High-energy Neutrino Interactions Research Articles

Present and future constraints on flavor-dependent long-range interactions of high-energy astrophysical neutrinos

The discovery of new, flavor-dependent neutrino interactions would provide compelling evidence of physics beyond the Standard Model. We focus on interactions generated by the anomaly-free, gauged, abelian lepton-number symmetries, specifically Le – Lμ, Le – Lτ , and Lμ – Lτ , that introduce a new matter potential sourced by electrons and neutrons, potentially impacting neutrino flavor oscillations. We revisit, revamp, and improve the constraints on these interactions that can be placed via the flavor composition of the diffuse flux of high-energy astrophysical neutrinos, with TeV–PeV energies, i.e., the proportion of νe, νμ, and ντ in the flux. Because we consider mediators of these new interactions to be ultra-light, lighter than 10−10 eV, the interaction range is ultra-long, from km to Gpc, allowing vast numbers of electrons and neutrons in celestial bodies and the cosmological matter distribution to contribute to this new potential. We leverage the present-day and future sensitivity of high-energy neutrino telescopes and of oscillation experiments to estimate the constraints that could be placed on the coupling strength of these interactions. We find that, already today, the IceCube neutrino telescope demonstrates potential to constrain flavor-dependent long-range interactions significantly better than existing constraints, motivating further analysis. We also estimate the improvement in the sensitivity due to the next-generation neutrino telescopes such as IceCube-Gen2, Baikal-GVD, KM3NeT, P-ONE, and TAMBO.

New approaches for gamma-hadron separation at the IceCube Neutrino Observatory

The IceCube Neutrino Observatory located at the geographic South Pole is composed of two detectors. One is the in-ice optical array, which measures high-energy muons from air showers and charged particles produced by the interaction of high-energy neutrinos in the ice. The other is an array of ice-Cherenkov tanks at the surface, called IceTop, which is used both as veto for the in-ice neutrino measurements and for detecting cosmic-ray air showers. In the next decade, the IceCube-Gen2 extension will increase the surface coverage including surface radio antennas and scintillator panels on the footprint of an extended optical array in the ice. The combination of the current surface and in-ice detectors can be exploited for the study of cosmic rays and the search for PeV gamma rays. The in-ice detector measures the high-energy muonic component of air showers, whereas the signal in IceTop is dominated by the electromagnetic component. The relative size of the muonic and electromagnetic components is different for gamma-and hadron-induced air showers. Thus, the gamma-hadron separation of cosmic rays is attempted using machine learning techniques including deep learning. Here, different approaches are presented. Finally, the prospects for the detection of PeV photons with IceCube-Gen2 will be discussed.

Design, Manufacture and Measurement of Three Permanent Magnet Dipoles for FASER Experiment

FASER, the ForwArd Search ExpeRiment, is designed to search for new, yet undiscovered, light and weakly-interacting particles and study the interactions of high-energy neutrinos. Three dipoles, one 1.5 m-long and the other two 1.0 m-long each, installed upstream of the ATLAS experiment at CERN, are required to achieve sufficient separation of pairs of oppositely charged, high-energy Standard Model particles originating from decays of new physics particles. The dipoles have an aperture of 200 mm in diameter and a required magnetic field at the centre ≥ 0.55 T. Due to tight space constraints, a design based on permanent magnet technology was proposed. This paper describes the design, manufacturing, assembly and magnetic measurement of these large Halbach array dipoles.

Effects of non-standard interaction on microscopic black holes from ultra-high energy neutrinos

If the universe has more than 4-dimensions, the TeV scale gravity theories predict formation of microscopic black holes due to interaction of ultra high energy neutrinos coming from some extragalactic origin with the nucleons present in the Earth’s atmosphere. The decay of these black holes can generate high multiplicity events which can be detected through neutrino telescopes. Ultra high energy neutrinos can also produce events without the formation of black holes which can be distinguished from the black hole events depending on their topological structure. In this work we study the effects of non-standard interaction on the production of these shower events. We find that new physics has inconsequential impact on the number of events produced through the generation of black holes. For events produced without the formation of black holes, new physics can only provide a marginal deviation. Therefore a large enhancement in the number of shower events over the standard model prediction can provide unambiguous signatures of TeV scale gravity in the form of microscopic black hole production.

