Speaker
Summary
Double Chooz (DC) is a reactor neutrino experiment running at Chooz nuclear power plant in
France. In 2011, DC first reported indication of non-zero ?13 in reactor neutrino oscillation by
a single detector at around oscillation maximum (far detector, FD). Until then only the upper
limit was given by the CHOOZ experiment. A robust observation of ?13 was followed in 2012 by the
Daya Bay and RENO experiments with multiple detectors. ?13 is most precisely measured by the
reactor experiments with the systematic uncertainties at per mille level and the value is used
as reference in current and future projects which aim to search for CP violation and mass
hierarchy in neutrino sector. Therefore, precision and accuracy of the reactor ?13 is a critical
matter and validation by multi-experiments based on different systematic uncertainty
compositions are essential. In the last analysis of DC with single detector, precision of ?13
was dominated by the reactor flux uncertainty after suppression of background and detector
related systematic uncertainties, and hence significant improvement is expected with two
detectors. DC finished construction of the second detector close to the reactor cores (near
detector, ND) and has accumulated more than 1 year of data with two detectors as of May 2016.
Thanks to nearly iso-flux experimental layout in DC, reactor flux uncertainties are strongly
suppressed to the lowest level in the world. In this talk a first look on the ND data and its
analysis will be shown.
