Electron Neutrino Research Articles

Fast flavor instability in hypermassive neutron star disk outflows

We examine the effect of neutrino flavor transformation by the fast flavor instability (FFI) on long-term mass ejection from accretion disks formed after neutron star mergers. Neutrino emission and absorption in the disk set the composition of the disk ejecta, which subsequently undergoes $r$-process nucleosynthesis upon expansion and cooling. Here we perform 28 time-dependent, axisymmetric, viscous-hydrodynamic simulations of accretion disks around hypermassive neutron stars (HMNSs) of variable lifetime, using a 3-species neutrino leakage scheme for emission and an annular-lightbulb scheme for absorption. We include neutrino flavor transformation due the FFI in a parametric way, by modifying the absorbed neutrino fluxes and temperatures, allowing for flavor mixing at various levels of flavor equilibration, and also in a way that aims to respect the lepton-number preserving symmetry of the neutrino self-interaction Hamiltonian. We find that for a promptly-formed black hole (BH), the FFI lowers the average electron fraction of the disk outflow due to a decrease in neutrino absorption, driven primarily by a drop in electron neutrino/antineutrino flux upon flavor mixing. For a long-lived HMNS, the disk emits more heavy lepton neutrinos and reabsorbs more electron neutrinos than for a BH, with a smaller drop in flux compensated by a higher neutrino temperature upon flavor mixing. The resulting outflow has a broader electron fraction distribution, a more proton-rich peak, and undergoes stronger radiative driving. Disks with intermediate HMNS lifetimes show results that fall in between these two limits. In most cases, the impact of the FFI on the outflow is moderate, with changes in mass ejection, average velocity, and average electron fraction of order $\sim 10\%$, and changes in the lanthanide/actinide mass fraction of up to a factor $\sim 2$.

Laser-assisted scattering of a muon neutrino by an electron within the framework of electroweak theory

In accordance with the electroweak theory, we perform a detailed analytical treatment of the differential cross-section (DCS) for the elastic scattering process in both absence and presence of a circularly polarized laser field. This scattering process is examined, in the first-Born approximation, by using Dirac–Volkov wave functions for charged particles within an external laser field. The theoretical results obtained for the differential cross-section without a laser field are compared with other theoretical results within the framework of Fermi theory. These results revealed to us the importance of using electroweak theory instead of Fermi approximation for studying high energy electroweak interactions. The differential cross section is modified significantly by inserting the electrons into an electromagnetic field. In addition, the influence of the laser strength and its frequency on the photons exchange between the colliding system and the laser field is also included and discussed. These effects are heavily related to the order and argument of the ordinary Bessel functions introduced in the theoretical calculation.

Elusive muonic WIMP

The Weakly Interacting Massive Particle (WIMP) paradigm is one of the most popular scenarios for Dark Matter (DM) theories that however is strongly constrained, in particular by direct detection experiments. We stick with the WIMP hypothesis and consider a Dirac fermion candidate for DM that interacts with the Standard Model (SM) via a spin-1 $Z'$, arising from the spontaneous breaking of an Abelian $U(1)'_{\mu}$ gauge symmetry, under which only second generation leptons and the DM are appropriately charged. Due to the charge assignment, the model is gauge anomalous and can only be interpreted as an effective field theory (EFT) at low energy. The $Z'$ couples at tree level only to the vector DM current, to the axial muon current and to left-handed muonic neutrinos, so the WIMP-nucleon cross section is beyond the experimental reach of spin-independent (SI) direct detection searches. We study the current bounds on this model coming from direct and indirect detection of DM, collider searches, contributions to $(g-2)_{\mu}$ and to neutrino trident production. We find that large regions of the parameter space remains to be explored. In the context of LHC searches, we study the impact of a muon-exclusive signal region for the $3\mu$ + ${E}^{{\rm miss}}_T$ channel with an invariant mass window around $m_{Z'}$. We show that this search can significantly improve the current collider bounds. Finally, from the anomalous nature of our EFT, there remain at low energy triboson anomalous interactions between the $Z'$ and the electroweak (EW) SM gauge bosons. We explore the possibilities of probing these interactions at the LHC and at a 100 TeV proton collider finding it extremely challenging. On the other hand, for a muon collider the resonant channel $\mu^{+}\mu^{-}\to Z'\to ZZ$ could be discovered in the most promising scenario with luminosity of $\mathcal{O}({\rm few}\; 10)$ ${\rm fb}^{-1}$.

