Tau Neutrino Research Articles

Analysis of the Results of the Neutrino-4 Experiment on the Search for the Sterile Neutrino and Comparison with Results of Other Experiments

We present new results of measurements of reactor antineutrino flux and spectrum dependence on the distance in the range 6-12 meters from the center of the reactor core at SM-3 reactor (Dimitrovgrad, Russia). Additional measurements were carried out and set of data to perform statistical analysis was almost doubled since the previous report. Using all collected data we performed the model independent analysis on the oscillation parameters $\Delta m^2_{14}$ and $\sin^2(2\theta_{14})$. The method of coherent summation of results of measurements allows us to directly observe the effect of oscillations. We observed an oscillation effect in vicinity of $\Delta m^2_{14} = (7.25\pm0.13_{st}\pm1.08_{sys}) \text{eV}^2$ and $\sin^2(2\theta_{14}) =0.26\pm0.08_{st}\pm 0.05_{sys}$. We provide a comparison of our results with results of other experiments on search for sterile neutrino. Combining the result of the Neutrino-4 and the results of measurements of the gallium anomaly and reactor anomaly we obtained value $\sin^2(2\theta_{14})\approx 0.19\pm0.04(4.6\sigma)$. Also was performed comparison of Neutrino-4 experimental results with results of other reactor experiments NEOS, DANSS, STEREO, PROSPECT and accelerator experiments MiniBooNE, LSND and the IceCube experiment also. Sterile neutrino mass which can be calculated using the Neutrino-4 data in assumption that $m^2_4 \approx \Delta m^2_{14}$ is $m_4 = (2.68 \pm 0.13)\text{eV}$. Considering estimations of mixing angles obtained in other experiments we can calculate masses of electron neutrino, muon neutrino and tau neutrino: $m^{\text{eff}}_{\nu_e} = (0.58 \pm 0.09)\text{eV}, m^{\text{eff}}_{\nu_{\mu}} = (0.42 \pm 0.24)\text{eV}, m^{\text{eff}}_{\nu_{\tau}} \leq 0.65\text{eV}$. Extended PMNS matrix for (3 + 1) model with one sterile neutrino is provided, neutrino flavor mixing scheme with sterile neutrino and global fit of reactor experiments.

First observation of a tau neutrino charged current interaction with charm production in the OPERA experiment

An event topology with two secondary vertices compatible with the decay of short-lived particles was found in the analysis of neutrino interactions in the OPERA target. The observed topology is compatible with tau neutrino charged current (CC) interactions with charm production and neutrino neutral current (NC) interactions with coverline{c} pair production. However, other processes can mimic this topology. A dedicated analysis was implemented to identify the underlying process. A Monte Carlo simulation was developed and complementary procedures were introduced in the kinematic reconstruction. A multivariate analysis technique was used to achieve an optimal separation of signal from background. Most likely, this event is a nu _{tau } CC interaction with charm production, the tau and charm particle decaying into 1 prong and 2 prongs, respectively. The significance of this observation is evaluated.

Probing light gauge bosons in tau neutrino experiments

The tau neutrino is probably the least studied particle in the standard model (SM), with only a handful of interaction events being identified so far. This can in part be attributed to their small production rate in the SM, which occurs mainly through ${D}_{s}$ meson decay. However, this also makes the tau neutrino flux measurement an interesting laboratory for additional new physics production modes. In this study, we investigate the possibility of tau neutrino production in the decay of light vector bosons. We consider four scenarios of anomaly-free $U(1)$ gauge groups corresponding to the $B\ensuremath{-}L$, $B\ensuremath{-}{L}_{\ensuremath{\mu}}\ensuremath{-}2{L}_{\ensuremath{\tau}}$, $B\ensuremath{-}{L}_{e}\ensuremath{-}2{L}_{\ensuremath{\tau}}$, and $B\ensuremath{-}3{L}_{\ensuremath{\tau}}$ numbers, analyze current constraints on their parameter spaces, and explore the sensitivity of DONuT as well as the future emulsion detector experiments $\mathrm{FASER}\ensuremath{\nu}$, SND@LHC, and SND@SHiP. We find that these experiments provide the leading direct constraints in parts of the parameter space, especially when the vector boson's mass is close to the mass of the $\ensuremath{\omega}$ meson.

