Scalar NSI: a unique tool for constraining absolute neutrino masses via neutrino oscillations

The origin of neutrino masses remains unknown. Both the vacuum mass and the dark mass generated by the neutrino interaction with dark matter (DM) particles or fields can fit the current oscillation data. The dark mass squared is proportional to the DM number density and, therefore, varies on the galactic scale with much larger values around the Galactic Center. This affects the group velocity and the arrival time delay of core-collapse supernovae (SN) neutrinos. This time delay, especially for the ν_{e} neutronization peak with a sharp time structure, can be used to distinguish the vacuum and dark neutrino masses. For illustration, we explore the potential of the Deep Underground Neutrino Experiment (DUNE), which is sensitive to ν_{e}. Our simulations show that DUNE can distinguish the two neutrino mass origins at more than 5σ C.L., depending on the observed local value of neutrino mass, the neutrino mass ordering, the DM density profile, and the SN location.

Neutrino oscillation and tritium beta decay experiments taken simultaneously\ninto account are able to access the so far imperceptible absolute neutrino\nmasses at the electronvolt level. The neutrino mass spectrum derived in this\nway is independent of the nature of neutrinos (Dirac or Majorana). Furthermore,\nthe lack of neutrinoless double beta decay gives additional constraints on the\nMajorana neutrino mass spectrum. A case of three neutrinos is examined.\nInfluence of different solutions to the solar neutrino deficit problem on the\nresults is discussed. Apart from the present situation, four qualitatively\ndistinct experimental situations which are possible in the future are\ninvestigated: when the two decay experiments give only upper bounds on\neffective neutrino masses, when either one of them gives a positive result, and\nwhen both give positive results. The discussion is carried out by taking into\naccount the present experimental errors of relevant neutrino parameters as well\nas their much more precise expected estimations (e.g. by $\\nu$ factories). It\nis shown in which cases the upgraded decay experiments simultaneously with\nneutrino oscillation data may be able to fix the absolute scale of the neutrino\nmass spectrum, answer the question of the neutrino nature and put some light on\nCP phases in the lepton sector.\n

Neutrino masses are yet unknown. We discuss the present state of effective electron antineutrino mass fromβdecay experiments; effective Majorana neutrino mass from neutrinoless double-beta decay experiments; neutrino mass squared differences from neutrino oscillation: solar, atmospheric, reactor, and accelerator-based experiments; sum of neutrino masses from cosmological observations. Current experimental challenges in the determination of neutrino masses are briefly discussed. The main focus is devoted to contemporary experiments.

Recent results from neutrino oscillation experiments have convincingly demonstrated that neutrinos have mass and they can mix. The neutrinoless double beta decay is the most sensitive process to determine the absolute scale of the neutrino masses, and the only one that can distinguish whether neutrino is a Dirac or a Majorana particle. A key ingredient for extracting the absolute neutrino masses from neutrinoless double beta decay experiments is a precise knowledge of the nuclear matrix elements (NME) for this process. Newly developed shell model approaches for computing the NME and half‐lifes for the two‐neutrino and neutrinoless double beta decay modes using modern effective interactions are presented. The implications of the new results on the experimental limits of the effective neutrino mass are discussed by comparing the decays of 48Ca and 76Ge.

This study examines the precise measurement of the largest leptonic mixing angle $\theta _{23}$ through the analysis of neutrino oscillation data samples. Our findings indicate that the $\overset{{(\_)}}{\nu }_{\mu }\rightarrow \overset{{{ {(}}}\_{{)}}}{\nu }_{e}$ appearance samples, rather than the $\overset{{{ {(}}}\_{{)}}}{\nu }_{\mu }\rightarrow \overset{{{ {(}}}\_{{)}}}{\nu }_{\mu }$ disappearance samples, are sensitive to testing the hypothesis of maximal mixing $\theta _{23} = \pi /4$, particularly if $\theta _{23}$ resides in the higher octant and $\sin ^2\theta _{23} < 0.54$. The former serves as the primary source for determining the octant of the $\theta _{23}$ mixing angle; however, the latter remains relevant for wide-band energy experiments like the Deep Underground Neutrino Experiment (DUNE) if $\theta _{23}$ deviates significantly from the maximal value. In the joint analysis of a coming accelerator-based long-baseline neutrino experiment, namely, Hyper-Kamiokande (T2HK) and DUNE with ultimate precision 1% on $\sin ^{2}\theta _{13}$, utilizing only appearance sub-samples can exclude the maximal mixing and determine the actual octant for about 64% of the currently allowed range of the $\theta _{23}$ angle. We argue, that despite the presence of parameter degeneracy, the precise measurement of $\theta _{23}$ exhibits minimal dependence on other unknown factors, including the CP-violation phase and neutrino mass ordering.