QED medium effects in (anti)neutrino-nucleus and electron-nucleus scattering: Elastic scattering on nucleons

Interpretation of current and future neutrino oscillation and electron scattering experiments requires knowledge of lepton-nucleon and lepton-nucleus interactions at the percent level. We study the exchange of photons between charged particles and the nuclear medium for (anti)neutrino-, electron-, and muon-induced reactions inside a large nucleus. While quantum electrodynamics (QED)-medium contributions are formally suppressed by two powers of the electromagnetic coupling constant α when compared to the leading-order cross sections, low-energy modes and the nuclear size enhance the effect by orders of magnitude. They require a proper infrared regularization, which we implement as a screening of the electromagnetic interactions at atomic length scales or above. We provide approximate analytic expressions for the distortion of (anti)neutrino-nucleus and charged lepton-nucleus cross sections and evaluate the QED-medium effects for realistic values of the screening scale on the example of elastic scattering with nucleons inside the nucleus. We find new permille- to percent-level effects, which were not considered in either (anti)neutrino-nucleus or electron-nucleus scattering.

Using DUNE to shed light on the electromagnetic properties of neutrinos

We study future DUNE sensitivity to various electromagnetic couplings of neutrinos, including magnetic moments, milli-charges, and charge radii. The DUNE PRISM capabilities play a crucial role in constraining the electron flavored couplings. We find that DUNE will be able to place the strongest beam based constraint on the muon-neutrino magnetic moment by improving on LSND’s bounds by roughly a factor of two, although Borexino’s constraint from solar neutrinos will be stronger. For the muon neutrino millicharge DUNE can place the leading beam based bound, with two orders of magnitude improvement compared to the existing COHERENT constraint, suggesting that DUNE can be useful for light mediators more generally. Despite this strength, the millicharge bounds are not competitive with strong bounds from stellar cooling, beta-decay, and matter stability. Finally, DUNE may be able to test the SM prediction for the muon neutrino charge radius, by placing a constraint two times better than CHARM-II and CCFR experiments.

Search for Astrophysical Neutrinos from 1FLE Blazars with IceCube

The majority of astrophysical neutrinos have undetermined origins. The IceCube Neutrino Observatory has observed astrophysical neutrinos but has not yet identified their sources. Blazars are promising source candidates, but previous searches for neutrino emission from populations of blazars detected in ≳GeV gamma rays have not observed any significant neutrino excess. Recent findings in multimessenger astronomy indicate that high-energy photons, coproduced with high-energy neutrinos, are likely to be absorbed and reemitted at lower energies. Thus, lower-energy photons may be better indicators of TeV–PeV neutrino production. This paper presents the first time-integrated stacking search for astrophysical neutrino emission from MeV-detected blazars in the first Fermi Large Area Telescope low energy (1FLE) catalog using ten years of IceCube muon–neutrino data. The results of this analysis are found to be consistent with a background-only hypothesis. Assuming an E−2 neutrino spectrum and proportionality between the blazars MeV gamma-ray fluxes and TeV–PeV neutrino flux, the upper limit on the 1FLE blazar energy-scaled neutrino flux is determined to be 1.64 × 10−12 TeV cm−2 s−1 at 90% confidence level. This upper limit is approximately 1% of IceCube’s diffuse muon–neutrino flux measurement.

