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A combined maximum-likelihood analysis of the high-energy astrophysical neutrino flux measured with IceCube

MG Aartsen, K Abraham, M Ackermann, J Adams, JA Aguilar, M Ahlers, M Ahrens, D Altmann, T Anderson, M Archinger, et al. (2015) ASTROPHYSICAL JOURNAL. 809(1).
abstract
Evidence for an extraterrestrial flux of high-energy neutrinos has now been found in multiple searches with the IceCube detector. The first solid evidence was provided by a search for neutrino events with deposited energies greater than or similar to 30 TeV and interaction vertices inside the instrumented volume. Recent analyses suggest that the extraterrestrial flux extends to lower energies and is also visible with throughgoing, nu(mu)-induced tracks from the Northern Hemisphere. Here, we combine the results from six different IceCube searches for astrophysical neutrinos in a maximum-likelihood analysis. The combined event sample features high-statistics samples of shower-like and track-like events. The data are fit in up to three observables: energy, zenith angle, and event topology. Assuming the astrophysical neutrino flux to be isotropic and to consist of equal flavors at Earth, the all-flavor spectrum with neutrino energies between 25 TeV and 2.8 PeV is well described by an unbroken power law with best-fit spectral index -2.50 +/- 0.09 and a flux at 100 TeV of (6.7(-1.2)(+1.1)) x 10(-18) GeV-1 s(-1) sr(-1) cm(-2). Under the same assumptions, an unbroken power law with index -2 is disfavored with a significance of 3.8 sigma (p = 0.0066%) with respect to the best fit. This significance is reduced to 2.1 sigma (p = 1.7%) if instead we compare the best fit to a spectrum with index -2 that has an exponential cut-off at high energies. Allowing the electron-neutrino flux to deviate from the other two flavors, we find a nu(e) fraction of 0.18 +/- 0.11 at Earth. The sole production of electron neutrinos, which would be characteristic of neutron-decay-dominated sources, is rejected with a significance of 3.6 sigma ( p = 0.014%).
Please use this url to cite or link to this publication:
author
organization
year
type
journalArticle (original)
publication status
published
subject
keyword
neutrinos, GAMMA-RAY SOURCES, methods: data analysis, astroparticle physics, COSMIC-RAYS, POINT-LIKE, PERFORMANCE, TELESCOPE, EMISSION, GALAXIES, SPECTRUM, SEARCHES, SIGNALS
journal title
ASTROPHYSICAL JOURNAL
Astrophys. J.
volume
809
issue
1
article number
98
pages
15 pages
Web of Science type
Article
Web of Science id
000361653500098
JCR category
ASTRONOMY & ASTROPHYSICS
JCR impact factor
5.909 (2015)
JCR rank
8/61 (2015)
JCR quartile
1 (2015)
ISSN
0004-637X
DOI
10.1088/0004-637X/809/1/98
project
IceCube
language
English
UGent publication?
yes
classification
A1
copyright statement
I have transferred the copyright for this publication to the publisher
id
7120882
handle
http://hdl.handle.net/1854/LU-7120882
date created
2016-03-01 10:37:14
date last changed
2017-02-28 14:46:59
@article{7120882,
  abstract     = {Evidence for an extraterrestrial flux of high-energy neutrinos has now been found in multiple searches with the IceCube detector. The first solid evidence was provided by a search for neutrino events with deposited energies greater than or similar to 30 TeV and interaction vertices inside the instrumented volume. Recent analyses suggest that the extraterrestrial flux extends to lower energies and is also visible with throughgoing, nu(mu)-induced tracks from the Northern Hemisphere. Here, we combine the results from six different IceCube searches for astrophysical neutrinos in a maximum-likelihood analysis. The combined event