Uses of ecosystem services provided by MPAs: How much do they impact the local economy? A southern Europe perspective

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Characterization of the spontaneous light emission of the PMTs used in the Double Chooz experiment

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 photomultiplier base and produced by the combined effect of heat and high voltage across the transparent epoxy resin covering the electric components. The correlation of the rate and the amplitude of the signal with the temperature has been observed. For the first detector in operation the induced background has been mitigated using online and offline analysis selections based on timing and light pattern of the signals, while a modification of the photomultiplier assembly has been implemented for the second detector in order to blacken the PMT bases

Muon capture on light isotopes measured with the Double Chooz detector

Using the Double Chooz detector, designed to measure the neutrino mixing angle θ13, the products of μ- capture on C12,C13,N14, and O16 have been measured. Over a period of 489.5 days, 2.3×106 stopping cosmic μ- have been collected, of which 1.8×105 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 β decays, and, in some cases, β-delayed neutrons. The most precise measurement of the rate of C12(μ-,ν)B12 to date is reported: 6.57-0.21+0.11×103s-1, or (17.35-0.59+0.35)% of nuclear captures. By tagging excited states emitting γs, the ground state transition rate to B12 has been determined to be 5.68-0.23+0.14×103s-1. The heretofore unobserved reactions C12(μ-,να)Li8,C13(μ-,νnα)Li8, and C13(μ-,νn)B12 are measured. Further, a population of βn decays following stopping muons is identified with 5.5σ significance. Statistics limit our ability to identify these decays definitively. Assuming negligible production of He8, the reaction C13(μ-,να)Li9 is found to be present at the 2.7σ level. Limits are set on a variety of other processes

Measurement of θ13 in Double Chooz using neutron captures on hydrogen with novel background rejection techniques

The Double Chooz collaboration presents a measurement of the neutrino mixing angle θ13 using reactor νe¯ (Formula presented.) 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 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. These improvements demonstrate the capability of precise measurement of reactor νe¯ (Formula presented.) without gadolinium loading. Spectral distortions from the νe¯ (Formula presented.) reactor flux predictions previously reported with the neutron capture on gadolinium events are confirmed in the independent data sample presented here. A value of sin2 2θ13 = 0.095− 0.039+ 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 sin2 2θ13 = 0.088 ± 0.033(stat+syst)