The Search for Theta_13: Results from Double Chooz

par Jaime Dawson (Laboratoire APC - Double Chooz)

lundi 16 avr. 2012, 14:00 → 15:00 Europe/Paris

Amphithéâtre (CPPM)

Neutrino oscillation has been clearly established via the study of solar, atmospheric, reactor and beam neutrinos. Combination of these results requires the existence of (at least) three-neutrino mixing. Great progress has been made in measuring the mixing angles (theta_12, theta_23) and the two mass squared differences. Until recently, the mixing angle theta_13 had yet to be measured. A measurement of theta_13, as well as completing the knowledge of the mixing angles, is crucial for future experiments since its size has a great bearing on the possibility to observe CP violation in the leptonic sector. The Double Chooz experiment is the first of the next wave of reactor experiments attempting to measure the mixing angle theta_13. The experiment consists of two detectors; one near, to effectively measure the neutrino spectrum and flux from the reactor, and one far, to observe any neutrino disappearance. The experiment is currently in its first phase, running with the far detector only whilst the near detector and laboratory are under construction. Preliminary results from 100 days of running were announced in November 2011, showing hints of oscillation with sin^2(2 theta_13) = 0.085 + 0.029(stat) + 0.042(syst). Combining this result with that of the accelerator experiment T2K excludes theta_13 = 0 at 3 sigma. Recently the reactor experiment Daya Bay confirmed this observation of theta_13. I will describe the Double Chooz experiment, the detector design and the status of the near detector. Data from the first phase will be presented, and the most pertinant backgrounds and sources of systematic uncertainties will be discussed. I will compare the Double Chooz results with the recent results from Daya Bay, and present the current status on our knowledge of the mixing angle theta_13.