Searching for High-energy Neutrino Emission from Galaxy Clusters with IceCube

Galaxy clusters have the potential to accelerate cosmic rays (CRs) to ultrahigh energies via accretion shocks or embedded CR acceleration sites. The CRs with energies below the Hillas condition will be confined within the cluster and eventually interact with the intracluster medium gas to produce secondary neutrinos and gamma rays. Using 9.5 yr of muon neutrino track events from the IceCube Neutrino Observatory, we report the results of a stacking analysis of 1094 galaxy clusters with masses ≳1014 M ⊙ and redshifts between 0.01 and ∼1 detected by the Planck mission via the Sunyaev–Zel’dovich effect. We find no evidence for significant neutrino emission and report upper limits on the cumulative unresolved neutrino flux from massive galaxy clusters after accounting for the completeness of the catalog up to a redshift of 2, assuming three different weighting scenarios for the stacking and three different power-law spectra. Weighting the sources according to mass and distance, we set upper limits at a 90% confidence level that constrain the flux of neutrinos from massive galaxy clusters (≳1014 M ⊙) to be no more than 4.6% of the diffuse IceCube observations at 100 TeV, assuming an unbroken E −2.5 power-law spectrum.

Deep-learning-based reconstruction of the neutrino direction and energy for in-ice radio detectors

Ultra-high-energy (UHE) neutrinos (>1016eV) can be measured cost-effectively using in-ice radio detection, which has been explored successfully in pilot arrays. A large radio detector is currently being constructed in Greenland with the potential to measure the first UHE neutrino, and an order-of-magnitude more sensitive detector is being planned with IceCube-Gen2. For such shallow radio detector stations, we present an end-to-end reconstruction of the neutrino energy and direction using deep neural networks (DNNs) developed and tested on simulated data. The DNN determines the energy with a standard deviation of a factor of two around the true energy (σ≈ 0.3 in log10(E)), which meets the science requirements of UHE neutrino detectors. For the first time, we are able to predict the neutrino direction precisely for all event topologies including the complicated electron neutrino charged-current (νe-CC) interactions. The obtained angular resolution shows a narrow peak at O(1°) with extended tails that push the 68% quantile for non-νe-CC (resp. νe-CC interactions) to 4°(5°). This highlights the advantages of DNNs for modeling the complex correlations in radio detector data, thereby enabling measurement of neutrino energy and direction.

Inverse tritium beta decay with relic neutrinos, solar neutrinos, and a Cr51 source

The inverse tritium beta decay (ITBD) reaction, $\nu_e + ^3$H $\to e^- + ^3$He, is a promising experimental tool for observing relic neutrinos created in the early Universe. This reaction has been selected by the PTOLEMY experiment for the search of relic neutrinos. Despite its potential, the ITBD reaction induced by any sources of neutrinos has yet to be observed. We show that an intense $^{51}$Cr radioactive neutrino source is suitable for observing the ITBD reaction for the first time. As the Sun is another source of intense electron neutrinos, we also examine the ITBD reaction rate from solar neutrinos. Based on our recent studies on the evolution of the helicity of relic neutrinos, we further present the ITBD rate for capturing relic neutrinos as a function of neutrino mass hierarchy, the Dirac versus Majorana nature of neutrino, and the mass of the lightest neutrino.

Impact of the Dresden-II and COHERENT neutrino scattering data on neutrino electromagnetic properties and electroweak physics

Coherent elastic neutrino-nucleus scattering (CEνNS) represents a powerful tool to investigate key electroweak physics parameters and neutrino properties since its first observation in 2017 by the COHERENT experiment exploiting the spallation neutron source at Oak Ridge National Laboratory. In light of the recent detection of such a process with antineutrinos produced by the Dresden-II reactor scattering off a germanium detector, we revisit the limits so far set on the neutrino magnetic moments, charge radii and millicharges as well as on the weak mixing angle. In order to do so, we also include the contribution of elastic neutrino-electron scattering, whose effect becomes non negligible in some beyond the Standard Model theories. By using different hypotheses for the germanium quenching factor and the reactor antineutrino flux, we provide a measurement of the weak mixing angle at the low-energy scale of the Dresden-II reactor experiment and, thanks to a combined analysis with the latest cesium iodide and argon data set released by the COHERENT Collaboration, we deliver updated limits for the neutrino electromagnetic properties. Interestingly, we are able to set a new best upper limit on the electron neutrino charge radius and significantly improve the other CEνNS-related limits on the neutrino electric charge and magnetic moment.

