Tau Neutrino Interactions Research Articles

The SHiP Experiment: Search for New Physics in the Neutrino Sector

The SHiP experiment (for Search for Hidden Particles) which will operate at the CERN Super Proton Synchrotron (SPS) is one of the most promising projects in the field of particle physics. The SPS 400-GeV/c proton beam will be dumped onto the molybdenum–tungsten target of the SHiP detector, and the data corresponding to 2 × 1020 protons on the target will be accumulated in five years of running. The experiment is aimed at a search for very weakly interacting neutral particles beyond the Standard Model framework referred to as novel physics particles: massive neutral leptons, axions, and “dark” photons. Possible existence of such particles can help explain such firmly established phenomena as the baryon asymmetry of the Universe, nonzero neutrino masses, and the presence of dark matter. Beyond that, the experimental program envisages extensive studies in neutrino physics. In particular, we aim at directly detecting the tau antineutrino—the only Standard Model particle which until now has escaped experimental detection. The envisaged search for the right-handed neutrino partners is particularly interesting: theoretically, their existence can help explain some observed phenomena not predicted by the Standard Model. Experimental investigations in the fields of tau-neutrino interactions (as the least studied sector of neutrino physics) and production of charmed particles and a search for interactions of particles of light dark matter will be carried out with a neutrino detector based on relativistic nuclear emulsion. The τ- and τ+ production events will be discriminated (whereby the production of tau antineutrinos will be directly detected) using special magnets developed for the SHiP emulsion detector. Presently, a prototype of the emulsion detector as a key element of the SHiP neutrino detector is being simulated, constructed, and tested. The nuclear-emulsion technology provides a record-high spatial resolution as required for detecting charged particles with extremely short lifetimes. The nuclear-emulsion data will be processed with the advanced automatic equipment available at the participating laboratories. Efficient scanning of large areas on nuclear emulsion relies on modern scanning equipment such as the PAVICOM measuring complex developed at the Lebedev Physical Institute. Thereby, one can efficiently process the data collected with any track detectors, including those irradiated by accelerator beams. On the whole, the construction of the SHiP detector poses a number of nontrivial physical and technical problems addressed by physicists from 62 laboratories operating in 16 countries.

Limits on the flux of tau neutrinos from 1 PeV to 3 EeV with the MAGIC telescopes

A search for tau neutrino induced showers with the MAGIC telescopes is presented. The MAGIC telescopes located at an altitude of 2200 m a.s.l. in the Canary Island of La Palma, can point towards the horizon or a few degrees below across an azimuthal range of about 80°. This provides a possibility to search for air showers induced by tau leptons arising from interactions of tau neutrinos in the Earth crust or the surrounding ocean. In this paper we show how such air showers can be discriminated from the background of very inclined hadronic showers by using Monte Carlo simulations. Taking into account the orography of the site, the point source acceptance and the event rates expected have been calculated for a sample of generic neutrino fluxes from photo-hadronic interactions in AGNs. The analysis of about 30 h of data taken towards the sea leads to a 90% C.L. point source limit for tau neutrinos in the energy range from 1.0 × 1015 eV to 3.0 × 1018 eV of about Eντ2×ϕ(Eντ)<2.0×10−4 GeV cm−2 s−1 for an assumed power-law neutrino spectrum with spectral index γ=−2. However, with 300 h and in case of an optimistic neutrino flare model, limits of the level down to Eντ2×ϕ(Eντ)<8.4×10−6 GeV cm−2 s−1 can be expected.

NOvA short-baseline tau-neutrino search

Three-flavor neutrino oscillations have successfully explained a wide range of neutrino oscillation experiment results. However, anomalous results, such as the electron-antineutrino appearance excess seen by LSND and MiniBooNE, do not fit the three-flavor paradigm and can be explained by the addition of a sterile neutrino at a larger mass scale than the existing three flavor mass states. This paper will present a novel method for selecting tau-neutrino interactions with high purity at the NOvA Near Detector using a convolutional neural network. Based on this method, the sensitivity to anomalous short-baseline tau-neutrino appearance due to sterile neutrino oscillations will be shown.

