Search Results (34)

This paper aims to explore the implications of $U{\left(1\right)}_{L_e-L_{\alpha }}$ gauge symmetries, where $\alpha =\tau ,\mu$, in the neutrino sector through type-(I+II) seesaw mechanisms. To achieve such a hybrid framework, we include a scalar triplet and three right-handed neutrinos. The model can successfully account for the active neutrino masses, mixing angles, mass squared differences, and the CP-violating phase within the $3\sigma$ bounds of NuFit v5.2 neutrino oscillation data. The presence of a new gauge boson at the MeV scale provides an explanation for the muon and electron $(g-2)$ within the confines of their experimental limits. Furthermore, we scrutinize the proposed models in the context of upcoming long-baseline neutrino experiments such as DUNE, P2SO, T2HK, and T2HKK. The findings reveal that P2SO and T2HK have the ability to probe both models in their $5\sigma$-allowed oscillation parameter region, whereas DUNE and T2HKK can conclusively test only the model with $U{\left(1\right)}_{L_e-L_{\mu }}$-symmetry within the $5\sigma$ parameter space if the true values of the oscillation parameters remain consistent with NuFit v5.2. Full article

Within the type-I seesaw mechanism, it is possible to have large (order one) light–heavy neutrino mixing even in the case of low right-handed neutrino mass scale (of the order of GeV). This implies large lepton flavor violation. As an example, we consider the process $\mu \to e\gamma$ that can have a branching of up to ${10}^{-8}$ within type-I seesaw (in contrast with the tiny value ${10}^{-54}$ expected). Such an enhancement of lepton flavor violation can be used to constraint the parameter space of long-lived particle experiments. Full article

Long-baseline neutrino experiments represent the optimal platforms for probing the lepton Yukawa sector of the Standard Model, and significant experiments are either under construction or in the planning stages. This review delves into the scientific motivations behind these facilities, which stem from the pivotal 2012 discovery of the ${\theta }_{13}$ mixing angle. We provide an overview of the two ongoing projects, DUNE and HyperKamiokande, detailing their physics potential and the technical hurdles they face. Furthermore, we briefly examine proposals for forthcoming endeavors and innovative concepts that could push beyond conventional Superbeam technology. Full article

This review provides a succinct overview of the basic aspects of neutrino physics. The topics covered include neutrinos in the standard model and the three-neutrino mixing scheme; the current status of neutrino oscillation measurements and what remains to be determined; the seesaw mechanisms for neutrino mass generation and the associated phenomenology, including the leptogenesis mechanism to explain the observed matter–antimatter asymmetry of the Universe; and models for the origin of the pattern of neutrino mixing and lepton masses based on discrete flavour symmetries and modular invariance. Full article

In the PMNS matrix, the relation $|U_{\mu i}| = |U_{\tau i}|$ (with $i=1,2,3$) is experimentally favored at the present stage. The possible implications of this relation on some hidden flavor symmetry has attracted a lot of interest in the neutrino community. In this paper, we analyze the implications of $|U_{\mu i}| = |U_{\tau i}|$ (with $i=1,2,3$) in the context of the canonical seesaw mechanism. We also show that the minimal $\mu -\tau$ symmetry proposed in JHEP 06 (2022) 034 is a possible but not necessary reason for the above-mentioned relation. Full article

The neutrino sector offers one of the most sensitive probes of new physics beyond the Standard Model of Particle Physics (SM). The mechanism of neutrino mass generation is still unknown. The observed suppression of neutrino masses hints at a large scale, conceivably of the order of the scale of a rand unified theory (GUT), which is a unique feature of neutrinos that is not shared by the charged fermions. The origin of neutrino masses and mixing is part of the outstanding puzzle of fermion masses and mixings, which is not explained ab initio in the SM. Flavor model building for both quark and lepton sectors is important in order to gain a better understanding of the origin of the structure of mass hierarchy and flavor mixing, which constitute the dominant fraction of the SM parameters. Recent activities in neutrino flavor model building based on non-Abelian discrete flavor symmetries and modular flavor symmetries have been shown to be a promising direction to explore. The emerging models provide a framework that has a significantly reduced number of undetermined parameters in the flavor sector. In addition, such a framework affords a novel origin of $\mathcal{C}$$\mathcal{P}$ violation from group theory due to the intimate connection between physical $\mathcal{C}$$\mathcal{P}$ transformation and group theoretical properties of non-Abelian discrete groups. Model building based on non-Abelian discrete flavor symmetries and their modular variants enables the particle physics community to interpret the current and anticipated upcoming data from neutrino experiments. Non-Abelian discrete flavor symmetries and their modular variants can result from compactification of a higher-dimensional theory. Pursuit of flavor model building based on such frameworks thus also provides the connection to possible UV completions: in particular, to string theory. We emphasize the importance of constructing models in which the uncertainties of theoretical predictions are smaller than, or at most compatible with, the error bars of measurements in neutrino experiments. While there exist proof-of-principle versions of bottom-up models in which the theoretical uncertainties are under control, it is remarkable that the key ingredients of such constructions were discovered first in top-down model building. We outline how a successful unification of bottom-up and top-down ideas and techniques may guide us towards a new era of precision flavor model building in which future experimental results can give us crucial insights into the UV completion of the SM. Full article