Toward a full description of MeV dark matter decoupling: A self-consistent determination of relic abundance and Neff

Thermal dark matter at the MeV mass scale has its abundance set during the highly nontrivial epochs of neutrino decoupling and electron annihilation. The technical obstacles attached to solving Boltzmann equations of multiple interacting sectors being both relativistic and nonrelativistic have to-date prevented the full treatment of this problem. Here, for the first time, we calculate the freeze-out of light dark matter, taking into account the energy transfer between the dark sector, neutrinos, and the electromagnetically interacting plasma from annihilation and elastic scattering processes alike. We develop a numerically feasible treatment that allows to track photon and neutrino temperatures across freeze-out and to arrive at a precision prediction of ${N}_{\mathrm{eff}}$ for arbitrary branching ratios of the dark matter annihilation channels. In addition, our treatment resolves for the first time the dark matter temperature evolution across freeze-out involving three sectors. It enters in the efficiency of velocity-dependent annihilation channels and for a flavor-blind $p$-wave annihilation into electron- and neutrino-pairs of all generations, we find the present Planck data exclude a complex scalar dark matter particle of mass of ${m}_{\ensuremath{\phi}}\ensuremath{\le}7\text{ }\text{ }\mathrm{MeV}$.

Absolute ν Mass Measurement with the DUNE Experiment.

Time of flight delay in the supernova neutrino signal offers a unique tool to set model-independent constraints on the absolute neutrino mass. The presence of a sharp time structure during a first emission phase, the so-called neutronization burst in the electron neutrino flavor time distribution, makes this channel a very powerful one. Large liquid argon underground detectors will provide precision measurements of the time dependence of the electron neutrino fluxes. We derive here a new ν mass sensitivity attainable at the future DUNE far detector from a future supernova collapse in our galactic neighborhood, finding a sub-eV reach under favorable scenarios. These values are competitive with those expected for laboratory direct neutrino mass searches.

Progress of the ECHo SDR Readout Hardware for Multiplexed MMCs

The electron capture in ^{163}Holmium (ECHo) experiment seeks to achieve sub-eV sensitivity of the electron neutrino mass through calorimetric decay spectroscopy of ^{163}Ho in large arrays of cryogenic magnetic microcalorimeters (MMCs). Microwave SQUID multiplexing serves to efficiently increase the number of readout channels, thus calorimeters per array and ultimately per cryostat. A corresponding frequency multiplexing room temperature software-defined radio (SDR) system is in development to enable the readout of this increased number of MMCs per cable. The SDR consists of a custom FPGA platform that provides signal generation and analysis capabilities, as well as tailored signal conversion and analog conditioning front end electronics that enable the room-temperature-to-cryogenic interface. Ultimately, the system will read out 400 multiplexer channels with double pixel detectors through a bandwidth of 4 GHz (IEEE C band). As high-resolution data converters are limited in sample rate, the C-band is split into five sub-bands using a two-stage mixing method. In this contribution, a prototype of the heterodyne RF design is presented. It comprises one of the five 800 MHz sub-bands for a target frequency range between 4 and 8 GHz. Furthermore, the second version of the A/D converter stage is presented, capable of generating and digitizing up to five complex basebands using 1 GSs^{-1} converters, the reference clocks and a flux-ramp signal. We will show first results of their single and combined characterization in the lab. The current state of the prototype hardware enables preliminary measurements, only limited in bandwidth and with slightly higher noise. Potential improvements could be derived and will be implemented in the full bandwidth, 5-sub-band RF PCB design.

Differential cross section measurement of charged current νe interactions without final-state pions in MicroBooNE

In this paper we present the first measurements of an exclusive electron neutrino cross section with the MicroBooNE experiment using data from the Booster neutrino beamline at Fermilab. These measurements are made for a selection of charged-current electron neutrinos without final-state pions. Differential cross sections are extracted in energy and angle with respect to the beam for the electron and the leading proton. The differential cross section as a function of proton energy is measured using events with protons both above and below the visibility threshold. This is done by including a separate selection of electron neutrino events without reconstructed proton candidates in addition to those with proton candidates. Results are compared to the predictions from several modern generators, and we find the data agrees well with these models. The data shows best agreement, as quantified by the p-value, with the generators that predict a lower overall cross section, such as GENIE v3 and NuWro.Received 5 August 2022Accepted 29 August 2022DOI:https://doi.org/10.1103/PhysRevD.106.L051102Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Physical SystemsNeutrinosParticles & Fields

