Double Chooz detector filled and measuring
reactor neutrino oscillations
The Double Chooz collaboration recently completed its neutrino detector which
will see anti-neutrinos coming from the Chooz nuclear power plant in theFrench Ardennes. The experiment is now ready to take data in order tomeasure fundamental neutrino properties with important consequences forparticle and astro-particle physics.
Neutrinos are electrically neutral elementary particles, three of a kind plus theirantiparticles. Though already postulated in 1930 their first experimental observation
was made in 1956. Because of their weak interaction with other particles, matter isalmost completely transparent to neutrinos and large sensitive detectors are needed
to capture them.
Neutrino oscillations were a major discovery in the late 90-ies and the corresponding
experiments were therefore included in the 2002 Nobel Prize. Oscillations describe
in-flight transformations of different neutrino species into each other and theobservation of this effect implies that neutrinos do have mass. The oscillations
depend on three mixing parameters, of which two are large and have already beenmeasured. The third one is called theta13 and is known to be smaller with an upper
limit coming from a previous experiment at Chooz. The new Double Chooz detector isthe first of a new generation of reactor neutrino experiments aiming at measuring thisfundamental parameter in neutrino physics which is a key area of particle physics
research. The results will also have important consequences for the feasibility of
future neutrino facilities which aim at even more precise measurements.
Double Chooz consists of two identical detectors. The first one at a distance of about1km from the reactor cores has now been filled with liquid scintillator and is beginningto take data. The measured number of neutrinos compared to the expected flux fromthe reactors will allow to considerably improve the sensitivity for theta13 already in2011. The second detector located at a distance of 400 m will start operating in 2012.
At this distance no significant transformation into another neutrino species isexpected. By comparing the results from both detectors theta13 can be determinedwith even higher precision.
Both detectors use an organic liquid scintillator, which was developed specifically forthis experiment. The neutrino target in the core of the detector consists of 10 m3 ofGadolinium doped scintillator which can to tag neutrons from inverse beta decays
which are induced by anti-neutrinos emitted by the reactors. The target is surroundedby three layers of other liquids in order to protect against other particles and todampen environmental radioactivity. These liquids are contained in very thin vessels,
to minimize inactive volumes inside the detector. The target is observed by 390
immersed photomultipliers, which convert the interactions into electronic signals.
These signals are processed in a data acquisition system which is ready to take dataover the next five years. The new detectors will ensure that neutrino physics will stay
one the most fruitful areas of particle physics, as it has been for the past 50 years.

The Double Chooz collaboration is composed of universities and research institutes
from Brazil, England, France, Germany, Japan, Russia, Spain and USA. The
participating institutions are:
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Brazil :თ CBPFთ UFABCთ UNICAMPFrance :თ APC – CNRS/IN2P3თ CEA/DSM/IRFU:- SPP & SPhN
- SEDI & SIS & SENAC
თ Subatech – CNRS/IN2P3
თ IPHC – CNRS/IN2P3
Germany :თ Eberhard-Karls Universität Tübingenთ Max Planck Institut für Kernphysik Heidelberg
თ Technische Universität Münchenთ Physikalisches Institut RWTH Aachen
თ Universität Hamburg
Japan :
თ Hiroshima Institute of Technology
თ Kobe University
თ Niigata University
თ Tohoku University
თ Tohoku Gakuin University
თ Tokyo Institute of Technology
თ Tokyo Metropolitan University
Russia :თ Institute for Nuclear Research RAS
თ Institute of Physical Chemistry RAS
თ RRC Kurchatov InstituteSpain :თ CIEMAT
UK :თ University of Sussex
USA :თ Argonne National Laboratory
თ Barnard Collegeთ University of Chicago
თ Columbia University
თ Drexel University
თ Illinois Institute of Technology
თ Kansas State Universityთ
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Lawrence Livermore National Laboratory
Massachusetts Institute of Technology
Sandia National Laboratories
University of Alabama
University of California at Davis
University of Notre Dame
University of Tennessee

More information about Double Chooz can be found at http://www.doublechooz.org/