Tau Neutrino Research Articles

The camera and readout for the Trinity Demonstrator and the EUSO-SPB2 Cherenkov telescope

We developed a modular silicon photomultiplier camera to detect Earth-skimming PeV to EeV tau neutrinos with the imaging atmospheric Cherenkov technique. We built two cameras, a 256-pixel camera for the Trinity Demonstrator located on Frisco Peak, Utah, and a 512-pixel camera for the Extreme Universe Observatory on a Super-Pressure Balloon II (EUSO-SPB2) Cherenkov Telescope. The front-end electronics are based on the Multipurpose Integrated Circuit (eMUSIC) Application Specific Integrated Circuits (ASICs), and the camera signals are sampled and digitized with the 100MS/s and 12-bit ASIC for General Electronics for TPC (AGET) system. Both cameras are liquid-cooled. We detail the camera concept and the results from characterizing the SiPMs, bench testing, and calibrating the two cameras.

Neutrino Oscillation Effects on the Luminosity of Neutrino-dominated Accretion Flows around Black Holes

A stellar-mass black hole surrounded by the neutrino-dominated accretion flow (NDAF) has been proposed as the central engine of gamma-ray bursts. In this work, we investigate the neutrino/antineutrino luminosity and annihilation luminosity from the NDAF and pair annihilation model, taking into account the neutrino oscillation above the accretion disk. The disk's hydrodynamical properties are modeled using an empirical solution previously derived with boundary conditions, including the effect of electron degeneracy and neutrino trapping. Our key parameters are the mass accretion rate and the black hole spin given in the ranges of Ṁ=0.1 –10 M ⊙ s−1 and 0 ≤ a < 1, respectively. Without neutrino oscillation, the obtained neutrino/antineutrino luminosity is ∼1051–1053 erg s−1, while the neutrino annihilation luminosity is found to be ∼1046–1051 erg s−1. In the presence of neutrino oscillation in the vacuum limit, the electron neutrino annihilation luminosity decreases by ≲22% through the flavor transformation, while the muon and tau neutrino luminosity can increase by up to ∼45% and 60%, respectively. As a result, the total annihilation luminosity can be reduced by up to ∼19% due to the oscillation process above the disk. Finally, we also investigate the case whereby the charge-conjugation-parity-symmetry-violating (CP-violating) phase is changed from δCP = 0° to 245°. However, our results reveal that the CP-violating phase has minimal impact on the neutrino annihilation luminosity.

An event generator for Lepton-Hadron deep inelastic scattering at NLO+PS with POWHEG including mass effects

We present a generator for lepton nucleon collisions in the DIS regime, focusing in particular on processes with a massive lepton and/or a massive quark in the final state. We have built a full code matching NLO QCD corrections to parton shower Monte Carlo programs in the POWHEG-BOX framework. Our code can be used to compute NLO+PS accurate fully differential predictions for neutral current and charged current processes, including processes with an incoming tau neutrino, and/or including charm quarks in the final state. We also made comparisons with available data and predictions for the new neutrino experiments at CERN.

Baryon number violation involving tau leptons

Baryon number violation is our most sensitive probe of physics beyond the Standard Model, especially through the study of nucleon decays. Angular momentum conservation requires a lepton in the final state of such decays, kinematically restricted to electrons, muons, or neutrinos. We show that operators involving taus, which are at first sight too heavy to play a role in nucleon decays, still lead to clean nucleon decay channels with tau neutrinos. While many of them are already constrained from existing two-body searches such as p → π+ν, other operators induce many-body decays such as p→ηπ+ν¯τ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ p\ o {\\eta \\pi}^{+}{\\overline{\ u}}_{\ au } $$\\end{document} and n → K+π−ντ that have never been searched for.

