Double Chooz and perspectives for future neutrino oscillation experiments
Prof. Dr. Tobias Lachenmaier (Physikalisches Institut, Universität Tübingen)

Double Chooz is a reactor neutrino experiment designed to determine the third mixing angle theta-13 in the neutrino mixing matrix. The flux of antineutrinos emitted by the two reactor cores of the Chooz nuclear power plant in France is measured at a distance of 1050 m, and compared to the calculated flux in the first phase of the experiment. After a first indication for disappearance of reactor electron antineutrinos in 2011, the collaboration published the result of 227.93 live days of data taking with one detector in 2012. The Double Chooz experiment has observed a deficit of electron antineutrinos, with 8,249 events observed compared the expectation of 8,937 events in the case of a vanishing third mixing angle. The deficit can be interpreted as evidence of a non-zero value for theta-13, and from a rate plus spectral shape analysis, a value of (102)° is found. This is in agreement with the results of other reactor neutrino experiments also published in 2012. A second phase with an additional identical detector, but closer to the reactor cores is under preparation. The large value of the third leptonic mixing angle leads to interesting options for future long baseline neutrino beam experiments searching for CP violation in the leptonic sector and for the determination of the neutrino mass hierarchy. In addition, while recent experiments have well established the standard picture of neutrino oscillations with three generations, still some anomalies persist. They could be explained by adding a sterile neutrino. Future experiments should be able to give a definite answer if the observed anomalies are linked to sterile neutrino states.