Far-forward neutrinos at the Large Hadron Collider

We present a new calculation of the energy distribution of high-energy neutrinos from the decay of charm and bottom hadrons produced at the Large Hadron Collider (LHC). In the kinematical region of very forward rapidities, heavy-flavor production and decay is a source of tau neutrinos that leads to thousands of charged-current tau neutrino events in a 1 m long, 1 m radius lead neutrino detector at a distance of 480 m from the interaction region. In our computation, next-to-leading order QCD radiative corrections are accounted for in the production cross-sections. Non-perturbative intrinsic-kT effects are approximated by a simple phenomenological model introducing a Gaussian kT -smearing of the parton distribution functions, which might also mimic perturbative effects due to multiple initial-state soft-gluon emissions. The transition from partonic to hadronic states is described by phenomenological fragmentation functions. To study the effect of various input parameters, theoretical predictions for {D}_s^{pm } production are compared with LHCb data on double-differential cross-sections in transverse momentum and rapidity. The uncertain- ties related to the choice of the input parameter values, ultimately affecting the predictions of the tau neutrino event distributions, are discussed. We consider a 3+1 neutrino mixing scenario to illustrate the potential for a neutrino experiment to constrain the 3+1 parameter space using tau neutrinos and antineutrinos. We find large theoretical uncertainties in the predictions of the neutrino fluxes in the far-forward region. Untangling the effects of tau neutrino oscillations into sterile neutrinos and distinguishing a 3+1 scenario from the standard scenario with three active neutrino flavours, will be challenging due to the large theoretical uncertainties from QCD.

Revisiting the B-physics anomalies in R-parity violating MSSM

In recent years, several deviations from the Standard Model predictions in semileptonic decays of B-meson might suggest the existence of new physics which would break the lepton-flavour universality. In this work, we have explored the possibility of using muon sneutrinos and right-handed sbottoms to solve these B-physics anomalies simultaneously in R-parity violating minimal supersymmetric standard model. We find that the photonic penguin induced by exchanging sneutrino can provide sizable lepton flavour universal contribution due to the existence of logarithmic enhancement for the first time. This prompts us to use the two-parameter scenario (C^mathrm{V}_9, , C^mathrm{U}_9) to explain b rightarrow s ell ^+ ell ^- anomaly. Finally, the numerical analyses show that the muon sneutrinos and right-handed sbottoms can explain b rightarrow s ell ^+ ell ^- and R(D^{(*)}) anomalies simultaneously, and satisfy the constraints of other related processes, such as B rightarrow K^{(*)} nu bar{nu } decays, B_s-bar{B}_s mixing, Z decays, as well as D^0 rightarrow mu ^+ mu ^-, tau rightarrow mu rho ^0, B rightarrow tau nu , D_s rightarrow tau nu , tau rightarrow K nu , tau rightarrow mu gamma , and tau rightarrow mu mu mu decays.

Reflections on the anomalous ANITA events: the Antarctic subsurface as a possible explanation

AbstractThe Antarctic Impulsive Transient Antenna (ANITA) balloon experiment was designed to detect radio signals initiated by high-energy neutrinos and cosmic ray (CR) air showers. These signals are typically discriminated by the polarization and phase inversions of the radio signal. The reflected signal from CRs suffer phase inversion compared to a direct ‘tau neutrino’ event. In this paper, we study subsurface reflection, which can occur without phase inversion, in the context of the two anomalous up-going events reported by ANITA. It is found that subsurface layers and firn density inversions may plausibly account for the events, while ice fabric layers and wind ablation crusts could also play a role. This hypothesis can be tested with radar surveying of the Antarctic region in the vicinity of the anomalous ANITA events. Future experiments should not use phase inversion as a sole criterion to discriminate between down-going and up-going events, unless the subsurface reflection properties are well understood.