Probing the mixing between sterile and tau neutrinos in the SHiP experiment

We study the expected sensitivity to the mixing between sterile and tau neutrinos directly from the tau neutrino disappearance in the high-energy fixed target experiment. Here, the beam energy is large enough to produce tau neutrinos at the target with large luminosity. During their propagation to the detector, tau neutrinos may oscillate into sterile neutrinos. By examining the energy spectrum of the observed tau neutrino events, we can probe the mixing between sterile and tau neutrinos directly. In this paper, we consider Scattering and Neutrino Detector (SND) at SHiP experiment as a showcase, which uses 400 GeV protons from SPS at CERN, and expect to observe 7,300 tau and anti-tau neutrinos from the 2 × 1020 POT for 5 years operation. Assuming the uncertainty of 10%, we find the sensitivity |Uτ4|2 ∼ 0.08 (90% CL) for ∆m412\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\Delta {m}_{41}^2 $$\\end{document} ∼ 500 eV2 with 10% background to the signal. We also consider a far SND at the end of the SHiP Hidden Sector Decay Spectrometer (HSDS), in which case the sensitivity would be enhanced to |Uτ4|2 ∼ 0.02. Away from this mass, the sensitivity becomes lower than |Uτ4|2 ∼ 0.15 for ∆m412\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\Delta {m}_{41}^2 $$\\end{document} ≲ 100 eV2 or ∆m412\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\Delta {m}_{41}^2 $$\\end{document} ≳ 104eV2.

Tau polarization in neutrino-nucleus interactions at the LHC energy range

Considering that the study of neutrino-nucleus interactions with incident neutrino energy ranges in the GeV–TeV range is feasible at the Large Hadron Collider, we investigate in this paper the degree of polarization P of the (anti)tau lepton produced in (anti)tau neutrino-tungsten interactions. We estimate the differential cross sections and the longitudinal and transverse components of the tau lepton polarization as a function of the tau lepton energy and distinct values of the scattering angle, assuming different values for the energy of the incoming (anti)tau neutrino. Different models for the treatment of the nuclear effects in the parton distribution functions are assumed as input in the calculations. Our results indicate that P&lt;1 for the neutrino energies reached at the LHC and are almost insensitive to the nuclear effects. Published by the American Physical Society 2024

Search for heavy neutral leptons in final states with electrons, muons, and hadronically decaying tau leptons in proton-proton collisions at s\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\sqrt{s} $$\\end{document} = 13 TeV

A search for heavy neutral leptons (HNLs) of Majorana or Dirac type using proton-proton collision data at s\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\sqrt{s} $$\\end{document} = 13 TeV is presented. The data were collected by the CMS experiment at the CERN LHC and correspond to an integrated luminosity of 138 fb−1. Events with three charged leptons (electrons, muons, and hadronically decaying tau leptons) are selected, corresponding to HNL production in association with a charged lepton and decay of the HNL to two charged leptons and a standard model (SM) neutrino. The search is performed for HNL masses between 10 GeV and 1.5 TeV. No evidence for an HNL signal is observed in data. Upper limits at 95% confidence level are found for the squared coupling strength of the HNL to SM neutrinos, considering exclusive coupling of the HNL to a single SM neutrino generation, for both Majorana and Dirac HNLs. The limits exceed previously achieved experimental constraints for a wide range of HNL masses, and the limits on tau neutrino coupling scenarios with HNL masses above the W boson mass are presented for the first time.

Search for a heavy neutral lepton that mixes predominantly with the tau neutrino

We report a search for a heavy neutral lepton (HNL) that mixes predominantly with ντ. The search utilizes data collected with the Belle detector at the KEKB asymmetric energy e+e− collider. The data sample was collected at and just below the center-of-mass energies of the ϒ(4S) and ϒ(5S) resonances and has an integrated luminosity of 915 fb−1, corresponding to (836±12)×106 e+e−→τ+τ− events. We search for production of the HNL (denoted N) in the decay τ−→π−N followed by its decay via N→μ+μ−ντ. The search focuses on the parameter-space region in which the HNL is long-lived, so that the μ+μ− originate from a common vertex that is significantly displaced from the collision point of the KEKB beams. Consistent with the expected background yield, one event is observed in the data sample after application of all the event-selection criteria. We report limits on the mixing parameter of the HNL with the τ neutrino as a function of the HNL mass. Published by the American Physical Society 2024

