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Signatures of secondary leptons in radio-neutrino detectors in ice

D. García-Fernández, A. Nelles, and C. Glaser
Phys. Rev. D 102, 083011 – Published 12 October 2020
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  • INTRODUCTION
  • PHYSICAL PROCESSES IN THE INTERACTION OF…
  • SIMULATION SETUP
  • ATMOSPHERIC MUONS
  • MUONS AND TAUS FROM NEUTRINO…
  • CONCLUSIONS
  • ACKNOWLEDGMENTS
  • APPENDICES
    • References

    Abstract

    The detection of the radio emission following a neutrino interaction in ice is a promising technique to obtain significant sensitivities to neutrinos with energies above Petaelectronvolts (1015  eV). The detectable radio emission stems from particle showers in the ice. So far, detector simulations have considered only the radio emission from the primary interaction of the neutrino. For this study, existing simulation tools have been extended to cover secondary interactions from muons and taus. We find that secondary interactions of both leptons add up to 25% to the effective volume of neutrino detectors. Also, muon and tau neutrinos can create several detectable showers, with the result that double signatures do not constitute an exclusive signature for tau neutrinos. We also find that the background of atmospheric muons from cosmic rays is non-negligible for in-ice arrays and that an air shower veto should be considered helpful for radio detectors.

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    • Received 30 March 2020
    • Accepted 18 September 2020

    DOI:https://doi.org/10.1103/PhysRevD.102.083011

    © 2020 American Physical Society

    Physics Subject Headings (PhySH)

    1. Research Areas
    Cosmic rays & astroparticlesExtrasolar neutrino astronomy
    Gravitation, Cosmology & Astrophysics

    Authors & Affiliations

    D. García-Fernández* and A. Nelles†

    • DESY, Platanenallee 6, 15738, Zeuthen, Germany and ECAP, Friedrich-Alexander Universitt Erlangen-Nrnberg, Erwin-Rommel-Strae 1, 91058 Erlangen, Germany

    C. Glaser‡

    • University of California, Irvine, California 92697, Irvine, USA and Uppsala University, Box 516, S-75120 Uppsala, Sweden

    • *daniel.garcia@desy.de
    • †anna.nelles@desy.de
    • ‡christian.glaser@physics.uu.se

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    Issue

    Vol. 102, Iss. 8 — 15 October 2020

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    Images

    • Figure 1
      Figure 1

      Top: Average number of (>1  PeV) showers produced by a tau as a function of the initial energy, classified by a shower-initiating secondary particle type. Bottom: Ratio of average number of showers per primary type over total number of particle showers for a tau. The shower primaries in the legend are noted as follows. Decay hads: hadron bundle created upon decay. e+e−: electron-positron pair. γ: bremsstrahlung photon. Decay π−,0,+: pion issued upon decay. Decay K−,0,+: kaon issued upon decay. Decay e−,+: electron or positron issued upon decay. PN hads: hadrons created by photonuclear interaction. See text for details.

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    • Figure 2
      Figure 2

      Top: Average number of (>1  PeV) showers produced by a muon as a function of the initial energy, classified by the primary type. Bottom: Ratio of average number of showers per primary type over total number of particle showers for a muon lepton. The shower primaries in the legend are noted as follows: e+e−: electron-positron pair. γ: bremsstrahlung photon. PN hads: hadrons created by photonuclear interaction. See text for details.

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    • Figure 3
      Figure 3

      Histogram of the average number of secondary showers per lepton as a function of shower energy. The initial lepton energies are 10 PeV, 100 PeV, 1 EeV, and 10 EeV. Dashed lines represent taus and solid lines represent muons.

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    • Figure 4
      Figure 4

      Muon flux rescaled with muon energy to the power of 3.7 and integrated on the upper hemisphere, given in GeV2.7  cm−2 s−1 as a function of the muon energy. These curves have been obtained using MCEq (version 1.2.1) with the cosmic-ray model from [48] and using four different models: EPOS-LHC (red), SYBILL23C (blue), and QGSJet-II-04 (black). The observation altitude is 2.7 km. Uncertainties due to cosmic-ray flux models and hadronic interaction models [56] are represented by the shaded region (68% C.L.).

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    • Figure 5
      Figure 5

      Histograms containing the average number of atmospheric muons detected by a 100-station array of 1.5σ dipoles at 100 m (solid lines) and 5 m of depth (dashed lines). The shaded bands represent the uncertainties induced by the cosmic-ray flux model, the hadronic model, and the statistical uncertainty of the effective area calculation, for the SIBYLL 2.3C model only. Shown are different hadronic models. Top: as a function of cosmic-ray energy in GeV. Bottom: as a function of the shower energy.

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    • Figure 6
      Figure 6

      Top: 2D triggering muon vertex distribution as a function of radial and vertical distances to antenna, for a 1.5σ dipole at 100 m. Muon energies lie between 300 PeV and 6100 PeV. Bottom: same as top, but for triggering events induced by neutrino first interactions. Neutrino energies lie between 1200 PeV and 2300 PeV.

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    • Figure 7
      Figure 7

      Neutrino (black) and atmospheric muon (red) zenith arrival directions. Solid and dashed lines indicate two different energy bins with ranges stated on the legend. For these two bins, the energy dependence seems to be weak. All the shown distributions are normalized to 1.

