Tau Neutrino Research Articles

Cosmic tau neutrino detection via Cherenkov signals from air showers from Earth-emerging taus.

We perform a new, detailed calculation of the flux and energy spectrum of Earth-emerging τ-leptons generated from the interactions of tau neutrinos and antineutrinos in the Earth. A layered model of the Earth is used to describe the variable density profile of the Earth. Different assumptions regarding the neutrino charged- and neutral-current cross sections as well as the τ-lepton energy loss models are used to quantify their contributions to the systematic uncertainty. A baseline simulation is then used to generate the optical Cherenkov signal from upward-moving extensive air showers generated by the τ-lepton decay in the atmosphere, applicable to a range of space-based instruments. We use this simulation to determine the neutrino sensitivity for E ν ≳ 10 PeV for a space-based experiment with performance similar to that for the Probe of Extreme Multi-Messenger Astrophysics (POEMMA) mission currently under study.

Anomalous ANITA air shower events and tau decays

Two unusual neutrino events in the Antarctic Impulse Transient Antenna (ANITA) appear to have been generated by air showers from a particle emerging from the Earth at angles 25-35 degrees above the horizon. We evaluate the effective aperture for ANITA with a simplified detection model to illustrate the features of the angular dependence of expected events for incident standard model tau neutrinos and for sterile neutrinos that mix with tau neutrinos. We apply our sterile neutrino aperture results to a dark matter scenario with long-lived supermassive dark matter that decay to sterile neutrino-like particles. We find that for up-going air showers from tau decays, from isotropic fluxes of standard model, sterile neutrinos or other particles that couple to the tau through suppressed weak interaction cross sections cannot be responsible for the unusual events.

Study of Tau Neutrino Production in Proton Nucleus Interactions

In the DsTau experiment at the CERN SPS, an independent direct way to study the tau neutrino production in high energy proton-nucleous interactions was proposed. Since the main source of tau neutrinos is a decay of Ds mesons, the project aims at measuring the differential cross-section of this reaction. The experimental method is based on the use of high-resolution emulsion detectors for the efficient registration of events with short-lived particle decays. The motivation of the project, details of the experimental technique, and the first results of the analysis of the data collected during test runs, which prove the feasibility of the study are presented.

Final results on neutrino oscillation parameters from the OPERA experiment in the CNGS beam

The OPERA experiment has conclusively observed the appearance of tau neutrinos in the muon neutrino CNGS beam. Exploiting the OPERA detector capabilities, it was possible to isolate high purity samples of $\nu_{e}$, $\nu_{\mu}$ and $\nu_{\tau}$ charged current weak neutrino interactions, as well as neutral current weak interactions. In this Letter, the full dataset is used for the first time to test the three-flavor neutrino oscillation model and to derive constraints on the existence of a light sterile neutrino within the framework of the $3+1$ neutrino model. For the first time, tau and electron neutrino appearance channels are jointly used to test the sterile neutrino hypothesis. A significant fraction of the sterile neutrino parameter space allowed by LSND and MiniBooNE experiments is excluded at 90% C.L. In particular, the best-fit values obtained by MiniBooNE combining neutrino and antineutrino data are excluded at 3.3 $\sigma$ significance.

Ultra-high energy neutrino searches and GW follow-up with the Pierre Auger Observatory

The surface detector array (SD) of the Pierre Auger Observatory is sensitive to neutrinos at energies in the 100 PeV to 100 EeV range. This sensitivity, together with its large acceptance, makes it a complementary detector to other neutrino telescopes, which have their peak sensitivities at lower energies. The neutrino-induced air showers that the SD of the Pierre Auger Observatory is sensitive to can be divided into those induced by interactions of neutrinos of any flavor deep in the atmosphere, and those induced by charged-current interactions of tau neutrinos in the Earth's crust. Both of these types can be efficiently distinguished from cosmic ray-induced air showers, provided that their zenith angles are larger than 60∘. As no neutrino candidates were found in the performed searches, we present limits on the diffuse all-flavor neutrino flux. Using these limits, we obtained constraints on cosmic-ray and neutrino production models. In the light of the recent observations of gravitational waves (GW), we also present the follow-up of LIGO/Virgo GW events. These include binary black hole merger events and also GW170817, the only binary neutron star merger ever observed directly.

