Speaker
Antonio Verdugo De Osa
(Centro de Investigaciones Energ. Medioambientales y Tecn. - (ES)
Description
Evidences of a contamination of the physics data with an instrumental background arising from light signals produced inside the photomultipliers assembly have been reported by several experiments over the past years. In some cases the instrumental background has been described as a fast (≈ 10 ns) flash of light or, in other cases, as train ( ≈ 1 µs) of pulses similar to the glowing in gas. That has been also the case of the Double Chooz detector, a reactor neutrino experiment which recently measured the θ13 mixing angle through the reactor antineutrino disappearance, where the unexpected background has been suppressed in the data analysis using the characteristic feature of the light emission. A specific study of the phenomena has been carried out in order to characterize the signals and to identify the processes underlying the effect. The mechanisms of light emission originating from the PMTs were identified and it has been found that the dominant one arises from the light produced by the combined effect of heat and high voltage across the epoxy resin covering the electric components. A correlation of the rate and the amplitude of the signal with the temperature has been observed. Additionally evidence of the impact of the seasonal variation of the detector temperature has found after three years of data taking. The results can be particularly relevant for other neutrino experiments that are known to use analogous optical units and similar materials.
Author
Antonio Verdugo De Osa
(Centro de Investigaciones Energ. Medioambientales y Tecn. - (ES)
