Charles E. Lane
The Double Chooz experiment returns to the site of the Chooz experiment with a pair of detectors for a differential neutrino flux measurement, providing sensitivity to sin^2(2theta13) > 0.03. Reaching this goal requires significant improvements in systematic uncertainties, based on the experience with previous reactor neutrino experiments.
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The proposed Double Chooz theta 13 experiment is described. Double Chooz will be an optimized reactor disappearance experiment similar to the original CHOOZ. The optimization includes an increase in the signal to noise by increasing the target volume to twice the original CHOOZ, reducing singles background with a non-scintillating oil buffer region around the target and carefully controlling systematic uncertainties by measuring the electron antineutrino flux of the source with a near detector. The Double Chooz far detector will be situated in the same cavern as CHOOZ but will detect ~50000 el…
The Double Chooz experiment is meant to search for the neutrino mixing angle theta13 taking advantage of the neutrinos generated at the nuclear power plant of Chooz. Double Chooz relies on neutrino flux measurements at two different locations, the so-called far and near detectors, although the first phase runs only with the far detector. The commissioning of the far detector started in January 2011 and first results improving the current limit on theta13 are expected by the summer 2011. The status of the Double Chooz experiment is presented.
The Double Chooz Reactor Neutrino Experiment in France plans to quickly measure the neutrino mixing angle theta-13, or limit it to sin^2 2-theta_13 less than 0.025. The physics reach, experimental site, detector structures, scintillator, photodetection, electronics, calibration and simulations are described. The possibility of using Double Chooz to explore the possible use of a antineutrino detector for non-proliferation goals is also presented.
Double Chooz is a reactor neutrino experiment which investigates the last neutrino mixing angle; theta-13. It is necessary to measure reactor neutrino disappearance with precision 1% or better to detect finite value of theta-13. This requirement is the most strict compared to other reactor neutrino experiments performed so far. The Double Chooz experiment makes use of a number of techniques to reduce the possible errors to achieve the sensitivity. The detector is now under construction and it is expected to take first neutrino data in 2009 and to measure sin^22theta-13 with a sensitivity of 0.…
The Double-Chooz experiment goal is to search for a non-vanishing value of the Theta13 neutrino mixing angle. This is the last step to accomplish prior moving towards a new era of precision measurements in the lepton sector. The current best constraint on the third mixing angle comes from the CHOOZ reactor neutrino experiment $\sin(2θ_{13})^{2}<0.2$ (90% C.L., $Δm_{atm}^{2}=2.0$ eV$^{2}$). Double-Chooz will explore the range of $\sin(2θ_{13})^{2}$ from 0.2 to 0.03-0.02, within three years of data taking. The improvement of the CHOOZ result requires an increase in the statistics, a reduction of…
Double Chooz experiment will search for a disappearance of the reactor neutrinos from Chooz reactor cores in Ardenne, France, in order to detect the yet unknown neutrino oscillation angle θ13. The far detector was completed in 2010 and data-taking has started in spring 2011. Status of data-taking is presented and some performance plots from physics data are shown in this paper for the first time. Also the prospect of experimental sensitivity is presented, in light of recent indication from T2K for a non-zero θ13 value.
There is broad consensus in the worldwide physics community as to the need for a new reactor-neutrino experiment to measure or limit the neutrino mixing angle $θ_{13}$. The Double Chooz Experiment, planned for operation in the years 2008-2011, will search for values of $\sin^2{2θ_{13}}$ down to $\approx$0.03. This will be the first new information on $θ_{13}$ in over a decade and will cover most of the remaining parameter space. A quick and relatively inexpensive project is made possible by the existing neutrino laboratory at the Chooz site.