This dissertation presents the search for large extra dimensions using the rich and unique accelerator beam neutrino data collected by the MINOS and MINOS+ experiments from 2005 to 2012 and 2013 to 2016, respectively. Most data from neutrino oscillation experiments are consistent with the standard three-flavor paradigm. With increasing experimental precision, potential effects from physics beyond the Standard Model that could modify neutrino oscillations in subtle ways can be explored. One such scenario involves additional spatial dimensions. Following the Large Extra Dimensions (LED) model, sterile neutrinos arising as Kaluza-Klein states in an extra dimension with size R can mix with the three active neutrinos in 3+1 spacetime, thereby altering the neutrino oscillation probabilities. In addition, this model provides a natural explanation for small Dirac neutrino masses through mass suppression by the volume of the large extra dimensions. In this work, two analysis strategie s are employed to search for large extra dimensions: the Far-over-Near analysis and the two-detector analysis. In the former, the ratio of the neutrino energy spectra measured in the MINOS Far and Near Detectors is used to constrain the LED model parameters, while in the latter the measured spectra are used simultaneously. MINOS reported the strongest constraint on R from a neutrino oscillation experiment, constraining R to be smaller than $0.45\,\mu\text{m}$ at 90\% C.L. in the limit of a vanishing lightest neutrino mass, using the Far-over-Near approach. Including MINOS+ data, which significantly increases the number of events at higher neutrino energies away from the three-flavor minimum where the model effects are larger, and using the two-detector technique, the size of extra dimensions is further constrained to be smaller than $0.30\,\mu\text{m}$ at 90\% C.L. Stronger limits are obtained for non-vanishing lightest neutrino masses.

This paper aims at solving several open questions in current neutrino physics: the neutrino mass hierarchy, the Dirac CP violating phase, the absolute mass of neutrinos, the nature of neutrinos (Dirac or Majorana), the Majorana matrix and the absolute value of the effective Majorana neutrino mass. In the research presented in this paper, we have shown that the precise definition of the mass splittings between neutrino mass eigenstates, done in the latest analysis of experimental data, can be of crucial importance for defining the nature of neutrino mass hierarchy. The Standard Model has three generations of fundamental matter particles. Three generations of the charged lepton mass show a hierarchical structure: mτ > mμ > me. Owing to that, there is a belief and it is considered that neutrinos may follow such hierarchical structure. In our calculations, we have also included the latest data obtained, based on the processing of measurement results, which showed that even with such data, obtained results favor the normal neutrino mass hierarchy. As for the individual neutrino mass calculated in this paper, in today’s neutrino physics it is only known that neutrino mass scale is bounded only from above, and both the Dirac and the Majorana character of neutrinos are compatible with all observations. Among some of the questions resolved in this paper, which are related to the properties of neutrinos, a positive answer was also given to the question of whether light neutrinos are self-conjugate particles or not.

