KM3NeT sensitivity to low energy astrophysical neutrinos

KM3NeT, a new generation of neutrino telescope, is currently being deployed in the Mediterranean Sea. While its two sites, ORCA and ARCA, were respectively designed for the determination of neutrino mass hierarchy and high-energy neutrino astronomy, this contribution presents a study of the detection potential of KM3NeT in the MeV-GeV energy range. At these low energies, the data rate is dominated by low-energy atmospheric muons and environmental noise due to bioluminescence and K-40 decay. The goal of this study is to characterize the environmental noise in order to optimize the selection of low-energy neutrino interactions and increase the sensitivity of KM3NeT to transient astrophysical phenomena, such as close-by core-collapse supernovae, solar flares, and extragalactic transients. In this contribution, we will study how using data science tools might improve the sensitivity of KM3NeT in these low-energy neutrino searches. We will first introduce the data sets and the different variables used to characterize KM3NeT’s response to the environmental noise. We will then compare the efficiency of various tools in identifying different components in the environmental noise and in disentangling low-energy neutrino interactions from the background events. We will conclude with the implication of low-energy neutrinos for future astrophysical transient searches.

Analysis of the first KM3NeT-ORCA data

ORCA, Oscillation Research with Cosmics in the Abyss, is the low energy KM3NeT neutrino underwater detector, located in the French Mediterranean Sea. It comprises a dense array of optical modules designed to detect Cherenkov light emitted from charged particles resulting from neutrino interactions in the vicinity of the detector. Its main physics goal is the determination of the neutrino mass hierarchy by quantifying the matter-induced effect on the oscillation probabilities of atmospheric neutrinos in the energy range, 3–50 GeV, where the effects of neutrino oscillation phenomena are dominant. In 2019, four detection units were operational. Two more had been added in early 2020. This work presents an overview of the detector performance in the 2019 configuration, as well as its sensitivity to neutrino oscillations.

Summary of the R&D of 20-inch MCP-PMTs for neutrino detection

The Jiangmen Underground Neutrino Observatory (JUNO) in China aiming to determine the neutrino mass hierarchy is under construction. A new kind of large area microchannel-plate photomultiplier tube (MCP-PMT) was put forward for the JUNO by the researchers in Institute of High Energy Physics (IHEP) in China. After breaking through several core technotical barriers, the 20-inch MCP-PMT prototype with great performance was successfully produced by the MCP-PMT group in China and got 75% PMT orders (15,000 pics) from JUNO. The mass production line and batch test system was completed in North Night Vision Technology Co., Ltd. (NNVT). The performance of the MCP-PMT including the gain, the quantum efficiency, the P/V ratio, the dark count rate and the transit time spread can be batch tested. During the mass production process, the technical progress in the cathode deposition method improved the quantum efficiency of the photocathode from 30% to 35%. The aging behaviour, temperature effect, the after-pulse distribution and the flash signal of the 20-inch MCP-PMT are all detailly studied. By August of 2020, the 15,000 MCP-PMTs, which will be installed as the central liquid scintillator detector of JUNO, have been completed and delivered to Jiangmen. The average QE at 400 nm for the 15,000 pieces of MCP-PMTs is 32%.

Controlled fermion mixing and FCNCs in a ∆(27) 3+1 Higgs Doublet Model

We propose a 3+1 Higgs Doublet Model based on the ∆(27) family symmetry supplemented by several auxiliary cyclic symmetries leading to viable Yukawa textures for the Standard Model fermions, consistent with the observed pattern of fermion masses and mixings. The charged fermion mass hierarchy and the quark mixing pattern is generated by the spontaneous breaking of the discrete symmetries due to flavons that act as Froggatt-Nielsen fields. The tiny neutrino masses arise from a radiative seesaw mechanism at one loop level, thanks to a preserved $$ {Z}_2^{(1)} $$ Z 2 1 discrete symmetry, which also leads to stable scalar and fermionic dark matter candidates. The leptonic sector features the predictive cobimaximal mixing pattern, consistent with the experimental data from neutrino oscillations. For the scenario of normal neutrino mass hierarchy, the model predicts an effective Majorana neutrino mass parameter in the range 3 meV ≲ mββ ≲ 18 meV, which is within the declared range of sensitivity of modern experiments. The model predicts Flavour Changing Neutral Currents which constrain the model, for instance, μ→e nuclear conversion processes and Kaon mixing are found to be within the reach of the forthcoming experiments.

