In this thesis, the question of neutrino mass hierarchy is investigated. For this purpose, possibilities of neutrino mass origin are mentioned and phenomenology of neutrino oscillations within three active neutrino framework is introduced. Using that, it is described what neutrino mass hierarchy is and why it would be good to know it. After that, an overview of approaches to this problem is provided, including outline of the JUNO experiment. The approach based on comparison of mass splitting measured in experiments with reactor antineutrinos and accelerator neutrinos is investigated in great detail. The final part of this thesis is measurement of resistive plate chamber properties, as this type of detector was considered to be used in the JUNO experiment (but eventually other type will be used instead).

The NOMAD experiment is a neutrino oscillation experiment, capable of identifying \nm, \nmb, \nel, \neb\ and \nt\ for use in oscillation analyses. A search for \mutoe\ oscillations is conducted, emphasising the development of two separate beam simulators, to provide the background, (no oscillation), \nel\ signal. Both beam descriptions include fits to the results of the SPY experiment that measured hadron production from a 450~GeV proton beam on beryllium target. An independent analysis of the raw SPY data to produce the particle yield is reported. A series of criteria are described for the selection and classification of neutrino events. These produce the data samples necessary for both tuning the beam simulation and determining the oscillation signal. The development of a GEANT and FLUKA based Monte Carlo beam simulator is presented, providing good agreement to the measured neutrino beam. This simulation method has sizeable variations depending on the beamline geometry, which is not known precisely. This causes large systematic errors. An empirical parametrisation is proposed and used for the first time in a NOMAD oscillation search. It uses the measured neutrino spectra at NOMAD, except the \nel, to infer the meson production at the target, and then predict the \nel\ spectrum. This method has good agreement with the data and is also insensitive to alterations of the beamline geometry, resulting in much smaller systematic errors. The reduction of the systematic errors allows the \mutoe\ oscillations search to be performed with much greater precision. Comparisons of the \nel/\nm\ ratio between the empirical parametrisation and data yields no evidence for \mutoe\ oscillations, setting a limit on the mixing parameter, $sin^2(2 \theta) &lt 1.9 \times 10^{-3} \mbox{(90\% CL)}$ at high $\Delta m^2$. The present sensitivity of the analysis on the mixing parameter is 0.0017.

The NOMAD experiment is a neutrino oscillation experiment, capable of identifying \nm, \nmb, \nel, \neb\ and \nt\ for use in oscillation analyses. A search for \mutoe\ oscillations is conducted, emphasising the development of two separate beam simulators, to provide the background, (no oscillation), \nel\ signal. Both beam descriptions include fits to the results of the SPY experiment that measured hadron production from a 450~GeV proton beam on beryllium target. An independent analysis of the raw SPY data to produce the particle yield is reported. A series of criteria are described for the selection and classification of neutrino events. These produce the data samples necessary for both tuning the beam simulation and determining the oscillation signal. The development of a GEANT and FLUKA based Monte Carlo beam simulator is presented, providing good agreement to the measured neutrino beam. This simulation method has sizeable variations depending on the beamline geometry, which is not known precisely. This causes large systematic errors. An empirical parametrisation is proposed and used for the first time in a NOMAD oscillation search. It uses the measured neutrino spectra at NOMAD, except the \nel, to infer the meson production at the target, and then predict the \nel\ spectrum. This method has good agreement with the data and is also insensitive to alterations of the beamline geometry, resulting in much smaller systematic errors. The reduction of the systematic errors allows the \mutoe\ oscillations search to be performed with much greater precision. Comparisons of the \nel/\nm\ ratio between the empirical parametrisation and data yields no evidence for \mutoe\ oscillations, setting a limit on the mixing parameter, $sin^2(2 \theta) &lt 1.9 \times 10^{-3} \mbox{(90\% CL)}$ at high $\Delta m^2$. The present sensitivity of the analysis on the mixing parameter is 0.0017.