In this article, we give a brief review of the origin of the neutrino mass in some interesting non-linear supersymmetric models with R-symmetry. These models are able to address and solve the most important problems of particle physics and provide mechanisms for neutrino mass generation and their mixing parameters in agreement with the current experimental data. Their prediction could be experimentally tested in the near future by collider experiments. Full article

We demonstrate that the Finite-Time-Path Field Theory is an adequate tool for calculating neutrino oscillations. We apply this theory using a mass-mixing Lagrangian which involves the correct Dirac spin and chirality structure and a Pontecorvo–Maki–Nakagawa–Sakata (PMNS)-like mixing matrix. The model is exactly solvable. The Dyson–Schwinger equations transform propagators of the input free (massless) flavor neutrinos into a linear combination of oscillating (massive) neutrinos. The results are consistent with the predictions of the PMNS matrix while allowing for extrapolation to early times. Full article

The Majorana phases of neutrino mixing matrix do not appear either in vacuum or in matter modified oscillation probabilities. It was previously shown that for some particular forms of decoherence, the neutrino oscillations do depend on Majorana phases. Here, we show that such dependence also occurs for neutrino decay scenarios where mass eigenstates are not the decay eigenstates. We calculate two flavour survival/oscillation probabilities in such a scenario and discuss their CP and CPT properties. Full article

The Scintillating Bubble Chamber (SBC) collaboration is developing liquid-noble bubble chambers for the detection of sub-keV nuclear recoils. These detectors benefit from the electron recoil rejection inherent in moderately-superheated bubble chambers with the addition of energy reconstruction provided from the scintillation signal. The ability to measure low-energy nuclear recoils allows the search for GeV-scale dark matter and the measurement of coherent elastic neutrino-nucleus scattering on argon from MeV-scale reactor antineutrinos. The first physics-scale detector, SBC-LAr10, is in the commissioning phase at Fermilab, where extensive engineering and calibration studies will be performed. In parallel, a functionally identical low-background version, SBC-SNOLAB, is being built for a dark matter search underground at SNOLAB. SBC-SNOLAB, with a 10 kg-yr exposure, will have sensitivity to a dark matter–nucleon cross section of $2\times {10}^{-42}$ cm${}^2$ at 1 GeV/$c^2$ dark matter mass, and future detectors could reach the boundary of the argon neutrino fog with a tonne-yr exposure. In addition, the deployment of an SBC detector at a nuclear reactor could enable neutrino physics investigations including measurements of the weak mixing angle and searches for sterile neutrinos, the neutrino magnetic moment, and the light Z’ gauge boson. Full article

A non-minimal approximation for effective masses of light and heavy neutrinos in the framework of a type-I seesaw mechanism with three generations of sterile Majorana neutrinos which recover the symmetry between quarks and leptons is considered. The main results are: $\left(a\right)$ the next-order corrections to the effective mass matrix of heavy neutrinos due to terms $\mathcal{O}\left(\theta M_D\right)$ are obtained, which modify the commonly used representation for the effective mass ($M_D$ is a Dirac neutrino mass when the electroweak symmetry is spontaneously broken); and $\left(b\right)$ the general form of the mixing matrix is found in non-minimal approximation parametrized by a complex $3\times 3$ matrix satisfying a nontrivial constraint. Numerical analysis within the $\nu$MSM framework demonstrates the very small effect of new contributions of direct collider observables as opposed to their possible significance for cosmological models. Full article

