LOWERING ICECUBE'S ENERGY THRESHOLD FOR POINT SOURCE SEARCHES IN THE SOUTHERN SKY

M G Aartsen,M Tselengidou,J Madsen,S Benzvi,K Meagher,J Kunnen,K Mase,G C Hill,R Maruyama,K Rawlins,D Pieloth,M Van Rossem,J M Conrad,K Andeen,G M Spiczak,S Fahey,S Toscano,S Vanheule,D V Pankova,C Ha,W Rhode,D Chirkin,L Brayeur,T Fuchs,D F Cowen,A Christov,G Neer,T Schmidt,L Köpke,D Grant,L Rädel,S Wickmann,A O’Murchadha,P A Evenson,F Mcnally,T Menne,T Ruhe,S Flis,J Tatar,S Vallecorsa,J Adams,G Kohnen,M Börner,M Wallraff,M Ahlers,S Miarecki,H Wissing,K.-H Becker,C Walck,K Helbing,M Lesiak-Bzdak,T R Wood,G S Japaridze,P Desiati,K Hultqvist,A Homeier,M Kowalski,M Wolf,D Bindig,N Van Eijndhoven,A Stasik,X W Xu,T Glüsenkamp,P A Toale,M Glagla,J Lünemann,J Vandenbroucke,J P A M De André,T Stanev,J Kemp,J Feintzeig,J P Dumm,K Ghorbani,J Veenkamp,K Wiebe,N Buzinsky,D Bose,M Rameez,G Yodh,D Seckel,K Woschnagg,J L Lanfranchi,T K Gaisser,R Koirala,J Hignight,H Niederhausen,S Sarkar,T Stezelberger,M Leuermann,S Coenders,K Hoshina,A Haj Ismail,D Soldin,J Becker Tjus,H Kolanoski,R Hellauer,T C Arlen,A Keivani,D R Nygren,U Katz,C Rott,N Kurahashi,M Richman,S Robertson,A Stößl,S Euler,X Bai,A H Cruz Silva,J L Kelley,M Song,J Felde,M Kroll,B Eichmann,S Hickford,A Karle,G Krückl,N Whitehorn,L Mohrmann,P Schlunder,M Day,D Lennarz,G T Przybylski,B J Whelan,R Nahnhauer,J Sandroos,A Turcati,T Karg,E Blaufuss,A Wallace,J J Beatty,R G Stokstad,R Maunu,J Braun,M Ahrens,D L Xu,G W Sullivan,J Kiryluk,A Schönwald,L Wille,M Usner,S W Barwick,S Tilav,O Botner,L Sabbatini,D Hebecker,M Bissok,C Pérez De Los Heros,M Casier,E Pinat,M Sutherland,C Finley,H Taavola,E Del Pino Rosendo,J Casey,S Schoenen,M Medici,A Obertacke Pollmann,M Archinger,A Sandrock,S Kopper,S C Nowicki,S Seunarine,D J Boersma,C Wendt,C.-C Fösig,C Kopper,J Posselt,G Merino,J C Díaz-Vélez,J Leuner,K Krings,S R Klein,G Maggi,K Holzapfel,S Kunwar,C H Wiebusch,D Berley,I Ansseau,C De Clercq,R Reimann,T Meures,M Mandelartz,K Satalecka,A Burgman,V Baum,E Unger,T Deyoung,D Altmann,B J P Jones,L Wills,M Stahlberg,J A Aguilar,M J Larson,F Huang,I Taboada,M Vehring,A Bernhard,A Terliuk,E Jacobi,T Hansmann,M Relich,G De Wasseige,S Böser,P B Price,H S Matis,A Meli,Z Griffith,E Hansen,D J Koskinen,L Gladstone,R Bay,L Gerhardt,J Gallagher,E Cheung,S Westerhoff,A Ishihara,K Abraham,M Zoll,L Classen,T Kintscher,E Middell,Ch Weaver,S In,C Pfendner,M Stamatikos,D Heereman,F Halzen,A Kappes,A R Fazely,R Konietz,D Tosi,B Hansmann,G Binder,J Daughhetee,K Hanson,M Ackermann,M Vraeghe,N L Strotjohann,M Kim,T Montaruli,S De Ridder,M Dunkman,T Palczewski,K Clark,S Schöneberg,D Ryckbosch,N Wandkowsky,G Golup,R Hoffmann,M N Tobin,E Bernardini,F Bos,M Labare,T Kuwabara,J Auffenberg,E Resconi,A Steuer,M Quinnan,W Huelsnitz,Ö Penek,V Di Lorenzo,P Berghaus,J A Pepper,A Hallgren,A Olivas,K Filimonov,M Kauer,A Goldschmidt,H.-P Bretz,K Jero,D Z Besson,C Krüger,A Omairat,B Eberhardt,K D Hoffman,G Tešić ,Lars Rickard Strom ,Spencer Axani ,Ali Kheirandish ,Krijn De Vries ,R Gaïor ,J Davis ,Sarah Mancina ,Matthías Huber ,Michael Schimp ,Dariusz Góra ,Hershal Pandya ,Thomas Ehrhardt ,Summer Blot ,Tyler Anderson ,D Williams ,J G González ,Marjon Moulai ,Martin Rongen ,J V Santen ,D Rysewyk ,Yang Xu ,S Ter–Antonyan ,M Vöge ,C Böhm ,Gisela Anton ,C Argüelles ,Benedikt Riedel ,Hrvoje Dujmović ,Maximilian Meier ,J P Yañez ,Minjin Jeong ,Lu Lu ,M Jurkovič ,Christian Haack ,Kendall Mahn ,Shigeru Yoshida ,Christoph Raab ,Lisa Johanna Schumacher ,Christian Spiering ,Gabriel Collin ,H.-P Dembinski ,Uwe Naumann

doi:10.3847/2041-8205/824/2/l28

Abstract

ABSTRACT Observation of a point source of astrophysical neutrinos would be a “smoking gun” signature of a cosmic-ray accelerator. While IceCube has recently discovered a diffuse flux of astrophysical neutrinos, no localized point source has been observed. Previous IceCube searches for point sources in the southern sky were restricted by either an energy threshold above a few hundred TeV or poor neutrino angular resolution. Here we present a search for southern sky point sources with greatly improved sensitivities to neutrinos with energies below 100 TeV. By selecting charged-current ν μ interacting inside the detector, we reduce the atmospheric background while retaining efficiency for astrophysical neutrino-induced events reconstructed with sub-degree angular resolution. The new event sample covers three years of detector data and leads to a factor of 10 improvement in sensitivity to point sources emitting below 100 TeV in the southern sky. No statistically significant evidence of point sources was found, and upper limits are set on neutrino emission from individual sources. A posteriori analysis of the highest-energy (∼100 TeV) starting event in the sample found that this event alone represents a 2.8σ deviation from the hypothesis that the data consists only of atmospheric background.

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