Electron Neutrino Research Articles

A hybrid type I + III inverse seesaw mechanism in U(1)R−L-symmetric MSSM

We show that, in a U(1)R−L-symmetric supersymmetric model, the pseudo-Dirac bino and wino can give rise to three light neutrino masses through effective operators, generated at the messenger scale between a SUSY breaking hidden sector and the visible sector. The neutrino-bino/wino mixing follows a hybrid type I+III inverse seesaw pattern. The light neutrino masses are governed by the ratio of the U(1)R−L-breaking gravitino mass, m3/2, and the messenger scale ΛM. The charged component of the SU(2)L-triplet, here the lightest charginos, mix with the charged leptons and generate flavor-changing neutral currents at tree level. We find that resulting lepton flavor violating observables yield a lower bound on the messenger scale, ΛM ≳ (500 − 1000) TeV for a simplified hybrid mixing scenario. We identify interesting mixing structures for certain U(1)R−L-breaking singlino/tripletino Majorana masses. For example, in some parameter regimes, bino or wino has no mixing with the electron neutrino. We also describe the rich collider phenomenology expected in this neutrino-mass generation mechanism.

Beyond tree level with solar neutrinos: Towards measuring the flavor composition and CP violation

After being produced as electron neutrinos (νe), solar neutrinos partially change their flavor to νμ and ντ en route to Earth. Although the flavor ratio of the νe flux to the total flux has been well measured, the νμ:ντ composition has not yet been experimentally probed. In this work we investigate the potential of the next-generation experiments for measuring the νμ:ντ flavor ratio by utilizing flavor-dependent radiative corrections in the cross sections for νμ and ντ scattering. Since the transition probabilities of νe to νμ and ντ depend on the leptonic CP phase, we also investigate the sensitivity to the CP phase and show that a statistical significance of ∼1σ could be reached through precision measurements of solar neutrino spectra.

Enhancement of the screening effect in semiconductor detectors in the presence of the neutrino magnetic moment

The theoretical framework of the neutrino electron excitation at low energies including the screening effect in semiconductor detectors is developed for the first time, both in the Standard Model of particle physics and in the presence of the neutrino magnetic moment. We apply the framework of the non-relativistic effective theory on the neutrino electron scattering and explore the contribution of the screening effect of semiconductors to the neutrino electron excitation based on the linear response theory. We calculate the corresponding numerical results with the popular silicon and germanium targets and show that excitation rates from the neutrino magnetic moment are dramatically enhanced by the screening effect and the sensitivity can be significantly improved to the level of 10−13μB, much better than the current best limits from the laboratory and astrophysical probes.

Search for Extended Sources of Neutrino Emission in the Galactic Plane with IceCube

The Galactic plane, harboring a diffuse neutrino flux, is a particularly interesting target in which to study potential cosmic-ray acceleration sites. Recent gamma-ray observations by HAWC and LHAASO have presented evidence for multiple Galactic sources that exhibit a spatially extended morphology and have energy spectra continuing beyond 100 TeV. A fraction of such emission could be produced by interactions of accelerated hadronic cosmic rays, resulting in an excess of high-energy neutrinos clustered near these regions. Using 10 years of IceCube data comprising track-like events that originate from charged-current muon neutrino interactions, we perform a dedicated search for extended neutrino sources in the Galaxy. We find no evidence for time-integrated neutrino emission from the potential extended sources studied in the Galactic plane. The most significant location, at 2.6σ post-trials, is a 1.°7 sized region coincident with the unidentified TeV gamma-ray source 3HWC J1951+266. We provide strong constraints on hadronic emission from several regions in the galaxy.

