Double Chooz and Reactor Neutrino Oscillation

Abstract

Recently, three reactor neutrino experiments, Daya Bay, Double Chooz and RENO have directly measured the last unknown neutrino mixing angle 13, also being independently measured by MINOS and T2K accelerator based experiments. This dissertation presents results from a search for reactor e avour oscillation using the Double Chooz far detector and in combination with the other experiments results. Using the neutron capture on Gadolinium (Hydrogen) selection method, a number of 8249 (36284) candidate electron antineutrino events were observed in a data taking period of 251.27 days with 33.71 (113.1) GW-ton-year (reactor power detector mass run time) exposure using a 10.3 (32.6) m3 ducial volume detector located 1050 m far from the two reactor cores of the Chooz nuclear power plant in France. The expectation in case of 13 = 0 is 8937 (36680) events, and the decit is interpreted as evidence of electron antineutrino disappearance. A combined rate and energy dependent t, using both neutron capture on Gadolinium and Hydrogen, nds sin2 213 = 0:100 0:034. In addition, the other important oscillation parameter, eective m2 31 (= ~m2 31) is measured for the rst time, using baseline dependence of the reactor neutrino disappearance. A global t is applied to the available data and ~m2 31 = 2:95+0:42 􀀀0:61 10􀀀3 eV2, sin2 213 = 0:099+0:016 􀀀0:012 are obtained by setting both parameters free. This result is complementary to ~m2 31 to be measured by spectrum shape analysis. The measured ~m2 31 is consistent with ~m2 32 measured by disappearance in MINOS, T2K and atmospheric neutrino experiments within errors. Finally, the measured sin2 213 is independent of ~m2 32, and consistent with the reactor and accelerator results.