sample features high-statistics samples of shower-like and track-like events. The data are fit in up to three observables: energy, zenith angle, and event topology. Assuming the astrophysical neutrino flux to be isotropic and to consist of equal flavors at Earth, the all-flavor spectrum with neutrino energies between 25 TeV and 2.8 PeV is well described by an unbroken power law with best-fit spectral index -2.50 +/- 0.09 and a flux at 100 TeV of (6.7(-1.2)(+1.1)) x 10(-18) GeV-1 s(-1) sr(-1) cm(-2). Under the same assumptions, an unbroken power law with index -2 is disfavored with a significance of 3.8 sigma (p = 0.0066\%) with respect to the best fit. This significance is reduced to 2.1 sigma (p = 1.7\%) if instead we compare the best fit to a spectrum with index -2 that has an exponential cut-off at high energies. Allowing the electron-neutrino flux to deviate from the other two flavors, we find a nu(e) fraction of 0.18 +/- 0.11 at Earth. The sole production of electron neutrinos, which would be characteristic of neutron-decay-dominated sources, is rejected with a significance of 3.6 sigma ( p = 0.014\%).},
  articleno    = {98},
  author       = {Aartsen, MG and Abraham, K and Ackermann, M and Adams, J and Aguilar, JA and Ahlers, M and Ahrens, M and Altmann, D and Anderson, T and Archinger, M and Arguelles, C and Arlen, TC and Auffenberg, J and Bai, X and Barwick, SW and Baum, V and Bay, R and Beatty, JJ and Tjus, JB and Becker, KH and Beiser, E and BenZvi, S and Berghaus, P and Berley, D and Bernardini, E and Bernhard, A and Besson, DZ and Binder, G and Bindig, D and Bissok, M and Blaufuss, E and Blumenthal, J and Boersma, DJ and Bohm, C and Borner, M and Bos, F and Bose, D and Boser, S and Botner, O and Braun, J and Brayeur, L and Bretz, HP and Brown, AM and Buzinsky, N and Casey, J and Casier, M and Cheung, E and Chirkin, D and Christov, A and Christy, B and Clark, K and Classen, L and Coenders, S and Cowen, DF and Silva, AHC and Daughhetee, J and Davis, JC and Day, M and de Andre, JPAM and De Clercq, C and Dembinski, H and De Ridder, Sam and Desiati, P and de Vries, KD and de Wasseige, G and de With, M and DeYoung, T and Diaz-Velez, JC and Dumm, JP and Dunkman, M and Eagan, R and Eberhardt, B and Ehrhardt, T and Eichmann, B and Euler, S and Evenson, PA and Fadiran, O and Fahey, S and Fazely, AR and Fedynitch, A and Feintzeig, J and Felde, J and Filimonov, K and Finley, C and Fischer-Wasels, T and Flis, S and Fuchs, T and Gaisser, TK and Gaior, R and Gallagher, J and Gerhardt, L and Ghorbani, K and Gier, D and Gladstone, L and Glagla, M and Glusenkamp, T and Goldschmidt, A and Golup, G and Gonzalez, JG and Goodman, JA and Gora, D and Grant, D and Gretskov, P and Groh, JC and Gross, A and Ha, C and Haack, C and Haj Ismail, Abd Al Karim and Hallgren, A and Halzen, F and Hansmann, B and Hanson, K and Hebecker, D and Heereman, D and Helbing, K and Hellauer, R and Hellwig, D and Hickford, S and Hignight, J and Hill, GC and Hoffman, KD and Hoffmann, R and Holzapfel, K and Homeier, A and Hoshina, K and Huang, F and Huber, M and Huelsnitz, W and Hulth, PO and Hultqvist, K and In, S and Ishihara, A and Jacobi, E and Japaridze, GS and Jero, K and Jurkovic, M and Kaminsky, B and Kappes, A and Karg, T and Karle, A and Kauer, M and Keivani, A and Kelley, JL and Kemp, J and Kheirandish, A and Kiryluk, J and Klas, J and Klein, SR and Kohnen, G and Kolanoski, H and Konietz, R and Koob, A and Kopke, L and Kopper, C and Kopper, S and Koskinen, DJ and Kowalski, M and Krings, K and Kroll, G and Kroll, M and Kunnen, J and Kurahashi, N and Kuwabara, T and Labare, Mathieu and Lanfranchi, JL and Larson, MJ and Lesiak-Bzdak, M and Leuermann, M and