The Double Chooz reactor neutrino experiment will be the next detector to search for a non vanishing theta(13) mixing angle with unprecedented sensitivity, which might open the way to unveiling CP violation in the leptonic sector. The measurement of this angle will be based on a precise comparison of the antineutrino spectrum at two identical detectors located at different distances from the Chooz nuclear reactor cores in France. Double Chooz is particularly attractive because of its capability to measure sin^2(2theta(13)) to 3 sigma significance if sin^2(2theta(13)) > 0.05 or to exclude sin^2…
We report first results of a search for the non-zero neutrino mixing angle θ_{13} from the Double Chooz experiment. Double Chooz aims to measure the mixing angle based on anti-electron-neutrino disappearance as a consequence of neutrino oscillation. A new generation of anti-electron-neutrino detector having 10 m^3 fiducial volume is located 1 km from the two 4.25 GW_{th} reactors at the Chooz Power Plant in France. Physics data taking has been continuing since April 2011. A ratio of observed-to-predicted event rate of 0.944 +/- 0.016 (stat) +/- 0.040 (syst) was obtained in 101 days of detector…
The Double Chooz experiment is the first of the next wave of reactor experiments searching for a non-vanishing value of the mixing angle theta_13. The experimental concept and detector design are presented, and the most pertinent backgrounds are discussed. Operation of the far detector is expected to begin by the end of 2009. Installation of the near detector will occur in 2010. Double Chooz has the capacity to measure sin^2(2theta_13) to 3 sigma if sin^2(2theta_13) >0.05 or exclude sin^2 (2theta_13) down to 0.03 at 90% for Delta m_31^2 = 2.5 x 10^-3 eV^2 with three years of data with both nea…
We discuss the potential of the proposed Double Chooz reactor experiment to measure the neutrino mixing angle $\sin^2 2θ_{13}$. We especially consider systematical uncertainties and their partial cancellation in a near and far detector operation, and we discuss implications of a delayed near detector startup. Furthermore, we introduce Triple Chooz, which is a possible upgrade scenario assuming a second, larger far detector, which could start data taking in an existing cavern five years after the first far detector. We review the role of the Chooz reactor experiments in the global context of fu…
It has recently been widely recognized that a reactor anti-neutrino disappearance experiment with two or more detectors is one of the most cost-effective ways to extend our reach in sensitivity for the neutrino mixing angle theta-13 without ambiguities from CP violation and matter effects. The physics capabilities of a new reactor experiment together with superbeams and neutrino factories have also been studied but these latter are considered by many to be more ambitious projects due to their higher costs, and hence to be farther in the future. We propose to contribute to an international coll…
The Double Chooz reactor neutrino experiment will be the next detector to search for a non vanishing theta13 mixing angle with unprecedented sensitivity, which might open the way to unveiling CP violation in the leptonic sector. The measurement of this angle will be based in a precise comparison of the antineutrino spectrum at two identical detectors located at different distances from the Chooz nuclear reactor cores in France. Double Chooz is particularly attractive because of its capability to measure sin2(2theta13) to 3 sigmas if sin2(2theta13) > 0.05 or to exclude sin2(2theta13) down to 0.…
Double Chooz is a long baseline neutrino oscillation experiment at Chooz, France. The purpose of this experiment is to measure the non-zero neutrino oscillation parameter theta13, a parameter for changing electron neutrinos into other neutrinos. This experiment uses reactors of the Chooz Nuclear Power Plant as a neutrino source. Double Chooz has published 2 result papers showing the measurement of the mixing angle, and 3rd publication is processing.
Among ongoing reactor-based experiments, Double Chooz is unique in obtaining data when the reactor cores are brought down for maintenance. These reactor-off data allow for a clean measurement of the backgrounds of the experiment, thus being of uppermost importance for the theta13 oscillation analysis. While the oscillation results published by the collaboration in 2011 and 2012 rely on background models derived from reactor-on data, in this talk we present an independent study based on the handle provided by 7.53 days of reactor-off data. A global fit to both theta13 and the total background i…
Since the first indication in 2011 of a non-vanishing value of $θ_{13}$ using reactor neutrinos by Double Chooz, this collaboration has developed new analyses leading to an increased precision on $θ_{13}$ and different cross-checks of the oscillation results. Beyond the update of the analysis based on neutron captures on Gd in 2012, Double Chooz has also released a consistent measurement of $θ_{13}$ by means of neutron captures on H. The combination of the n-Gd and n-H data samples, as well as 7.23 days of reactor off data, in a global rate+shape analysis yields $\sin^22θ_{13} = 0.109\pm 0.035…
The Double Chooz experiment will use the electron antineutrinos produced by the Chooz nuclear power station to search for a non-vanishing value of the Theta_13 neutrino mixing angle. Double Chooz will be the first of a new generation of neutrino experiments using identical detectors at different distances from the neutrino source to reduce the systematic errors due to the uncertainties on the neutrino flux and to the detector acceptance. The far detector is expected to be operative by the beginning of 2010. Installation of the near detector will occur in 2010.
