Search for tau neutrinos with the MAGIC telescopes: improving selection criteria^*

¹ University of Rijeka, Department of Physics, 51000 Rijeka
² Deutsches Elektronen-Synchrotron (DESY), D-15738 Zeuthen, Germany
³ Humboldt University of Berlin, Institut für Physik D-12489 Berlin Germany
⁴ Università di Padova and INFN, I-35131 Padova, Italy
⁵ Institute of Nuclear Physics Polish Academy of Sciences, PL-31342 Krakow, Poland
⁶ Max-Planck-Institut für Physik, D-80805 München, Germany
⁷ the full list of MAGIC members is available at: wwwmagic.mppmu.mpg.de

^* original title was: Search for tau neutrinos with the MAGIC telescopes: the quest continues
^a e-mail: marina.manganaro@phy.uniri.hr

Published online: 13 May 2019

Abstract

MAGIC, a system of two Cherenkov telescopes located at the Roque de los Muchachos Observatory (2200 a.s.l.) in the Canary Island of La Palma, has lately been engaged in an unconventional task: the search for a signature of particle showers induced by earth-skimming cosmic tau neutrinos arising from the ocean, in the PeV to EeV energy range. When pointing at the sea, the MAGIC telescopes can collect data in a range of about 5 deg in zenith and 80 deg in azimuth: the analysis of the shower images from ~30 hours of data, together with the simulations of upward-going tau neutrino showers, shows that the air showers induced by tau neutrinos can be discriminated from the hadronic background coming from a similar direction. We have calculated the point source acceptance and the expected event rates, assuming an incoming v_ flux consistent with IceCube measurements, and for a sample of generic neutrino fluxes from photohadronic interactions in AGNs and GRBs. A 90% C.L. upper limit on the tau-neutrino point source flux of 2.0 × 10^–4 GeV cm^–2 s^–1 has been obtained. The presented results can also be important for future Cherenkov experiments such as the Cherenkov Telescope Array. This next generation ground-based observatory can have a much better possibility to detect v_, given its larger FOV and much larger effective area.