[Paper Review] Arrays is Space to detect Upward Tau and Highest Altitude Showers

Daniele Fargion|arXiv (Cornell University)|Jul 5, 2001

Astrophysics and Cosmic Phenomena3 citations

TL;DR

This paper proposes detecting ultra-high-energy (UHE) upward tau neutrinos and associated air showers—UPTAUS, HORTAUS, and HIAS—using space-based and high-altitude balloon arrays. By leveraging Earth's magnetic field to deflect shower particles into twin-beam arcs and exploiting unique energy-dependent shower development in thin atmospheric layers, the method enables detection of rare UHE neutrino interactions via distinctive morphological and directional signatures.

ABSTRACT

Ultra High Energy, UHE, upward Tau neutrinos Tau, anti-neutrino Tau, above hundred TeVs and up to tens PeV energies, of relevant astrophysical nature, may lead to UHE Taus and consequent Up-ward Tau air-Showers {UPTAUS} after interaction on Earth crust surface. The UPTAUS discover may open a new UHE Tau Neutrino Astrophysics. A new generation of Gamma, X, optical and Radio Arrays in Space may discover, in the same Auger spirit, such up-coming Air-showers as well as an additional Tau signal: the nearly Horizontal Tau AIR-Shower {HORTAUS} originated by UHE neutrinos tau at 10^{19} eV energies arising from a thin Earth crust corona at few tens of degree below the horizons; a degree above the horizons, there should be over common diffused cosmic ray albedo, an additional High Altitudes (nearly Horizontal) Showers {HIAS}, by more common Cosmic Rays primaries at PeVs up to EeV and ZeV energies, both of hadronic or of electro-magnetic $γ$ nature. Mini-arrays detectors in high Altitude Balloons tails facing the horizons and the Earth below may also reveal both UPTAUS, and HIAS, and more rarely HORTAUS. Gamma Burst, Cherenkov flashes and rarer muons observed by high mountains peak arrays or high quota balloon array may better probe UPTAUS and HORTAUS. Present and future X-Gamma satellites as Beppo-Sax may be also able to discover HORTAUS and HIAS discovering transient events by UHE source (as the Crab) while in occultation by Earth. Because of the large shower distances and the Earth magnetic field, HIAS and HORTAUS showers will be split in a {Twin-Beams} fan-shaped wide arc, orthogonal to the terrestrial magnetic field, with a strong azimuths modulation. Gamma bursts with rare single muons or neutrons at the horizon, associated with HIAS, HORTAUS may be discovered by Glast and AMS satellite.

Motivation & Objective

• To explore the detectability of ultra-high-energy (UHE) upward tau neutrinos ($\nu_{\tau}$) and their decay products as air showers.
• To address the challenge of Earth's opacity to UHE neutrinos by identifying rare interaction windows in the Earth's crust and atmosphere.
• To propose new detection strategies for UPTAUS (upward tau air showers), HORTAUS (nearly horizontal tau showers), and HIAS (high-altitude showers) using space-based and high-altitude platforms.
• To differentiate these novel shower types from conventional downward air showers based on geometry, energy dependence, and magnetic field effects.
• To enable new astrophysical probes of UHE neutrino sources through distinctive shower morphologies and azimuthal modulations.

Proposed method

• Modeling UHE $\nu_{\tau}$ interactions in Earth's crust at $10^{14}$–$10^{16}$ eV energies to produce upward tau air showers (UPTAUS).
• Using the Landau-Pomeranchuk-Migdal (LPM) effect and tau decay kinematics to predict shower development and composition (hadronic, electromagnetic, or hybrid).
• Applying transcendental equations for shower slant depth and decay length to determine optimal shower initiation altitudes ($h_1$, $h_3$) for HIAS and HORTAUS.
• Simulating magnetic field deflection of shower particles into twin-beam, fan-shaped arcs orthogonal to Earth's magnetic field, with strong azimuthal modulation.
• Analyzing trajectory and energy dependence of HIAS and HORTAUS to distinguish them from direct UPTAUS and background cosmic ray albedo.
• Proposing high-altitude balloon arrays and satellite-based instruments (e.g., GLAST, AMS) to detect these rare events via timing, spectral, and angular signatures.

Experimental results

Research questions

• RQ1 Can UHE $\nu_{\tau}$ interactions in the Earth's crust produce detectable upward tau air showers (UPTAUS) at energies above 100 TeV?
• RQ2 What is the optimal energy and geometry for HORTAUS (nearly horizontal tau showers) to form from tangential $\nu_{\tau}$ interactions near the GZK cutoff?
• RQ3 How do Earth's magnetic fields influence the trajectory and angular distribution of shower particles from UPTAUS and HORTAUS?
• RQ4 Can high-altitude balloon and satellite arrays distinguish HIAS (high-altitude showers from UHECRs) from UPTAUS and HORTAUS based on morphology and timing?
• RQ5 What are the characteristic shower development depths and decay lengths for HIAS and HORTAUS, and how do they vary with energy and particle type?

Key findings

• UPTAUS are predicted to form at $10^{15}$–$10^{16}$ eV energies, with shower development occurring at high altitudes (44–42 km) due to reduced atmospheric density.
• The HORTAUS shower initiation occurs at a characteristic height of 23 km, with a tau decay length of 546 km, enabling detection up to $1.11 \times 10^{19}$ eV.
• For HIAS, the optimal shower development altitude is $h_{1_{\text{Had.}}} = 44.08 - 8.55 \ln[1 + 0.02523 \ln(E/10^{19}\text{eV})]$ km for hadronic showers.
• The HIAS and HORTAUS trajectories are bent into twin-beam, fan-shaped arcs by Earth's magnetic field, with maximum deflection at east-west directions and minimal at north-south.
• The magnetic deflection leads to a strong azimuthal modulation of shower intensity, providing a unique signature for distinguishing these events from background.
• High-altitude balloon arrays at 20–30 km altitude are optimal for detecting HIAS and HORTAUS, as they can observe events both above and below the horizon, unlike ground-based detectors.