Uncovering secret neutrino interactions at tau neutrino experiments

We investigate the potential of future tau neutrino experiments for identifying the ντ appearance in probing secret neutrino interactions, which is very important in a variety of fields, such as neutrino physics, dark matter physics, grand unified theories, astrophysics, and cosmology. The reference experiments include the DUNE far detector utilizing the atmospheric data, which is for the first time probing secret interactions, the Forward Liquid Argon Experiment (FLArE100) detector at the Forward Physics Facility, and emulsion detector experiments such as SND@LHC, FASERν, AdvSND, FASERν2, and SND@SHiP. For concreteness, we consider a reference scenario in which the hidden interactions among the neutrinos are mediated by a single light gauge boson Z′ with a mass at most below the sub-GeV scale and an interaction strength gαβ between the active neutrinos να and νβ. We confirm that these experiments have the capability to significantly enhance the current sensitivities on gαβ for mZ′≲500 MeV due to the production of high-energy neutrinos and excellent ability to detect tau neutrinos. Our analysis highlights the crucial role of “downward-going” DUNE atmospheric data in the search for secret neutrino interactions because of the rejection of backgrounds dominated in the upward-going events. Specifically, ten years of DUNE atmospheric data can provide the best sensitivities on geτ and gμτ which are about 2 orders of magnitude improvement. In addition, the beam-based experiments such as FLArE100 and FASERν2 can improve the current constraint on geτ and gμτ by more than an order of magnitude after the full running of the high luminosity LHC with the integrated luminosity of 3 ab−1. For geμ and gee the SHiP experiment can play the most important role in the high-energy region of mZ′&gt;few 100 MeV, and FLArE100 and FASERν2 can set the most stringent constraints for mZ′ less than few keV, in particular, if atmospheric flux uncertainty reduces DUNE sensitivity. Although our analysis is proceeded under our reference scenario of secret Z′, our analysis strategies can be readily applicable to other types of secret interactions such as Majoron models. Published by the American Physical Society 2024

Discovery potential of the Glashow resonance in an air shower neutrino telescope* *Project Supported by the ``CUG Scholar'' Scientific Research Funds at China University of Geosciences (Wuhan) (2024014)

The in-ice or in-water Cherenkov neutrino telescope, such as IceCube, has already proved its power in measuring the Glashow resonance by searching for the bump around arising from the W-boson production. There are many proposals for the next few decades for observations of cosmic tau neutrinos with extensive air showers, also known as tau neutrino telescopes. The air shower telescope is, in principle, sensitive to the Glashow resonance via the channel followed by the tau decay in the air (e.g., TAMBO, which has a geometric area of approximately ). Using a thorough numerical analysis, we find that the discovery significance can be up to 90% with a TAMBO-like setup if PeV neutrinos primarily originate from neutron decays, considering the flux parameters measured by IceCube as the input. The presence of new physics affecting the neutrino flavor composition can also increase the significance. However, if ultrahigh-energy neutrinos are dominantly produced from meson decays, it will be statistically difficult for an advanced proposal such as TAMBO to discriminate the Glashow resonance induced by from the intrinsic background. We have identified several limitations for such advanced telescopes, in comparison with the in-ice or in-water telescope, when measuring resonances: (i) a suppressed branching ratio of 11% for the decay ; (ii) the smearing effect and reduced acceptance because the daughter neutrino takes away 75% of the energy from the W decay; and (iii) a large attenuation effect for Earth-skimming neutrinos with the resonance.

νe → νe scattering with massive Dirac or Majorana neutrinos and general interactions

We calculate the neutrino-electron elastic scattering cross section, extending the results previously obtained in ref. [1], in the presence of generic new interactions that take into account all the effects caused by finite neutrino masses. We address the potential significance of a heavy neutrino sector during precision measurements, particularly for tau neutrinos scattering with masses in the MeV range, for which the existing upper bounds on |Uτ4|2 would result in conceivably measurable contributions. Finally, we comment on the possibility to distinguish between Dirac and Majorana neutrinos, including the analysis of the new emerging parameters and its application to illustrative model-dependent scenarios.