Leuner, J and Lunemann, J and Madsen, J and Maggi, G and Mahn, KBM and Maruyama, R and Mase, K and Matis, HS and Maunu, R and McNally, F and Meagher, K and Medici, M and Meli, Athina and Menne, T and Merino, G and Meures, T and Miarecki, S and Middell, E and Middlemas, E and Miller, J and Mohrmann, L and Montaruli, T and Morse, R and Nahnhauer, R and Naumann, U and Niederhausen, H and Nowicki, SC and Nygren, DR and Obertacke, A and Olivas, A and Omairat, A and O'Murchadha, A and Palczewski, T and Paul, L and Pepper, JA and de los Heros, CP and Pfendner, C and Pieloth, D and Pinat, E and Posselt, J and Price, PB and Przybylski, GT and Putz, J and Quinnan, M and Radel, L and Rameez, M and Rawlins, K and Redl, P and Reimann, R and Relich, M and Resconi, E and Rhode, W and Richman, M and Richter, S and Riedel, B and Robertson, S and Rongen, M and Rott, C and Ruhe, T and Ruzybayev, B and Ryckbosch, Dirk and Saba, SM and Sabbatini, L and Sander, HG and Sandrock, A and Sandroos, J and Sarkar, S and Schatto, K and Scheriau, F and Schimp, M and Schmidt, T and Schmitz, M and Schoenen, S and Schoneberg, S and Schonwald, A and Schukraft, A and Schulte, L and Seckel, D and Seunarine, S and Shanidze, R and Smith, MWE and Soldin, D and Spiczak, GM and Spiering, C and Stahlberg, M and Stamatikos, M and Stanev, T and Stanisha, NA and Stasik, A and Stezelberger, T and Stokstad, RG and Stossl, A and Strahler, EA and Strom, R and Strotjohann, NL and Sullivan, GW and Sutherland, M and Taavola, H and Taboada, I and Ter-Antonyan, S and Terliuk, A and Tesic, G and Tilav, S and Toale, PA and Tobin, MN and Tosi, D and Tselengidou, M and Unger, E and Usner, M and Vallecorsa, S and Vandenbroucke, J and van Eijndhoven, N and Vanheule, Sander and van Santen, J and Veenkamp, J and Vehring, M and Voge, M and Vraeghe, Matthias and Walck, C and Wallace, A and Wallraff, M and Wandkowsky, N and Weaver, C and Wendt, C and Westerhoff, S and Whelan, BJ and Whitehorn, N and Wichary, C and Wiebe, K and Wiebusch, CH and Wille, L and Williams, DR and Wissing, H and Wolf, M and Wood, TR and Woschnagg, K and Xu, DL and Xu, XW and Xu, Y and Yanez, JP and Yodh, G and Yoshida, S and Zarzhitsky, P and Zoll, M},
  issn         = {0004-637X},
  journal      = {ASTROPHYSICAL JOURNAL},
  keyword      = {neutrinos,GAMMA-RAY SOURCES,methods: data analysis,astroparticle physics,COSMIC-RAYS,POINT-LIKE,PERFORMANCE,TELESCOPE,EMISSION,GALAXIES,SPECTRUM,SEARCHES,SIGNALS},
  language     = {eng},
  number       = {1},
  pages        = {15},
  title        = {A combined maximum-likelihood analysis of the high-energy astrophysical neutrino flux measured with IceCube},
  url          = {http://dx.doi.org/10.1088/0004-637X/809/1/98},
  volume       = {809},
  year         = {2015},
}

Chicago
Aartsen, MG, K Abraham, M Ackermann, J Adams, JA Aguilar, M Ahlers, M Ahrens, et al. 2015. “A Combined Maximum-likelihood Analysis of the High-energy Astrophysical Neutrino Flux Measured with IceCube.” Astrophysical Journal 809 (1).
APA
Aartsen, M., Abraham, K., Ackermann, M., Adams, J., Aguilar, J., Ahlers, M., Ahrens, M., et al. (2015). A combined maximum-likelihood analysis of the high-energy astrophysical neutrino flux measured with IceCube. ASTROPHYSICAL JOURNAL, 809(1).
Vancouver
1.
Aartsen M, Abraham K, Ackermann M, Adams J, Aguilar J, Ahlers M, et al. A combined maximum-likelihood analysis of the high-energy astrophysical neutrino flux measured with IceCube. ASTROPHYSICAL JOURNAL. 2015;809(1).
MLA
Aartsen, MG, K Abraham, M Ackermann, et al. “A Combined Maximum-likelihood Analysis of the High-energy Astrophysical Neutrino Flux Measured with IceCube.” ASTROPHYSICAL JOURNAL 809.1 (2015): n. pag. Print.