The Deep Underground Neutrino Experiment (DUNE) is a long-baseline neutrino oscillation experiment that aims to measure whether CP is violated in the leptonic sector (if violated, how much) and unambiguously determine the neutrino mass ordering. DUNE consists of near and far detectors that rely on liquid argon time projection chamber (LArTPC) technology to observe neutrino interactions. The near detector (ND) will be placed in Fermilab, near the neutrino source, while the far detector (FD) will be deployed in Sanford Lab, 1.5 km deep underground, which is 1300 km away from the source. LArTPCs provide excellent particle identification and calorimetry; however, detecting neutrons is challenging, as they do not leave direct ionization signals in LArTPCs. Neutrons can carry away up to 25% of the neutrino energy, introducing a significant uncertainty in DUNE measurements. The DUNE near detector (ND) features a novel modular LArTPC with pixelated charge readout, which enhances event recons truction. The modular design enables precise correlation between ionization signals and light signals in a high-rate environment, improving the identification of delayed energy depositions from neutrons in neutrino interactions. We introduce a neutron tagging technique using the 2x2 Demonstrator, a small-scale prototype of the DUNE ND LArTPC. The analysis utilizes Monte Carlo simulations and deep-learning techniques to identify neutron-induced energy depositions and reconstruct low-energy activity.

Next generation tritium decay experiments to determine the absolute neutrino mass require high-precision measurements of β -decay electron energies close to the kinematic end point. To achieve this, the development of high phase-space density sources of atomic tritium is required, along with the implementation of methods to control the motion of these atoms to allow extended observation times. A promising approach to efficiently and accurately measure the kinetic energies of individual β -decay electrons generated in these dilute atomic gases, is to determine the frequency of the cyclotron radiation they emit in a precisely characterised magnetic field. This cyclotron radiation emission spectroscopy technique can benefit from recent developments in quantum technologies. Absolute static-field magnetometry and electrometry, which is essential for the precise determination of the electron kinetic energies from the frequency of their emitted cyclotron radiation, can be performed using atoms in superpositions of circular Rydberg states. Quantum-limited microwave amplifiers will allow precise cyclotron frequency measurements to be made with maximal signal-to-noise ratios and minimal observation times. Exploiting the opportunities offered by quantum technologies in these key areas, represents the core activity of the Quantum Technologies for Neutrino Mass project. Its goal is to develop a new experimental apparatus that can enable a determination of the absolute neutrino mass with a sensitivity on the order of 10 meV / c 2 .

A bstract We present a comprehensive model independent analysis of all breaking patterns resulting from ∆(96) ⋊ H CP in the tri-direct CP approach of the minimal seesaw model with two right-handed neutrinos. The three generations of left-handed lepton doublets are assumed to transform as the irreducible triplet 3 0 of ∆(96), and the two right-handed neutrinos are assigned to singlets. In the case that both flavon fields ϕ atm and ϕ sol transform as triplet $$ {\overline{\textbf{3}}}_{\textbf{0}} $$ 3 ¯ 0 , only one phenomenologically viable lepton mixing pattern is obtained for normal ordering neutrino masses. The lepton mixing matrix is predicted to be the TM1 pattern, with neutrino masses, mixing angles, and CP violation phases depending on only three real input parameters. When ϕ sol is assigned to the $$ {\overline{\textbf{3}}}_{\textbf{1}} $$ 3 ¯ 1 representation, an additional real parameter x must be included. Then we find 42 (12) independent phenomenologically interesting mixing patterns for normal (inverted) ordering neutrino masses, and the corresponding predictions for lepton mixing parameters and neutrino masses are obtained. Furthermore, we perform a detailed numerical analysis for five (one) example breaking patterns with some benchmark values of x for normal (inverted) ordering. For the five normal examples, the absolute values of the first columns of the PMNS matrix are fixed to be $$ {\left(\sqrt{\frac{2}{3}},\frac{1}{\sqrt{6}},\frac{1}{\sqrt{6}}\right)}^T $$ 2 3 1 6 1 6 T , $$ \frac{1}{5}{\left(\sqrt{17},2,2\right)}^T $$ 1 5 17 2 2 T , $$ \frac{1}{\sqrt{38}}{\left(5,2,3\right)}^T $$ 1 38 5 2 3 T , $$ \frac{1}{\sqrt{57}}{\left(\sqrt{37},\sqrt{10},\sqrt{10}\right)}^T $$ 1 57 37 10 10 T and $$ \frac{1}{3}{\left(\sqrt{6},1,\sqrt{2}\right)}^T $$ 1 3 6 1 2 T , respectively. For the inverted example, the absolute value of the third column of the PMNS matrix is $$ \frac{1}{2\sqrt{11}}{\left(1,5,3\sqrt{2}\right)}^T $$ 1 2 11 1 5 3 2 T .