The tracking detector of the FASER experiment

FASER is a new experiment designed to search for new light weakly-interacting long-lived particles (LLPs) and study high-energy neutrino interactions in the very forward region of the LHC collisions at CERN. The experimental apparatus is situated 480 m downstream of the ATLAS interaction-point aligned with the beam collision axis. The FASER detector includes four identical tracker stations constructed from silicon microstrip detectors. Three of the tracker stations form a tracking spectrometer, and enable FASER to detect the decay products of LLPs decaying inside the apparatus, whereas the fourth station is used for the neutrino analysis. The spectrometer has been installed in the LHC complex since March 2021, while the fourth station is not yet installed. FASER will start physics data taking when the LHC resumes operation in early 2022. This paper describes the design, construction and testing of the tracking spectrometer, including the associated components such as the mechanics, readout electronics, power supplies and cooling system.

Tau Appearance from High-Energy Neutrino Interactions.

High-energy muon and electron neutrinos yield a non-negligible flux of tau neutrinos as they propagate through Earth. In this Letter, we address the impact of this additional component in the PeV and EeV energy regimes for the first time. Above 300TeV, this contribution is predicted to be significantly larger than the atmospheric background, and it alters current and future neutrino telescopes' capabilities to discover a cosmic tau-neutrino flux. Further, we demonstrate that Earth-skimming neutrino experiments, designed to observe tau neutrinos, will be sensitive to cosmogenic neutrinos even in extreme scenarios without a primary tau-neutrino component.

Closing the neutrino BSM gap: Physics potential of atmospheric through-going muons at DUNE

Many Beyond-Standard Model physics signatures are enhanced in high-energy neutrino interactions. To explore these signatures, ultra-large Cherenkov detectors such as IceCube exploit event samples with charged current muon neutrino interactions > 1 TeV. Most of these interactions occur below the detector volume, and produce muons that enter the detector. However, the large spacing between detectors leads to inefficiency for measuring muons with energies below or near the critical energy of 400 GeV. In response, IceCube has built a densely instrumented region within the larger detector. This provides large samples of well-reconstructed interactions that are contained within the densely instrumented region, extending up to energies of ~50 GeV. This leaves a gap of relatively unexplored atmospheric-neutrino events with energies between 50 GeV and 1 TeV in the ultra-large detectors. In this paper we point out that interesting Beyond Standard Model signatures may appear in this energy window, and that early running of the DUNE far detectors can give insight into new physics that may appear in this range.

Modeling of the tau and muon neutrino-induced optical Cherenkov signals from upward-moving extensive air showers

We present a detailed modeling and computation methodology to determine the optical Cherenkov signals produced by upward-moving extensive air showers (EASs) induced by $\ensuremath{\tau}$-leptons and muons, sourced from the interaction of high-energy astrophysical neutrinos interacting in the Earth. Following and extending the physics modeling and Cherenkov signal simulations performed in M. H. Reno et al. [Phys. Rev. D 100, 063010 (2019)], this scheme encompasses a new, state-of-the-art computation of the muon neutrino propagation inside the Earth and the contribution to the $\ensuremath{\tau}$-lepton muon decay channel. The modeling takes into account all possible $\ensuremath{\tau}$-lepton decay and muon energy loss channels that feed the optical Cherenkov emission, produced by both tau and muon initiated EASs. The EAS modeling uses the electron energy, angular, and lateral distributions in the EAS and their evolution as well as the wavelength dependence of the Cherenkov emission and its atmospheric attenuation. The results presented here are focused on the detection capabilities of suborbital (balloon-borne) and orbital (satellite) based instruments. The latter case was calculated for POEMMA [The Probe Of Extreme MultiMessenger Astrophysics] to compare to that presented in M. H. Reno et al. [Phys. Rev. D 100, 063010 (2019)], specifically including the muon-decay channel of $\ensuremath{\tau}$-leptons and the muonic EAS Cherenkov signal from muon neutrino interactions in the Earth. By detailing all these individual contributions to the optical Cherenkov emission and detection, we show how the ensemble that includes muonic channels provides a large detection capability for space-based, high-energy cosmic neutrino detection. Specifically, we show that for neutrino energies $\ensuremath{\lesssim}10\text{ }\text{ }\mathrm{PeV}$, the upward-EAS sensitivity due to muon neutrino interactions in the Earth begin to dominate over that for tau neutrino interactions, effectively extending the neutrino sensitivity to lower energies.