Geuine tripartite entanglement in three-flavor neutrino oscillations

The violation of Leggett–Garg inequalities tested the quantumness of neutrino oscillations (NOs) across macroscopic distances. The quantumness can be quantified by using the tools of the quantum resource theories. Recently, a new genuine tripartite entanglement measure (Xie et al. in Phys Rev Lett 127:040403, 2021), concurrence fill, is defined as the square root of the area of the concurrence triangle satisfying all genuine multipartite entanglement conditions. It has several advantages compared to other existing tripartite measures. Here, we focus on using concurrence fill to quantify the tripartite entanglement in three-flavor NOs. Concurrence fill can reach its maximum 0.89 for the experimentally-observed electron antineutrino oscillations, but it cannot for the muon antineutrino oscillations. In both cases, we compare its performance with other three tripartite entanglement measures, including the generalized geometric measure (GGM), the three-pi entanglement, and the genuinely multipartite concurrence (GMC), in the neutrino propagation, and accordingly show that concurrence fill contains the most quantum resource. Furthermore, concurrence fill and the three-pi entanglement are always smooth, while GGM and GMC measures have several sharp peaks. The genuine tripartite quantification of the quantumness of three-flavor NOs represents the first step towards the further potential application of neutrinos on quantum information processing.

Cosmic ray muon clustering for the MicroBooNE liquid argon time projection chamber using sMask-RCNN

In this article, we describe a modified implementation of Mask Region-based Convolutional Neural Networks (Mask-RCNN) for cosmic ray muon clustering in a liquid argon TPC and applied to MicroBooNE neutrino data. Our implementation of this network, called sMask-RCNN, uses sparse submanifold convolutions to increase processing speed on sparse datasets, and is compared to the original dense version in several metrics. The networks are trained to use wire readout images from the MicroBooNE liquid argon time projection chamber as input and produce individually labeled particle interactions within the image. These outputs are identified as either cosmic ray muon or electron neutrino interactions. We find that sMask-RCNN has an average pixel clustering efficiency of 85.9% compared to the dense network's average pixel clustering efficiency of 89.1%. We demonstrate the ability of sMask-RCNN used in conjunction with MicroBooNE's state-of-the-art Wire-Cell cosmic tagger to veto events containing only cosmic ray muons. The addition of sMask-RCNN to the Wire-Cell cosmic tagger removes 70% of the remaining cosmic ray muon background events at the same electron neutrino event signal efficiency. This event veto can provide 99.7% rejection of cosmic ray-only background events while maintaining an electron neutrino event-level signal efficiency of 80.1%. In addition to cosmic ray muon identification, sMask-RCNN could be used to extract features and identify different particle interaction types in other 3D-tracking detectors.

Exploiting a future galactic supernova to probe neutrino magnetic moments

A core-collapse supernova (SN) offers an excellent astrophysical laboratory to test non-zero neutrino magnetic moments. In particular, the neutronization burst phase, which lasts for a few tens of milliseconds post-bounce, is dominated by electron neutrinos and can offer exceptional discovery potential for transition magnetic moments. We simulate the neutrino spectra from the burst phase in forthcoming neutrino experiments like the Deep Underground Neutrino Experiment (DUNE), and the Hyper-Kamiokande (HK), by taking into account spin-flavour conversions of supernova neutrinos caused by interactions with ambient magnetic fields. We find that the sensitivities to neutrino transition magnetic moments which can be explored by these experiments for a galactic SN are an order to several orders of magnitude better than the current terrestrial and astrophysical limits. Additionally, we also discuss how this realization might provide light on three important neutrino properties: (a) the Dirac/Majorana nature, (b) the neutrino mass ordering, and (c) the neutrino mass-generation mechanism.

