Reconstruction Of Neutrino Events Research Articles

Results of the track-like neutrino event reconstruction at the BAIKAL-GVD neutrino telescope

Baikal-GVD is a 1 km3 – scale neutrino telescope being constructed in Lake Baikal. Presently the sensitive volume of the detector constitutes about 0.5 km3. Muons being produced in muon and partly tau-neutrino interactions in the vicinity of the telescope ongoing through the W-boson exchange propagate at large distances in Lake water. Reconstructed muon trajectory provides the most precise probe of the neutrino direction attainable at large-volume neutrino telescopes. Angular resolution can be as good as 0.5° for muon tracks of sufficient length. The status of the data analysis in the muon channel at the Baikal-GVD is discussed.

A hybrid 3D/2D field response calculation for liquid argon detectors with PCB based anode plane

Liquid Argon Time Projection Chamber (LArTPC) technology is commonly utilized in neutrino detector designs. It enables detailed reconstruction of neutrino events with high spatial precision and low energy threshold. Its field response (FR) model describes the time-dependent electric currents induced in the anode-plane electrodes when ionization electrons drift nearby. An accurate and precise FR is a crucial input to LArTPC detector simulations and charge reconstruction. Established LArTPC designs have been based on parallel wire planes. It allows accurate and computationally economic two-dimensional (2D) FR models utilizing the translational symmetry along the direction of the wires. Recently, novel LArTPC designs utilize electrodes formed on printed circuit board (PCB) in the shape of strips with through holes. The translational symmetry is no longer a good approximation near the electrodes and a new FR calculation that employs regions with three dimensions (3D) has been developed. Extending the 2D models to 3D would be computationally expensive. Fortuitously, the nature of strips with through holes allows for a computationally economic approach based on the finite-difference method (FDM). In this paper, we present a new software package pochoir that calculates LArTPC field response for these new strip-based anode designs. This package combines 3D calculations in the volume near the electrodes with 2D far-field solutions to achieve fast and precise field response computation. We apply the resulting FR to simulate and reconstruct samples of cosmic-ray muons and 39Ar decays from a Vertical Drift (VD) detector prototype operated at CERN. We find the difference between real and simulated data within 5%. Current state-of-the-art LArTPC software requires a 2D FR which we provide by averaging over one dimension and estimate that variations lost in this average are smaller than 7%.

Wire-cell 3D pattern recognition techniques for neutrino event reconstruction in large LArTPCs: algorithm description and quantitative evaluation with MicroBooNE simulation

Wire-Cell is a 3D event reconstruction package for liquid argon time projection chambers. Through geometry, time, and drifted charge from multiple readout wire planes, 3D space points with associated charge are reconstructed prior to the pattern recognition stage. Pattern recognition techniques, including track trajectory and dQ/dx (ionization charge per unit length) fitting, 3D neutrino vertex fitting, track and shower separation, particle-level clustering, and particle identification are then applied on these 3D space points as well as the original 2D projection measurements. A deep neural network is developed to enhance the reconstruction of the neutrino interaction vertex. Compared to traditional algorithms, the deep neural network boosts the vertex efficiency by a relative 30% for charged-current νe interactions. This pattern recognition achieves 80–90% reconstruction efficiencies for primary leptons, after a 65.8% (72.9%) vertex efficiency for charged-current νe (νμ) interactions. Based on the resulting reconstructed particles and their kinematics, we also achieve 15-20% energy reconstruction resolutions for charged-current neutrino interactions.

Pulse shape particle identification by a single large hemispherical photomultiplier tube

In neutrino experiments, hemispherical photomultiplier tubes (PMTs) are often used to cover large surfaces or volumes to maximize the photocathode coverage with a minimum number of channels. Instrumentation is often coarse, and neutrino event reconstruction and particle identification (PID) is usually done through the morphology of PMT hits. In future neutrino experiments, it may be desirable to perform PID from a few hits, or even a single hit, by utilizing pulse shape information. In this report, we study the principle of pulse shape PID using a single 25.4 cm hemispherical PMT in a spherical glass housing for future neutrino telescopes. We use the Fermilab Test Beam Facility (FTBF) MTest beam line to demonstrate that with pulse shape PID, it is possible to statistically separate 2 GeV electrons from 8 GeV pions, where the total charge deposition is ̃20 PE in our setup. Such techniques can be applied to future neutrino telescopes focusing on low-energy physics, including the IceCube-Upgrade.

Enhancing neutrino event reconstruction with pixel-based 3D readout for liquid argon time projection chambers

In this paper we explore the potential improvements in neutrino event reconstruction that a 3D pixelated readout could offer over a 2D projective wire readout for liquid argon time projection chambers. We simulate and study events in two generic, idealized detector configurations for these two designs, classifying events in each sample with deep convolutional neural networks to compare the best 2D results to the best 3D results. In almost all cases we find that the 3D readout provides better reconstruction efficiency and purity than the 2D projective wire readout, with the advantages of 3D being particularly evident in more complex topologies, such as electron neutrino charged current events. We conclude that the use of a 3D pixelated detector could significantly enhance the reach and impact of future liquid argon TPC experiments physics program, such as DUNE.

The Antares And Km3Net Neutrino Telescopes: Status And Outlook For Acoustic Studies

The ANTARES detector has been operating continuously since 2007 in the Mediterranean Sea, demonstrating the feasibility of an undersea neutrino telescope. Its superior angular resolution in the reconstruction of neutrino events of all flavors results in unprecedented sensitivity for neutrino source searches in the southern sky at TeV energies, so that valuable constraints can be set on the origin of the cosmic neutrino flux discovered by theIceCube detector. The next generation KM3NeT neutrino telescope is now under construction, featuring two detectors with the same technology but different granularity: ARCA designed to search for high energy (TeV-PeV) cosmic neutrinos and ORCA designed to study atmospheric neutrino oscillations at the GeV scale, focusing on the determination of the neutrino mass hierarchy. Both detectors use acoustic devices for positioning calibration, and provide testbeds for acoustic neutrino detection.

