UC Irvine

Neutrinos exhibit a unique behavior compared to other Standard Model particles: neutrino oscillations. This phenomenon is the periodic change of probability to interact with certain lepton flavors as they propagate. Measuring the oscillation parameters accurately is crucial to exploring the unanswered questions related to neutrino physics, most notably the possibility that these particles violate the CP symmetry or that there are more than three generations of them.

The Daya Bay Reactor Neutrino Experiment is known for making the first unambiguous determination of the non-zero value of the θ13 mixing angle and producing the most precise measurements of this parameter ever since. Located in Southern China, Daya Bay utilizes eight strategically placed identically-designed detectors to measure the disappearance ofelectron antineutrinos from six nuclear reactor cores. The antineutrino interactions are identified through the double coincidence signature of the inverse beta decay. The neutron from this interaction can get captured on a nucleus of either gadolinium (nGd) or hydrogen (nH). Given that the statistical samples are entirely separate and the systematics largely decoupled, the nH and nGd measurements are virtually independent of one another. This makes the nH analysis valuable as a precise cross-check to the nGd analysis.

Daya Bay’s world-leading measurement of θ13 is the result of analyzing the former. The measurement of the latter sample is presented in this thesis, including the event selection, removal of background events, evaluation of the systematic uncertainties, and fitting procedure, ultimately leading to the best fit results of sin2 2θ13 = 0.0776 ± 0.0053 and∆m2 ee = (2.80 ± 0.14) × 10−3 eV2. This measurement is among the second most precise measurements of θ13 globally.