Tau energy loss and ultrahigh energy skimming tau neutrinos

We consider propagation of high energy earth-skimming taus produced in interactions of astrophysical tau neutrinos. For astrophysical tau neutrinos we take generic power-law flux, $E^{-2}$ and the cosmogenic flux initiated by the protons. We calculate tau energy loss in several approaches, such as dipole models and the phenomenological approach in which parameterization of the $F_2$ is used. We evaluate the tau neutrino charged-current cross section using the same approaches for consistency. We find that uncertainty in the neutrino cross section and in the tau energy loss partially compensate giving very small theoretical uncertainty in the emerging tau flux for distances ranging from $2$ km to $100$ km and for the energy range between $10^6$ GeV and $10^{11}$ GeV, focusing on energies above $10^8$ GeV. When we consider uncertainties in the neutrino cross section, inelasticity in neutrino interactions and the tau energy loss, which are not correlated, i.e. they are not all calculated in the same approach, theoretical uncertainty ranges from about $30\%$ and $60 \%$ at $10^8$ GeV to about factors of 3.3 and 3.8 at $10^{11}$ GeV for the $E^{-2}$ flux and the cosmogenic flux, respectively, for the distance of 10 km rock. The spread in predictions significantly increases for much larger distances, e.g., $\sim 1,000$ km. Most of the uncertainty comes from the treatment of photonuclear interactions of the tau in transit through large distances. We also consider Monte Carlo calculation of the tau propagation and we find that the result for the emerging tau flux is in agreement with the result obtained using analytic approach. Our results are relevant to several experiments that are looking for skimming astrophysical taus, such as the Pierre Auger Observatory, HAWC and Ashra. We evaluate the aperture for the Auger and discuss briefly application to the the other two experiments.

SHiP: a new facility with a dedicated detector for studying tau neutrino properties

SHiP (Search for Hidden Particles) is a new general purpose fixed target facility at the CERN SPS accelerator, with the aim of search for New Physics which has small coupling with standard particles by searching for long lived beyond standard model particles with masses below a few GeV/c2. The SHiP facility is a high intensity beam bump, the 400GeV proton beam extracted from the SPS will be dumped on a heavy target with the aim of integrating 2×1020 pot in 5 years. A dedicated detector, based on the OPERA-like ECC (Emulsion Cloud Chamber), will provide tau and anti-tau neutrino detection capability to study ντ and ν‾τ cross-sections with a statistics a few 100 times larger than the DONUT experiment. Moreover, the structure functions F4 and F5 which is only accessible by tau neutrino interactions can be measured first time. SHiP is the unique chance to study tau and anti tau neutrino properties.

Ultrahigh-energy neutrino follow-up of gravitational wave events GW150914 and GW151226 with the Pierre Auger Observatory

On September 14, 2015 the Advanced LIGO detectors observed their first gravitational-wave (GW) transient GW150914. This was followed by a second GW event observed on December 26, 2015. Both events were inferred to have arisen from the merger of black holes in binary systems. Such a system may emit neutrinos if there are magnetic fields and disk debris remaining from the formation of the two black holes. With the surface detector array of the Pierre Auger Observatory we can search for neutrinos with energy above 100 PeV from point-like sources across the sky with equatorial declination from about -65 deg. to +60 deg., and in particular from a fraction of the 90% confidence-level (CL) inferred positions in the sky of GW150914 and GW151226. A targeted search for highly-inclined extensive air showers, produced either by interactions of downward-going neutrinos of all flavors in the atmosphere or by the decays of tau leptons originating from tau-neutrino interactions in the Earth's crust (Earth-skimming neutrinos), yielded no candidates in the Auger data collected within $\pm 500$ s around or 1 day after the coordinated universal time (UTC) of GW150914 and GW151226, as well as in the same search periods relative to the UTC time of the GW candidate event LVT151012. From the non-observation we constrain the amount of energy radiated in ultrahigh-energy neutrinos from such remarkable events.

Distributions for tau neutrino interactions observed through the decay τ→μντν¯μ

We investigate the problem of identifying $\nu_\tau$-induced reactions in large neutrino telescopes. We concentrate on events with tracks and showers where the respective energies $E_\mu$ and $E_X$ are measured separately. Then we compute analytically and numerically event distributions in two variables $r_l = E_X/E_l$ and $y'=E_{\text{X}}/(E_{\mu}+E_{X})$. We find that the $y'$-distribution is especially useful because in the $\nu_\tau$-induced reactions the distribution has a minimum at $y'=0.75$ and then increases as $y'\rightarrow1$. This is different in $\nu_\mu$-induced reactions where the $y'$-distribution decreases monotonically. The results are demonstrated with figures where one can estimate the required sensitivity of the experiments. Another attractive property is that in several ratios the neutrino flux factorizes and drops out. We hope the results of this article will be useful for searches of tau (anti)neutrinos of energies above 100 GeV to several TeV in the present and planned large volume neutrino telescopes.