Studies on the anomalous magnetic and electric dipole moments of the tau-neutrino in pp collisions at the LHC

Using the effective Lagrangians formalism, we study the radiative process $ pp\rightarrow (\gamma, Z) \rightarrow \nu_{\tau} \bar{\nu}_{\tau} \gamma +X$ in pp collisions at $ \sqrt{s}=$8, 13, 14, 33 TeV. Furthermore, we estimate limits at the 95% C.L. on the dipole moments of the tau-neutrino using integrated luminosities $ \mathcal{L}=$20, 50, 100, 200, 500, 1000, 3000 fb-1 collected with the ATLAS detector at the LHC and we consider systematic uncertainties $ \delta_{sys}=$0, 5, 10%. We found that the LHC at high energy and high luminosity should provide the following limits on the anomalous magnetic and electric dipole moments of the tau-neutrino: $ \tilde{\kappa}_{\nu_\tau} = 1.251\times 10^{-6}$ and $ \tilde{d}_{\nu_\tau} = 2.424\times 10^{-17}$ ecm at 95% C.L. for $ \sqrt{s} =33$ TeV and $\mathcal{L}=3000$ fb-1. We conclude that the process under consideration is a good prospect for probing the dipole moments of the tau-neutrino at the LHC. Our study complements other studies on the dipole moments of the tau-neutrino at pp, $ e^{+}e^{-}$, $ \gamma e^{-}$ and $ \gamma\gamma$ colliders.

Neutrino Flavor Transitions as Mass State Transitions

Experiments have shown that transitions occur between electron neutrino, muon neutrino, and tau neutrino flavors. Some experiments indicate the possible existence of a fourth neutrino known as the sterile neutrino. The question arises: do all neutrino flavors participate in transitions between flavors? These transitions are viewed as mass state transitions in parametrized relativistic dynamics (PRD). PRD frameworks have been developed for neutrino flavor transitions associated with the mixing of two mass states or the mixing of three mass states. This paper presents an extension of the framework to neutrino flavor transitions associated with the mixing of four mass states.

The SHiP experiment and the RPC technology

The discovery of the Higgs boson has fully confirmed the Standard Model of particles and fields. Nevertheless, there are still fundamental phenomena, like the existence of dark matter and the baryon asymmetry of the Universe, which deserve an explanation that could come from the discovery of new particles. The SHiP experiment at CERN meant to search for very weakly coupled particles in the few GeV mass domain has been recently proposed. The existence of such particles, foreseen in Beyond Standard Models, is largely unexplored. A beam dump facility using high intensity 400 GeV protons is a copious source of such unknown particles in the GeV mass range. The beam dump is also a copious source of neutrinos and in particular it is an ideal source of tau neutrinos, the less known particle in the Standard Model. We report the physics potential of such an experiment and describe the use of the RPC technology therein. An anchillary measurement of the charm cross-section will be carried out in July 2018 and RPC are used as a muon detector. We also describe the design and construction of these new chambers.