Detection techniques and investigation of different neutrino experiments

Neutrino physics is an experimentally driven field. So, we investigate the different detection techniques available in the literature and study the various neutrino oscillation experiments in a chronological manner. Our primary focus is on the construction and detection mechanisms of each experiment. Today, we know a lot about this mysterious ghostly particle by performing different experiments at different times with different neutrino sources, viz. solar, atmospheric, reactor, accelerators and high-energy astrophysical; and they have contributed in the determination of neutrino parameters. Yet the problems are far from over. We need to determine more precise values of the already known parameters and unravel the completely unknown parameters. Some of the unknowns are absolute masses of neutrino, types of neutrino, mass hierarchy, octant degeneracy and existence of leptonic CP phase(s). We analyze the neutrino experiments into the past, present and the future (or proposed). We include SNO, Kamiokande, K2K, MINOS, MINOS+, Chooz, NEMO and ICARUS in the past; while Borexino, Double Chooz, Super-K, T2K, IceCube, KamLAND, NO[Formula: see text]A, RENO and Daya Bay in the present; and SNO+, Hyper-K, T2HK, JUNO, RENO-50, INO, DUNE, SuperNEMO, KM3NeT, P2O, LBNO and PINGU in the proposed experiments. We also discuss the necessities of upgrading the present ones to those of the proposed ones thereby summarizing the potentials of the future experiments. We conclude this paper with the current status of the neutrinos.

Electric dipole moments in the extended scotogenic models

Electric dipole moments (EDMs) of charged leptons arise from a new source of CP violation in the lepton sector. In this paper, we calculate the EDMs of the charged leptons in the minimal scotogenic model with two singlet fermions, and the models extended with one or two triplet fermions instead of the singlet fermions, taking into account the constraints of the neutrino oscillation data, the charged lepton flavor violation and perturbative unitarity bound for the Yukawa couplings. We show that the hybrid model with one singlet and one triplet fermions predicts an electron EDM larger than the other models in both normal and inverted neutrino mass hierarchy. We find some parameter space has already been ruled out by the current upper bound of the electron EDM and further parameter space can be explored by future experiments.

Characterization of cubic Li$$_{2}$$$$^{100}$$MoO$$_4$$ crystals for the CUPID experiment

The CUPID Collaboration is designing a tonne-scale, background-free detector to search for double beta decay with sufficient sensitivity to fully explore the parameter space corresponding to the inverted neutrino mass hierarchy scenario. One of the CUPID demonstrators, CUPID-Mo, has proved the potential of enriched Li$$_{2}$$ 2 $$^{100}$$ 100 MoO$$_4$$ 4 crystals as suitable detectors for neutrinoless double beta decay search. In this work, we characterised cubic crystals that, compared to the cylindrical crystals used by CUPID-Mo, are more appealing for the construction of tightly packed arrays. We measured an average energy resolution of ($$6.7\pm 0.6$$ 6.7 ± 0.6 ) keV FWHM in the region of interest, approaching the CUPID target of 5 keV FWHM. We assessed the identification of $$\alpha $$ α particles with and without a reflecting foil that enhances the scintillation light collection efficiency, proving that the baseline design of CUPID already ensures a complete suppression of this $$\alpha $$ α -induced background contribution. We also used the collected data to validate a Monte Carlo simulation modelling the light collection efficiency, which will enable further optimisations of the detector.

Sterile neutrino dark matter and leptogenesis in Left-Right Higgs Parity

The standard model Higgs quartic coupling vanishes at (109 − 1013) GeV. We study SU(2)L× SU(2)R× U(1)B−L theories that incorporate the Higgs Parity mechanism, where this becomes the scale of Left-Right symmetry breaking, vR. Furthermore, these theories solve the strong CP problem and predict three right-handed neutrinos. We introduce cosmologies where SU(2)R× U(1)B−L gauge interactions produce right-handed neutrinos via the freeze-out or freeze-in mechanisms. In both cases, we find the parameter space where the lightest right-handed neutrino is dark matter and the decay of a heavier one creates the baryon asymmetry of the universe via leptogenesis. A theory of flavor is constructed that naturally accounts for the lightness and stability of the right-handed neutrino dark matter, while maintaining sufficient baryon asymmetry. The dark matter abundance and successful natural leptogenesis require vR to be in the range (1010− 1013) GeV for freeze-out, in remarkable agreement with the scale where the Higgs quartic coupling vanishes, whereas freeze-in requires vR ≳ 109 GeV. The allowed parameter space can be probed by the warmness of dark matter, precise determinations of the top quark mass and QCD coupling by future colliders and lattice computations, and measurement of the neutrino mass hierarchy.