• Energy Research

The OPERA neutrino experiment in the underground Gran Sasso Laboratory (LNGS) was designed to perform the first detection of neutrino oscillations in direct appearance mode in the νμ → ντ channel, the ντ signature being the identification of the τ-lepton created in its charged current interaction. The hybrid apparatus consists of a large mass emulsion film/lead target complemented by electronic detectors. Placed in the LNGS, it is exposed to the high-energy long-baseline CERN Neutrino beam to Gran Sasso (CNGS) 730 km away from the neutrino source. The observation of a first ντ candidate event was reported in 2010. In this paper, we discuss the result of the analysis of the data taken during the first two years of operation (2008–2009) underlining the major improvements brought to the analysis chain and to the Monte Carlo simulations. The statistical significance of the one event observed so far is then evaluated to 95%. New Journal of Physics, 14 ISSN:1367-2630

The OPERA neutrino experiment in the underground Gran Sasso Laboratory (LNGS) was designed to perform the first detection of neutrino oscillations in direct appearance mode in the νμ → ντ channel, the ντ signature being the identification of the τ-lepton created in its charged current interaction. The hybrid apparatus consists of a large mass emulsion film/lead target complemented by electronic detectors. Placed in the LNGS, it is exposed to the high-energy long-baseline CERN Neutrino beam to Gran Sasso (CNGS) 730 km away from the neutrino source. The observation of a first ντ candidate event was reported in 2010. In this paper, we discuss the result of the analysis of the data taken during the first two years of operation (2008–2009) underlining the major improvements brought to the analysis chain and to the Monte Carlo simulations. The statistical significance of the one event observed so far is then evaluated to 95%. New Journal of Physics, 14 ISSN:1367-2630

We report the measurement of the longitudinal diffusion constant in liquid argon with the DarkSide-50 dual-phase time projection chamber. The measurement is performed at drift electric fields of 100 V/cm, 150 V/cm, and 200 V/cm using high statistics $^{39}$Ar decays from atmospheric argon. We derive an expression to describe the pulse shape of the electroluminescence signal (S2) in dual-phase TPCs. The derived S2 pulse shape is fit to events from the uppermost portion of the TPC in order to characterize the radial dependence of the signal. The results are provided as inputs to the measurement of the longitudinal diffusion constant DL, which we find to be (4.12 $\pm$ 0.04) cm$^2$/s for a selection of 140keV electron recoil events in 200V/cm drift field and 2.8kV/cm extraction field. To study the systematics of our measurement we examine datasets of varying event energy, field strength, and detector volume yielding a weighted average value for the diffusion constant of (4.09 $\pm$ 0.09) cm$^2$ /s. The measured longitudinal diffusion constant is observed to have an energy dependence, and within the studied energy range the result is systematically lower than other results in the literature.

We report the measurement of the longitudinal diffusion constant in liquid argon with the DarkSide-50 dual-phase time projection chamber. The measurement is performed at drift electric fields of 100 V/cm, 150 V/cm, and 200 V/cm using high statistics $^{39}$Ar decays from atmospheric argon. We derive an expression to describe the pulse shape of the electroluminescence signal (S2) in dual-phase TPCs. The derived S2 pulse shape is fit to events from the uppermost portion of the TPC in order to characterize the radial dependence of the signal. The results are provided as inputs to the measurement of the longitudinal diffusion constant DL, which we find to be (4.12 $\pm$ 0.04) cm$^2$/s for a selection of 140keV electron recoil events in 200V/cm drift field and 2.8kV/cm extraction field. To study the systematics of our measurement we examine datasets of varying event energy, field strength, and detector volume yielding a weighted average value for the diffusion constant of (4.09 $\pm$ 0.09) cm$^2$ /s. The measured longitudinal diffusion constant is observed to have an energy dependence, and within the studied energy range the result is systematically lower than other results in the literature.