The OPERA experiment is designed to perform first direct observation of $nu_{tau}$ appearance in an almost pure $nu_{mu}$ beam. The OPERA detector is a hybrid set-up which combines a lead/emulsion target with various electronic detectors. It is located in Gran Sasso Laboratory (LNGS), 730 km away from CERN where neutrino beam is produced. A good electron identification in the ECC brick would also allow OPERA to search for $nu_{mu}rightarrownu_{e}$ oscillations. We have studied electron identification in the Emulsion Cloud Chamber (ECC) brick which was exposed to CERN SPS H4 electron beam. Emulsion scanning was performed in LNGS scanning laboratory. FEDRA framework was used for the data analysis. In total, we have found 30 electron showers in the brick. The characteristics of each shower have been studied. The background base-track contamination in the shower was estimated as $20pm 4$. This is mainly due to shower overlap of electrons and passing through cosmic rays.

The OPERA experiment is designed to search for nu-tau appearance in almost pure CERN-SPS nu-mu beam. The OPERA detector is placed in the Gran Sasso underground laboratory which is 730 km away from CERN. It is a hybrid set-up which combines a lead/emulsion target with various electronic detectors. The detector is composed of two super modules(SM) which contains about 150,000 ECC bricks. Each of the brick is obtained by stacking 56 lead plates with 57 emulsion films. Behind the each brick, an emulsion film doublet, called Changeable Sheet (CS) is attached in order to confirm tracks produced in neutrino interactions. The CS requires very low background track density in order to ensure the expected performance in the experiment. The background tracks in CS can be erased by a special treatment called as refreshing. A refreshing facility was constructed in the LNGS laboratory. The METU group has participated in the construction of the facility and the production of the CS films from the beginning. The main steps of emulsion refreshing and the test results on emulsion quality after the refreshing will be discussed. A Monte Carlo simulation is performed in order to estimate background to nu-mu to nu-tau oscillation due to D0 production and decay in the ECC brick. It is found that this background is significant for the short decay path topology of the tau lepton.

OPERA stands for Oscillation Project with Emulsion t-Racking Apparatus. The main goal of the OPERA experiment is to search for tau neutrino appearance in almost pure muon neutrino beam. The detector is located at Gran Sasso, 730 km away from the neutrino source, at CERN. In this thesis, the reconstruction efficiency and purity of neutrino interactions in the OPERA target have been studied by using Monte Carlo simulation. The efficiency of primary vertex reconstruction for muon neutrino Charge Current (CC) events is estimated as 83.2 percent. The main source of inefficiency is due to Quasi-elastic like topologies in which only one track is reconstructed. The purity of primary vertex tracks is found to be 99 percent. On the other hand, the reconstruction efficiency for muon neutrino CC charm events is estimated to be 90.2 percent, while the purity of the primary tracks is 67 percent. The low purity is due the fact that the secondary vertex tracks are wrongly assigned in the primary vertex. This spoils the purity.

The OPERA experiment was designed to search for nu-mu to nu-tau oscillations through the observation of nu-tau charged-current interactions in the OPERA target. This search requires a massive detector and very high spatial accuracy. Both requirements are ful

The emulsion target of the CHORUS detector was exposed to the wide-band neutrino beam of the CERN SPS between the years 1994 and 1997. In total about 130.000 neutrino interactions were located in the nuclear emulsion target and fully reconstructed. Detailed DATA and Monte Carlo (MC) comparisons were done in order to test reliability of the detector simulation. There is reasonable agreement between DATA and MC. The ratio of deep inelastic neutral-current (NC) to the deep inelastic (DIS) charged-current(CC) $nu_{mu}$ interactions was measured to be frac{NC_{dis}}{CC_{dis}}=0.350pm0.003$. This measurement was compared with the previous measurements. Based on three double charm decays found in NC interactions we measured the ratio of double charm cross-section in NC $nu_{mu}$ interactions to be [ frac{sigma (cbar{c}nu_mu)}{sigma_{NC}}=(3.37^{+3.06}_{-2.51}(stat.)pm 0.51(syst.))times 10^{-3}. ] One double charm decay has been observed in CC $nu_{mu}$ interactions the upper limit on associated charm production in $nu_{mu}$ CC interaction has been found to be [ frac{sigma cbar{c}mu^{-})}{sigma_{CC}}&lt / 9.69 times 10^{-4}. ] at 90% C.L.