Search for astrophysical tau neutrinos in three years of IceCube data

The IceCube Neutrino Observatory has observed a diffuse flux of TeV-PeV astrophysical neutrinos at 5.7{\sigma} significance from an all-flavor search. The direct detection of tau neutrinos in this flux has yet to occur. Tau neutrinos become distinguishable from other flavors in IceCube at energies above a few hundred TeV, when the cascade from the tau neutrino charged current interaction becomes resolvable from the cascade from the tau lepton decay. This paper presents results from a dedicated search for tau neutrinos with energies between 214 TeV and 72 PeV. The analysis searches for IceCube optical sensors that observe two separate pulses in a single event - one from the tau neutrino interaction, and a second from the tau decay. This is the first IceCube tau neutrino search to be more sensitive to tau neutrinos than to any other neutrino flavor. No candidate events were observed in three years of IceCube data. For the first time, a differential upper limit on astrophysical tau neutrinos is derived around the PeV energy region, which is nearly three orders of magnitude lower in energy than previous limits from dedicated tau neutrino searches.

Diffuse flux results from the ANTARES neutrino telescope

The ANTARES neutrino telescope is located in the Mediterranean Sea off the coast of France and offers a high visibility of the Galactic plane. Its main scientific goal is the detection of cosmic neutrinos, which is achieved by measuring the Cherenkov light emitted by the products of neutrino interactions. A limit on the all-sky diffuse neutrino flux has been set using muon-neutrinos, and a new analysis provides an improved sensitivity by also using showers created in electron- and tau-neutrino interactions. In addition, the high visibility of the Galactic plane is exploited in a dedicated analysis focussing on the Galactic plane. In this analysis the diffuse muon-neutrino flux of a region around the Galactic plane is compared with the flux from multiple equivalent off-source regions. Results of these analyses using five years of data will be reported.

Detection of a second [formula omitted] event

OPERA is a neutrino oscillation experiment aiming to prove the tau neutrino appearance for the first time. A tau decay is identified by the detection of its characteristic decay topologies in nuclear emulsion films. OPERA reported the detection of a first tau neutrino event in 2010. We recently detected a second tau neutrino event in the 2011 run sample. The primary vertex has two charged particles of which one exhibits a three-prong vertex in the plastic base of a film after a flight length of 1.54 mm. It satisfies all the selection criteria to be a tau neutrino interaction. Especially the azimuthal angle in the transverse plane between the tau candidate track and the primary track is almost 180 degrees. The number of tau to 3π signal events expected in the analyzed sample is 0.18, the number of background events is 0.05. Considering all modes, the signal expectation is 1.91 events and the background 0.18 events.

Evidence for the Appearance of Atmospheric Tau Neutrinos in Super-Kamiokande

Super-Kamiokande atmospheric neutrino data were fit with an unbinned maximum likelihood method to search for the appearance of tau leptons resulting from the interactions of oscillation-generated tau neutrinos in the detector. Relative to the expectation of unity, the tau normalization is found to be 1.42 ± 0.35(stat)(-0.12)(+0.14)(syst) excluding the no-tau-appearance hypothesis, for which the normalization would be zero, at the 3.8σ level. We estimate that 180.1 ± 44.3(stat)(-15.2)(+17.8) (syst) tau leptons were produced in the 22.5 kton fiducial volume of the detector by tau neutrinos during the 2806 day running period. In future analyses, this large sample of selected tau events will allow the study of charged current tau neutrino interaction physics with oscillation produced tau neutrinos.

Downward-going tau neutrinos and Dark Matter

We discuss the possibility of detecting the downward-going tau neutrino flux from Dark Matter annihilation inside the Sun. In our analysis we focused on the hadronic showers produced by charged-current tau neutrino interactions followed by hadronic tau decay. We include the various sources of tau neutrino backgrounds as well as experimental sources of background due to misidentification of electron and muon events. We find that the downward–going tau neutrino signal has potentially very good prospects for Mton-scale Cherenkov detectors, if the level of misidentification of non–tau events is at the level of percent. In this case, within few years of exposure, a 5 σ significance discovery is potentially reachable for Dark Matter masses in the range from 20 to 300 GeV.

Electron–muon identification by atmospheric shower in a new concept of an EAS detector

We show the test results for TOF resolution and μ/e separation capabilities of a prototype element (Iori and Sergi, 2008 [1]), intended for deployment in an array capable of measuring large zenith angle cosmic rays as well as detecting the signature of Ultra High Energy tau neutrino interactions using the Earth skimming strategy (Fargion et al., 2004 [2], Feng et al., 2002 [3], Beacom et al., 2003 [4], Zas, 2005 [5]). The module was designed to recognize single particles and determine the direction of motion (up/down) and measure the trajectory angles. It uses two pairs of scintillator counters, named towers, each composed by two tiles (20×20cm2, 1.4cm thick), separated by 160cm. Each tile is read by one low voltage R5783 Hamamatsu photomultiplier (PMT). Two PMT boxes are attached to a metal structure that defines the axis of the array. Each tile is embedded in a PVC box which also contains the PMT. The PMT has excellent time resolution (≈400ps) for good TOF precision. The PMT signal was digitized by the MATAQ board in coincidence with KASCADE-GRANDE (KG) shower Delagnes and Breton, 2001 [6].