New signal of atmospheric tau neutrino appearance: Sub-GeV neutral-current interactions in JUNO

We propose the first practical method to detect atmospheric tau neutrino appearance at sub-GeV energies, which would be an important test of νμ→ντ oscillations and of new-physics scenarios. In the Jiangmen Underground Neutrino Observatory (JUNO; starts in 2024), active-flavor neutrinos eject neutrons from carbon via neutral-current quasielastic scattering. This produces a two-part signal: the prompt part is caused by the scattering of the neutron in the scintillator, and the delayed part by its radiative capture. Such events have been observed in KamLAND, but only in small numbers and were treated as a background. With νμ→ντ oscillations, JUNO should measure a clean sample of 55 events/yr; with simple νμ disappearance, this would instead be 41 events/yr, where the latter is determined from Super-Kamiokande charged-current measurements at similar neutrino energies. Implementing this method will require precise laboratory measurements of neutrino-nucleus cross sections or other developments. With those, JUNO will have 5σ sensitivity to tau-neutrino appearance in five years of exposure, and likely sooner. Published by the American Physical Society 2024

All-sky Search for Transient Astrophysical Neutrino Emission with 10 Years of IceCube Cascade Events

Neutrino flares in the sky are searched for in data collected by IceCube between 2011 and 2021 May. This data set contains cascade-like events originating from charged-current electron neutrino and tau neutrino interactions and all-flavor neutral-current interactions. IceCube’s previous all-sky searches for neutrino flares used data sets consisting of track-like events originating from charged-current muon neutrino interactions. The cascade data set is statistically independent of the track data sets, and while inferior in angular resolution, the low-background nature makes it competitive and complementary to previous searches. No statistically significant flare of neutrino emission was observed in an all-sky scan. Upper limits are calculated on neutrino flares of varying duration from 1 hr to 100 days. Furthermore, constraints on the contribution of these flares to the diffuse astrophysical neutrino flux are presented, showing that multiple unresolved transient sources may contribute to the diffuse astrophysical neutrino flux.

Collimated muon beam proposal for probing neutrino charge-parity violation

AbstractThe phenomenon of neutrino oscillation is of great theoretical and experimental interest for our understand of the nature of the neutrino and its implication for physics beyond the standard Model. Currently available neutrino oscillation experiments can already constrain neutrino mixing parameters with a confidence level up to 3 standard deviations (σ). However, it remains challenging to provide a deterministic constraint on the Charge-Parity (CP) violation phase of the neutrino mixing matrix. Here, we propose an experimental setup that exploits collimated muon beams to probe neutrino CP-violation. In our proposed acceleration experiment, a 45 GeV positron source with additional muon collimation, interfaces with near-future neutrino detectors like DUNE and T2K, to probe neutrino CP-violation phase with a significantly higher sensitivity than obtained with the neutrino detectors alone, and to determine tau neutrino properties. Simulations estimate the collection of 104 tau (anti-) neutrino in 5 years, and a sensitivity of over 7 standard deviations for δCP = ∣π/2∣ in 5 years. Collecting ντ appearance events from μ− and μ+ beams over 10 years can attain a 3-4 standard deviation sensitivity. This proposal may serve as a tau factory.

Observation of Seven Astrophysical Tau Neutrino Candidates with IceCube.

We report on a measurement of astrophysical tau neutrinos with 9.7yr of IceCube data. Using convolutional neural networks trained on images derived from simulated events, seven candidate ν_{τ} events were found with visible energies ranging from roughly 20TeV to 1PeV and a median expected parent ν_{τ} energy of about 200TeV. Considering backgrounds from astrophysical and atmospheric neutrinos, and muons from π^{±}/K^{±} decays in atmospheric air showers, we obtain a total estimated background of about 0.5 events, dominated by non-ν_{τ} astrophysical neutrinos. Thus, we rule out the absence of astrophysical ν_{τ} at the 5σ level. The measured astrophysical ν_{τ} flux is consistent with expectations based on previously published IceCube astrophysical neutrino flux measurements and neutrino oscillations.

NaNu: Proposal for a neutrino experiment at the SPS collider located at the North Area of CERN

Several experiments have been proposed in the recent years to study the nature of tau neutrinos, in particular aiming for a first observation of tau anti-neutrinos as well as new constrains on the strange-quark content of the nucleon. We propose a new low-cost neutrino experiment at the CERN North area, named NaNu (North Area NeUtrino), compatible with the realization of the future SHADOWS and HIKE experiments at the same experimental area.