Nuclear effects in high-energy neutrino interactions

Neutrino telescopes like IceCube, KM3NeT and Baikal-GVD offer physicists the opportunity to study neutrinos with energies far beyond the reach of terrestrial accelerators. These neutrinos are used to study high-energy neutrino interactions and to probe the Earth through absorption tomography. Current studies of TeV neutrinos use cross sections which are calculated for free nucleons with targets which are assumed to contain equal numbers of protons and neutrons. Here we consider modifications of high-energy neutrino interactions due to two nuclear effects: modifications of the parton densities in the nucleus, referred to here as shadowing, and the effect of non-isoscalar targets, with unequal numbers of neutrons and protons. Both these effects depend on the interaction medium. Because shadowing is larger for heavier nuclei, such as iron, found in the Earth's core, it introduces a zenith-angle dependent change in the absorption cross section. These modifications increase the cross sections by 1-2\% at energies below 100 TeV (antishadowing), and reduce it by 3-4\% at higher energies (shadowing). Nuclear effects also alter the inelasticity distribution of neutrino interactions in water/ice by increasing the number of low inelasticity interactions, with a larger effect for $\nu$ than $\bar\nu$. These effects are particularly large in the energy range below a few TeV. These effects could alter the cross sections inferred from events with tracks originating within the active detector volume as well as the ratio $\nu/\bar\nu$ inferred from inelasticity measurements. The uncertainties in these nuclear effects are larger than the uncertainties on the free-proton cross sections and will thus limit the systematic precision of future high-precision measurements at neutrino telescopes.

Connecting ANITA anomalous events to a nonthermal dark matter scenario

The ANtarctic Impulsive Transient Antenna (ANITA) collaboration has observed two EeV-energy, upward going events originating from below the horizon. As no standard model (SM) particles, propagating through the earth at such energy and exit angles, can give rise to the required survival probability for the observed events, several beyond standard model (BSM) proposals have come up. We propose a scenario where a $Z_2$ odd sector is responsible for such anomalous events. The next to lightest $Z_2$ odd particle or the next to lightest stable particle (NLSP), created from ultra high energy neutrino interactions with nucleons, can pass through the earth and then decay into the lightest $Z_2$ odd particle or the lightest stable particle (LSP) and a tau lepton. The long-lived nature of the NLSP requires its coupling with the LSP to be very small, keeping the LSP out of thermal equilibrium in the early universe. The LSP can then be a non-thermal dark matter while the tau leptons produced from NLSP decay after passing through the earth can explain the ANITA events. We first show that a purely non-thermal dark matter scenario can not give rise to the required event rates while a hybrid scenario where dark matter can have both thermal as a well non-thermal contribution to its relic abundance, serves the purpose.

Observation of Radar Echoes from High-Energy Particle Cascades.

We report the observation of radar echoes from the ionization trails of high-energy particle cascades. Data were taken at the SLAC National Accelerator Laboratory, where the full electron beam (∼10^{9} e^{-} at ∼10 GeV/e^{-}) was directed into a plastic target to simulate an ultrahigh-energy neutrino interaction. The target was interrogated with radio waves, and coherent radio reflections from the cascades were detected with properties consistent with theoretical expectations. This is the first definitive observation of radar echoes from high-energy particle cascades, which may lead to a viable neutrino detection technology for energies ≳10^{16} eV.