From [formula omitted] production asymmetry at the LHC to prompt ντ at IceCube

The description of the heavy meson production at large energies and forward rapidities at the LHC is fundamental to derive realistic predictions of the prompt atmospheric neutrino flux at the IceCube Observatory. In particular, the prompt tau neutrino flux is determined by the decay of Ds mesons produced in cosmic ray–air interactions at high energies and large values of the Feynman-xF variable. Recent data of the LHCb Collaboration indicate a production asymmetry for Ds+ and Ds− mesons, which cannot be explained in terms of the standard modeling of the hadronization process. In this paper we demonstrate that this asymmetry can be described assuming an asymmetric strange sea (s(x)≠s¯(x)) in the proton wave function and taking into account the dominant charm and subdominant strange fragmentation into Ds mesons. Moreover, we show that the strange quark fragmentation contribution is dominant at large-xF (≥0.3). The prompt ντ flux is calculated and the enhancement associated with the strange quark fragmentation contribution, disregarded in previous calculations, is estimated. The considered scenario leads to quite sizable enhancement of the high-energy τ-neutrino flux.

Studies of an air-shower imaging system for the detection of ultrahigh-energy neutrinos

We discuss the acceptance and sensitivity of a small air-shower imaging system to detect earth-skimming ultrahigh-energy tau neutrinos. The instrument we study is located on top of a mountain and has an azimuthal field of view of $360^\circ$. We find that the acceptance and sensitivity of such a system is close to maximal if it is located about 2 km above ground, has a vertical field of view of $5^\circ$, allows the reconstruction of an at least $0.3^\circ$ long air-shower image, and features an effective light-collection area of $10$ m$^2$ in any direction. After three years of operation, an imaging system with these features achieves an all-flavor neutrino flux sensitivity of $5\times10^{-9}$ GeV cm$^{-2}$ s$^{-1}$ sr$^{-1}$ at $2\times10^8$ GeV.

Erratum: Comprehensive approach to tau-lepton production by high-energy tau neutrinos propagating through the Earth [Phys. Rev. D 97 , 023021 (2018)

4 MoreReceived 26 January 2019DOI:https://doi.org/10.1103/PhysRevD.99.069902© 2019 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasNeutrino interactionsTechniquesCosmic ray & astroparticle detectorsMonte Carlo methodsParticles & Fields

{brightarrow ctau nu } transitions in the standard model effective field theory

The R(D^{(*)}) anomalies observed in Brightarrow D^{(*)}tau nu decays have attracted much attention in recent years. In this paper, we study the Brightarrow D^{(*)}tau nu , Lambda _brightarrow Lambda _ctau nu , B_crightarrow (J/psi ,,eta _c)tau nu , Brightarrow X_ctau nu , and B_crightarrow tau nu decays, all being mediated by the same quark-level brightarrow ctau nu transition, in the Standard Model Effective Field Theory. The most relevant dimension-six operators for these processes are Q_{lq}^{(3)}, Q_{ledq}, Q^{(1)}_{lequ}, and Q^{(3)}_{lequ} in the Warsaw basis. Evolution of the corresponding Wilson coefficients from the new physics scale Lambda =1 TeV down to the characteristic scale mu _bsimeq m_b is performed at three-loop in QCD and one-loop in EW/QED. It is found that, after taking into account the constraint {{mathcal {B}}}(B_crightarrow tau nu )lesssim 10%, a single left[ C_{lq}^{(3)}right] _{3323}(Lambda ) or left[ C^{(3)}_{lequ}right] _{3332}(Lambda ) can still be used to resolve the R(D^{(*)}) anomalies at 1sigma , while a single left[ C^{(1)}_{lequ}right] _{3332}(Lambda ) is already ruled out by the measured R(D^{(*)}) at more than 3sigma . By minimizing the chi ^2(C_i) function constructed based on the current data on R(D), R(D^*), P_tau (D^*), R(J/psi ), and R(X_c), we obtain eleven most trustworthy scenarios, each of which can provide a good explanation of the R(D^{(*)}) anomalies at 1sigma . To further discriminate these different scenarios, we predict thirty-one observables associated with the processes considered under each NP scenario. It is found that most of the scenarios can be differentiated from each other by using these observables and their correlations.

