Non-standard Neutrino Research Articles

Precision measurements and tau neutrino physics in a future accelerator neutrino experiment

We investigate prospects of building a future accelerator-based neutrino oscillation experiment in China, including site selection, beam optimization and tau neutrino physics aspects. CP violation, non-unitary mixing and non-standard neutrino interactions are discussed. We simulate neutrino beam setups based on muon and beta decay techniques and compare Chinese laboratory sites by their expected sensitivities. A case study on the Super Proton–Proton Collider and the China JinPing Laboratory is also presented. It is shown that the muon-decay-based beam setup can measure the Dirac CP phase by about 14.2° precision at 1σ CL, whereas non-unitarity can be probed down to ∣α ij ∣ ≲ 0.37 (i ≠ j = 1, 2, 3) and non-standard interactions to 0.11 (, μ, τ) at 90% CL, respectively.

Neutrino masses and magnetic moments of electron and muon in the Zee Model

We explore parameter space in the Zee Model to resolve the long-standing tension of the electron and muon anomalous magnetic moment (AMM). The model comprises a second Higgs doublet and a charged singlet at electroweak scale and generates Majorana neutrino masses at one-loop level; the neutral partner of the SU(2)L doublet contributes to the AMM of electron and muon via one loop and two-loop corrections. We propose two minimal flavor structures that can explain these anomalies while fitting the neutrino oscillation data. We find that the neutral Higgs resides in the mass range of roughly 10–300 GeV or 1–30 GeV, depending on the flavor structures. The model is consistent with constraints from colliders, electroweak precision data, and lepton flavor violation. To be comprehensive, we examine the constraints from the electric dipole moment (EDM) and find a region of parameter space that gives a sizable contribution to muon EDM while simultaneously giving corrections to muon AMM. In addition to the light scalar, the two charged scalars with masses as low as 100 GeV can induce nonstandard neutrino interactions εee as large as 8%, potentially hinting at new physics. We also investigate the projected capability of future lepton colliders to probe the currently allowed parameter space consistent with both electron and muon AMMs via direct searches in the ℓ+ℓ− → ℓ+ℓ−(H → ℓ+ℓ−) channel.

A Review of the Tension between the T2K and NOνA Appearance Data and Hints to New Physics

In this article, we review the status of the tension between the long-baseline accelerator neutrino experiments T2K and NOνA. The tension arises mostly due to the mismatch in the apappearance data of the two experiments. We explain how this tension arises based on νμ→νe and ν¯μ→ν¯e oscillation probabilities. We define the reference point of vacuum oscillation, maximal θ23 and δCP and compute the νe/ν¯e appearance events for each experiment. We then study the effects of deviating the unknown parameters from the reference point and the compatibility of any given set of values of unknown parameters with the data from T2K and NOνA. T2K observes a large excess in the νe appearance event sample compared to the expected νe events at the reference point, whereas NOνA observes a moderate excess. The large excess in T2K dictates that δCP be anchored at −90° and that θ23 > π/4 with a preference for normal hierarchy. The moderate excess at NOνA leads to two degenerate solutions: (a) NH, 0 < δCP < 180°, and θ23 > π/4; (b) IH, −180° < δCP < 0, and θ23 > π/4. This is the main cause of tension between the two experiments. We review the status of three beyond standard model (BSM) physics scenarios, (a) non-unitary mixing, (b) Lorentz invariance violation, and (c) non-standard neutrino interactions, to resolve the tension.

Science with Neutrino Telescopes in Spain

The primary scientific goal of neutrino telescopes is the detection and study of cosmic neutrino signals. However, the range of physics topics that these instruments can tackle is exceedingly wide and diverse. Neutrinos coming from outside the Earth, in association with other messengers, can contribute to clarify the question of the mechanisms that power the astrophysical accelerators which are known to exist from the observation of high-energy cosmic and gamma rays. Cosmic neutrinos can also be used to bring relevant information about the nature of dark matter, to study the intrinsic properties of neutrinos and to look for physics beyond the Standard Model. Likewise, atmospheric neutrinos can be used to study an ample variety of particle physics issues, such as neutrino oscillation phenomena, the determination of the neutrino mass ordering, non-standard neutrino interactions, neutrino decays and a diversity of other physics topics. In this article, we review a selected number of these topics, chosen on the basis of their scientific relevance and the involvement in their study of the Spanish physics community working in the KM3NeT and ANTARES neutrino telescopes.