R&D on Trigger Resistive Plate Chambers for the Search for Hidden Particles Experiment

The main goals of the Search for Hidden Particles (SHiP) experiment are to observe hidden particles and to run a high-statistics study of tau neutrino events. Two different types of resistive plate chambers (RPCs) will be used in the future SHiP experiment: one for triggers to select the decayed muons emitted via tau neutrino interactions and one for precision time measurements of charged particles, which are expected from the decays of hidden particles. In the present research, we constructed and tested a prototype RPC module to study the fundamental detector performance of the muon trigger RPCs in the tau neutrino detector of the SHiP experiment. The required detector characteristics, such as the intrinsic noise rate, the time response, and the spatial resolution, were proven through the test of the present prototype detector with cosmic muons.

Heavy-Quark expansion for {{bar{B}}_srightarrow D^{(*)}_s} form factors and unitarity bounds beyond the {SU(3)_F} limit

We carry out a comprehensive analysis of the full set of {bar{B}}_q rightarrow D_q^{(*)} form factors for spectator quarks q=u,d,s within the framework of the Heavy-Quark expansion (HQE) to order {mathcal {O}}left( alpha _s, 1/m_b, 1/m_c^2right) . In addition to the available lattice QCD calculations we make use of two new sets of theoretical constraints: we produce for the first time numerical predictions for the full set of {bar{B}}_s rightarrow D_s^{(*)} form factors using Light-Cone sum rules with B_s-meson distribution amplitudes. Furthermore, we reassess the QCD three-point sum rule results for the Isgur-Wise functions entering all our form factors for both q=u,d and q=s spectator quarks. These additional constraints allow us to go beyond the commonly used assumption of SU(3)_F symmetry for the {{bar{B}}}_srightarrow D_s^{(*)} form factors, especially in the unitarity constraints which we impose throughout our analysis. We find the coefficients of the IW functions emerging at {mathcal {O}}left( 1/m_c^2right) to be consistent with the naive {mathcal {O}}left( 1right) expectation, indicating a good convergence of the HQE. While we do not find significant SU(3) breaking, the explicit treatment of q=s as compared to a simple symmetry assumption renders the unitarity constraints more effective. We find that the (pseudo)scalar bounds are saturated to a large degree, which affects our theory predictions. We analyze the phenomenological consequences of our improved form factors by extracting |V_{cb}| from {bar{B}}rightarrow D^{(*)}ell nu decays and producing theoretical predictions for the lepton-flavour universality ratios R(D), R(D^*), R(D_s) and R(D_s^*), as well as the tau - and D_q^* polarization fractions for the {bar{B}}_qrightarrow D_q^{(*)}tau nu modes.

A Search for IceCube Events in the Direction of ANITA Neutrino Candidates

Abstract During the first three flights of the Antarctic Impulsive Transient Antenna (ANITA) experiment, the collaboration detected several neutrino candidates. Two of these candidate events were consistent with an ultra-high-energy upgoing air shower and compatible with a tau neutrino interpretation. A third neutrino candidate event was detected in a search for Askaryan radiation in the Antarctic ice, although it is also consistent with the background expectation. The inferred emergence angle of the first two events is in tension with IceCube and ANITA limits on isotropic cosmogenic neutrino fluxes. Here we test the hypothesis that these events are astrophysical in origin, possibly caused by a point source in the reconstructed direction. Given that any ultra-high-energy tau neutrino flux traversing the Earth should be accompanied by a secondary flux in the TeV–PeV range, we search for these secondary counterparts in 7 yr of IceCube data using three complementary approaches. In the absence of any significant detection, we set upper limits on the neutrino flux from potential point sources. We compare these limits to ANITA’s sensitivity in the same direction and show that an astrophysical explanation of these anomalous events under standard model assumptions is severely constrained regardless of source spectrum.

The DsTau Experiment: A Study for Tau-Neutrino Production

For clarifying the validity of the Lepton Universality hypothesis, one of the fundamental statements of the Standard Model, the interaction cross section for all three flavors of leptons have to be known with high precision. In neutrino sector, for electron and muon neutrinos, the interaction cross section is known fairly well, but for tau neutrino only poor estimations exist. In particular, the most direct measurement by the DONuT experiment was performed with rather poor accuracy due to low statistics and an uncertainty of the tau neutrino flux. The DsTau experiment proposes to study tau-neutrino production process and thus to improve significantly the accuracy of calculations of tau neutrino flux for neutrino accelerator experiments. To study reactions providing most of tau neutrinos, the experiment uses a setup based on high resolution nuclear emulsions, capable to register short lived particle decays created in proton-nucleus interactions. The present report is an overview of the DsTau experiment together with some of the preliminary results from the pilot run.