The first results from Double Chooz with 100 days of data measured $\sin^2(2θ_{13}) = 0.086 \pm 0.051$. Backgrounds contribute significantly to the systematic uncertainty budget. Using the incoming neutrino directionality we will attempt to further separate the inverse beta decay signal from backgrounds. The CHOOZ experiment completed a similar analysis and found that the neutrino source can be located to within a cone of half-aperture of 18 degrees at the 68% C.L. We study the possible improvement of this result by Double Chooz.
This is a contribution paper from the Double Chooz experiment to the special issue of NPB on neutrino oscillations. The physics and a history of the reactor theta13 experiments, as well as Double Chooz experiment and its neutrino oscillation analyses are reviewed.
Double Chooz main target is to measure Theta13 oscillation parameter by comparing reactor neutrino fluxes in two identical detectors located respectively at 400 m and 1 km away from the 2 Chooz reactor cores. The far detector is now under construction, while we have just completed the design phase of the near one. In this report I will discuss the detector principle, sensitivity and its present construction status.
Tremendous progress has been achieved in neutrino oscillation physics during the last few years. However, the smallness of the $\t13$ neutrino mixing angle still remains enigmatic. The current best constraint comes from the CHOOZ reactor neutrino experiment $\s2t13 < 0.2$ (at 90% C.L., for $\adm2=2.0 10^{-3} \text{eV}^2$). We propose a new experiment on the same site, Double-CHOOZ, to explore the range of $\s2t13$ from 0.2 to 0.03, within three years of data taking. The improvement of the CHOOZ result requires an increase in the statistics, a reduction of the systematic error below one percent…
Precise measurement of the neutrino mixing angle $θ_{13}$ is the primary goal of the Double Chooz Experiment (DC), which is located in Chooz, France. The inverse beta decay process provides a unique signature of reactor anti-neutrino interactions, giving prompt signals from positron annihilation and delayed signals from neutron capture by either Gadolinium (Gd) or Hydrogen (H). This paper is dedicated to the latest nH analysis in Double Chooz. Typically, The Gd analysis is primary since fewer background events are involved. However, with accurate estimates of backgrounds and a precise reconstr…
This paper describes the characterization studies under low magnetic fields of the Hamamatsu R7081 photomultipliers that are being used in the Double Chooz experiment. The design and performances of the magnetic shielding that has been developed for these photomultipliers are also reported.
We investigate the possible effects of short-baseline antinu_e disappearance implied by the reactor antineutrino anomaly on the Double-Chooz determination of theta_{13} through the normalization of the initial antineutrino flux with the Bugey-4 measurement. We show that the effects are negligible and the value of theta_{13} obtained by the Double-Chooz collaboration is accurate only if Delta m^2_{41} is larger than about 3 eV^2. For smaller values of Delta m^2_{41} the short-baseline oscillations are not fully averaged at Bugey-4 and the uncertainties due to the reactor antineutrino anomaly ca…
The implications of extra sterile neutrinos for the Double Chooz experiment is expounded. The so-called ``3+2'' mass spectrum with 2 sterile neutrinos mixed with the active ones, is still allowed by the global neutrino data including MiniBooNE. We probe its impact on the resultant reactor antineutrino signal at the near and far detector of the Double Chooz experiment. The oscillations driven by the additional mass squared difference due to the sterile states bring an energy independent constant suppression at both the near and far detectors. We study to what extent the measurement of $θ_{13}$ …
The goal of Double Chooz experiment is a precise measurement of the last unknown mixing angle theta_13 using two identical detectors placed at far and near sites from Chooz reactor cores. The detector is optimized for reactor-neutrino detection using specially developed 10-inch PMTs. We developed two types of measurement systems and evaluated 400 PMTs before the installation. Those PMTs fulfill our requirements, and a half of those have been installed to the far detector in 2009. The character and performance data of the PMTs are stored in a database and will be referenced in analysis and MC s…
The hemispherical 10" photomultiplier tube (PMT) R7081 from Hamamatsu Photonics K.K. (HPK) is used in various experiments in particle and astroparticle physics. We describe the test and calibration of 474 PMTs for the reactor antineutrino experiment Double Chooz. The unique test setup at Max-Planck-Institut für Kernphysik Heidelberg (MPIK) allows one to calibrate 30 PMTs simultaneously and to characterize the single photo electron response, transit time spread, linear behaviour and saturation effects, photon detection efficiency and high voltage calibration.