I discuss neutrino mixing ansatze, such as the generalized Tri-bimaximal and bi-large mixing patterns, and their utility in describing neutrino oscillation data. Unitarity tests and probes of the absolute neutrino mass scale are briefly discussed. A short overview of neutrino mass generation is given, including an orbifold approach to the flavor problem and the resulting implications, e.g. the golden quark-lepton mass relation, neutrinoless double beta decay and neutrino oscillation predictions.

The most direct way to get information on neutrino masses is the investigation of weak decays and tritium is the best candidate due to its high specific activity and low endpoint energy. The relevance of this approach is based on the following arguments: • Neutrinos are not massless as we have convincing evidence for neutrino oscillations from experiments detecting atmospheric and solar neutrinos. The signals are interpreted as differences in the squares of neutrino masses from which a lower bound for the neutrino masses can be derived. • As these differences are rather small one can set limits for all neutrino masses from the lowest upper bound which is set by the Mainz group from tritium β decay: mv2 = −1.6 ± 2.5 ± 2.1 eV2/c4 corresponding to an upper limit of mv < 2.2 eV/c2 (95 % C.L.). Hence the sum of the three neutrino masses is less than about 7 eV/c2 The results are of interest for cosmology as neutrinos are part of the hot dark matter. The minimum total mass deduced from oscilation experiments is about equal to the sum of the stellar masses. The present upper bound from the direct mass measurements is about equal to the limit given by structure formation. The result of the two presently working experiments in Mainz and Troitsk and their systematic uncertainties will be presented. These experiment have almost reached their sensitivity limits. A next generation experiment KATRIN will be set up at Forschungszentrum Karlsruhe. Its aim is to push the sensitivity limit to mv < 0.3 eV/c2 (90 % C.L.). This would fully cover the cosmologically relevant parameter space and set the neutrino mass scale to discriminate between models with degenerated and hierachical neutrino mass scenarios.

In this talk I present the results from our global fit to neutrino oscillation data. Neutrino oscillation experiments have reached a very good level in precision. Due to correlations among parameters a global fit combining many different datasets can give more precise results than a single experiment on its own. I will present the results of the latest global fit performed by our group and focus on the remaining unknowns in the standard picture: Atmospheric octant, CP violation and neutrino mass ordering.

We define the theoretical framework and deduce the conditions under which\nmulti-messenger astronomy can provide useful information about neutrino masses\nand their ordering. The framework uses time differences between the arrival of\nneutrinos and the other light messenger, i.e. the graviton, emitted in\nastrophysical catastrophes. We also provide a preliminary feasibility study\nelucidating the experimental reach and challenges for planned neutrino\ndetectors such as Hyper-Kamiokande as well as future several megaton detectors.\nThis study shows that future experiments can be useful in testing independently\nthe cosmological bounds on absolute neutrino masses. Concretely the success of\nsuch measurements depends crucially on the available rate of astrophysical\nevents and further requires development of high resolution timing besides the\nadvocated need of megaton size detectors.\n

We propose two different seesaw models namely, type I and inverse seesaw to realise light Dirac neutrinos within the framework of A4 discrete flavour symmetry. The additional fields and their transformations under the flavour symmetries are chosen in such a way that naturally predicts the hierarchies of different elements of the seesaw mass matrices in these two types of seesaw mechanisms. For generic choices of flavon alignments, both the models predict normal hierarchical light neutrino masses with the atmospheric mixing angle in the lower octant. Apart from predicting interesting correlations between different neutrino parameters as well as between neutrino and model parameters, the model also predicts the leptonic Dirac CP phase to lie in a specific range −π/3 to π/3. While the type I seesaw model predicts smaller values of absolute neutrino mass, the inverse seesaw predictions for the absolute neutrino masses can saturate the cosmological upper bound on sum of absolute neutrino masses for certain choices of model parameters.