Monogamy properties of quantum correlations in neutrino oscillations

The monogamy relation of quantum states has limited the shareability properties of quantum resources in multiparty quantum systems. It plays a vital role in information distribution and transformation over many sites in quantum communications. Here, we focus on the monogamy relations of quantum correlations in the context of three-flavor neutrino oscillations, related to the squared entanglement of formation, the squared of quantum discord and its geometric variant. The monogamy relations in terms of the squared entanglement of formation work for the electron and muon antineutrino oscillations, suggesting that the bipartite entanglement measured by squared entanglement of formation of the three-flavor neutrino system set a limitation to the sum of pairwise squared entanglement of formation. Furthermore, we found that the squared quantum discord is also monogamous in three-flavor neutrino system. As a comparison, we test the monogamy of the quantum discord in neutrino oscillations with the result that the quantum discord is not monogamous. In addition, it is found that the bipartite geometric quantum discord of three-flavor systems is equal to the sum of the pairwise geometric quantum discord, i.e., the monogamy relation for geometric quantum discord is saturated for three-flavor neutrino system. These monogamy relations of quantum correlations provide a way for studying the distribution of quantum resources in neutrino oscillations, which is of significance to explore the further applications of neutrino oscillations in quantum communications.

The potential to probe solar neutrino physics with LiCl water solution

A solar neutrino detector relying on the charged-current (CC) interaction of nu _e on mathrm{{}^{7}Li} is attractive. The total CC interaction cross-section weighted by the solar ^8B electron neutrino spectrum is approximately 60 times that of the neutrino-electron elastic scattering process. The final state effective kinetic energy after the CC interaction on mathrm{{}^{7}Li} directly reflects the neutrino energy, which stands in sharp contrast to the plateau structure of recoil electrons of the elastic scattering. The recent measurement of the optical properties of saturated LiCl water solution, especially the long attenuation length, has once again aroused our interest in LiCl. In this work, with new B(GT) experimental measurements, the CC cross-section on mathrm{{}^{7}Li} is reevaluated to be 3.759times 10^{-42}~textrm{cm}^2. Given the high solubility of LiCl of 74.5 g/100 g water at 10 ^circ C and the high natural abundance of 92.41% of mathrm{{}^{7}Li}, a solar neutrino detection proposal is made. The detector with high concentration LiCl water solution has a comparable CC event rate of nu _e on mathrm{{}^{7}Li} with that of neutrino-electron elastic scattering. The contained mathrm{{}^{35}Cl}, mathrm{{}^{6}Li}, and H also make a delayed-coincidence detection for {{bar{nu }}}_e possible. The advantages of studying the upturn effect of solar neutrino oscillation, light sterile neutrinos, and Earth matter effect are investigated in detail. The sensitivities in discovering solar neutrino upturn and light sterile neutrinos are presented.

Observation of seasonal variations of the flux of high-energy atmospheric neutrinos with IceCube

Atmospheric muon neutrinos are produced by meson decays in cosmic-ray-induced air showers. The flux depends on meteorological quantities such as the air temperature, which affects the density of air. Competition between decay and re-interaction of those mesons in the first particle production generations gives rise to a higher neutrino flux when the air density in the stratosphere is lower, corresponding to a higher temperature. A measurement of a temperature dependence of the atmospheric nu _{mu } flux provides a novel method for constraining hadronic interaction models of air showers. It is particularly sensitive to the production of kaons. Studying this temperature dependence for the first time requires a large sample of high-energy neutrinos as well as a detailed understanding of atmospheric properties. We report the significant (> 10 ; sigma ) observation of a correlation between the rate of more than 260,000 neutrinos, detected by IceCube between 2012 and 2018, and atmospheric temperatures of the stratosphere, measured by the Atmospheric Infrared Sounder (AIRS) instrument aboard NASA’s AQUA satellite. For the observed 10% seasonal change of effective atmospheric temperature we measure a 3.5(3)% change in the muon neutrino flux. This observed correlation deviates by about 2-3 standard deviations from the expected correlation of 4.3% as obtained from theoretical predictions under the assumption of various hadronic interaction models.

Heavy Neutral Leptons from Stopped Muons and Pions

Stopped muons, which are generic in pion-at-rest experiments, can shed light on heavy neutral leptons (HNLs) in unexplored parameter spaces. If the HNL is lighter than the muon, the HNL can be produced from decays of muons and pions. The HNL will travel from the production location and decay into visible Standard Model (SM) modes, leaving signals inside downstream detectors. We find that in the case that the HNL dominantly mixes with muon neutrinos, the LSND constraint on the mixing angle squared is stronger than all the previous constraints by more than an order of magnitude. In this study, we recast the LSND measurement of the ν – e scattering. Future experiments such as PIP2-BD could further improve the sensitivity, provided they can distinguish the HNL events from backgrounds induced by the SM neutrinos.