The latest results from the Double Chooz experiment on the neutrino mixing angle $θ_{13}$ are presented. A detector located at an average distance of 1050 m from the two reactor cores of the Chooz nuclear power plant has accumulated a live time of 467.90 days, corresponding to an exposure of 66.5 GW-ton-year (reactor power $\times$ detector mass $\times$ live time). A revised analysis has boosted the signal efficiency and reduced the backgrounds and systematic uncertainties compared to previous publications, paving the way for the two detector phase. The measured $\sin^2 2θ_{13} = 0.090^{+0.03…
In 2011 and 2012, three reactor neutrino experiments, Double Chooz, Daya Bay and RENO showed positive signals of reactor neutrino disappearance and measured a mixing parameter sin^2(2th13) at average baselines 1.05, 1.65 and 1.44km, respectively. It is possible to measure effective Dm31^2 from distortion of neutrino energy spectrum (E dependence of the oscillation) in those experiments. However, since it requires a precise energy calibration, such measurements have not been reported yet. Dm31^2 can also be measured from baseline (L) dependence of the neutrino oscillation. In this paper, Dm31^2…
The establishment of the neutrino oscillations phenomenon as a solution to both solar and atmospheric neutrino anomalies had two consequences: a new oscillation mode, labelled $\mathbf{θ_{13}}$, and the possibility to observe CP violation, if $\mathbf{θ_{13}}$ was sizeable. CP violation implies that neutrino oscillations behave differently for neutrinos and anti-neutrinos -- a rare fundamental phenomenon key for our understanding of the Universe. The experimental demonstration of $\mathbf{θ_{13}}$ has aided the completion of a quest lasting half a century. The best $\mathbf{θ_{13}}$ knowledge …
First Measurement of Neutrino Emissions from Spent Nuclear Fuel by the Double Chooz Experiment
Double Chooz实验利用反应堆停堆数据首次定量测量乏核燃料等产生的残余中微子流，结果与反应堆模拟预测值高度吻合，为核保障等领域提供支撑。
The oscillation results published by the Double Chooz collaboration in 2011 and 2012 rely on background models substantiated by reactor-on data. In this analysis, we present a background-model-independent measurement of the mixing angle $θ_{13}$ by including 7.53 days of reactor-off data. A global fit of the observed neutrino rates for different reactor power conditions is performed, yielding a measurement of both $θ_{13}$ and the total background rate. The results on the mixing angle are improved significantly by including the reactor-off data in the fit, as it provides a direct measurement o…
The Double Chooz experiment has determined the value of the neutrino oscillation parameter $θ_{13}$ from an analysis of inverse beta decay interactions with neutron capture on hydrogen. This analysis uses a three times larger fiducial volume than the standard Double Chooz assessment, which is restricted to a region doped with gadolinium (Gd), yielding an exposure of 113.1 GW-ton-years. The data sample used in this analysis is distinct from that of the Gd analysis, and the systematic uncertainties are also largely independent, with some exceptions, such as the reactor neutrino flux prediction. …
We present a search for signatures of neutrino mixing of electron anti-neutrinos with additional hypothetical sterile neutrino flavors using the Double Chooz experiment. The search is based on data from 5 years of operation of Double Chooz, including 2 years in the two-detector configuration. The analysis is based on a profile likelihood, i.e.\ comparing the data to the model prediction of disappearance in a data-to-data comparison of the two respective detectors. The analysis is optimized for a model of three active and one sterile neutrino. It is sensitive in the typical mass range $5 \cdot …
