Low-threshold ultrahigh-energy neutrino search with the Askaryan Radio Array.

ARA

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Abstract

In the pursuit of the measurement of the still-elusive ultrahigh-energy (UHE) neutrino flux at energies of order EeV, detectors using the in-ice Askaryan radio technique have increasingly targeted lower trigger thresholds. This has led to improved trigger-level sensitivity to UHE neutrinos. Working with data collected by the Askaryan Radio Array (ARA), we search for neutrino candidates at the lowest threshold achieved to date, leading to improved analysis-level sensitivities. A neutrino search on a data set with 208.7 days of livetime from the reduced-threshold fifth ARA station is performed, achieving a 68% analysis efficiency over all energies on a simulated mixed-composition neutrino flux with an expected background of 0.10-0.04+0.06 events passing the analysis. We observe one event passing our analysis and proceed to set a neutrino flux limit using a Feldman-Cousins construction. We show that the improved trigger-level sensitivity can be carried through an analysis, motivating the phased array triggering technique for use in future radio-detection experiments. We also include a projection using all available data from this detector. Finally, we find that future analyses will benefit from studies of events near the surface to fully understand the background expected for a large-scale detector.

Original languageEnglish
Article number122006
Pages (from-to)1-15
Number of pages16
JournalPhysical Review D
Volume105
Issue number12
DOIs
Publication statusPublished - 27 Jun 2022

Bibliographical note

Funding Information:
K. H. was the main author of this manuscript and led the analysis discussed. The ARA Collaboration designed, constructed, and now operates the ARA detectors. We would like to thank IceCube and specifically the winterovers for the support in operating the detector. Data processing and calibration, Monte Carlo simulations of the detector and of theoretical models and data analyses were performed by a large number of collaboration members, who also discussed and approved the scientific results presented here. We are thankful to the Raytheon Polar Services Corporation, Lockheed Martin, and the Antarctic Support Contractor for field support and enabling our work on the harshest continent. We are thankful to the National Science Foundation (NSF) Office of Polar Programs and Physics Division for funding support. We further thank the Taiwan National Science Councils Vanguard Program NSC 92-2628-M-002-09 and the Belgian F. R. S.-FNRS Grant No. 4.4508.01. K. H. thanks the NSF for support through the Graduate Research Fellowship Program Grant No. DGE-1746045. B. A. C. thanks the NSF for support through the Astronomy and Astrophysics Postdoctoral Fellowship under Grant No. 1903885, as well as the Institute for Cyber-Enabled Research at Michigan State University. A. C. thanks the NSF for Grant No. 1806923 and also acknowledges the Ohio Supercomputer Center. S. A. W. thanks the NSF for support through CAREER Grant No. 2033500. D. B. acknowledges support from National Research Nuclear University MEPhi (Moscow Engineering Physics Institute). A. V. thanks the Sloan Foundation and the Research Corporation for Science Advancement, the Research Computing Center and the Kavli Institute for Cosmological Physics at the University of Chicago for the resources they provided. R. N. thanks the Leverhulme Trust for their support. K. D.dV. is supported by European Research Council under the European Unions Horizon research and innovation program (Grant agreement 763 No. 805486). D. B., I. K., and D. S. thank the NSF for support through the IceCube EPSCoR Initiative (Award No. 2019597).

Publisher Copyright:
© 2022 American Physical Society.

Copyright:
Copyright 2022 Elsevier B.V., All rights reserved.

Keywords

  • astro-ph.HE
  • astro-ph.IM

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