Tachyonic Neutrinos: From the Cosmic Rays to Extragalactic Supernovae

The possibility of neutrinos moving at faster-than-light speeds can be modeled using terms in the Lagrangian that violate Lorentz symmetry, but the question of whether m2<0 and v>c tachyonic neutrinos exist is an empirical question. It remains unresolved despite evidence from cosmic ray and other data that the electron neutrino has an effective mν2≈−0.25eV2, which would require that one or more mass states is also tachyonic. In 2013, the 3+3 model of the neutrino masses, which includes one tachyonic mass state, was proposed based on supernova SN 1987A neutrino data. Here, we update evidence for tachyonic electron neutrinos and the 3+3 model and discuss one test which could prove conclusive. The update of earlier evidence includes many new elements, including new data which make the earlier cosmic ray evidence more robust, new results on cosmic ray composition, the ankle of the spectrum, leptonic cosmic ray data, and the statistical significance of finding the three large neutrino masses stipulated in the 3+3 model. Barring a galactic supernova, which occur only around twice a century, a decisive test of the 3+3 model could involve observing an extragalactic supernova neutrino burst, that is, a cluster of neutrinos in a specific time window well beyond what chance would predict. Even though existing searches for such bursts have yielded only upper limits on the extragalactic supernova frequency within a certain distance, it is shown that the choice of a one-day window for possible neutrino clusters in time might be far more sensitive. A search using a one-day time window could be conducted using existing data, and if a signal is found it would confirm the 3+3 model. Of course, the absence of any day-long neutrino burst would not disprove the model, since it could mean only that the nearest supernova during the period when detectors were active was simply too far to be detected. Finally, apart from testing the 3+3 model, an alternative type of search is suggested using existing hadronic cosmic ray data (from the IceCube Collaboration) that might verify the tachyonic neutrino hypothesis.

Development and characterisation of high-resolution microcalorimeter detectors for the ECHo-100k experiment

The goal of the ECHo experiment is a direct determination of the absolute scale of the neutrino mass by the analysis of the end-point region of the 163Ho electron capture (EC) spectrum. The results of the first phase of the experiment, ECHo-1k, have paved the way for the current phase, ECHo-100k, which aims at a sensitivity below 2eV on the effective electron neutrino mass. In order to reach this goal, a new generation of high-resolution magnetic microcalorimeters with embedded 163Ho have been developed and characterised. The design has been optimised to meet all the challenging requirements of the ECHo-100k experimental phase, such as excellent energy resolution, wafer scale implantation and multi-chip operation with multiplexing read-out. We present the optimisation studies, the final design of the detector array and the first characterisation studies. The obtained results demonstrate that the detectors fully match and even surpass the requirements for the current experimental phase, ECHo-100k.

Observation of Collider Muon Neutrinos with the SND@LHC Experiment.

We report the direct observation of muon neutrino interactions with the SND@LHC detector at the Large Hadron Collider. A dataset of proton-proton collisions at sqrt[s]=13.6 TeV collected by SND@LHC in 2022 is used, corresponding to an integrated luminosity of 36.8 fb^{-1}. The search is based on information from the active electronic components of the SND@LHC detector, which covers the pseudorapidity region of 7.2<η<8.4, inaccessible to the other experiments at the collider. Muon neutrino candidates are identified through their charged-current interaction topology, with a track propagating through the entire length of the muon detector. After selection cuts, 8 ν_{μ} interaction candidate events remain with an estimated background of 0.086 events, yielding a significance of about 7 standard deviations for the observed ν_{μ} signal.

First Direct Observation of Collider Neutrinos with FASER at the LHC.