The simulation of the sensitivity of the Antarctic Impulsive Transient Antenna (ANITA) to Askaryan radiation from cosmogenic neutrinos interacting in the Antarctic Ice

A Monte Carlo simulation program for the radio detection of Ultra High Energy (UHE) neutrino interactions in the Antarctic ice as viewed by the Antarctic Impulsive Transient Antenna (ANITA) is described in this article. The program, icemc, provides an input spectrum of UHE neutrinos, the parametrization of the Askaryan radiation generated by their interaction in the ice, and the propagation of the radiation through ice and air to a simulated model of the third and fourth ANITA flights. This paper provides an overview of the icemc simulation, descriptions of the physics models used and of the ANITA electronics processing chain, data/simulation comparisons to validate the predicted performance, and a summary of the impact of published results.

Universe's Worth of Electrons to Probe Long-Range Interactions of High-Energy Astrophysical Neutrinos.

Astrophysical searches for new long-range interactions complement collider searches for new short-range interactions. Conveniently, neutrino flavor oscillations are keenly sensitive to the existence of long-ranged flavored interactions between neutrinos and electrons, motivated by lepton-number symmetries of the standard model. For the first time, we probe them using TeV-PeV astrophysical neutrinos and accounting for all large electron repositories in the local and distant Universe. The high energies and colossal number of electrons grant us unprecedented sensitivity to the new interaction, even if it is extraordinarily feeble. Based on IceCube results for the flavor composition of astrophysical neutrinos, we set the ultimate bounds on long-range neutrino flavored interactions.

High-energy neutrino interaction physics with IceCube

Although they are best known for studying astrophysical neutrinos, neutrino telescopes like IceCube can study neutrino interactions, at energies far above those that are accessible at accelerators. In this writeup, I present two IceCube analyses of neutrino interactions at energies far above 1 TeV. The first measures neutrino absorption in the Earth, and, from that determines the neutrino-nucleon cross-section at energies between 6.3 and 980 TeV. We find that the cross-sections are 1.30 +0.21 -0.19 (stat.) +0.39 -0.43 (syst.) times the Standard Model crosssection. We also present a measurement of neutrino inelasticity, using νμ charged-current interactions that occur within IceCube. We have measured the average inelasticity at energies from 1 TeV to above 100 TeV, and found that it is in agreement with the Standard Model expectations. We have also performed a series of fits to this track sample and a matching cascade sample, to probe aspects of the astrophysical neutrino flux, particularly the flavor ratio.

Live monitoring and quasi-online event reconstruction for KM3NeT

KM3NeT is a new generation neutrino telescope in the abyss of the Mediterranean Sea. It will instrument a volume of several cubic kilometres of sea water in its final configuration. Currently, the project is in its first phase with the aim of constructing and installing 31 detection units up to 700 m in height, each equipped with 18 digital optical modules. The optical modules are equipped with 31 3-inch photomultipliers to detect the Cherenkov light of charged secondary particles produced in high-energy neutrino interactions. This contribution describes a live detector monitoring system, which enables real-time parameter control and a reconstruction of events soon after the data acquisition. It also allows a rapid response to or provision of external alarms of multi-messenger campaigns. The data acquisition system of KM3NeT provides pre-filtered data in event form, as well as general detector status messages. The events will be processed almost in real-time – with a delay in the range of minutes – using fast reconstruction mechanisms. This allows for high-level monitoring of the detector status using derived distributions, such as time and charge distributions and event rates. The resulting data is displayed on a web page using a dedicated, flexible web service. The same service also displays low-level monitoring data such as trigger rates, PMT hit rates and the general status of the optical modules.

SiPM application for a detector for UHE neutrinos tested at Sphinx station

We present the preliminary test results of the prototype detector, working at Sphinx Observatory Center, Jungfraujoch (~3800m a.s.l.) HFSJG – Switzerland. This prototype detector is designed to measure large zenith angle showers produced by high energy neutrino interactions in the Earth crust. This station provides us an opportunity to understand if the prototype detector works safely (or not) under hard environmental conditions (the air temperature changes between −25°C and −5°C). The detector prototype is using silicon photomultiplier (SiPM) produced by SensL and DRS4 chip as read-out part. Measurements at different temperature at fixed bias voltage (~29.5V) were performed to reconstruct tracks by Time Of Flight.

