Observation of Seven Astrophysical Tau Neutrino Candidates with IceCube
R. Abbasi, M. Ackermann, J. Adams, Sanjib Kumar Agarwalla, J. A. Aguilar, M. Ahlers, Jean-Marco Alameddine, N. M. Amin, K. Andeen, G. Anton, C. Argüelles, Y. Ashida, S. Athanasiadou, S. N. Axani, X. Bai, V. A. Balagopal, M. Baricevic, S. W. Barwick, Vedant Basu, R. Bay, J. J. Beatty, J. Becker Tjus, J. Beise, Chiara Bellenghi, Charlotte Benning, S. BenZvi, D. Berley, E. Bernardini, D. Z. Besson, E. Blaufuss, Summer Blot, Federico Bontempo, Julia Book, Caterina Boscolo Meneguolo, S. Böser, O. Botner, J. Böttcher, Etienne Bourbeau, J. Braun, B. Brinson, J. Brostean-Kaiser, R. T. Burley, R. S. Busse, Delaney Butterfield, Michael Campana, K. Carloni, Erin Carnie-Bronca, Sharmistha Chattopadhyay, Thien Nhan Chau, C. Chen, Z. Chen, D. Chirkin, S. Choi, Brian Clark, Lew Classen, A. Coleman, G. H. Collin, A. Connolly, J. M. Conrad, P. Coppin, Pablo Correa, D. F. Cowen, Pranav Dave, C. De Clercq, J. J. DeLaunay, Diyaselis Delgado, S. Deng, Kunal Deoskar, Aman Mukeshbhai Desai, P. Desiati, K. D. de Vries, G. de Wasseige, T. DeYoung, Alejandro Diaz, J. C. Díaz–Vélez, Markus Dittmer, Alba Domi, H. Dujmovic, M. A. DuVernois, Thomas Ehrhardt, P. Eller, E. Ellinger, Sharif El Mentawi, Dominik Elsässer, R. Engel, H. Erpenbeck, John Evans, P. A. Evenson, Kwok Lung Fan, K. Fang, Kareem Ramadan Farrag, A. R. Fazely, Nora Feigl, Sebastian Fiedlschuster, Aaron Fienberg, C. Finley, L. Fischer, D. B. Fox, A. Franckowiak, Alexander Fritz
Abstract
We report on a measurement of astrophysical tau neutrinos with 9.7 yr of IceCube data. Using convolutional neural networks trained on images derived from simulated events, seven candidate ν_{τ} events were found with visible energies ranging from roughly 20 TeV to 1 PeV and a median expected parent ν_{τ} energy of about 200 TeV. Considering backgrounds from astrophysical and atmospheric neutrinos, and muons from π^{±}/K^{±} decays in atmospheric air showers, we obtain a total estimated background of about 0.5 events, dominated by non-ν_{τ} astrophysical neutrinos. Thus, we rule out the absence of astrophysical ν_{τ} at the 5σ level. The measured astrophysical ν_{τ} flux is consistent with expectations based on previously published IceCube astrophysical neutrino flux measurements and neutrino oscillations.