We report the first direct observation of neutrino interactions at a particle collider experiment. Neutrino candidate events are identified in a 13.6TeV center-of-mass energy pp collision dataset of 35.4 fb^{-1} using the active electronic components of the FASER detector at the Large Hadron Collider. The candidates are required to have a track propagating through the entire length of the FASER detector and be consistent with a muon neutrino charged-current interaction. We infer 153_{-13}^{+12} neutrino interactions with a significance of 16 standard deviations above the background-only hypothesis. These events are consistent with the characteristics expected from neutrino interactions in terms of secondary particle production and spatial distribution, and they imply the observation of both neutrinos and anti-neutrinos with an incident neutrino energy of significantly above 200GeV.

Toward the confirmation of atmospheric neutrino oscillations

Abstract The atmospheric muon neutrino deficit, which was possible evidence of νμ↔ντ oscillation, was reported by the Kamiokande experiment from 1988. Many experimental efforts were made to examine the Kamiokande results. Experiments which contributed to the confirmation of νμ↔ντ oscillation are reviewed. Especially, long-baseline neutrino-oscillation experiments are described in detail.

Search for supersymmetry in final states with missing transverse momentum and three or more b-jets in 139 fb^{-1} of proton–proton collisions at sqrt{s} = 13 TeV with the ATLAS detector

A search for supersymmetry involving the pair production of gluinos decaying via off-shell third-generation squarks into the lightest neutralino (tilde{chi }^0_1) is reported. It exploits LHC proton–proton collision data at a centre-of-mass energy sqrt{s} = 13 TeV with an integrated luminosity of 139 fb^{-1} collected with the ATLAS detector from 2015 to 2018. The search uses events containing large missing transverse momentum, up to one electron or muon, and several energetic jets, at least three of which must be identified as containing b-hadrons. Both a simple kinematic event selection and an event selection based upon a deep neural-network are used. No significant excess above the predicted background is found. In simplified models involving the pair production of gluinos that decay via off-shell top (bottom) squarks, gluino masses less than 2.44 TeV (2.35 TeV) are excluded at 95% CL for a massless tilde{chi }^0_1. Limits are also set on the gluino mass in models with variable branching ratios for gluino decays to bbar{b}tilde{chi }^0_1,tbar{t}tilde{chi }^0_1 and tbar{b}tilde{chi }^-_1/bar{t}btilde{chi }^+_1.

Cosmic birefringence from neutrino and dark matter asymmetries

In light of the recent measurement of the nonzero Cosmic Microwave Background (CMB) polarization rotation angle from the Planck 2018 data, we explore the possibility that such a cosmic birefringence effect is induced by coupling a fermionic current with photons via a Chern-Simons-like term. We begin our discussion by rederiving the general formulae of the cosmic birefringence angle with correcting a mistake in the previous study.We then identify the fermions in the current as the left-handed electron neutrinos and asymmetric dark matter (ADM) particles, since the rotation angle is sourced by the number density difference between particles and antiparticles. For the electron neutrino case, with the value of the degeneracy parameter ξν e recently measured by the EMPRESS survey, we find a large parameter space which can explain the CMB photon polarization rotations. On the other hand, for the ADM solution, we consider two benchmark cases with Mχ = 5 GeV and 5 keV. The former is the natural value of the ADM mass if the observed ADM and baryon asymmetry in the Universe are produced by the same mechanism, while the latter provides a warm DM candidate. In addition, we explore the experimental constraints from the CMB power spectra and the DM direct detections.

Calculations of the Binding-Energy Differences for Highly-Charged Ho and Dy Ions

The binding-energy differences for ^{{163}}{text{H}}{{{text{o}}}^{{q + }}} and ^{{163}}{text{D}}{{{text{y}}}^{{q + }}} ions with ionization degrees q = 38, 39, and 40 are calculated. The calculations are performed using the large-scale relativistic configuration-interaction and relativistic coupled-clusters methods. The contributions from quantum-electrodynamics, nuclear-recoil, and frequency-dependent Breit-interaction effects are taken into account. The final uncertainty does not exceed 1 eV. Combining the obtained results with the binding-energy difference for neutral atoms calculated in [I.M. Savelyev, M.Y. Kaygorodov, Y.S. Kozhedub, I.I. Tupitsyn, and V.M. Shabaev, Phys. Rev. A 105, 012806 (2022)], we get the secondary differences of the ion–atom binding energies. These values can be used to evaluate the amount of energy released in the electron capture process in ^{{163}}{text{Ho}} atom (the Q value), provided mass differences of highly charged ions ^{{163}}{text{H}}{{{text{o}}}^{{q + }}} and ^{{163}}{text{D}}{{{text{y}}}^{{q + }}} is known from experiment. The Q value is required by experiments on the determination of the absolute scale of the electron neutrino mass by studying the beta-decay process.

