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KM3NeT Collaboration(Aiello, S. et al), Alves Garre, S., Calvo, D., Carretero, V., Colomer, M., Garcia Soto, A., et al. (2022). Combined sensitivity of JUNO and KM3NeT/ORCA to the neutrino mass ordering. J. High Energy Phys., 03(3), 055–31pp.
Abstract: This article presents the potential of a combined analysis of the JUNO and KM3NeT/ORCA experiments to determine the neutrino mass ordering. This combination is particularly interesting as it significantly boosts the potential of either detector, beyond simply adding their neutrino mass ordering sensitivities, by removing a degeneracy in the determination of Delta M-31(2) between the two experiments when assuming the wrong ordering. The study is based on the latest projected performances for JUNO, and on simulation tools using a full Monte Carlo approach to the KM3NeT/ORCA response with a careful assessment of its energy systematics. From this analysis, a 5 sigma determination of the neutrino mass ordering is expected after 6 years of joint data taking for any value of the oscillation parameters. This sensitivity would be achieved after only 2 years of joint data taking assuming the current global best-fit values for those parameters for normal ordering.
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KM3NeT Collaboration(Aiello, S. et al), Alves Garre, S., Calvo, D., Carretero, V., Colomer, M., Gozzini, S. R., et al. (2022). Nanobeacon: A time calibration device for the KM3NeT neutrino telescope. Nucl. Instrum. Methods Phys. Res. A, 1040, 167132–13pp.
Abstract: The KM3NeT Collaboration is currently constructing a multi-site high-energy neutrino telescope in the Mediterranean Sea consisting of matrices of pressure-resistant glass spheres, each holding a set of 31 small-area photomultipliers. The main goals of the telescope are the observation of neutrino sources in the Universe and the measurement of the neutrino oscillation parameters with atmospheric neutrinos. A relative time synchronisation between photomultipliers of the nanosecond order needed to guarantee the required angular resolution of the detector. Due to the large detector volumes to be instrumented by KM3NeT, a cost reduction of the different systems is a priority. To this end, the inexpensive Nanobeacon has been designed and developed by the KM3NeT Collaboration to be used for detector time-calibration studies. At present, more than 600 & nbsp;Nanobeacons have been already produced. The characterisation of the optical pulse and the wavelength emission profile of the devices is critical for the time calibration. The optical pulse rise time has been quantified as less than 3 ns, while the Full Width Half Maximum is less than 6 ns. The wavelength drift, due to a variation of the supply voltage, has also been qualified as lower than 10 nm for the full range of the Nanobeacon. In this paper, more details about the main features of the Nanobeacon design, production and operation, together with the main properties of the light pulse generated are described.
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KM3NeT Collaboration(Aiello, S. et al), Alves Garre, S., Calvo, D., Carretero, V., Colomer, M., Hernandez-Rey, J. J., et al. (2021). Sensitivity to light sterile neutrino mixing parameters with KM3NeT/ORCA. J. High Energy Phys., 10(10), 180–26pp.
Abstract: KM3NeT/ORCA is a next-generation neutrino telescope optimised for atmospheric neutrino oscillations studies. In this paper, the sensitivity of ORCA to the presence of a light sterile neutrino in a 3+1 model is presented. After three years of data taking, ORCA will be able to probe the active-sterile mixing angles theta(14), theta(24), theta(34) and the effective angle theta(mu e), over a broad range of mass squared difference Delta m(41)(2) similar to [10(-5), 10] eV(2), allowing to test the eV-mass sterile neutrino hypothesis as the origin of short baseline anomalies, as well as probing the hypothesis of a very light sterile neutrino, not yet constrained by cosmology. ORCA will be able to explore a relevant fraction of the parameter space not yet reached by present measurements.
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KM3NeT Collaboration(Aitllo, S. et al), Alves Garre, S., Calvo, D., Carretero, V., Garcia Soto, A., Gozzini, S. R., et al. (2023). Probing invisible neutrino decay with KM3NeT/ORCA. J. High Energy Phys., 04(4), 090–30pp.
Abstract: In the era of precision measurements of the neutrino oscillation parameters, upcoming neutrino experiments will also be sensitive to physics beyond the Standard Model. KM3NeT/ORCA is a neutrino detector optimised for measuring atmospheric neutrinos from a few GeV to around 100 GeV. In this paper, the sensitivity of the KM3NeT/ORCA detector to neutrino decay has been explored. A three-flavour neutrino oscillation scenario, where the third neutrino mass state v3 decays into an invisible state, e.g. a sterile neutrino, is considered. We find that KM3NeT/ORCA would be sensitive to invisible neutrino decays with 1/alpha 3 = T3/m3 < 180 ps/eV at 90% confidence level, assuming true normal ordering. Finally, the impact of neutrino decay on the precision of KM3NeT/ORCA measurements for theta(23), Delta m(31)(2) and mass ordering have been studied. No significant effect of neutrino decay on the sensitivity to these measurements has been found.
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LAGUNA-LBNO Collaboration(Agarwalla, S. K., et al), Cervera-Villanueva, A., Gomez-Cadenas, J. J., & Sorel, M. (2014). The mass-hierarchy and CP-violation discovery reach of the LBNO long-baseline neutrino experiment. J. High Energy Phys., 05(5), 094–38pp.