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    • Figure 8
      Figure 8

      Three-dimensional plot of a double-cascade event. The first shower is caused by a 1.84 EeV neutrino. The resulting tau travels for several hundred meters and creates a hadronic shower via photonuclear interaction. The red line represents the particle trajectories, while the red cones indicate the Cherenkov cones for both showers. The three triggered stations are represented by grey dots, and the yellow lines are the paths followed by the waves (direct and refracted) that arrive at the stations. The axes units are meters.

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    • Figure 9
      Figure 9

      Top panel: tau neutrino effective volumes for a 10×10 square array of 100 m deep dipoles, with 1.5σ threshold. The bands represent the uncertainty assuming a Poisson distribution. There are different types of effective volume depicted in the figure. The events that have been triggered at least by the shower induced by the first neutrino interaction are represented by the “first interaction” (FI) curve. The events not triggered by the first neutrino interactions but by secondary interactions constitute the “no FI” curve. The “decay” curve represents events triggered by the products of the tau decay. The events triggered by the tau stochastic losses during propagation result in the effective volume denoted by “tau loss.” The “FI+decay” curve represents the effective volume from events triggered by the neutrino first interaction and the tau decay. The curve noted as “FI+losses” is calculated using events triggered by the neutrino first interaction and at least a stochastic energy loss, while the “loss(es)+decay” shower is the effective volume from events triggered by one or several tau stochastic losses and the tau decay. The “total” curve contains the total effective volume. Note that, since the effective volumes are not mutually exclusive, the total curve is not the sum of all the others. Bottom panel: ratio of the total effective volume over the first interaction effective volume.

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    • Figure 10
      Figure 10

      Same as Fig. 9, but with different types of effective volumes: single, events triggered by one interaction (cascade) only; multiple cascades, event triggered by more than one interaction; and >2 cascades, event triggered by more than two interactions. The total effective volume is also shown.

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    • Figure 11
      Figure 11

      Top panel: muon neutrino effective volumes for an 10×10 square array of 100 m deep dipoles, with 1.5σ threshold. The bands represent the uncertainty assuming a Poisson distribution. There are different types of effective volume depicted in the figure. The events that have been triggered at least by the shower induced by the neutrino interaction are represented by the FI curve. The events triggered by the muon stochastic losses during propagation result in the effective volume denoted by “mu loss.” The curve noted as FI+losses is calculated using events triggered by the neutrino first interaction and at least a stochastic energy loss. The total curve contains the total effective volume. Note that, since the effective volumes are not mutually exclusive, the total curve is not the sum of all the others. Decay triggers are negligible for muons, so the effective volumes containing decays and the no FI volume are ignored. Bottom panel: ratio of the total effective volume over the first interaction effective volume.

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    • Figure 12
      Figure 12

      Same as Fig. 11, but with different types of effective volumes: single, events triggered by one interaction (cascade) only; multiple cascades, event triggered by more than one interaction; and less than two cascades, event triggered by more than two interactions. The total effective volume is also shown.

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    • Figure 13
      Figure 13

      Top panel: all-flavor neutrino effective volumes for a 10×10 square array of 100 m deep dipoles, with 1.5σ threshold. The shades represent the 1σ uncertainty assuming a poissonian distribution. Total and FI volumes are shown. The fractional contributions for each flavor (assuming a 1:1:1 flux) are also shown. Bottom panel: ratio of the total effective volume over the first interaction effective volume.

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    • Figure 14
      Figure 14

      Top: distribution of the number of multiple cascades induced by tau neutrinos and detected by a 10×10 dipole array for several neutrino energy bins. Bottom: same as top, but with the number of stations triggered by multiple-cascade events.

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    • Figure 15
      Figure 15

      Same as Fig. 14 but for muon neutrinos.

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    • Figure 16
      Figure 16

      Top: distribution of the distances between cascades of double-cascade tau neutrino events detected by a 10×10 dipole array for several neutrino energy bins. All the distributions are normalized to 1. Bottom: same as top, but with the signal arrival times at the station. The antenna distance between nearest neighbors is 1.25 km for this study.

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    • Figure 17
      Figure 17

      Top: distribution of the distances between cascades of double-cascade muon neutrino events detected by a 10×10 dipole array for several neutrino energy bins. Bottom: same as top, but with the signal arrival times at the station.

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    • Figure 18
      Figure 18

      Same as Fig. 16, bottom, but for double-cascade events stemming from tau neutrinos detected by a single antenna. The distribution for muon neutrinos is very similar.

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    • Figure 19
      Figure 19

      Top: histograms containing the average number of atmospheric muons detected by a 100-station array as a function of cosmic-ray energy in GeV for several hadronic models. Numbers for 100 independent envelope dipole phased arrays are shown (∼1  Hz noise trigger rate), located near Summit Station, Greenland, as well as surface LPDA trigger (∼10  mHz noise trigger rate) on the Ross Ice Shelf. The shaded bands represent the uncertainties induced by the cosmic-ray flux model, the hadronic model, and the effective area calculation, for the SIBYLL 2.3C model only. See text for details. Bottom: same as top, but as a function of muon shower energy.

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