Boxing with neutrino oscillations

Current Science, 2017

Neutrinos are massless as proposed in the Standard Model of particle physics. However, neutrino experiments in the last few decades have revealed that neutrinos flavour oscillate, a scenario possible only if they have mass and mixing. Existence of neutrino mass was the first conclusive evidence of physics beyond the Standard Model, and explaining the smallness of the neutrino masses and peculiar mixing angles still remains a challenge for model-builders proposing beyond Standard Model scenarios. We give a brief introduction to the phenomenon of neutrino oscillations and showcase some recent work where we look for physics beyond the three-generation neutrino oscillation paradigm and its impact on future experiments.

Progress in Particle and Nuclear Physics, 1999

This review is focused on neutrino mixing and neutrino oscillations in the light of the recent experimental developments. After discussing possible types of neutrino mixing for Dirac and Majorana neutrinos and considering in detail the phenomenology of neutrino oscillations in vacuum and matter, we review all existing evidence and indications in favour of neutrino oscillations that have been obtained in the atmospheric, solar and LSND experiments. We present the results of the analyses of the neutrino oscillation data in the framework of mixing of three and four massive neutrinos and investigate possibilities to test the different neutrino mass and mixing schemes obtained in this way. We also discuss briefly future neutrino oscillation experiments. 7 Conclusions 88 A Properties of Majorana neutrinos and fields 92 1 Notice that in the Goldhaber et al. experiment the helicity of the electron neutrino was measured. The helicity of the muon neutrino was measured in several experiments (for the references see the review of V.L. Telegdi [13]). The best accuracy in the measurement of the muon neutrino was achieved in the experiment by Grénacs et al. [14].

The State of the Art of Neutrino Physics

The recent wide recognition of the existence of neutrino oscillations concludes the pioneer stage of these studies and poses the problem of how to communicate effectively the basic aspects of this branch of science. In fact, the phenomenon of neutrino oscillations has peculiar features and requires to master some specific idea and some amount of formalism. The main aim of these introductory notes is exactly to cover these aspects, in order to allow the interested students to appreciate the modern developments and possibly to begin to do research in neutrino oscillations. iii Preface The structure of these notes is the following. In the first section, we describe the context of the discussion. Then we will introduce the concept of neutrino mixing and analyze its implications. Next, we will examine the basic formalism of neutrino oscillations, recalling a few interesting applications. Subsequently, we discuss the modifications to neutrino oscillations that occur when these particles propagate in the matter. Finally, we offer a brief summary of the results and outline the perspectives. Several appendices supplement the discussion and collect various technical details. We strive to describe all relevant details of the calculations, in order to allow the Reader to understand thoroughly and to appreciate the physics of neutrino oscillation. Instead, we do not aim to achieve completeness and/or to collect the most recent results. We limit the reference list to a minimum: We cite the seminal papers of this field in the next section, mention some few books and review papers in the last section, and occasionally make reference to certain works that are needed to learn more or on which we relied to some large extent for an aspect or another. These choices are dictated not only by the existence of a huge amount of research work on neutrinos, but also and most simply in view of the introductory character of these notes. We assume that the Reader knows special relativity and quantum mechanics, and some basic aspects of particle physics. As a rule we will adopt the system of "natural units" of particle physics, defined by the choices = c = 1 In the equations, the repeated indices are summed, whenever this is not reason of confusion. Our metric is defined by xp = x µ p µ = x 0 p 0 − x • p where x = (x 0 , x) and p = (p 0 , p) are two quadrivectors. Unless stated otherwise, we will use the Dirac (or non-relativistic) representation of the Dirac matrices; see the appendices for technical details.

Universe, 2021

We review some of the main results of the quantum field theoretical approach to neutrino mixing and oscillations. We show that the quantum field theoretical framework, where flavor vacuum is defined, permits to give a precise definition of flavor states as eigenstates of (non-conserved) lepton charges. We obtain the exact oscillation formula which in the relativistic limit reproduces the Pontecorvo oscillation formula and illustrate some of the contradictions arising in the quantum mechanics approximation. We show that the gauge theory structure underlies the neutrino mixing phenomenon and that there exist entanglement between mixed neutrinos. The flavor vacuum is found to be an entangled generalized coherent state of SU (2). We also discuss flavor energy uncertainty relations, which imposes a lower bound on the precision of neutrino energy measurements and we show that the flavor vacuum inescapably emerges in certain classes of models with dynamical symmetry breaking.

2022

The phenomenon of neutrino mixing and oscillations has a deep quantum nature, which can be conveniently described in a quantum information language. This allows for an efficient investigation of the quantum correlations involved in this phenomenon and their possible use as quantum resources. Furthemore, complete complementarity relations provide a full characterization of such correlations.

Journal of High Energy Physics, 2021

We formulate an alternative approach based on unitarity triangles to describe neutrino oscillations in presence of non-standard interactions (NSI). Using perturbation theory, we derive the expression for the oscillation probability in case of NSI and cast it in terms of the three independent parameters of the leptonic unitarity triangle (LUT). The form invariance of the probability expression (even in presence of new physics scenario as long as the mixing matrix is unitary) facilitates a neat geometric view of neutrino oscillations in terms of LUT. We examine the regime of validity of perturbative expansions in the NSI case and make comparisons with approximate expressions existing in literature. We uncover some interesting dependencies on NSI terms while studying the evolution of LUT parameters and the Jarlskog invariant. Interestingly, the geometric approach based on LUT allows us to express the oscillation probabilities for a given pair of neutrino flavours in terms of only three...

