fromthe different fusion process allows to constrain the abundances of different elementsas well as temperature and pressure conditions inside the Sun.Comparing the measured solar neutrino flux to the observed photon luminosityof the Sun allows to test the fundamental idea that the Sun shines by nuclear fusion.It takes a few thousands of years for visible light produced in the Sun’s core toreach the Sun’s surface, whereas neutrinos are emitted immediately. Neutrino flux12