Nonperturbative features of the axial current

We study the nonperturbative structure of the axial current and evaluate the two-point light-cone distribution amplitudes (DA) associated with the correlator \int d\xi exp(-iq\xi)<0|\bar{\psi}(x)\Gamma\psi(y)J_{\mu}^{5}(\xi)|0> within the instanton vacuum model in the leading order in O(1/N_c). Due to the built-in chiral symmetry, four of eight axial DAs are related to that for pions. Knowledge of these nonperturbative objects is important for phenomenological study of high-energy neutrino interactions and semileptonic decays of heavy quarks. We provide a code for evaluation of these DAs and an interpolation formula valid in the region Q^2 < 1 GeV^2.

DIFFRACTIVE INTERACTION OF NEUTRINOS

Interactions of high-energy neutrinos expose hadronic properties, in particular, contain a strong diffractive channel. The Adler relation (AR) between soft interactions of neutrinos and pions, might look as a manifestation of pion dominance. However, neutrinos cannot fluctuate to pions because of conservation of the lepton current, and interact via much heavier hadronic components. This fact leads to nontrivial relations between interactions of different hadronic species, in particular, it links diagonal and off-diagonal diffractive interactions of pions. Absorptive corrections break these relations making the AR impossible to hold universally, for any target and at any energy.

Indirect probes of supersymmetry breaking in the JEM-EUSO observatory

In this paper we propose indirect probes of the supersymmetry-breaking scale, through observations in the Extreme Universe Space Observatory onboard the Japanese Experiment Module (JEM-EUSO). We consider scenarios where the lightest supersymmetric particle is the gravitino, and the next-to-lightest supersymmetric particle (NLSP) is a long-lived slepton. We demonstrate that JEM-EUSO will be able to probe models where the NLSP decays, therefore probing supersymmetry-breaking scales below $5\ifmmode\times\else\texttimes\fi{}{10}^{6}\text{ }\text{ }\mathrm{GeV}$. The observatory field of view will be large enough to detect a few tens of events per year, depending on its energy threshold. This is complementary to a previous proposal [I. Albuquerque et al., Phys. Rev. Lett. 92, 221802 (2004)] where it was shown that $1\text{ }\text{ }{\mathrm{km}}^{3}$ neutrino telescopes can directly probe this scale. NLSPs will be produced by the interaction of high-energy neutrinos in the Earth. Here we investigate scenarios where they subsequently decay, either in the atmosphere after escaping the Earth or right before leaving the Earth, producing taus. These can be detected by JEM-EUSO and have two distinctive signatures: one, they are produced in the Earth and go upwards in the atmosphere, which allows discrimination from atmospheric taus, and second, as NLSPs are always produced in pairs, coincident taus will be a strong signature for these events. Assuming that the neutrino flux is equivalent to the Waxman-Bahcall limit, we determine the rate of taus from NLSP decays reaching JEM-EUSO's field of view.

VSiPMT for underwater neutrino telescopes

Underwater neutrino telescopes are nowadays considered among the most important aims in the field of astroparticle physics. Their structure consists of a cubic-kilometer three-dimensional array of photosensitive devices aimed at the detection of the Cherenkov light emitted by charged particles produced by high energy neutrino interactions with the Earth.To date, a crucial role in this kind of experiments has been played by PhotoMultiplier Tubes (PMTs), however they suffer from many drawbacks such as linearity-to-gain relationship and difficulty in single photon counting. The next generation of experiments will require further improvements in photon detectors performances, therefore alternatives to PMTs are currently under study.In particular the most promising development in this field is represented by the rapidly emerging CMOS p-n Geiger-mode avalanche photodiode technology (G-APD or SiPM), that will allow the detection of high-speed single photons with high gain and linearity. In order to overcome the limit of small sensitive surfaces we suggest an innovative design for a modern hybrid, high gain, silicon based Vacuum Silicon Photomultiplier Tube (VSiPMT) based on the combination of a SiPM with a hemispherical vacuum glass PMT standard envelope. In this work we describe the full SiPM characterization realized by our group and we present the results of our Geant4-based simulations of electron backscattering over the SiPM surface.