B rightarrow c tau nu _{tau } Decays: a catalogue to compare, constrain, and correlate new physics effects

In this article, we predict the standard model (SM) values of the asymmetric and angular observables in Brightarrow D^{(*)}tau nu _{tau } decays, using the results of the new up-to-date analysis in Brightarrow D^{(*)}ell nu _{ell }. We also revisit the SM prediction of the inclusive ratio {mathcal {R}}_{X_c}, and we give its values in different schemes of the charm quark mass. This is the first analysis which includes all the known corrections in the SM. In addition, we analyze the brightarrow ctau nu _tau decay modes in a model-independent framework of effective field theory beyond the standard model. Considering all the possible combinations of the effective operators in b rightarrow c tau nu _{tau } decays and using the Akaike information criterion, we find the scenarios which can best explain the available data on these channels. In the selected scenarios, best-fit values and correlations of the new parameters are extracted. Using these results, predictions are made on various observables in the exclusive and inclusive semitaunic b rightarrow c decays. The graphical correlations between these observables are shown, which are found to be useful in discriminating various new physics scenarios.

Geometrical constraints of observing very high energy Earth-skimming neutrinos from space

The detection of very-high-energy (VHE) neutrinos (Eν ≳ 10 PeV) is a challenge that future generations of experiments are being designed and constructed to address. One promising method relies on using the Earth as a neutrino target for indirect detection of skimming tau neutrinos interacting within the Earth and producing tau leptons that are able to escape and decay in the atmosphere. The tau decay produces upward-moving Extensive Air Showers (EASs). A space-based or suborbital instrument observing the ground near the Earth limb can search for the beamed Cherenkov signal produced by the up-going EAS resulting from the tau-lepton decay. In this paper, we derive the geometrical constraints for such an observation in general and for the specific case of the Probe Of Extreme Multi-Messenger Astrophysics (POEMMA) mission currently under study, focusing on the Cherenkov signal detection. We show that, using reasonable orbital parameters, POEMMA can achieve full-sky coverage to search for potential neutrino sources over the length of its mission. We also show that follow-up of a transient Target-of-Opportunity (ToO), such as a flaring source, can be achieved within an orbit time scale depending on the source location on the celestial sphere and its relative position with respect to the Sun and the Moon.

Production of keV sterile neutrinos in supernovae: New constraints and gamma-ray observables

We study the production of sterile neutrinos in supernovae, focusing in particular on the keV--MeV mass range, which is the most interesting range if sterile neutrinos are to account for the dark matter in the Universe. Focusing on the simplest scenario in which sterile neutrinos mixes only with muon or tau neutrino, we argue that the production of keV--MeV sterile neutrinos can be strongly enhanced by a Mikheyev--Smirnov--Wolfenstein (MSW) resonance, so that a substantial flux is expected to emerge from a supernova, even if vacuum mixing angles between active and sterile neutrinos are tiny. Using energetics arguments, this yields limits on the sterile neutrino parameter space that reach down to mixing angles of the order of $\sin^2 2\theta \lesssim 10^{-14}$ and are up to an order of magnitude stronger than those from X-ray observations. While supernova limits suffer from larger systematic uncertainties than X-ray limits they apply also to scenarios in which sterile neutrinos are not abundantly produced in the early Universe. We also compute the flux of $\mathcal{O}(\text{MeV})$ photons expected from the decay of sterile neutrinos produced in supernovae, but find that it is beyond current observational reach even for a nearby supernova.

Tau neutrinos in IceCube, KM3NeT and the Pierre Auger Observatory

In 2018, the IceCube collaboration reported evidence for the identification of a blazar as an astrophysical neutrino source. That evidence is briefly summarised here before focusing on the prospects of tau neutrino physics in IceCube, both at high energies (astrophysical neutrinos) and at lower energies (atmospheric neutrino oscillations). In addition, future neutrino detectors such as KM3NeT and the IceCube Upgrade and their tau neutrino physics potential are discussed. Finally, the detection mechanism for high-energy (tau) neutrinos in the Pierre Auger Observatory and the resulting flux upper limits are presented.