Downward-going tau neutrinos as a new prospect of detecting dark matter

Dark matter trapped in the Sun produces a flux of all flavors of neutrinos, which then reach the Earth after propagating out of the Sun and oscillating from the production point to the detector. The typical signal which is looked at refers to the muon neutrino component and consists of a flux of up-going muons in a neutrino detector. We propose instead a novel signature: the possibility of looking at the tau neutrino component of the dark matter signal, which is almost background-free in the downward-going direction, since the tau neutrino amount in atmospheric neutrinos is negligible and in the down-going baseline atmospheric muon-neutrinos have no time to sizably oscillate. We analyze the prospects of studying the downward-going tau neutrinos from dark matter annihilation (or decay) in the Sun in Cherenkov detectors, by looking at hadronic showers produced in the charged-current tau neutrino interactions and subsequent tau decay. We discuss the various sources of background (namely the small tau neutrino component in atmospheric neutrinos, both from direct production and from oscillations; tau neutrinos from solar corona interactions; the galactic tau neutrino component) as well as sources of background due to misidentification of electron and muon events. We find that the downward-going tau neutrinos signal has potentially very good prospects for Mton scale Cherenkov detectors, the main limitation being the level of misidentification of non-tau events, which need to be kept at level of percent. Several tens of events per year (depending on the dark matter mass and annihilation/decay channel) are potentially collectible with a Mton scale detector, and a 5 sigma significance discovery is potentially reachable for dark matter masses in the range from 20 to 300 GeV with a few years of exposure on a Mton detector.

Atmospheric tau neutrinos in a multikiloton liquid argon detector

An ultra-large Liquid Argon Time Projection Chamber-based neutrino detector will have the uncommon ability to detect atmospheric tau neutrino events. This paper discusses the most promising modes for identifying charged current tau neutrino interactions, and shows that, with simple kinematic cuts, ~30 tau neutrinos can be isolated in a 100 kt*yr exposure, with greater than 4 sigma significance. This sample is sufficient to perform flux-averaged total cross-section and cross-section shape parameterization measurements -- the first steps toward using tau neutrinos to search for physics beyond the Standard Model.

Constraining nonstandard neutrino-quark interactions with solar, reactor and accelerator data

We present an analysis of nonstandard neutrino interactions (NSI) of electron and tau neutrinos with down-quark using solar, reactor and accelerator data. We include new solar data from SNO phase III and Borexino, as well as new KamLAND data and solar fluxes. We combine these results with the CHARM data allowing us to better constrain the axial and axial-vector electron and tau-neutrino NSI parameters.

Tau neutrino and antineutrino cross sections

Tau neutrino and antineutrino interactions with nucleons in large underground or under ice detectors will be important signals of astrophysical and atmospheric sources of neutrinos. We present here a theoretical update of the deep inelastic scattering contribution to the tau neutrino and antineutrino charged current cross sections with isoscalar nucleon targets and proton targets for incident neutrinos and antineutrinos in the energy range from 10 GeV to 10 TeV. Next-to-leading order quantum chromodynamic corrections, target mass corrections and heavy quark effects are included. Uncertainties in the cross section associated with the structure functions a low momentum transfers, the input parton distribution functions, scale dependence and flavor number scheme are discussed.

Erratum: Constraining nonstandard neutrino-quark interactions with solar, reactor, and accelerator data [Phys. Rev. D80, 105009 (2009)

We present a reanalysis of nonstandard neutrino-down-quark interactions of electron and tau neutrinos using solar, reactor and accelerator data. In addition updating the analysis by including new solar data from SNO phase III and Borexino, as well as new KamLAND data and solar fluxes, a key role is played in our analysis by the combination of these results with the CHARM data. The latter allows us to better constrain the axial and axial-vector electron and tau-neutrino nonstandard interaction parameters characterizing the deviations from the Standard Model predictions.

Simulation of tau neutrino interaction in an emulsion track detector

Simulation of the interactions between tau neutrinos ντ and the material of the emulsion track detector using Geant4 software is described. The purpose of the work is to generate artificial events and to estimate, on their basis, the reconstruction accuracy for the geometric parameters (vertex coordinates, impact parameters, and track kink angles) and distributions of these parameters used in the selection criteria of the OPERA experiment.

Constraining nonstandard neutrino-quark interactions with solar, reactor, and accelerator data

We present a reanalysis of nonstandard neutrino-down-quark interactions of electron and tau neutrinos using solar, reactor, and accelerator data. In addition updating the analysis by including new solar data from SNO phase III and Borexino, as well as new KamLAND data and solar fluxes, a key role is played in our analysis by the combination of these results with the CHARM data. The latter allows us to better constrain the axial and axial-vector electron and tau-neutrino nonstandard interaction parameters characterizing the deviations from the standard model predictions.