Nonstandard interactions in hyperons decay with di-neutrinos in the final state

Rare decays of hyperons involving di-neutrinos in the final state [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text] in the Standard Model and beyond are studied. It is claimed that the branching ratios (Brs) calculated in this work are larger than the previously calculated values. For the search of NP the nonstandard neutrino interactions (NSI) are explored and constrains on NSI free parameters [Formula: see text] are found. Stringent bounds on [Formula: see text] of [Formula: see text] are obtained. It is shown that Brs could be closed to BES-III, if the constraints are [Formula: see text]. We predict that these reactions with the current value of parameter of [Formula: see text] will be in sensitivity of BES-III. To check the validity of our approach we also calculate Brs of these reactions by using 331 model and finding them consistent with previously available values of the same model.

Msw Effect, and Non-Standard Neutrino Interaction Induced by Conformal Coupling

Msw Effect, and Non-Standard Neutrino Interaction Induced by Conformal Coupling

Probing neutrino decay scenarios by using the Earth matter effects on supernova neutrinos

The observation of Earth matter effects in the spectrum of neutrinos coming from a next galactic core-collapse supernova (CCSN) could, in principle, reveal if neutrino mass ordering is normal or inverted. One of the possible ways to identify the mass ordering is through the observation of the modulations that appear in the spectrum when neutrinos travel through the Earth before they arrive at the detector. These features in the neutrino spectrum depend on two factors, the average neutrino energies, and the difference between the primary neutrino fluxes of electron and other flavors produced inside the supernova. However, recent studies indicate that the Earth matter effect for CCSN neutrinos is expected to be rather small and difficult to be observed by currently operating or planned neutrino detectors mainly because of the similarity of average energies and fluxes between electron and other flavors of neutrinos, unless the distance to CCSN is significantly smaller than the typically expected one, ∼ 10 kpc. Here, we are looking towards the possibility if the non-standard neutrino properties such as decay of neutrinos can enhance the Earth matter effect. In this work we show that invisible neutrino decay can potentially enhance significantly the Earth matter effect for both νe and ν̅e channels at the same time for both mass orderings, even if the neutrino spectra between electron and other flavors of neutrinos are very similar, which is a different feature not expected for CCSN neutrinos with standard oscillation without the decay effect.

Neutrino oscillations through the Earth’s core

Neutrinos have two properties that make them fairly unique from other known particles: extremely low cross sections and flavor changing oscillations. With a good knowledge of the oscillation parameters soon in hand, it will become possible to detect low-energy atmospheric neutrinos sensitive to the forward elastic scattering off electrons in the Earth's core providing a measurement of the core properties and the matter effect itself. As the dynamics of the Earth's core are complicated and in a difficult to probe environment, additional information from upcoming neutrino experiments will provide feedback into our knowledge of geophysics as well as useful information about exoplanet formation and various new physics scenarios including dark matter. In addition, we can probe the existence of the matter effect in the Earth and constrain the non-standard neutrino interaction parameter $\epsilon_{ee}^\oplus$. We show how DUNE's sensitivity to low-energy atmospheric neutrino oscillations can provide a novel constraint on the density and radius of the Earth's core at the 9\% level and the Earth's matter effect at the 5\% level. Finally, we illuminate the physics behind low-energy atmospheric neutrino resonances in the Earth.

Non-standard neutrino and Z\u2032 interactions at the FASER\u03bd and the LHC

We study the impact of non-standard neutrino interactions in the context of a new gauge boson Z′ in neutral-current deep-inelastic scattering performed in ForwArd Search ExpeRiment-ν (FASERν) and in monojet production at the Large Hadron Collider (LHC). We simulate the neutral-current deep-inelastic neutrino-nucleon scattering νN → νN at FASERν in the presence of an additional Z′ boson, and estimate the anticipated sensitivities to the gauge coupling in a wide range of Z′ mass. At the LHC, we study the effect of Z′ on monojet production, which can be enhanced in regions with large missing transverse momenta. We then use the recent results from ATLAS with an integrated luminosity of 139 fb−1 to improve the limits on the gauge coupling of Z′. We interpret such limits on Z′ gauge couplings as bounds on effective non-standard neutrino interactions. We show that the FASERν and the LHC results cover the medium and high energy scales, respectively, and complement one another.

Exploring NSI using oscillation dip and valley in atmospheric neutrino experiments

We present a new approach to probe flavor-changing neutral-current non-standard neutrino interaction parameter εμτ using the oscillation dip and valley features. We use the simulated up/down ratio of reconstructed muons events at the proposed Iron Calorimeter (ICAL) detector at the India-based Neutrino Observatory to demonstrate that in presence of NSI parameter ε μτ, the oscillation dip location shifts and oscillation valley bends. Utilizing the charge identification capability of ICAL, the opposite shifts in the oscillation dip locations and the contrast in the oscillation valley curvatures for μ− and μ+ can be used to place 90% C.L. bounds of about 2% on |εμτ| using 500 kt• yr exposure. In our procedure, we take care of statistical fluctuations, systematic errors, and uncertainties in neutrino oscillation parameters.