Measurement of atmospheric tau neutrino appearance with IceCube DeepCore

We present a measurement of atmospheric tau neutrino appearance from oscillations with three years of data from the DeepCore sub-array of the IceCube Neutrino Observatory. This analysis uses atmospheric neutrinos from the full sky with reconstructed energies between 5.6 GeV and 56 GeV to search for a statistical excess of cascade-like neutrino events which are the signature of nutau interactions. For CC+NC (CC-only) interactions, we measure the tau neutrino normalization to be 0.73 +0.30 -0.24 (0.57 +0.36 -0.30) and exclude the absence of tau neutrino oscillations at a significance of 3.2 sigma (2.0 sigma) These results are consistent with, and of similar precision to, a confirmatory IceCube analysis also presented, as well as measurements performed by other experiments.

Neutrino Oscillations and Decoherence in Short-GRB Progenitors

Abstract Neutrinos are produced in cosmic accelerators, like active galactic nuclei, blazars, supernova remnants and gamma-ray bursts (GRBs). On their way to the Earth they experience flavor oscillations. The interactions of the neutrinos coming from the source with other particles, e.g., intergalactic primordial neutrinos or heavy-mass right-handed neutrinos, on their way to the detector may transform the original wavepacket in pointer states. This phenomenon, known as decoherence, becomes important in the reconstruction of processes at the source. In this work, we study neutrino emission in short GRBs by adopting the Fireshell Model. We consider e − e +-pair annihilation as the main channel for neutrino production. We compare the properties of the neutrino flux with the characteristic photon signal produced once the transparency condition is reached. We study the effects of flavor oscillations and decoherence as neutrinos travel from the region near the black hole event horizon outward. We consider the source to be in thermal equilibrium and calculate energy distribution functions for electrons and neutrinos. To compute the effects of decoherence we use a Gaussian model. In this scenario, the emitted electron–neutrinos transform into pointer states consisting of 67.8% electron–neutrinos and 32.2% as a combination of mu and tau neutrinos. We found that decoherence plays an important role in the evolution of the neutrino wavepacket, leading to the detected pointer states on Earth.

Prompt neutrinos and intrinsic charm at SHiP

We present a new evaluation of the far-forward neutrino plus antineutrino flux and number of events from charm hadron decays in a 400 GeV proton beam dump experiment like the Search for Hidden Particles (SHiP). Using next-to-leading order perturbative QCD and a model for intrinsic charm, we include intrinsic transverse momentum effects and other kinematic angular corrections. We compare this flux to a far-forward flux evaluated with next-to-leading order perturbative QCD, without intrinsic transverse momentum, that used the angular distribution of charm quarks rather than the neutrinos from their decays. The tau neutrino plus antineutrino number of events in the perturbative QCD evaluation is reduced by a factor of about three when intrinsic transverse momentum and the full decay kinematics are included. We show that intrinsic charm contributions can significantly enhance the number of events from neutrinos from charm hadron decays. Measurements of the number of events from tau neutrino plus antineutrino interactions and of the muon charge asymmetry as a function of energy can be used to constrain intrinsic charm models.

A New Concept for High-Elevation Radio Detection of Tau Neutrinos

Cosmic neutrinos are expected to include a significant flux of tau neutrinos due to flavor mixing over astronomical length scales. However, the tau-neutrino content of astrophysical neutrinos is poorly constrained and a significant flux of cosmogenic tau neutrinos awaits discovery. Earth-skimming tau neutrinos undergo charged-current interactions that result in a tau lepton exiting the Earth. The tau lepton decay generates anextensive air shower and geomagnetic radio emission. To target the tau neutrinos, we present a new tau neutrino detector concept that uses phased antenna arrays placed on high elevation mountains. Simulation studies indicate that a modest array size and small number of stations can achieve competitive sensitivity, provided the receivers are at highs enough elevation.