Neutrino Oscillations in Matter using the Adjugate of the Hamiltonian

We revisit neutrino oscillations in constant matter density for a number of different scenarios: three flavors with the standard Wolfenstein matter potential, four flavors with standard matter potential and three flavors with non-standard matter potentials. To calculate the oscillation probabilities for these scenarios one must determine the eigenvalues and eigenvectors of the Hamiltonians. We use a method for calculating the eigenvalues that is well known, determination of the zeros of determinant of matrix $(\lambda I -H)$, where H is the Hamiltonian, I the identity matrix and $\lambda$ is a scalar. To calculate the associated eigenvectors we use a method that is little known in the particle physics community, the calculation of the adjugate (transpose of the cofactor matrix) of the same matrix, $(\lambda I -H)$. This method can be applied to any Hamiltonian, but provides a very simple way to determine the eigenvectors for neutrino oscillation in matter, independent of the complexity of the matter potential. This method can be trivially automated using the Faddeev-LeVerrier algorithm for numerical calculations. For the above scenarios we derive a number of quantities that are invariant of the matter potential, many are new such as the generalization of the Naumov-Harrison-Scott identity for four or more flavors of neutrinos. We also show how these matter potential independent quantities become matter potential dependent when off-diagonal non-standard matter effects are included.Comment: 34 page

The present and future status of heavy neutral leptons

Artículo escrito por un elevado número de autores, solo se referencian el que aparece en primer lugar, los autores pertenecientes a la UAM y el nombre del grupo de colaboración, si lo hubiereThe existence of nonzero neutrino masses points to the likely existence of multiple Standard Model neutral fermions. When such states are heavy enough that they cannot be produced in oscillations, they are referred to as heavy neutral leptons (HNLs). In this white paper, we discuss the present experimental status of HNLs including colliders, beta decay, accelerators, as well as astrophysical and cosmological impacts. We discuss the importance of continuing to search for HNLs, and its potential impact on our understanding of key fundamental questions, and additionally we outline the future prospects for next-generation future experiments or upcoming accelerator run scenario

Semi-Visible Dark Photon Phenomenology at the GeV Scale

In rich dark sector models, dark photons heavier than tens of MeV can behave as semi-visible particles: their decays contain both visible and invisible final states. We present models containing multiple dark fermions which allow for such decays and inscribe them in the context of inelastic dark matter and heavy neutral leptons scenarios. Our models represent a generalization of the traditional inelastic dark matter model by means of a charge conjugation symmetry. We revisit constraints on dark photons from $e^+e^-$ colliders and fixed target experiments, including the effect of analysis vetoes on semi-visible decays, $A^\prime \to \psi_i (\psi_j \to \psi_k \ell^+\ell^-)$. We find that in some cases, the BaBar and NA64 experiments no longer exclude large kinetic mixing, $\varepsilon \sim 10^{-2}$, and, specifically, the related explanation of the discrepancy in the muon $(g-2)$. This reopens an interesting window in parameter space for dark photons with exciting discovery prospects. We point out that a modified missing-energy search at NA64 can target short-lived $A^\prime$ decays and directly probe the newly-open parameter space.Comment: 41 pages, 22 figures, version published in PR

A panorama of new-physics explanations to the MiniBooNE excess

The MiniBooNE low-energy excess stands as an unexplained anomaly in short-baseline neutrino oscillation experiments. It has been shown that it can be explained in the context of dark sector models. Here, we provide an overview of the possible new-physics solutions based on electron, photon, and dilepton final states. We systematically discuss the various production mechanisms for dark particles in neutrino-nucleus scattering. Our main result is a comprehensive fit to the MiniBooNE energy spectrum in the parameter space of dark neutrino models, where short-lived heavy neutral leptons are produced in neutrino interactions and decay to $e^+e^-$ pairs inside the detector. For the first time, other experiments will be able to directly confirm or rule out dark neutrino interpretations of the MiniBooNE low-energy excess.Comment: 35 pages, 21 figure

DarkNews: a Python-based event generator for heavy neutral lepton production in neutrino-nucleus scattering

We introduce DarkNews, a lightweight Python-based Monte-Carlo generator for beyond-the-Standard-Model neutrino-nucleus scattering. The generator handles the production and decay of heavy neutral leptons via additional vector or scalar mediators, as well as through transition magnetic moments. DarkNews samples pre-computed neutrino-nucleus upscattering cross sections and heavy neutrino decay rates to produce dilepton and single-photon events in accelerator neutrino experiments. We present two case studies with differential distributions for models that can explain the MiniBooNE excess. The aim of this code is to aid the neutrino theory and experimental communities in performing searches and sensitivity studies for new particles produced in neutrino upscattering.Comment: 18 pages, 6 tables, 8 figure

