NEXT Collaboration(Henriques, C. A. O. et al), Benlloch-Rodriguez, J. M., Carcel, S., Carrion, J. V., Diaz, J., Felkai, R., et al. (2022). Neutral Bremsstrahlung Emission in Xenon Unveiled. Phys. Rev. X, 12(2), 021005–23pp.
Abstract: We present evidence of non-excimer-based secondary scintillation in gaseous xenon, obtained using both the NEXT-White time projection chamber (TPC) and a dedicated setup. Detailed comparison with first-principle calculations allows us to assign this scintillation mechanism to neutral bremsstrahlung (NBrS), a process that is postulated to exist in xenon that has been largely overlooked. For photon emission below 1000 nm, the NBrS yield increases from about 10(-2) photon/e(-) cm(-1) bar(-1) at pressure-reduced electric field values of 50 V cm(-1) bar(-1) to above 3 x 10(-1) photon/e(-) cm(-1) bar(-1) at 500 V cm(-1) bar(-1). Above 1.5 kV cm(-1) bar(-1), values that are typically employed for electroluminescence, it is estimated that NBrS is present with an intensity around 1 photon/e(-) cm(-1) bar(-1), which is about 2 orders of magnitude lower than conventional, excimer-based electroluminescence. Despite being fainter than its excimeric counterpart, our calculations reveal that NBrS causes luminous backgrounds that can interfere, in either gas or liquid phase, with the ability to distinguish and/or to precisely measure low primary-scintillation signals (S1). In particular, we show this to be the case in the "buffer region, where keeping the electric field below the electroluminescence threshold does not suffice to extinguish secondary scintillation. The electric field leakage in this region should be mitigated to avoid intolerable levels of NBrS emission. Furthermore, we show that this new source of light emission opens up a viable path toward obtaining S2 signals for discrimination purposes in future single-phase liquid TPCs for neutrino and dark matter physics, with estimated yields up to 20-50 photons/e(-) cm(-1).
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DUNE Collaboration(Abud, A. A. et al), Antonova, M., Barenboim, G., Cervera-Villanueva, A., De Romeri, V., Fernandez Menendez, P., et al. (2022). Low exposure long-baseline neutrino oscillation sensitivity of the DUNE experiment. Phys. Rev. D, 105(7), 072006–32pp.
Abstract: The Deep Underground Neutrino Experiment (DUNE) will produce world-leading neutrino oscillation measurements over the lifetime of the experiment. In this work, we explore DUNE's sensitivity to observe charge-parity violation (CPV) in the neutrino sector, and to resolve the mass ordering, for exposures of up to 100 kiloton-megawatt-calendar years (kt-MW-CY), where calendar years include an assumption of 57% accelerator uptime based on past accelerator performance at Fermilab. The analysis includes detailed uncertainties on the flux prediction, the neutrino interaction model, and detector effects. We demonstrate that DUNE will be able to unambiguously resolve the neutrino mass ordering at a 4 sigma (5 sigma) level with a 66 (100) kt-MW-CY far detector exposure, and has the ability to make strong statements at significantly shorter exposures depending on the true value of other oscillation parameters, with a median sensitivity of 3 sigma for almost all true delta(CP) values after only 24 kt-MW-CY. We also show that DUNE has the potential to make a robust measurement of CPV at a 3 sigma level with a 100 kt-MW-CY exposure for the maximally CP-violating values delta(CP) = +/-pi/2. Additionally, the dependence of DUNE's sensitivity on the exposure taken in neutrino-enhanced and antineutrino-enhanced running is discussed. An equal fraction of exposure taken in each beam mode is found to be close to optimal when considered over the entire space of interest.
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NEXT Collaboration(Novella, P. et al), Carcel, S., Carrion, J. V., Diaz, J., Martin-Albo, J., Martinez, A., et al. (2022). Measurement of the Xe-136 two-neutrino double-beta-decay half-life via direct background subtraction in NEXT. Phys. Rev. C, 105(5), 055501–8pp.
Abstract: We report a measurement of the half-life of the Xe-136 two-neutrino double-beta decay performed with a novel direct-background-subtraction technique. The analysis relies on the data collected with the NEXT-White detector operated with Xe-136-enriched and Xe-136-depleted xenon, as well as on the topology of double-electron tracks. With a fiducial mass of only 3.5 kg of Xe, a half-life of 2.34(-0.46)(+0.80) (stat)(-0.17)(+0.30) (sys) x 10(21) yr is derived from the background-subtracted energy spectrum. The presented technique demonstrates the feasibility of unique background-model-independent neutrinoless double-beta-decay searches.
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DUNE Collaboration(Abud, A. A. et al), Antonova, M., Barenboim, G., Cervera-Villanueva, A., De Romeri, V., Fernandez Menendez, P., et al. (2022). Scintillation light detection in the 6-m drift-length ProtoDUNE Dual Phase liquid argon TPC. Eur. Phys. J. C, 82(7), 618–29pp.
Abstract: DUNE is a dual-site experiment for long-baseline neutrino oscillation studies, neutrino astrophysics and nucleon decay searches. ProtoDUNE Dual Phase (DP) is a 6 x 6 x 6 m(3) liquid argon time-projection-chamber (LArTPC) that recorded cosmic-muon data at the CERN Neutrino Platform in 2019-2020 as a prototype of the DUNE Far Detector. Charged particles propagating through the LArTPC produce ionization and scintillation light. The scintillation light signal in these detectors can provide the trigger for non-beam events. In addition, it adds precise timing capabilities and improves the calorimetry measurements. In ProtoDUNE-DP, scintillation and electroluminescence light produced by cosmic muons in the LArTPC is collected by photomultiplier tubes placed up to 7m away from the ionizing track. In this paper, the ProtoDUNE-DP photon detection system performance is evaluated with a particular focus on the different wavelength shifters, such as PEN and TPB, and the use of Xe-doped LAr, considering its future use in giant LArTPCs. The scintillation light production and propagation processes are analyzed and a comparison of simulation to data is performed, improving understanding of the liquid argon properties.
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Double Chooz collaboration(de Kerret, H. et al), & Novella, P. (2022). The Double Chooz antineutrino detectors. Eur. Phys. J. C, 82(9), 804–34pp.
Abstract: This article describes the setup and performance of the near and far detectors in the Double Chooz experiment. The electron antineutrinos of the Chooz nuclear power plant were measured in two identically designed detectors with different average baselines of about 400 m and 1050 m from the two reactor cores. Over many years of data taking the neutrino signals were extracted from interactions in the detectors with the goal of measuring a fundamental parameter in the context of neutrino oscillation, the mixing angle 013. The central part of the Double Chooz detectors was a main detector comprising four cylindrical volumes filled with organic liquids. From the inside towards the outside there were volumes con- taining gadolinium-loaded scintillator, gadolinium-free scintillator, a buffer oil and, optically separated, another liquid scintillator acting as veto system. Above this main detector an additional outer veto system using plastic scintillator strips was installed. The technologies developed in Double Chooz were inspiration for several other antineutrino detectors in the field. The detector design allowed implementation of efficient background rejection techniques including use of pulse shape information provided by the data acquisition system. The Double Chooz detectors featured remarkable stability, in particular for the detected photons, as well as high radiopurity of the detector components.
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