Physics Potential of the IceCube Upgrade

The IceCube Neutrino Observatory is a cubic-kilometer Cherenkov detector at the South Pole. The planned Upgrade project, which consists of seven new strings, will be deployed with densely spaced optical modules to improve the neutrino detection capability at a few GeV level. The goal of IceCube Upgrade is to provide world-leading sensitivity to neutrino oscillations and to take unique measurements of tau neutrino appearance with high precision. It also serves as a R&D platform for the future IceCube-Gen2 experiment. The newly designed DOMs will provide improved detection efficiency and directional resolution for Cherenkov photons. Furthermore, new calibration devices will be introduced which will provide a better understanding of the ice properties, thereby reduce the detector systematic uncertainties. The resulting calibration improvement from the Upgrade will be applied to the entire archival data of IceCube collected for more than 10 years, with an expected improvement of the angular and spatial resolution of the detected astrophysical neutrino events. The Upgrade can be regarded as the first stage in the development of IceCube-Gen2, the next-generation neutrino telescope at the South Pole.

Observing EeV neutrinos through Earth: GZK and the anomalous ANITA events

Tau neutrinos are unique cosmic messengers, especially at extreme energies. When they undergo a charged-current interaction, the short lifetime of the produced tau gives rise to secondary tau neutrinos that carry a significant fraction of the primary neutrino energy. Here we apply this effect, known as tau neutrino regeneration, to extremely high energy neutrinos passing through Earth. We find that for most column depths, with the exception of propagation through the core, Earth-traversing tau neutrinos emerge at \U0001d4aa(PeV) energies. We use these secondaries to estimate the expected signal from cosmogenic fluxes at IceCube and find a non-negligible contribution to the astrophysical component above 1 PeV . We also constrain the anomalous ANITA observations via the accompanying secondaries expected at IceCube. We calculate that ANITA should see fewer than 10−7 events in the reported direction, regardless of assumed source energy spectrum, ruling out the possibility that these events are astrophysical in origin under Standard Model assumptions.

DsTau: study of tau neutrino production with 400 GeV protons from the CERN-SPS

In the DsTau experiment at the CERN SPS (NA65), an independent and direct way to measure tau neutrino production following high energy proton interactions was proposed. As the main source of tau neutrinos is a decay of Ds mesons, produced in proton-nucleus interactions, the project aims at measuring a differential cross section of this reaction. The experimental method is based on a use of high resolution emulsion detectors for effective registration of events with short lived particle decays. Here we present the motivation of the study, details of the experimental technique, and the first results of the analysis of the data collected during test runs, which prove feasibility of the full scale study of the process in future.

Dataset of tau neutrino interactions recorded by the OPERA experiment

We describe the dataset of very rare events recorded by the OPERA experiment. The events represent tracks of particles associated with tau neutrino interactions coming from the transformation of muon neutrinos due to a process known as neutrino oscillations. The events have been published on the CERN Open Data Portal. We describe the dataset semantics and the interactive event display visualisation tool accompanying the data release.

Detecting and studying high-energy collider neutrinos with FASER at the LHC

Neutrinos are copiously produced at particle colliders, but no collider neutrino has ever been detected. Colliders produce both neutrinos and anti-neutrinos of all flavors at very high energies, and they are therefore highly complementary to those from other sources. FASER, the Forward Search Experiment at the LHC, is ideally located to provide the first detection and study of collider neutrinos. We investigate the prospects for neutrino studies with FASERnu , a proposed component of FASER, consisting of emulsion films interleaved with tungsten plates with a total target mass of 1.2 t, to be placed on-axis at the front of FASER. We estimate the neutrino fluxes and interaction rates, describe the FASERnu detector, and analyze the characteristics of the signals and primary backgrounds. For an integrated luminosity of 150~text {fb}^{-1} to be collected during Run 3 of the 14 TeV LHC in 2021–23, approximately 1300 electron neutrinos, 20,000 muon neutrinos, and 20 tau neutrinos will interact in FASERnu , with mean energies of 600 GeV to 1 TeV. With such rates and energies, FASER will measure neutrino cross sections at energies where they are currently unconstrained, will bound models of forward particle production, and could open a new window on physics beyond the standard model.