The Emergence of Weak Interaction

The view of the Standard Model on the β decay of neutrons through weak interaction is that neutrons break down ‎to form ‎protons P and weak bosons W^- and finally into protons‎, electron and anti-electron neutrinos. The three ‎quarks (U,d,d) that ‎compose neutrons are joined by strong interaction, so bonds formed by strong interaction ‎supposedly cannot be broken ‎by weak interaction, which is far weaker than strong interaction. Nevertheless, ‎neutrons do decay. Further, the three ‎quarks (U,d,d) that form neutrons are fundamental particles, and it should ‎not be possible for other fundamental particles to ‎emerge from these three fundamental particles. Nevertheless, not ‎only does (U,d,d) change into (U,U,d), but electrons ‎and anti-electron-neutrinos, which are fundamental particles, ‎also emerge. This must not have a double meaning. As shown ‎here, there are multiple contradictions in weak ‎interaction of the Standard Model.‎ In this paper, weak interaction is mediated by the π‎-ons group that results from ‎the working of strong interaction step 1 ‎that was described in a previous paper and acts on the nucleons group ‎‎(‎‎P‎ ‎,P ̅ ‎‎,n,n ̅ ‎ ‎) that resulted from step 2. In other ‎words, at the point immediately prior to the emergence of weak ‎interaction, all the particles that existed in the universe were ‎used in order to make weak interaction emerge. The ‎weak interaction in this paper refers to the strong interaction bonds ‎composed of neutrons and ‎π^±‎-ons first being ‎dissolved by strong interaction. As such, the reason why neutrons change to ‎protons is just because the ‎‎d-quark of ‎the neutron is replaced with the ‎U‎-quark of the‎ π^±‎-on.‎

Axion–neutrino couplings and the effective neutrino mass

In this work, we study the interaction between a complex neutral scalar boson, the axion and neutrinos, as a possible channel for the generation of the neutrino mass. We calculate one-loop corrections to the neutrino propagator and determine the value of the neutrino mass induced by the interactions with axions. We have obtained a set of relationships between the axion mass, the electron–neutrino mass and the strength of the coupling using current experimental limits on the nonobservation of the neutrinoless double beta decay.

Inelastic charged-current interactions of supernova neutrinos in two-phase liquid xenon dark matter detectors

It is known that neutrinos from supernova (SN) bursts can potentially give rise to nuclear recoil (NR) signals arising from the neutral current (NC) process of coherent elastic neutrino-nucleus scattering ($\mathrm{CE}\ensuremath{\nu}\mathrm{NS}$) interactions of the neutrinos with xenon nuclei in future, large (multiton scale) liquid xenon (LXe) detectors employed for dark matter searches, depending on the SN progenitor mass and distance to the SN. In this paper, we show that the same detectors will also be sensitive to inelastic charged-current (CC) interactions of the SN electron neutrinos (${\ensuremath{\nu}}_{e}\mathrm{CC}$) with xenon nuclei. Such interactions, while creating an electron in the final state, also leave the postinteraction target nucleus in an excited state, the subsequent deexcitation of which produces, among other particles, $\ensuremath{\gamma}$ rays and neutrons. The electron and deexcitation $\ensuremath{\gamma}$ rays will give ``electron recoil'' (ER) type signals, while the deexcitation neutrons---the so-called ``neutrino-induced neutrons'' (${\ensuremath{\nu}}_{e}\mathrm{In}$)---produce, through their multiple scattering on the xenon nuclei, further xenon nuclear recoils that will also give NR signals (in addition to those produced through the $\mathrm{CE}\ensuremath{\nu}\mathrm{NS}$ interactions). We discuss the observable scintillation and ionization signals associated with SN neutrino-induced $\mathrm{CE}\ensuremath{\nu}\mathrm{NS}$ and ${\ensuremath{\nu}}_{e}\mathrm{CC}$ events in a generic LXe detector and argue that upcoming, sufficiently large LXe detectors should be able to detect both these types of events due to neutrinos from reasonably close-by SN bursts. We also note that since the total CC-induced ER and NR signals receive contributions predominantly from ${\ensuremath{\nu}}_{e}\mathrm{CC}$ interactions while the $\mathrm{CE}\ensuremath{\nu}\mathrm{NS}$ contribution comes from NC interactions of all six species of neutrinos, identification of the ${\ensuremath{\nu}}_{e}\mathrm{CC}$ and $\mathrm{CE}\ensuremath{\nu}\mathrm{NS}$ origin events may offer the possibility of extracting useful information about the distribution of the total SN explosion energy going into different neutrino flavors.