Two neutrino mixing angles have been measured, and much of the neutrino community is turning its attention to the unmeasured mixing angle, $\quq$, whose best limit comes from the reactor neutrino experiment CHOOZ.\cite{bib:chooz} New two detector reactor neutrino experiments are being planned, along with more ambitious accelerator experiments, to measure or further limit $\quq$. Here I will overview how to measure $\quq$ using reactor neutrinos, mention some experiments that were considered and are not going forward, and review the current status of four projects: Double Chooz in France, Daya …
We describe a muon track reconstruction algorithm for the reactor anti-neutrino experiment Double Chooz. The Double Chooz detector consists of two optically isolated volumes of liquid scintillator viewed by PMTs, and an Outer Veto above these made of crossed scintillator strips. Muons are reconstructed by their Outer Veto hit positions along with timing information from the other two detector volumes. All muons are fit under the hypothesis that they are through-going and ultrarelativistic. If the energy depositions suggest that the muon may have stopped, the reconstruction fits also for this h…
The Double Chooz Experiment presents an indication of reactor electron antineutrino disappearance consistent with neutrino oscillations. A ratio of 0.944 $\pm$ 0.016 (stat) $\pm$ 0.040 (syst) observed to predicted events 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 measurement as an anchor point. The deficit can be interpreted as an indication of a non-ze…
We present new results based on the entire CHOOZ data sample. We find (at 90% confidence level) no evidence for neutrino oscillations in the anti_nue disappearance mode, for the parameter region given by approximately Delta m**2 > 7 x 10**-4 eV^2 for maximum mixing, and sin**2(2 theta) = 0.10 for large Delta m**2. Lower sensitivity results, based only on the comparison of the positron spectra from the two different-distance nuclear reactors, are also presented; these are independent of the absolute normalization of the anti_nue flux, the cross section, the number of target protons and the dete…
We present in this article a detailed quantitative discussion of the measurement of the leptonic mixing angle theta_13 through currently scheduled reactor neutrino oscillation experiments. We thus focus on Double Chooz (Phase I & II), Daya Bay (Phase I & II) and RENO experiments. We perform a unified analysis, including systematics, backgrounds and accurate experimental setup in each case. Each identified systematic error and background impact has been assessed on experimental setups following published data when available and extrapolating from Double Chooz acquired knowledge otherwise. After…
Liquid scintillators are a common choice for neutrino physics experiments, but their capabilities to perform background rejection by scintillation pulse shape discrimination is generally limited in large detectors. This paper describes a novel approach for a pulse shape based event classification developed in the context of the Double Chooz reactor antineutrino experiment. Unlike previous implementations, this method uses the Fourier power spectra of the scintillation pulse shapes to obtain event-wise information. A classification variable built from spectral information was able to achieve an…
This final article about the CHOOZ experiment presents a complete description of the electron antineutrino source and detector, the calibration methods and stability checks, the event reconstruction procedures and the Monte Carlo simulation. The data analysis, systematic effects and the methods used to reach our conclusions are fully discussed. Some new remarks are presented on the deduction of the confidence limits and on the correct treatment of systematic errors.