Supernova Preshock Neutronization Burst as a Probe of Nonstandard Neutrino Interactions

Abstract A core-collapse supernova (CCSN) provides a unique astrophysical site for studying neutrino–matter interactions. Prior to the shock-breakout neutrino burst during the collapse of the iron core, a preshock ν e burst arises from the electron capture of nuclei and it is sensitive to the low-energy coherent elastic neutrino–nucleus scattering (CEνNS) which dominates the neutrino opacity. Since the CEνNS depends strongly on nonstandard neutrino interactions (NSIs), which are completely beyond the standard model and yet to be determined, the detection of the preshock burst thus provides a clean way to extract the NSI information. Within the spherically symmetric general-relativistic hydrodynamic simulation for the CCSN, we investigate the NSI effects on the preshock burst. We find that the NSI can maximally enhance the peak luminosity of the preshock burst almost by a factor of three, reaching a value comparable to that of the shock-breakout burst. Future detection of the preshock burst will have critical implications on astrophysics, neutrino physics, and physics beyond the standard model.

A geometrical look at neutrino oscillation probabilities with non-standard interactions

In this talk, we discuss an alternative description of neutrino flavor oscillations using leptonic unitarity triangles (LUT) which allows for geometric visualization of neutrino oscillations. After a brief review of the LUT description of neutrino oscillations for propagation in vacuum and in matter with standard interactions, we discuss how we can extend this approach to describe neutrino oscillations in presence of new physics. We consider non-standard neutrino interactions (NSI) as the toy model of new physics. The content presented in this talk is based on Ref. [1].

All-flavor constraints on nonstandard neutrino interactions and generalized matter potential with three years of IceCube DeepCore data

We report constraints on nonstandard neutrino interactions (NSI) from the observation of atmospheric neutrinos with IceCube, limiting all individual coupling strengths from a single dataset. Furthermore, IceCube is the first experiment to constrain flavor-violating and nonuniversal couplings simultaneously. Hypothetical NSI are generically expected to arise due to the exchange of a new heavy mediator particle. Neutrinos propagating in matter scatter off fermions in the forward direction with negligible momentum transfer. Hence the study of the matter effect on neutrinos propagating in the Earth is sensitive to NSI independently of the energy scale of new physics. We present constraints on NSI obtained with an all-flavor event sample of atmospheric neutrinos based on three years of IceCube DeepCore data. The analysis uses neutrinos arriving from all directions, with reconstructed energies between 5.6 GeV and 100 GeV. We report constraints on the individual NSI coupling strengths considered singly, allowing for complex phases in the case of flavor-violating couplings. This demonstrates that IceCube is sensitive to the full NSI flavor structure at a level competitive with limits from the global analysis of all other experiments. In addition, we investigate a generalized matter potential, whose overall scale and flavor structure are also constrained.

EFT at FASER\u03bd

We investigate the sensitivity of the FASERν detector to new physics in the form of non-standard neutrino interactions. FASERν, which will be installed 480 m downstream of the ATLAS interaction point, will for the first time study interactions of multi-TeV neutrinos from a controlled source. Our formalism — which is applicable to any current and future neutrino experiment — is based on the Standard Model Effective Theory (SMEFT) and its counterpart, Weak Effective Field Theory (WEFT), below the electroweak scale. Starting from the WEFT Lagrangian, we compute the coefficients that modify neutrino production in meson decays and detection via deep-inelastic scattering, and we express the new physics effects in terms of modified flavor transition probabilities. For some coupling structures, we find that FASERν will be able to constrain interactions that are two to three orders of magnitude weaker than Standard Model weak interactions, implying that the experiment will be indirectly probing new physics at the multi-TeV scale. In some cases, FASERν constraints will become comparable to existing limits — some of them derived for the first time in this paper — already with 150 fb−1 of data.

Self-interacting neutrinos, the Hubble parameter tension, and the cosmic microwave background

We perform a comprehensive study of cosmological constraints on nonstandard neutrino self-interactions using cosmic microwave background and baryon acoustic oscillation data. We consider different scenarios for neutrino self-interactions distinguished by the fraction of neutrino states allowed to participate in self-interactions and how the relativistic energy density, ${N}_{\mathrm{eff}}$, is allowed to vary. Specifically, we study cases in which all neutrino states self-interact and ${N}_{\mathrm{eff}}$ varies; two species free-stream, which we show alleviates tension with laboratory constraints, while the energy in the additional interacting states varies; and a variable fraction of neutrinos self-interact with either the total ${N}_{\mathrm{eff}}$ fixed to the Standard Model value or allowed to vary. In no case do we find compelling evidence for new neutrino interactions or nonstandard values of ${N}_{\mathrm{eff}}$. In several cases, we find additional modes with neutrino decoupling occurring at lower redshifts ${z}_{\mathrm{dec}}\ensuremath{\sim}{10}^{3--4}$. We do a careful analysis to examine whether new neutrino self-interactions solve or alleviate the so-called ${H}_{0}$ tension and find that, when all Planck 2018 CMB temperature and polarization data are included, none of these examples eases the tension more than allowing a variable ${N}_{\mathrm{eff}}$ comprised of free-streaming particles. Although we focus on neutrino interactions, these constraints are applicable to any light relic particle.