We propose a phenomenological model of two-zeros Majorana neutrino mass matrix based on the $A_4$ symmetry, where the structure of mixing matrix is a unimodular second scheme of trimaximal $T{M}_2$, and the charged lepton mass matrix is diagonal. We show that, among seven possible two-zero textures with $A_4$ symmetry, only two textures, namely the texture with $M_{ee}=0$ and $M_{e\mu }=0$ and its permutation, are acceptable in the non-perturbation method, since the results associated with these two textures are consistent with the experimental data. We obtain a unique relation between our phases, namely $\rho +\sigma =\varphi \pm \pi$, and an effective equation ${sin}^2{\theta }_{13}=\frac{2}{3}{R}_{\nu }$ where $R_{\nu }=\frac{\delta m^2}{\Delta m^2}$. Then, only by using the experimental ranges of $R_{\nu }$, we obtain the allowable range of the unknown parameter $\varphi$ as the phase of $T{M}_2$ mixing matrix, which leads to obtaining not only the ranges of all neutrino oscillation parameters of the model (which agree well with experimental data) but also with the masses of neutrinos, the Dirac and Majorana phases and the Jarlskog parameter, and to predict the normal neutrino mass hierarchy. Finally, we show that all the predictions regarding our two specific textures agree with the corresponding data reported from neutrino oscillation, cosmic microwave background and neutrinoless double beta decay. Full article

We present a method to identify symmetry groups of the Yukawa sector of the three-Higgs-doublet model and to determine the implication that the symmetry has on the lepton masses and mixing. The method can accommodate different hypotheses about the group representation assignments, and thus support the exploration of candidate symmetry groups. For one particular representation selection scheme we apply the computer-implemented method to scan all discrete groups of order less than 1035. It can be proven that none of these groups defines a flavor symmetry that implies masses and neutrino mixing angles consistent with the experimental lepton data, although several cases are found that are partially or approximately consistent. Full article

The overall characteristics of the solar and atmospheric neutrino oscillations are approximately consistent with a tribimaximal form of the mixing matrix U of the lepton sector. Exact tribimaximal mixing leads to ${\theta }_{13}=0$. However, the results from the Daya Bay and RENO experiments have established, such that in comparison to the other neutrino mixing angles, ${\theta }_{13}$ is small. Moreover, the atmospheric and solar mass splitting differ by two orders of magnitude. These significant differences constitutes the great enthusiasm and main motivation for our research herein reported. Keeping the behavior of U as tribimaximal, we would make a response to the following questions: at some level, whether or not the small parameters such as the solar neutrino mass splitting and $U_{e3}$, which vanish in a new framework, can be interpreted as a modified FL neutrino mass model? Subsequently, a minimal single perturbation leads to nonzero values for both of them? Our minimal perturbation matrix is constructed solely from computing the third mass eigenstate, using the rules of perturbation theory. Let us point out that, unlike other investigations, this matrix is not adopted on an ad hoc basis, but is created following a series of steps that we will describe. Also in compared to the original FL neutrino mass model which generalize it by inserting phase factors, our work is more accurate. Subsequently, we produce the following results that add new contributions to the literature: (a) we obtain a realistic neutrino mixing matrix with $\delta \ne 0$ and ${\theta }_{23}={45}^{\circ }$; (b) the solar mass splitting term is dominated by an imaginary term, which could induce the existence of Majorana neutrinos, along with explaining a large CP violation in nature; (c) the ordering of the neutrino masses is normal; however, at the end of the allowed range, it becomes more degenerate ($97\%$); (d) we also obtain the allowed range of the mass parameters, which not only are in accordance with the experimental data but also allow falsifiable predictions for the masses of the neutrinos and the CP violating phases which none of these results has been achieved in the original FL neutrino mass model. Finally, let us emphasize that the results obtained by our framework here are much more efficient compared to those obtained in previous works in terms of currently available experimental data (namely, the best fit column). Full article

The ${\nu }_{\mu }\to {\nu }_e$ oscillation probability over a short baseline (≲1 km) would be negligible for the case when the mixing matrix for three active neutrinos is unitary. However, in the case of a non-unitary mixing of three neutrinos, this probability would be non-negligible due to the so-called “zero distance” effect. Hence, the near detector of accelerator experiments such as NO$\nu$A can provide strong constraints on the parameters of the non-unitary mixing with very large statistics. By analyzing the NO$\nu$A near-detector data, we find that the non-unitary mixing does not improve fits to the ${\nu }_e$ or ${\nu }_{\mu }$ events over the standard unitary mixing. This leads to constraints on the non-unitary parameters: ${\alpha }_{00}>0.911$, $|{\alpha }_{10}|<0.020$, and ${\alpha }_{11}>0.952$ at 90% C.L. A combined analysis with the near- and far-detector data does not change these constraints significantly. Full article