| Neutrino physics is the frontier of cosmology physics, astrophysics and particle physics. Neutrino oscillation is the only evidence of physics beyond the standard model in particle physics, and is a key to search for new physics. Among the six parameters of the neutrino mixing matrix, the value of θ13 is the most important for future neutrino experiments. The DayaBay reactor neutrino experiment as a high precision, low back-ground, low energy experiment, all backgrounds should be well investigated, such as the measurement of the mixing phase angle δ and the neutrino mass hierarchy. Among all the backgrounds, those caused by cosmic muon spallation are particularly important.Firstly, we study the 8He/9Li background and fast neutron background in IBD can-didates, obtain their rate and spectrum used for θ13 analysis. In the study of 8He/9Li background, we divide antineutrino detector(AD) muons into six slices according to muon’s energy deposited in AD, it is required that there should be neutrons afer a se-lected muon, the obtained time interval distribution between the fast neutron’s prompt signal to the privious AD muon is fitted to get the number of 8He/9Li in IBD candi-dates, the total error is taken to be 50%. For the small statistics, we use the theoretical 8He/9Li energy spectrum in the analysis. For the fast neutron background, it’s spec-trum induced by RPC tagged muons and OWS tagged muons is used to calculate the number in IBD candidates, take the total error as 40%.We also study the fast neutron energy spectrum induced by IWS tagged muons. Considering the time shift between different systems, we use the "first hit time" instead of "trigger time" to select events. Through the detailed study of the background, we obtain the fast neutron energy spectrum that is used for in the future study of fast neutron backgounds in IBD events.To study muon physics, we introduce the FLUKA simulation tool, the geometry of three dayabay experiment halls are setted up, the FORTRAN language is used in muon generator. To study its physics, FLUKA events are generated event by event and information of each event is saved into ROOT files for the following study of neutron yield and isotopes yield.We study the neutron yield induced by muons of three different enrgys in each experiment hall. We select neutrons after AD muons and WP muons respectively, cal-culate the neutron yield and do the efficiency and error study from FLUKA simulation data, perform the power law fitting finally.We study the isotopes induced by muons, calculate the yield of 12B, 12N and 9C in dayabay neutrino experiment. For the high muon rate and the small detector, we have tried two methods to select isotopes after AD muons:1. Divide AD muons into five slices according to the muon’s energy deposited in AD, the energy separation are 20-60-500-1500-2500-5000 MeV In this method, the muon rates in the first three slices are still high, this lead to a bad fitting.2. Divide AD muons into three slices according to the muon’s deposited energy in AD, the energy separation are 20-1500-2500-5000 MeV. For the muon reduction in the first slice, no other AD muons which energy is 20-1500 MeV in the [-100,100]ms time window of this selected AD muons is required. |
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