Recent Results from the Antares Neutrino Telescope

Antares, the first undersea neutrino telescope, has been continuously operating since 2007 in the Mediterranean Sea. The transparency of the water allows for a very good angular resolution in the reconstruction of neutrino events of all flavors. This results in an unmatched sensitivity for neutrino source searches, in a large fraction of the Southern Sky, at TeV energies. As a consequence, Antares provides valuable constraints on the origin of the cosmic neutrino flux discovered by the IceCube Collaboration. Based on an all-flavor dataset spanning nine years of operation of the detector, the latest results of Antares searches for neutrino point sources, and for diffuse neutrino emission from the entire sky as well as from several interesting regions such as the Galactic Plane, are presented. Several results have been obtained through a joint analysis with the IceCube Collaboration. Concerning the multi-messenger program, the focus is made on the follow-up searches of IceCube alerts, in particular the one related to the TXS 0506+056 blazar, thought to be the first extragalactic high-energy neutrino source identified so far.

A Method for Measuring the Optical Parameters of Deep-Sea Water

The accurate knowledge of the optical properties of deep-sea water is of great importance for the neutrino event reconstruction process in underwater cosmic neutrino telescopes. In this study we present a method to measure the parameters describing the absorption and scattering characteristics of deep-sea water. The device, specifically developed and deployed for measuring the aforementioned parameters, is described. The experimental measurements are presented and the obtained results are discussed.

Measurement of light scattering in deep sea

The deep-sea neutrino telescope in the Mediterranean Sea, being prepared by the KM3NET collaboration, will contain thousands of optical sensors to readout. The accurate knowledge of the optical properties of deep-sea water is of great importance for the neutrino event reconstruction process. In this study we describe our progress in designing an experimental setup and studying a method to measure the parameters describing the absorption and scattering characteristics of deep-sea water. Three PMTs will be used to measure in situ the scattered light emitted from six laser diodes in three different wavelengths covering the Cherenkov radiation spectrum. The technique for the evaluation of the parameters is based on Monte Carlo simulations and our results show that we are able to determine these parameters with satisfying precision.

High-energy neutrino fluxes and flavor ratio in the Earth’s atmosphere

We calculate the atmospheric neutrino fluxes in the energy range 100 GeV--10 PeV with the use of several known hadronic models and a few parametrizations of the cosmic-ray spectra which take into account the knee. The calculations are compared with the atmospheric neutrino measurements by Frejus, AMANDA, IceCube, and ANTARES. An analytic description is presented for the conventional (${\ensuremath{\nu}}_{\ensuremath{\mu}}+{\overline{\ensuremath{\nu}}}_{\ensuremath{\mu}}$) and (${\ensuremath{\nu}}_{e}+{\overline{\ensuremath{\nu}}}_{e}$) energy spectra, averaged over zenith angles, which can be used to obtain test data of the neutrino event reconstruction in neutrino telescopes. The sum of the calculated atmospheric ${\ensuremath{\nu}}_{\ensuremath{\mu}}$ flux and the IceCube best-fit astrophysical flux gives the evidently higher flux as compared to the IceCube59 data, giving rise the question concerning the hypothesis of the equal flavor composition of the high-energy astrophysical neutrino flux. Calculations show that the transition from the atmospheric electron neutrino flux to the predominance of the astrophysical neutrinos occurs at 30--100 TeV if the prompt neutrino component is taken into consideration. The neutrino flavor ratio, extracted from the IceCube data, does not tend to increase with the energy as is expected for the conventional neutrino flux in the energy range 100 GeV--30 TeV. A depression of the ratio ${R}_{{\ensuremath{\nu}}_{\ensuremath{\mu}}/{\ensuremath{\nu}}_{e}}$ possibly indicates that the atmospheric electron neutrino flux obtained in the IceCube experiment contains an admixture of the astrophysical neutrinos in the range 10--50 TeV.

Neutrino Event Reconstruction in a Liquid Argon TPC

We present some preliminary findings and results from activities in Europe and the USA working towards an automated, algorithmic, reconstruction of particle interactions in liquid argon time projection chambers.

Study of the effects induced by lead on the emulsion films of the OPERA experiment

The OPERA neutrino oscillation experiment is based on the use of the Emulsion Cloud Chamber (ECC). In the OPERA ECC, nuclear emulsion films acting as very high precision tracking detectors are interleaved with lead plates providing a massive target for neutrino interactions. We report on studies related to the effects occurring from the contact between emulsion and lead. A low radioactivity lead is required in order to minimize the number of background tracks in emulsions and to achieve the required performance in the reconstruction of neutrino events. It was observed that adding other chemical elements to the lead, in order to improve the mechanical properties, may significantly increase the level of radioactivity on the emulsions. A detailed study was made in order to choose a lead alloy with good mechanical properties and an appropriate packing technique so as to have a low enough effective radioactivity.

Parameterization of e and γ initiated showers in the NOMAD lead-glass calorimeter

A description of the response of the NOMAD electromagnetic calorimeter to electrons and photons is discussed. In particular, the dependence of the two-dimensional shower shape on the angle and energy of the incident particle is parametrized by analytical functions. Some applications to the neutrino event reconstruction are also reported.