The Double Chooz Experiment presents an indication of reactor electron antineutrino disappearance consistent with neutrino oscillations. An observed-to-predicted ratio of events of 0.944 ± 0.016 (stat) ± 0.040 (syst) was obtained in 101 days of running at the Chooz Nuclear Power Plant in France, with two 4.25 GW th reactors. The results were obtained from a single 10 m 3 fiducial volume detector located 1050 m from the two reactor cores. The reactor antineutrino flux prediction used the Bugey4 flux measurement after correction for differences in core composition. The deficit can be interpreted as an indication of a non-zero value of the still unmeasured neutrino mixing parameter sin 2 2θ13. Analyzing both the rate of the prompt positrons and their energy spectrum we find sin 2 2θ13= 0.086 ± 0.041 (stat) ±0.030 (syst), or, at 90% CL, 0.017 < sin 2 2θ13 < 0.16. We report first results of a search for a non-zero neutrino oscillation [1] mixing angle, θ 13 , based on reactor antineutrino disappearance. This is the last of the three neutrino oscillation mixing angles [2,3] for which only upper limits [4,5] are available. The size of θ 13 sets the required sensitivity of long-baseline oscillation experiments attempting to measure CP violation in the neutrino sector or the mass hierarchy.In reactor experiments [6,7] addressing the disappearance ofν e , θ 13 determines the survival probability of electron antineutrinos at the "atmospheric" squaredmass difference, ∆m 2 atm . This probability is given by:where L is the distance from reactor to detector in meters and E the energy of the antineutrino in MeV. The full formula can be found in Ref.[1]. Eq. 1 provides a direct way to measure θ 13 since the only additional input is the well measured value of |∆m 2 atm | = (2.32Other running reactor experiments [9,10] are using the same technique.Electron antineutrinos of < 9 MeV are produced by reactors and detected through inverse beta decay (IBD): ν e + p → e + + n. Detectors based on hydrocarbon liquid scintillators provide the free proton targets. The IBD signature is a coincidence of a prompt positron signal followed by a delayed neutron capture. We present here our first results with a detector located ∼ 1050 m from the two 4.25 GW th thermal power reactors of the Chooz Nuclear Power Plant and under a 300 MWE rock overburden. The analysis is based on 101 days of data including 16 days with one reactor off and one day with both reactors off.The antineutrino flux of each reactor depends on its thermal power and, for the four main fissioning isotopes, 235 U, 239 Pu, 238 U, 241 Pu, their fraction of the total fuel content, their energy released per fission, and their fission and capture cross-sections. The fission rates and associated errors were evaluated using two predictive and complementary reactor simulation codes: MURE [17,18] and DRAGON [19]. This allowed a study of the sensitivity to the important reactor parameters (e.g.. thermal power, boron concentration, temperatures and densities). The quality of these simulations...

This paper describes the design and construction of the MicroBooNE liquid argon time projection chamber and associated systems. MicroBooNE is the first phase of the Short Baseline Neutrino program, located at Fermilab, and will utilize the capabilities of liquid argon detectors to examine a rich assortment of physics topics. In this document details of design specifications, assembly procedures, and acceptance tests are reported.

The Double Chooz experiment has observed 8,249 candidate electron antineutrino events in 227.93 live days with 33.71 GW-ton-years (reactor power × detector mass × livetime) exposure using a 10.3 m 3 fiducial volume detector located at 1050 m from the reactor cores of the Chooz nuclear power plant in France. The expectation in case of θ13= 0 is 8,937 events. The deficit is interpreted as evidence of electron antineutrino disappearance. From a rate plus spectral shape analysis we find sin 2 2θ13 = 0.109 ± 0.030(stat) ± 0.025(syst). The data exclude the no-oscillation hypothesis at 99.8% CL (2.9σ).

Our knowledge of the fundamental particles of nature and their interactions is summarized by the standard model of particle physics. Advancing our understanding in this field has required experiments that operate at ever higher energies and intensities, which produce extremely large and information-rich data samples. The use of machine-learning techniques is revolutionizing how we interpret these data samples, greatly increasing the discovery potential of present and future experiments. Here we summarize the challenges and opportunities that come with the use of machine learning at the frontiers of particle physics.

The ProtoDUNE-SP detector is a single-phase liquid argon time projection chamber with an active volume of 7.2× 6.1× 7.0 m3. It is installed at the CERN Neutrino Platform in a specially-constructed beam that delivers charged pions, kaons, protons, muons and electrons with momenta in the range 0.3 GeV/c to 7 GeV/c. Beam line instrumentation provides accurate momentum measurements and particle identification. The ProtoDUNE-SP detector is a prototype for the first far detector module of the Deep Underground Neutrino Experiment, and it incorporates full-size components as designed for that module. This paper describes the beam line, the time projection chamber, the photon detectors, the cosmic-ray tagger, the signal processing and particle reconstruction. It presents the first results on ProtoDUNE-SP's performance, including noise and gain measurements, dE/dx calibration for muons, protons, pions and electrons, drift electron lifetime measurements, and photon detector noise, signal sensitivity and time resolution measurements. The measured values meet or exceed the specifications for the DUNE far detector, in several cases by large margins. ProtoDUNE-SP's successful operation starting in 2018 and its production of large samples of high-quality data demonstrate the effectiveness of the single-phase far detector design.