International Journal of Modern Physics A, 1997

These notes present a critique of the standard three-flavor neutrino oscillation framwork. The design proposal of the MINOS at Fermilab based on a two mass eigenstate framework may require serious reconsideration if there is strong mixing between all three flavors of neutrinos. For the LSND and KARMEN neutrino oscillation experiments, the amplitude of neutrino oscillation of the "one mass scale dominance" framework vanishes for certain values of mixing angles as a result of opposite signs of two equal and opposite contributions. Recent astronomical observations leave open the possibility that one of the neutrino mass eigenstates may be non-relativistic in some instances. Neutrino oscillation phenomenology with a superposition of two relativistic, and one non-relativistic, mass eigenstates is constructed. It is concluded that if the transition from the non-relativistic to the relativistic regime happens for energies relevant to the Reactor and the LSND neutrino oscillation experiments then one must consider an ab intio analysis of the existing data.

2004

We present a derivation of the flavor neutrino states which describe neutrinos produced or detected in charged-current weak-interaction processes, including those operating in neutrino oscillation experiments. We also present a covariant derivation of the probability of neutrino oscillations which is consistent with the fact that flavor is Lorentz-invariant. Finally, we clarify the negative answers to three commonly asked questions: "Do charged leptons oscillate?"; "Is the standard phase wrong by a factor of 2?" "Are flavor neutrinos described by Fock states?".

Pramana, 2000

A brief introduction to the phenomena of vacuum neutrino oscillations and resonant flavour conversion is presented with a heavy pedagogic leaning. Variants of these ideas, e.g., neutrino helicity flip in a magnetic field, violation of the equivalence principle, etc. are outlined. A few vexing issues pertaining to the quantum mechanics of neutrino oscillations are discussed. Expectations from some of the future experiments are summarized.

2001

We present a simple but general treatment of neutrino oscillations in the framework of quantum mechanics using plane waves and intuitive wave packet principles when necessary. We attempt to clarify some confusing statements that have recently appeared in the literature.

Physica Scripta, 2003

Using an analogy with the well-known double-slit experiment, we show that the standard phase of neutrino oscillations is correct, refuting recent claims of a factor of two correction. We also improve the wave packet treatment of neutrino oscillations taking into account explicitly the finite coherence time of the detection process.

arXiv (Cornell University), 2024

We propose a new mixing scheme for neutrinos which eventually can be linked to a neutrino mass matrix texture bearing a suitable correlation (m22 + 2 m13 = 0) among its elements. The texture predicts three mass eigenvalues in the light of normal ordering, in addition to the Majorana phases. The texture is realized from A4 × Z10 × Z2 group in the framework of general type-I+II seesaw mechanism.

Thinking, Observing and Mining the Universe, 2004

We review the status of the neutrino oscillations physics, with a particular emphasis on the present knowledge of the neutrino mass-mixing parameters. We consider first the ν µ → ν τ flavor transitions of atmospheric neutrinos. It is found that standard oscillations provide the best description of the SK+K2K data, and that the associated mass-mixing parameters are determined at ±1σ (and N DF = 1) as: ∆m 2 = (2.6 ± 0.4) × 10 −3 eV 2 and sin 2 2θ = 1.00 +0.00 −0.05 . Such indications, presently dominated by SK, could be strengthened by further K2K data. Then we point out that the recent data from the Sudbury Neutrino Observatory, together with other relevant measurements from solar and reactor neutrino experiments, in particular the KamLAND data, convincingly show that the flavor transitions of solar neutrinos are affected by Mikheyev-Smirnov-Wolfenstein (MSW) effects. Finally, we perform an updated analysis of two-family active oscillations of solar and reactor neutrinos in the standard MSW case. * Speaker.

Nuclear Physics B - Proceedings Supplements, 2011

Description of neutrino oscillation in the case of Non-Standard neutrino Interaction (NSI) is briefly presented. The NSI causes the entanglement between internal degrees of freedom of neutrinos (mass, spin, flavour) and other accompanying particles in the production and detection processes. In such case neutrinos are mostly in the mixed states. Role of the density matrix in description of neutrino oscillation process is shortly explained.

2006

Higher-dimensional models of neutrino physics with one or more right-handed neutrinos in the bulk have attracted considerable attention in recent years. However, a critical issue for such models is to find a way of introducing the required flavor dependence needed for generating neutrino oscillations. In this paper, we point out that a natural "minimal" framework that accomplishes this can be constructed by combining the bulk-neutrino hypothesis for right-handed neutrinos with the splitfermion scenario for left-handed neutrinos. This combination leads to a unique flavor signature for neutrino phenomenology which easily incorporates large flavor mixing angles. This hybrid scenario also has a number of additional important features. For example, one previous difficulty of the splitfermion scenario applied to neutrinos has been that the mass matrix is exponentially sensitive to neutrino displacements within the brane. However, in our hybrid scenario, the interactions between the brane and bulk naturally convert this dependence from exponential to linear. Another important feature is that our hybrid scenario provides its own natural regulator for Kaluza-Klein sums. Thus, in our scenario, all Kaluza-Klein summations are manifestly finite, even in cases with multiple extra dimensions. But most importantly, our mechanism completely decouples the effective neutrino flavor mixing angles from the sizes of the overlaps between the neutrino wavefunctions within the brane. Thus, we are able to obtain large neutrino mixing angles even when these neutrinos have significant spatial separations and their overlaps vanish.