Abstract: The next generation neutrino observatory proposed by the LBNO collaboration will address fundamental questions in particle and astroparticle physics. The experiment consists of a far detector, in its first stage a 20 kt LAr double phase TPC and a magnetised iron calorimeter, situated at 2300 km from CERN and a near detector based on a highpressure argon gas TPC. The long baseline provides a unique opportunity to study neutrino flavour oscillations over their 1st and 2nd oscillation maxima exploring the L/E behaviour, and distinguishing effects arising from delta(CP) and matter. In this paper we have reevaluated the physics potential of this setup for determining the mass hierarchy (MH) and discovering CP-violation (CPV), using a conventional neutrino beam from the CERN SPS with a power of 750 kW. We use conservative assumptions on the knowledge of oscillation parameter priors and systematic uncertainties. The impact of each systematic error and the precision of oscillation prior is shown. We demonstrate that the first stage of LBNO can determine unambiguously the MH to > 5 sigma C.L. over the whole phase space. We show that the statistical treatment of the experiment is of very high importance, resulting in the conclusion that LBNO has similar to 100% probability to determine the MH in at most 4-5 years of running. Since the knowledge of MH is indispensable to extract delta(CP) from the data, the first LBNO phase can convincingly give evidence for CPV on the 3 sigma C.L. using today's knowledge on oscillation parameters and realistic assumptions on the systematic uncertainties.
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Pierre Auger Collaboration(Abreu, P. et al), & Pastor, S. (2012). Search for Point-like Sources of Ultra-high Energy Neutrinos at the Pierre Auger Observatory and Improved Limit on the Diffuse Flux of Tau Neutrinos. Astrophys. J. Lett., 755(1), L4–7pp.
Abstract: The surface detector array of the Pierre Auger Observatory can detect neutrinos with energy E-nu between 10(17) eV and 10(20) eV from point-like sources across the sky south of +55 degrees and north of -65 degrees declinations. A search has been performed for highly inclined extensive air showers produced by the interaction of neutrinos of all flavors in the atmosphere (downward-going neutrinos), and by the decay of tau leptons originating from tau neutrino interactions in Earth's crust (Earth-skimming neutrinos). No candidate neutrinos have been found in data up to 2010 May 31. This corresponds to an equivalent exposure of similar to 3.5 years of a full surface detector array for the Earth-skimming channel and similar to 2 years for the downward-going channel. An improved upper limit on the diffuse flux of tau neutrinos has been derived. Upper limits on the neutrino flux from point-like sources have been derived as a function of the source declination. Assuming a differential neutrino flux k(PS) . E-nu(-2). from a point-like source, 90% confidence level upper limits for k(PS) at the level of approximate to 5x10(-7) and 2.5x10(-6) GeV cm(-2) s(-1) have been obtained over a broad range of declinations from the searches for Earth-skimming and downward-going neutrinos, respectively.
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Real, D., & Calvo, D. (2023). Silicon Photomultipliers for Neutrino Telescopes. Universe, 9(7), 326–14pp.
Abstract: Neutrino astronomy has opened a new window to the extreme Universe, entering into a fruitful era built upon the success of neutrino telescopes, which have already given a new step forward in this novel and growing field by the first observation of steady point-like sources already achieved by IceCube. Neutrino telescopes equipped with Silicon PhotoMultipliers (SiPMs) will significantly increase in number, because of their excellent time resolution and the angular resolution, and will be in better condition to detect more steady sources as well as the unexpected. The use of SiPMs represents a challenge to the acquisition electronics because of the fast signals as well as the high levels of dark noise produced by SiPMs. The acquisition electronics need to include a noise rejection scheme by implementing a coincidence filter between channels. This work discusses the advantages and disadvantages of using SiPMs for the next generation of neutrino telescopes, focusing on the possible developments that could help for their adoption in the near future.
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Real, D., Calvo, D., Zornoza, J. D., Manzaneda, M., Gozzini, R., Ricolfe-Viala, C., et al. (2024). Fast Coincidence Filter for Silicon Photomultiplier Dark Count Rate Rejection. Sensors, 24(7), 2084–12pp.
Abstract: Silicon Photomultipliers find applications across various fields. One potential Silicon Photomultiplier application domain is neutrino telescopes, where they may enhance the angular resolution. However, the elevated dark count rate associated with Silicon Photomultipliers represents a significant challenge to their widespread utilization. To address this issue, it is proposed to use Silicon Photomultipliers and Photomultiplier Tubes together. The Photomultiplier Tube signals serve as a trigger to mitigate the dark count rate, thereby preventing undue saturation of the available bandwidth. This paper presents an investigation into a fast and resource-efficient method for filtering the Silicon Photomultiplier dark count rate. A low-resource and fast coincident filter has been developed, which removes the Silicon Photomultiplier dark count rate by using as a trigger the Photomultiplier Tube input signals. The architecture of the coincidence filter, together with the first results obtained, which validate the effectiveness of this method, is presented.
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Zornoza, J. D. (2021). Review on Indirect Dark Matter Searches with Neutrino Telescopes. Universe, 7(11), 415–10pp.
Abstract: The search for dark matter is one of the hottest topics in Physics today. The fact that about 80% of the matter of the Universe is of unknown nature has triggered an intense experimental activity to detect this kind of matter and a no less intense effort on the theory side to explain it. Given the fact that we do not know the properties of dark matter well, searches from different fronts are mandatory. Neutrino telescopes are part of this experimental quest and offer specific advantages. Among the targets to look for dark matter, the Sun and the Galactic Center are the most promising ones. Considering models of dark matter densities in the Sun, neutrino telescopes have put the best limits on spin-dependent cross section of proton-WIMP scattering. Moreover, they are competitive in the constraints on the thermally averaged annihilation cross-section for high WIMP masses when looking at the Galactic Centre. Other results are also reviewed.
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