Ultra-High-Energy Cosmic Rays  

In General
* Idea: Cosmic rays with energies above 1018 eV, equivalent to the kinetic energy of a tennis ball moving at 100 km/h.
* Status: At E ~ 1018 eV, some events show directionality; The rate falls almost to zero at 1020 eV, but there may be about 5 events/km2/sr/cy at higher energies; 2003, Auger being built [@ news pw(03)oct]; 2004, The total number of events is 6 (11 in AGASA?), so the evidence may be considered flimsy, and there are systematics that are not understood, and might be settled by the Auger project; 2005, AGASA actually has 59 events at E > 4 × 1019 eV, roughly isotropic, and Auger has started seeing UHECR showers; 2007, The Pierre Auger detector shows that the very largest of cosmic ray showers, those with an energy higher than 57 EeV, correlate pretty well with known AGNs; 2010, The most energetic event recorded (by Fly's Eye) and the highest-energy Auger event (148 EeV) point to distant quasars; 2012, Relationship with GRBs questioned by IceCube results showing too few neutrinos.
@ Intros: Cronin et al SA(97)jan; O'Halloran et al PT(98)jan; Musser SA(99)jan; De Marco ap/05-proc.
@ Reviews: Kampert JPCS(08)-a0801; Smida a1001-proc; Zavrtanik CP(10); Stanev a1011-conf; Letessier-Selvon & Stanev RMP(11); Kotera & Olinto ARAA(11)-a1101; Sidhu a1102 [and detection]; Aloisio a1104-conf [propagation, spectrum]; Mostafa a1111-proc; Olinto JPCS(12)-a1201; Stanev a1201-conf; Aloisio a1211-conf; Kampert EPJwc(13)-a1305, BJP(13)-a1305-TX, a1404-proc; Kotera & Olinto AJP(14)jul [RL]; de Naurois a1510-proc [20 GeV to 100s of TeV]; Aloisio a1603-conf [and neutrinos]; Dova CERN-a1604-ln; Dawson et al PETP-a1703.
@ General references: Bhattacharjee & Sigl PRP(00)ap/98; Frampton ap/98-conf; Yoshida & Dai JPG(98)ap; Biermann et al NPPS(00)ap [M87?]; Anchordoqui et al PRD(01)hp/00 [monopoles?]; Nagano & Watson RMP(00); Bertou et al IJMPA(00)ap; Billoir & Letessier-Selvon ap/00; Sigl LNP(00)ap, Sci(01)ap, AP(02), AP(03); Olinto PRP(00)ap; Watson ap/01-conf, CP(02); Sarkar hp/02-conf; Dick et al NPPS(03)ap/02 [and dark matter]; Starobinsky & Tkachev JETPL(02)ap [theory]; Olinto NPPS(02)ap; Blasi ap/03-conf; Sigl APPB(04)ap-proc; Olinto AIP(05)ap/04; Stenkin NPPS(06)ap/04; Gaisser & Stanev NPA(06)ap/05; issue NPPS(06)151#1; Medina-Tanco ap/06-proc; Kachelriess a0801-ln; Olinto et al a0903-rp; Teshima & Watson NJP(09); Aloisio et al APP(11)-a0907; Capdevielle et al ed-NPPB(09); Berezinsky a1307-conf [signatures and models].
@ Composition: Abbasi et HiRes ApJ(05)ap/04; Allard et al JCAP(08)-a0805; Boyle MPLA(08) [TRACER]; Unger et Auger a0902-proc; Abbasi et HiRes PRL(10) [proton-dominated]; Schwarzschild PT(10)may; Wilk & Włodarczyk JPG(11)-a1006; Plum et PA a1501-proc; Biermann et al a1610-proc.

blue bullet Other aspects: see cosmic rays [including history, detectors]; propagation [including acceleration mechanisms].
blue bullet Special types: see astrophysical neutrinos; cosmic-ray sources.
blue bullet Related topics: see matter phenomenology in quantum gravity; modified lorentz symmetry, phenomenology and tests; spacetime foam.

Observation
* Oh-My-God-Particle: A 3.2 × 1020 eV particle event observed on Oct 15, 1991.
@ First events: Hayashida et al PRL(94) [AGASA, 1 event], PRL(96) + pn(96)jul [AGASA, 36 events, directionality].
@ Pierre Auger: Mantsch ap/06-conf; Zech ap/06-proc; Kampert IJMPE(07)ap/06-conf; Vorobiov ap/06-conf; Matthiae a0807-conf; Blümer JPSJ(09)-a0807-proc; Roulet JPCS(08)-a0809; Cronin a0911-conf; Harari IJMPD(11) [rev]; Conceiçao a1111-proc [results]; Pierre Auger Collaboration a1307 [prospects]; Khanin & Mortlock MNRAS(16)-a1601 [the 69 highest-energy cosmic rays detected].
@ Other status: Anchordoqui et al IJMPA(03)hp/02; Stecker JPG(03)ap; Kachelrieß CRP(04)hp-in; Stanev AIP(04)ap; Bergman & Belz JPG(07)-a0704 [composition].
@ Spectrum: Pierre Auger ap/05-conf; Letessier-Selvon AIP(06)ap/05 [and anisotropy]; De Marco & Stanev PRD(05); Yamamoto for PA AIP(06)ap, a0707-conf; Connolly et al PRD(06)ap [comparison of experiments]; Roth et Auger a0706-conf; Pierre Auger Collaboration a0906-conf; Kistler & Yüksel a0912 [electrons and positrons]; Pierre Auger Collaboration PLB(10)-a1002.
@ Anisotropy: Anchordoqui et al PRD(03) [search]; HiRes collaboration ApJL(04)ap, NPPS(04)ap, APP(07)ap/05 [none found]; Mollerach & Roulet JCAP(05) [search method]; De Marco et al JCAP(06)ap/05 [simulations]; Kachelrieß & Serpico PLB(06) [Compton-Getting effect]; Mikhailov a0705-conf; Kalashev et al JCAP(08)-a0710 [space-based detectors]; Kashti NPA(09)-a0901-proc; Abraham et Auger a0906-conf; Pierre Auger Collaboration JCAP(11)-a1106 [and chemical composition], JCAP(12), ApJS(12)-a1210 [distribution of arrival directions]; Zotov a1402-wd [above 1 PeV]; Deligny et Pierre Auger Collaboration JPCS(14)-a1403 [distribution of arrival directions above 10 PeV]; news pt(14)jul [hotspot seen by the Telescope Array experiment]; Ivanov IJMPD(16)-a1602 [none found].
@ Photons: Pierre Auger APP(08)-a0712 [above 1019 eV]; Fomin et al a1702 [\(\sim 10^{16}\;{\rm to}\;10^{17.5}\) eV primaries].
@ Related topics: Illana et al PRD(07)hp/06 [new physics]; Erlykin & Wolfendale a0907 [time variation of flux]; Pisanti a1007-proc [ground-based experiments]; Panasyuk et al JPCS(15)-a1501 [orbital experiments].


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