Measuring the sterile neutrino mass in spallation source and direct detection experiments

We explore the complementarity of direct detection (DD) and spallation source (SS) experiments for the study of sterile neutrino physics. We focus on the sterile baryonic neutrino model: an extension of the Standard Model that introduces a massive sterile neutrino with couplings to the quark sector via a new gauge boson. In this scenario, the inelastic scattering of an active neutrino with the target material in both DD and SS experiments gives rise to a characteristic nuclear recoil energy spectrum that can allow for the reconstruction of the neutrino mass in the event of a positive detection. We first derive new bounds on this model based on the data from the COHERENT collaboration on CsI and LAr targets, which we find do not yet probe new areas of the parameter space. We then assess how well future SS experiments will be able to measure the sterile neutrino mass and mixings, showing that masses in the range ~15 − 50 MeV can be reconstructed. We show that there is a degeneracy in the measurement of the sterile neutrino mixing that substantially affects the reconstruction of parameters for masses of the order of 40 MeV. Thanks to their lower energy threshold and sensitivity to the solar tau neutrino flux, DD experiments allow us to partially lift the degeneracy in the sterile neutrino mixings and considerably improve its mass reconstruction down to 9 MeV. Our results demonstrate the excellent complementarity between DD and SS experiments in measuring the sterile neutrino mass and highlight the power of DD experiments in searching for new physics in the neutrino sector.

Development of proton beam irradiation system for the NA65/DsTau experiment

Tau neutrino is the least studied lepton of the Standard Model (SM). The NA65/DsTau experiment targets to investigate Ds , the parent particle of the ντ , using the nuclear emulsion-based detector and to decrease the systematic uncertainty of ντ flux prediction from over 50 % to 10 % for future beam dump experiments. In the experiment, the emulsion detectors are exposed to the CERN SPS 400 GeV proton beam. To provide optimal conditions for the reconstruction of interactions, the protons are required to be uniformly distributed over the detector's surface with an average density of 105 cm-2 and the fluctuation of less than 10%. To address this issue, we developed a new proton irradiation system called the target mover. The new target mover provided irradiation with a proton density of 1.01 × 105 cm-2 and the density fluctuation of 1.9 ± 0.3% in the DsTau 2021 run.

A direct detection view of the neutrino NSI landscape

In this article, we study the potential of direct detection experiments to explore the parameter space of general non-standard neutrino interactions (NSI) via solar neutrino scattering. Due to their sensitivity to neutrino-electron and neutrino-nucleus scattering, direct detection provides a complementary view of the NSI landscape to that of spallation sources and neutrino oscillation experiments. In particular, the large admixture of tau neutrinos in the solar flux makes direct detection experiments well-suited to probe the full flavour space of NSI. To study this, we develop a re-parametrisation of the NSI framework that explicitly includes a variable electron contribution and allows for a clear visualisation of the complementarity of the different experimental sources. Using this new parametrisation, we explore how previous bounds from spallation source and neutrino oscillation experiments are impacted. For the first time, we compute limits on NSI from the first results of the XENONnT and LUX-ZEPLIN experiments, and we obtain projections for future xenon-based experiments. These computations have been performed with our newly developed software package, SNuDD. Our results demonstrate the importance of using a more general NSI parametrisation and indicate that next generation direct detection experiments will become powerful probes of neutrino NSI.

Probing heavy sterile neutrinos at neutrino telescopes via the dipole portal

The question of how heavy a sterile neutrino can be probed in experiments leads us to investigate the Primakoff production of heavy sterile neutrinos from ultrahigh-energy neutrinos via the magnetic dipole portal. Despite the suppression from the small magnetic moment, the transition is significantly enhanced by tiny t-channel momentum transfers, similar to the resonant production of pions and axions in an external electromagnetic field. Based on the current IceCube measurement of astrophysical neutrinos up to PeV energies, strong constraints can already be derived on the transition magnetic moments of sterile neutrinos up to TeV masses. Moreover, we investigate the sensitivity of future tau neutrino telescopes, which are designed for EeV cosmogenic neutrino detection. We find that sterile neutrino masses as large as 30TeV can be probed at tau neutrino telescopes such as GRAND, POEMMA, and Trinity.