Heavy Neutral Leptons via Axion-Like Particles at Neutrino Facilities

Heavy neutral leptons (HNLs) are often among the hypothetical ingredients behind nonzero neutrino masses. If sufficiently light, they can be produced and detected in fixed-target-like experiments. We show that if the HNLs belong to a richer -- but rather generic -- dark sector, their production mechanism can deviate dramatically from expectations associated to the standard-model weak interactions. In more detail, we postulate that the dark sector contains an axion-like particle (ALP) that naturally decays into HNLs. Since ALPs mix with the pseudoscalar hadrons, the HNL flux might be predominantly associated to the production of neutral mesons (e.g., $\pi^0$, $\eta$) as opposed to charge hadrons (e.g., $\pi^\pm$, $K^\pm$). In this case, the physics responsible for HNL production and decay are not directly related and experiments like DUNE might be sensitive to HNLs that are too weakly coupled to the standard model to be produced via weak interactions, as is generically the case of HNLs that play a direct role in the type-I seesaw mechanism.Comment: 5 pages, 4 figure

Laundry soap production from the respective tallows of goat, sheep and cow: evaluation of physicochemical properties for the best

Tallow mainly consists of triglycerides, whose major constituents are derived from stearic, palmitic and oleic acids, and its usage reduces production cost of soap, adds lather stability and hardness to soap. Laundry soaps were produced with variation on amount of tallow (sourced from cow, sheep and goat) and labelled as A, B, C, D and E formulations. The respective tallows were characterized in terms of saponification value and acid value and determined to be 192.14 and 2.24mg KOH/g (cow tallow); 200.56 and 2.38mgKOH/g (sheep tallow) and 197.75 and 1.96 mgKOH/g (goat tallow). The physicochemical properties of soap which determine its area of usage and cleansing properties were determined. The properties considered in this work were hardness, moisture content, foam capacity, pH, free acidity content, and total fatty matter. The hardness, moisture content, foam capacity, pH, free acidity content and total fatty matter of the produced soaps were determined and ranged between mild-deep penetration level; 11-21%; 1-9cm; 8-10.5; 0.16-0.82% and 40-86% respectively. From the comparative analysis, soap made from sheep tallow has the lowest penetration level (with formulations B and E), lowest free acidity content of 0.16% (with formulation A), highest total fatty matter of 86% (using formulation E), highest foam height of 9cm (with formulation A), lowest moisture content of 11% (with formulation A) and mild alkalinity of 8 (with formulations A, B and E). These results showed that the soaps produced from sheep tallow are the best in terms of hardness, lather and skin friendliness, due to its high degree of longer carbon chain lengths of fatty acids. These values satisfy the standard limit set for good quality laundry soap by National Agency for Food and Drug Administration and Control and Encyclopaedia of Industrial Chemical Analysis, respectively

The present and future status of heavy neutral leptons

The existence of nonzero neutrino masses points to the likely existence of multiple Standard Model neutral fermions. When such states are heavy enough that they cannot be produced in oscillations, they are referred to as heavy neutral leptons (HNLs). In this white paper, we discuss the present experimental status of HNLs including colliders, beta decay, accelerators, as well as astrophysical and cosmological impacts. We discuss the importance of continuing to search for HNLs, and its potential impact on our understanding of key fundamental questions, and additionally we outline the future prospects for next-generation future experiments or upcoming accelerator run scenarios.Peer reviewe

Visible decay of astrophysical neutrinos at IceCube

Neutrino decay modifies neutrino propagation in a unique way; not only is there flavor changing as there is in neutrino oscillations, there is also energy transport from initial to final neutrinos. The most sensitive direct probe of neutrino decay is currently IceCube which can measure the energy and flavor of neutrinos traveling over extragalactic distances. For the first time, we calculate the flavor transition probability for the cases of visible and invisible neutrino decay, including the effects of the expansion of the Universe, and consider the implications for IceCube. As an example, we demonstrate how neutrino decay addresses a tension in the IceCube data

A dark seesaw solution to low energy anomalies: MiniBooNE, the muon (g − 2), and BaBar

A recent update from MiniBooNE has strengthened the observed 4.8σexcess of e-like events. Motivated by this and other notable deviations from standard model predictions, such as the muon (g−2), we propose a solution to low energy anomalies through a dark neutrino sector. The model is renormalizable and can also explain light neutrino masses with an anomaly-free and dark U(1)′gauge symmetry broken at the GeV scale. Large kinetic mixing leads to s-channel production of heavy neutral leptons at e+e−colliders, where we point out and explain a 2σexcess observed in the BaBar monophoton data. Our model is also compatible with anomalous e-like events seen at old accelerator experiments, as well as with an excess of double vertex signatures observed at CCFR.©2021 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY licens