Search for neutrino non-standard interactions with ANTARES and KM3NeT-ORCA

Non-standard interactions (NSIs) in the propagation of neutrinos in matter can lead tosignificant deviations in neutrino oscillations expected within the standard 3-neutrinoframework. These additional interactions would result in an anomalous flux of neutrinosobservable at neutrino telescopes. The ANTARES detector and its next-generation successor,KM3NeT, located in the abyss of the Mediterranean Sea, have the potential to measuresub-dominant effects in neutrino oscillations, coming from non-standard neutrino interactions.In this contribution, a likelihood-based search for NSIs with 10 years of atmospheric muon-neutrinodata recorded with ANTARES is reported and sensitivity projections for KM3NeT/ORCA, based on realistic detector simulations, are shown. The bounds obtained with ANTARES in the NSI μ - τ sector constitute the most stringent limits up to date.

Formula omitted] and non-standard neutrino interactions

We discuss the modes B→K(⁎)νν¯ in the context of non-standard neutrino interactions that add incoherently to the SM rates. We consider two scenarios: an additional light neutrino; and neutrino lepton flavour violation. We find that an additional light neutrino that interacts with SM fields via a non-universal Z′ can increase RK(⁎)ν by up to a factor of two without conflicting with Bs−B¯s mixing. This model then predicts rates for Bs→τ+τ− up to six times larger than the SM. In the context of neutrino lepton flavour violation mediated by leptoquarks we find that the current experimental upper bounds on RK(⁎)ν are already more constraining than direct bounds from Bs→τℓ and B→K(⁎)τℓ modes for ℓ=e,μ.

Constraining nonstandard neutrino interactions at electron colliders

The presence of nonstandard neutrino interactions (NSI) has a large effect on the precision measurements at next generation neutrino oscillation experiments. Other type of experiments are needed to constrain the NSI parameter space. We study the constraints on NSI with electrons from current and future $e^+e^-$ collider experiments including Belle II, STCF and CEPC. We find that Belle II and STCF will provide competitive and complementary bounds on electron-type NSI parameters compared to the current global analysis, and strong improvements for the constraints on tau-type NSI. In addition, CEPC alone will impose stringent constraints on the parameter space of NSI with electrons. We find that the degeneracy between the left-handed (vector) and right-handed (axial-vector) NSI parameters can be lifted by combining the data from three different running modes, and the allowed ranges for $|\epsilon_{ee}^{eL}|$ ($|\epsilon_{ee}^{eV}|$) and $|\epsilon_{ee}^{eR}|$ ($|\epsilon_{ee}^{eA}|$) can be constrained to be smaller than 0.002 at CEPC even if both of them are present.

New Sources of Leptonic CP Violation at the DUNE Neutrino Experiment

We check the capability of the DUNE neutrino experiment to detect new sources of leptonic CP violation beside the single phase expected in the Standard Model. We illustrate our strategy based on the measurement of CP asymmetries in the case that new physics will show up as nonstandard neutrino interactions and sterile neutrino states and show that the most promising one, once the experimental errors are taken into account in both scenarios, is the one related to the νμ→νe transition.

Effects of nonstandard neutrino self-interactions and magnetic moment on collective Majorana neutrino oscillations

We derive the effective Hamiltonian describing collective oscillations of Majorana neutrinos with a transition magnetic moment, allowing for the presence of scalar and pseudoscalar nonstandard neutrino self-interactions (NSSIs). Using this Hamiltonian, we analyze new flavor instability channels of collective oscillations in a core-collapse supernova environment that open up in the presence of a small but nonzero neutrino magnetic moment. It turns out that, contrary to certain claims in the literature, within the minimally extended Standard Model (i.e., without NSSIs), no new instabilities arise within the linear order, nor do they produce any observable signatures in the neutrino flavor-energy spectra, at least for magnetic moments up to $10^{-15}~\mu_{\text{B}}$ and quite realistic fields of the order of $10^{12}~$Gauss. On the other hand, in the presence of NSSIs, new fast and slow instabilities mixing neutrinos and antineutrinos appear, which show up in the spectra even for tiny magnetic moments of the order of $10^{-24}~\mu_{\text{B}}$, leading to considerable distortions of the spectra and nonstandard spectral splits. We study sensitivity of collective oscillations to these, NSSI-induced instabilities in detail and discuss the observability of the NSSI couplings triggering them.