We report on an upward traveling, radio-detected cosmic-ray-like impulsive event with characteristics closely matching an extensive air shower. This event, observed in the third flight of the ...Antarctic Impulsive Transient Antenna (ANITA), a NASA-sponsored long-duration balloon payload, is consistent with a similar event reported in a previous flight. These events could be produced by the atmospheric decay of an upward-propagating τ lepton produced by a ν_{τ} interaction, although their relatively steep arrival angles create tension with the standard model neutrino cross section. Each of the two events have a posteriori background estimates of ≲10^{-2} events. If these are generated by τ-lepton decay, then either the charged-current ν_{τ} cross section is suppressed at EeV energies, or the events arise at moments when the peak flux of a transient neutrino source was much larger than the typical expected cosmogenic background neutrinos.
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The Askaryan Radio Array (ARA) is an ultrahigh energy (UHE, > 1017 eV) neutrino detector designed to observe neutrinos by searching for the radio waves emitted by the relativistic products of ...neutrino-nucleon interactions in Antarctic ice. In this paper, we present constraints on the diffuse flux of ultrahigh energy neutrinos between 1016 and 1021 eV resulting from a search for neutrinos in two complementary analyses, both analyzing four years of data (2013–2016) from the two deep stations (A2, A3) operating at that time. We place a 90% CL upper limit on the diffuse all flavor neutrino flux at 1018 eV of EF(E) = 5.6 × 10−16 cm−2 s−1 sr−1. This analysis includes four times the exposure of the previous ARA result and represents approximately 1 / 5 th the exposure expected from operating ARA until the end of 2022.
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Recently, the ANITA collaboration reported on two upward-going extensive air shower events consistent with a primary particle that emerges from the surface of the Antarctic ice sheet. These events ...may be of ν τ origin, in which the neutrino interacts within the Earth to produce a τ lepton that emerges from the Earth, decays in the atmosphere, and initiates an extensive air shower. In this paper we estimate an upper bound on the ANITA acceptance to a diffuse ν τ flux detected via τ -lepton-induced air showers within the bounds of standard model uncertainties. By comparing this estimate with the acceptance of Pierre Auger Observatory and IceCube and assuming standard model interactions, we conclude that a ν τ origin of these events would imply a neutrino flux at least two orders of magnitude above current bounds.
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The dark photon A^{'} and the dark Higgs boson h^{'} are hypothetical constituents featured in a number of recently proposed dark sector models. Assuming prompt decays of both dark particles, we ...search for their production in the so-called Higgstrahlung channel e^{+}e^{-}→A^{'}h^{'}, with h^{'}→A^{'}A^{'}. We investigate ten exclusive final states with A^{'}→e^{+}e^{-}, μ^{+}μ^{-}, or π^{+}π^{-} in the mass ranges 0.1 GeV/c^{2} <m_{A^{'}}<3.5 GeV/c^{2} and 0.2 GeV/c^{2} <m_{h^{'}}<10.5 GeV/c^{2}. We also investigate three inclusive final states 2(e^{+}e^{-})X, 2(μ^{+}μ^{-})X, and (e^{+}e^{-})(μ^{+}μ^{-})X, where X denotes a dark photon candidate detected via missing mass, in the mass ranges 1.1 GeV/c^{2} <m_{A^{'}}<3.5 GeV/c^{2} and 2.2 GeV/c^{2} <m_{h^{'}}<10.5 GeV/c^{2}. Using the entire 977 fb^{-1} data set collected by Belle, we observe no significant signal. We obtain individual and combined 90% credibility level upper limits on the branching fraction times the Born cross section, B×σ_{Born}, on the Born cross section σ_{Born}, and on the dark photon coupling to the dark Higgs boson times the kinetic mixing between the standard model photon and the dark photon, α_{D}×ε^{2}. These limits improve upon and cover wider mass ranges than previous experiments. The limits from the final states 3(π^{+}π^{-}) and 2(e^{+}e^{-})X are the first placed by any experiment. For α_{D} equal to 1/137, m_{h^{'}}< 8 GeV/c^{2}, and m_{A^{'}}<1 GeV/c^{2}, we exclude values of the mixing parameter ε above ∼8×10^{-4}.
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We report experimental test-beam results on dielectric-loaded waveguide detectors that utilize microwave Cherenkov signals to time and characterize high energy particle showers. These results are ...used to validate models and produce high-fidelity simulations of timing plane systems that yield picosecond time tags and millimeter-level spatial coordinates for the shower centroid. These timing planes, based on the Askaryan effect in solid dielectrics, are most effective at the high center-of-momentum energies planned for the Future Circular Collider (FCC-hh). They will be of particular interest in the forward region due to their high radiation immunity. We use our beam test results and geant4 simulations to validate a hybrid microwave detector model, which is used to simulate a reference timing plane design for the FCC forward calorimeters. Our results indicate that 0.5–3 ps particle timing is possible for a wide range of collision products in the reference FCC hadron collider detector, even with current technology.
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The ANtarctic Impulsive Transient Antenna (ANITA) NASA long-duration balloon payload completed its fourth flight in December 2016, after 28 days of flight time. ANITA is sensitive to impulsive ...broadband radio emission from interactions of ultrahigh-energy neutrinos in polar ice (Askaryan emission). We present the results of two separate blind analyses searching for signals from Askaryan emission in the data from the fourth flight of ANITA. The more sensitive analysis, with a better expected limit, has a background estimate of 0.64−0.45+0.69 and an analysis efficiency of 82±2%. The second analysis has a background estimate of 0.34−0.16+0.66 and an analysis efficiency of 71±6%. Each analysis found one event in the signal region, consistent with the background estimate for each analysis. The resulting limit further tightens the constraints on the diffuse flux of ultrahigh-energy neutrinos at energies above 1019.5 eV.
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Abstract
The balloon-borne ANITA 1 experiment is designed to detect
ultra-high energy neutrinos via radio emissions produced by in-ice
showers. Although initially purposed for interactions within the
...Antarctic ice sheet, ANITA also demonstrated the ability to
self-trigger on radio emissions from ultra-high energy charged
cosmic rays 2 (CR) interacting in the Earth's atmosphere. For
showers produced above the Antarctic ice sheet, reflection of the
down-coming radio signals at the Antarctic surface should result in
a polarity inversion prior to subsequent observation at the ∼35–40
km altitude ANITA gondola. Based on data taken during the ANITA-1
and ANITA-3 flights, ANITA published two anomalous instances of
upcoming cosmic-rays with measured polarity opposite the remaining
sample of ∼50 UHECR signals 3, 4. The steep observed upwards
incidence angles (25–30 degrees relative to the horizontal) require
non-Standard Model physics if these events are due to in-ice
neutrino interactions, as the Standard Model cross-section would
otherwise prohibit neutrinos from penetrating the long required
chord of Earth. Shoemaker et al. 5 posit that glaciological
effects may explain the steep observed anomalous events. We herein
consider the scenarios offered by Shoemaker et al. and find them to
be disfavored by extant ANITA and HiCal experimental data. We note
that the recent report of four additional near-horizon anomalous
ANITA-4 events 6, at >3σ significance, are incompatible with
their model, which requires significant signal transmission into the
ice.
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