A study on cosmic muons has been performed for the two identical near and far neutrino detectors of the Double Chooz experiment, placed at $\sim$120 and $\sim$300 m.w.e. underground respectively, including the corresponding simulations using the MUSIC simulation package. This characterization has allowed to measure the muon flux reaching both detectors to be (3.64 $\pm$ 0.04) $\times$ 10$^{-4}$ cm$^{-2}$s$^{-1}$ for the near detector and (7.00 $\pm$ 0.05) $\times$ 10$^{-5}$ cm$^{-2}$s$^{-1}$ for the far one. The seasonal modulation of the signal has also been studied observing a positive corre…
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 x detector mass x livetime) exposure using a 10.3 cubic meter fiducial volume detector located at 1050 m from the reactor cores of the Chooz nuclear power plant in France. The expectation in case of theta13 = 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 \pm 0.030(stat) \pm 0.025(syst). The data exclude the no-oscillation hypothesis …
Double Chooz is unique among modern reactor-based neutrino experiments studying $\bar ν_e$ disappearance in that data can be collected with all reactors off. In this paper, we present data from 7.53 days of reactor-off running. Applying the same selection criteria as used in the Double Chooz reactor-on oscillation analysis, a measured background rate of 1.0$\pm$0.4 events/day is obtained. The background model for accidentals, cosmogenic $β$-$n$-emitting isotopes, fast neutrons from cosmic muons, and stopped-$μ$ decays used in the oscillation analysis is demonstrated to be correct within the un…
A $θ_{13}$ oscillation analysis based on the observed antineutrino rates at the Double Chooz far and near detectors for different reactor power conditions is presented. This approach provides a so far unique simultaneous determination of $θ_{13}$ and the total background rates without relying on any assumptions on the specific background contributions. The analysis comprises 865 days of data collected in both detectors with at least one reactor in operation. The oscillation results are enhanced by the use of 24.06 days (12.74 days) of reactor-off data in the far (near) detector. The analysis c…
Initial results are presented from CHOOZ, a long-baseline reactor-neutrino vacuum-oscillation experiment. Electron antineutrinos were detected by a liquid scintillation calorimeter located at a distance of about 1 km. The detector was constructed in a tunnel protected from cosmic rays by a 300 MWE rock overburden. This massive shielding strongly reduced potentially troublesome backgrounds due to cosmic-ray muons, leading to a background rate of about one event per day, more than an order of magnitude smaller than the observed neutrino signal. From the statistical agreement between detected and…
The Double Chooz experiment presents improved measurements of the neutrino mixing angle $θ_{13}$ using the data collected in 467.90 live days from a detector positioned at an average distance of 1050 m from two reactor cores at the Chooz nuclear power plant. Several novel techniques have been developed to achieve significant reductions of the backgrounds and systematic uncertainties with respect to previous publications, whereas the efficiency of the $\barν_{e}$ signal has increased. The value of $θ_{13}$ is measured to be $\sin^{2}2θ_{13} = 0.090 ^{+0.032}_{-0.029}$ from a fit to the observed…
The CHOOZ experiment measured the antineutrino flux at a distance of about 1 Km from two nuclear reactors in order to detect possible neutrino oscillations with squared mass differences as low as 10**-3 eV**2 for full mixing. We show that the data analysis of the electron antineutrino events, collected by our liquid scintillation detector, locates the antineutrino source within a cone of half-aperture of about 18 degrees at the 68% C.L.. We discuss the implications of this experimental result for tracking down a supernova explosion.
The yields and production rates of the radioisotopes $^9$Li and $^8$He created by cosmic muon spallation on $^{12}$C, have been measured by the two detectors of the Double Chooz experiment. The identical detectors are located at separate sites and depths, which means they are subject to different muon spectra. The near (far) detector has an overburden of $\sim$120 m.w.e. ($\sim$300 m.w.e.) corresponding to a mean muon energy of $32.1\pm2.0\,\mathrm{GeV}$ ($63.7\pm5.5\,\mathrm{GeV}$). Comparing the data to a detailed simulation of the $^9$Li and $^8$He decays, the contribution of the $^8$He rad…
The Double Chooz experiment measures the neutrino mixing angle $θ_{13}$ by detecting reactor $\barν_e$ via inverse beta decay. The positron-neutron space and time coincidence allows for a sizable background rejection, nonetheless liquid scintillator detectors would profit from a positron/electron discrimination, if feasible in large detector, to suppress the remaining background. Standard particle identification, based on particle dependent time profile of photon emission in liquid scintillator, can not be used given the identical mass of the two particles. However, the positron annihilation i…
