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Title: Measurement of θ 13 in Double Chooz using neutron captures on hydrogen with novel background rejection techniques

We observed a measurement of the Double Chooz collaboration and the neutrino mixing angle θ13 using reactor $$\bar{v}$$e via the inverse beta decay reaction in which the neutron is captured on hydrogen. Our 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 1050 m from two reactor cores. Several novel techniques have been developed to achieve significant reductions of the backgrounds and systematic uncertainties. Accidental coincidences, the dominant background in this analysis, are suppressed by more than an order of magnitude with respect to our previous publication by a multi-variate analysis. Furthermore, these improvements demonstrate the capability of precise measurement of reactor $$\bar{v}$$e without gadolinium loading. Spectral distortions from the $$\bar{v}$$e reactor flux predictions previously reported with the neutron capture on gadolinium events are confirmed in the independent data sample presented here. A value of sin213= 0.0950.039+0.038 (stat+syst) is obtained from a fit to the observed event rate as a function of the reactor power, a method insensitive to the energy spectrum shape. A simultaneous fit of the hydrogen capture events and of the gadolinium capture events yields a measurement of sin213 = 0.088 ± 0.033(stat+syst).
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Publication Date:
OSTI Identifier:
1326937
Grant/Contract Number:
NA0000979
Type:
Accepted Manuscript
Journal Name:
Journal of High Energy Physics (Online)
Additional Journal Information:
Journal Name: Journal of High Energy Physics (Online); Journal Volume: 2016; Journal Issue: 1; Journal ID: ISSN 1029-8479
Publisher:
Springer Berlin
Research Org:
Tokyo Inst. of Technology (Japan). Dept. of Physics
Sponsoring Org:
USDOE
Contributing Orgs:
The Double Chooz Collaboration
Country of Publication:
United States
Language:
English
Subject:
21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS oscillation; electroweak interaction; neutrino detectors and telescopes; flavor physics