Laser-induced proton decay

In this research paper, we investigate the decay of the proton into neutron, positron and electron neutrino in the presence of an external electromagnetic field with circular polarization. Different physical quantities related to this decay process, such as proton’s decay rate and its lifetime, are calculated based on the S-matrix approach. The proton and positron are treated as Dirac–Volkov states, while the neutron and electron neutrino are free-states. We have found that, though it can not occur in vacuum, the proton’s decay process into neutron, positron and electron neutrino becomes possible in the presence of laser field with high intensities near or close to the Schwinger limit. In addition, near this limit and for some frequencies, the proton’s lifetime can be comparable to that of the neutron, and the required laser strength, from which this decay becomes possible, depends on the chosen laser source.

Search for direct pair production of sleptons and charginos decaying to two leptons and neutralinos with mass splittings near the W-boson mass in sqrt{s} = 13 TeV pp collisions with the ATLAS detector

A search for the electroweak production of pairs of charged sleptons or charginos decaying into two-lepton final states with missing transverse momentum is presented. Two simplified models of R-parity-conserving supersymmetry are considered: direct pair-production of sleptons left(overset{sim }{ell}overset{sim }{ell}right) , with each decaying into a charged lepton and a {overset{sim }{chi}}_1^0 neutralino, and direct pair-production of the lightest charginos left({overset{sim }{chi}}_1^{pm }{overset{sim }{chi}}_1^{mp}right) , with each decaying into a W-boson and a {overset{sim }{chi}}_1^0 . The lightest neutralino left({overset{sim }{chi}}_1^0right) is assumed to be the lightest supersymmetric particle (LSP). The analyses target the experimentally challenging mass regions where mleft(overset{sim }{ell}right)-mleft({overset{sim }{chi}}_1^0right) and mleft({overset{sim }{chi}}_1^{pm}right)-mleft({overset{sim }{chi}}_1^0right) are close to the W-boson mass (‘moderately compressed’ regions). The search uses 139 fb−1 of sqrt{s} = 13 TeV proton-proton collisions recorded by the ATLAS detector at the Large Hadron Collider. No significant excesses over the expected background are observed. Exclusion limits on the simplified models under study are reported in the left(overset{sim }{ell },{overset{sim }{chi}}_1^0right) and left({overset{sim }{chi}}_1^{pm }{overset{sim }{chi}}_1^0right) mass planes at 95% confidence level (CL). Sleptons with masses up to 150 GeV are excluded at 95% CL for the case of a mass-splitting between sleptons and the LSP of 50 GeV. Chargino masses up to 140 GeV are excluded at 95% CL for the case of a mass-splitting between the chargino and the LSP down to about 100 GeV.

Complete complementarity relations for three-flavor neutrino oscillations

We study quantum correlations encoded in a three-flavor neutrino system by using complete complementarity relations (CCR). Due to the presence of local coherence in two-flavor subsystems, the CCR has an additional contribution not present in the two flavor mixing case. We investigate such coherence for the three possible bipartite subsystems of the global state both for an electron and a muon neutrino system.

Elastic Neutrino–Atom Scattering as a Probe of Neutrino Millicharge and Magnetic Moment

Neutrino scattering on a target at low-energy transfer is one of the basic tools for searching for neutrino electromagnetic properties. We consider the effects of the neutrino millicharge and magnetic moment on the atomic recoil spectrum in elastic neutrino–atom scattering. The results of our calculations of differential cross sections for elastic collisions of tritium neutrinos with the H, 2H, 3He, and 4He atomic targets show that the corresponding experiments can achieve sensitivity to the indicated neutrino electromagnetic characteristics by orders of magnitude better than the available measurements of elastic neutrino–electron and neutrino–nucleus collisions.