The SHiP physics program at CERN

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, the neutrino masses 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 is proposed to search for very weakly coupled particles in the few GeV mass domain where the existence of such particles 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 very intense source of neutrinos and, in particular, of tau neutrinos, the less known particle in the Standard Model. We report the physics potential of such an experiment. An ancillary measurement of the charm cross-section was carried out in July 2018 and the data are under analysis and we report preliminary results. Moreover, a prototype of the neutrino detector is being designed to possibly take data at the LHC in its Run3 of operation. We describe the proposed detector and the physics case.

Study of tau neutrino production in proton-nucleus interactions

Tau neutrino properties are not so well known in comparison to those of muon or electron neutrinos. The tau neutrino interaction cross-section was directly measured by the DONUT experiment in 2008 on a basis of 9 registered tau neutrinos, and with a large systematical error of 50% due to a poor knowledge of the tau neutrino flux in this beam dump experiment. However, more accurate measurement of the cross section is needed for future neutrino experiments. It would also allow testing the Lepton Universality (LU) of Standard Model in neutrino interactions. Recently several results for B-meson decays (LHCb, Babar) demonstrated hints of possible LU violation. The tau neutrinos are produced in the Ds meson decays to tau, Ds → τ vT, and the cascade decay of the tau τ → vT X. DsTau experiment has been proposed to study the tau neutrino production at CERN SPS. It will measure the Ds production differential cross-section in the proton-tungsten interactions. This will allow reducing of the uncertainty due to the tau neutrino flux in the DONUT result from 50% to 10%. The peculiar Ds cascade decay topology ("double kink") in a few mm range will be detected by nuclear emulsion tracker thanks to its excellent spatial resolution (∼50nm).In 2016 and 2017, we made test beam exposures of nuclear emulsion modules at CERN SPS 400GeV/c proton beam followed by the pilot run in August 2018. A physics run in 2021 is scheduled. The status and prospects of the DsTau project as well as a review of the modern nuclear emulsion technique and the methods of its data analysis are presented.

New results from the OPERA experiment in the CNGS neutrino beam

A new analysis of full OPERA data set was performed, based on looser selection criteria and multivariate approach. Oscillation parameters and tau neutrino cross-section have been determined with a reduced statistical uncertainty, and the discovery of tau neutrino appearance is confirmed at 6.1σ level. Moreover, the search for electron neutrino events has been extended to the full dataset, exploiting an improved method for the electron neutrino energy estimation. New limits have been set in the 3+1 neutrino model.

Limits on the charged Higgs parameters in the two Higgs doublet model using CMS sqrt{s}=13 TeV results

The latest CMS results on the upper limits on sigma _{H^pm }BR(H^pm rightarrow tau ^pm nu ) and sigma _{H^pm }BR(H^+ rightarrow t{bar{b}}) for sqrt{s}=13 TeV at an integrated luminosity of 35.9 hbox {fb}^{-1} are used to impose constraints on the charged Higgs H^pm parameters within the Two Higgs Doublet Model (2HDM). The 2HDM is the simplest extension of the Standard Model (SM) under the same gauge symmetry to contain charged Higgs and is relatively little constrained compared to the Minimal Supersymmetric Standard Model (MSSM). The latest results lead to much more stringent constraints on the charged Higgs parameter space than for the earlier 8 TeV results. The CMS collaboration also studied the exotic bosonic decays H^pm rightarrow W^pm A and A rightarrow mu ^+ mu ^- for the first time and put upper limits on the BR(trightarrow H^+ b) for the light charged Higgs boson. These constraints lead to the exclusion of parameter space which is not excluded by the tau nu channel. For comparison the exclusion regions from flavor physics constraints are also discussed.

タウニュートリノ生成研究(DsTau実験)におけるチャーム粒子解析

タウニュートリノ生成研究(DsTau実験)におけるチャーム粒子解析