We discuss the minimum requirements for a neutrino beta beam if theta_13 is discovered by an upcoming reactor experiment, such as Double Chooz or Daya Bay. We require that both neutrino mass hierarchy and leptonic CP violation can be measured to competitive precisions with a single-baseline experiment in the entire remaining theta_13 range. We find that for very high isotope production rates, such as they might be possible using a production ring, a (B,Li) beta beam with a gamma as low as 60 could already be sufficient to perform all of these measurements. If only the often used nominal source…
Neutrino oscillation scenarios involving large angle $ν_μ \to ν_e$ oscillations are disfavoured in the parameter range $Δm^2/eV^2 >~ 10^{-3}$ by recent results from the CHOOZ reactor-based $\barν_e$ disappearance experiment. For this reason we extend our previous work on up-down asymmetries for various oscillation scenarios by computing up-down asymmetries and the R ratio for the entire conceivable range $10^{-4} - 10^{-1} eV^2$ of $Δm^2$. Matter effects in the Earth play a crucial role. We perform a $χ^2$ fit to the data. We find that, because of the matter effect, the three-flavour maximal m…
During the commissioning of the first of the two detectors of the Double Chooz experiment, an unexpected and dominant background caused by the emission of light inside the optical volume has been observed. A specific study of the ensemble of phenomena called "Light Noise" has been carried out in-situ, and in an external laboratory, in order to characterize the signals and to identify the possible processes underlying the effect. Some mechanisms of instrumental noise originating from the PMTs were identified and it has been found that the leading one arises from the light emission localized on …
The Double Chooz collaboration presents a measurement of the neutrino mixing angle $θ_{13}$ using reactor $\overlineν_{e}$ observed via the inverse beta decay reaction in which the neutron is captured on hydrogen. This measurement is based on 462.72 live days data, approximately twice as much data as in the previous such analysis, collected with a detector positioned at an average distance of 1050m from two reactor cores. Several novel techniques have been developed to achieve significant reductions of the backgrounds and systematic uncertainties. Accidental coincidences, the dominant backgrou…
The status of theta13 measurements from Daya Bay, RENO and Double Chooz experiments is reviewed.
There is an observed deficit of about 6\% in the expected rate of anti-neutrino interactions when averaging over many different reactor experiments. While the significance of the deficit is low (98.6 \% CL), there is speculation that a non-interacting "sterile" neutrino could be the cause. In this paper we explore the possibility of a two-reactor/one-detector experiment at intermediate distances (100-500 meters) to look for a sterile neutrino in the mass range implied by this deficit. A method for probing $Δm^2$ phase space is developed using interference patterns between two oscillated spectr…
We consider a model where sterile neutrinos can propagate in a large compactified extra dimension giving rise to Kaluza-Klein (KK) modes and the standard model left-handed neutrinos are confined to a 4-dimensional spacetime brane. The KK modes mix with the standard neutrinos modifying their oscillation pattern. We examine former and current experiments such as CHOOZ, KamLAND, and MINOS to estimate the impact of the possible presence of such KK modes on the determination of the neutrino oscillation parameters and simultaneously obtain limits on the size of the largest extra dimension. We found …
Using the Double Chooz detector, designed to measure the neutrino mixing angle $θ_{13}$, the products of $μ^-$ capture on $^{12}$C, $^{13}$C, $^{14}$N and $^{16}$O have been measured. Over a period of 489.5 days, $2.3\times10^6$ stopping cosmic $μ^-$ have been collected, of which $1.8\times10^5$ captured on carbon, nitrogen, or oxygen nuclei in the inner detector scintillator or acrylic vessels. The resulting isotopes were tagged using prompt neutron emission (when applicable), the subsequent beta decays, and, in some cases, $β$-delayed neutrons. The most precise measurement of the rate of $^{…
The disappearance of reactor antineutrinos in the Double Chooz experiment is used to investigate the possibility of neutrino-antineutrino oscillations arising due to the breakdown of Lorentz invariance. We find no evidence for this phenomenon and set the first limits on 15 coefficients describing neutrino-antineutrino mixing within the framework of the Standard-Model Extension.
Recent studies of atmospheric neutrinos and the results from CHOOZ and Palo-Verde experiment call for new and more sensitive searches for neutrino oscillations at reactors. The main goal of the project considered here is to look for very small mixing angle oscillations of electron neutrinos in the atmospheric neutrino mass parameter region around Δm^2 ~3 10^-3 eV^2 and to define the element U_{e3} of the neutrino mixing matrix (U_{e3}is the contribution of the mass-3 state to the electron neutrino flavor state). The practical goal of the project is to decrease, relative to the CHOOZ, the stati…
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