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Topic: GZK cutoff

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	Re: Why do we expect GZK cutoff at the energies 6x10^19 eV ?
		The GZK cutoff is not due to proton pair production.
		You don't calculate the GZK cutoff exactly at the threshhold, but rather at the delta (1232 MeV) resonance where the cross section is largest.
		The GZK cutoff is not sharp, since the cross-sections vary with energy and the CMB photons have a wide distribution.
	www.madsci.org /posts/archives/2005-05/1115145530.Ph.r.html (244 words)

	More About PAO
		There is a general agreement on the fact that the conventional acceleration mechanisms have difficulties in explaining the observations made of UHE cosmic rays up to the end of the spectrum.
		The corresponding attenuation lengths are less than a few tens of Mpc: this is the origin of the GZK cutoff.
		Above the GZK cutoff the rate is roughly 10 events per century and per square kilometer for a standard ground detector.
	www.p-ng.si /public/pao/paop.php (1253 words)

	debate (Site not responding. Last check: 2007-10-21)
		The rate of events at energies beyond the GZK cutoff as presented by the two collaborations in Hamburg were incompatible with one another.
		In the presence of a cutoff that would be a 4.0 sigma deviation.
		If one extends a straight line fit to the HR1 data into the GZK region, 11 events are expected where in the last three bins 4 are observed; that makes for a 2.3 sigma discrepancy between data and a straight line extrapolation for a continuing HR1 spectrum.
	astro.uchicago.edu /~olinto/aspen/debate (2754 words)

	Why do we expect GZK cutoff at the energies 6x10^19 eV ? (Site not responding. Last check: 2007-10-21)
		Subject: Why do we expect GZK cutoff at the energies 6x10^19 eV ?
		As far as I know the proton pair production threshold energy is ~5x10^17ev,and GZK (Greisen-Zatsepin-Kuzmin) threshold energy is ~6x10^19eV.
		Re: Why do we expect GZK cutoff at the energies 6x10^19 eV ?
	www.madsci.org /posts/archives/2005-05/1115145530.Ph.q.html (91 words)

	Probing theories with cosmic rays (Site not responding. Last check: 2007-10-21)
		One can generalize the GZK effect to heavy nuclei which lose their nucleons by spallation on the CMB photons at a quick rate.
		This cutoff effect is visible on Fig.2 where the dotted line shows the way the energy spectrum is expected to end.
		Many ways were explored in order to “violate the GZK cutoff”: supersymmetric (new) particles; non- standard neutrinos within the framework of recent developments based on extra-dimensions and exchange of spin-2 bosons or gravitons; violation of the Lorentz invariance of Special Relativity and so on.
	www.europhysicsnews.com /full/17/article2/article2.html (3422 words)

	Energy Citations Database (ECD) - Energy and Energy-Related Bibliographic Citations
		There is so far no indication of the GZK cutoff in the energy spectrum at 5x10{sup 19} eV.
		A cutoff would be expected if the sources of the cosmic rays were distributed uniformly throughout the cosmos.
		The sources of cosmic rays with energy above the GZK cutoff must be at a distance {<=}100 Mpc, and if they are protons they are very likely to point to these sources.
	www.osti.gov /energycitations/product.biblio.jsp?osti_id=20478651 (331 words)

	KICP Seminars: Spring 2002
		This GZK cutoff is actually a kind of absorption edge in the cosmic ray spectrum: if these particles originate at distances large compared to a few Mpc, then they should be scattered and absorbed by the cosmic microwave background, which appear as gamma-rays in the rest frame of the particles.
		Such scattering must in turn yield pions and thus neutrinos, and these high energy GZK neutrinos are perhaps the clearest signature of the cosmic-ray scattering process from which they arise.
		We discuss a series of new initiatives aimed at discovering the GZK neutrinos, exploiting the Askaryan effect: strong coherent radio emission from high energy cascades in solid dielectric media such as natural ice and rock salt.
	cfcp.uchicago.edu /seminars/archive_2002Spring.html (1355 words)

	Ultra High Energy Cosmic Rays
		It is postulated that Ultra High Energy Cosmic Rays (UHECRs) are actually short duration Cosmic Ray Bursts produced as side effects of the process which causes what the author calls Stellar Gamma-ray Flashes (SGFs), commonly known as Gamma-Ray Bursts (GRBs).
		They say that energy losses suffered by ultra high energy cosmic rays by meson-producing interactions with photons of the big-bang relic background radiation would have a profound effect on what we can "see." (This is the Greisen-Zatsepin-Kuzmin (GZK) cutoff problem.
		The Ritzian time-compressions, hypothesized for close counters of stellar bodies, would also time-compress whatever cosmic rays that happened to be headed our way from the sources.
	www.ebicom.net /~rsf1/uhecrs.htm (1366 words)

	CRIS 2004 (Site not responding. Last check: 2007-10-21)
		The Cosmic Ray International Seminar, devoted to ultra high energy cosmic rays (UHECR) about the GZK cutoff, will be held in Catania.
		CRIS (originally Catania Relativistic Ion Studies) Conference is devoted to debating a specific hot topic in physics.
		GZK cutoff, the controversial discrepancy still existing between experimental data,
	www.ct.infn.it /~cris/description.html (375 words)

	Astrophysics and Theory
		On the statistical significance of the GZK feature in the spectrum of ultra high energy cosmic rays.
		Reassessment of the GZK cutoff in the spectrum of UHE cosmic rays in a universe with low photon-baryon ratio.
		GZK Violation - a Tempest in a (Magnetic) Teapot?.
	auger.cnrs.fr /propagation.html (2403 words)

	[No title] (Site not responding. Last check: 2007-10-21)
		Certainly near and above the expected GZK energy cutoff there could well be a difference.
		A northern site with more exposure to sources within the GZK radius could measure a somewhat different energy spectrum near the expected cutoff and a dramatically different spectrum above the cutoff.
		Similarly, north/south composition differences may be expected due to a concentration of nearby sources easily seen from one hemisphere but not from the other.
	www.physics.utah.edu /~sommers/faq/c4.html (150 words)

	My Silly Life: GZK cutoff to crackpots in one Google search (Site not responding. Last check: 2007-10-21)
		My Silly Life: GZK cutoff to crackpots in one Google search
		GZK cutoff to crackpots in one Google search
		I was Googling for "GZK cutoff", since I had just read an article disputing the existence of the GZK cutoff
	www.airynothing.com /blogs/archives/003151.html (453 words)

	[No title]
		However, cosmic rays above a certain energy, the GZK cutoff, will interact with and be absorbed by the cosmic microwave background radiation and will be unable to reach us over extra galactic distances.
		In my talk, I will discuss the current experimental measurements on the spectrum, composition and source direction of UHE cosmic rays concentrating on data from the HiRes Experiment in Utah.
		I will describe our current understanding of this data as well as the experimental controversy regarding the GZK cutoff.
	www.ph.hunter.cuny.edu /Seminars/Schnetzer.doc (194 words)

	[No title] (Site not responding. Last check: 2007-10-21)
		We argue in favor of the astrophysical model valid at energies 1.10^{18} - 8.10^{19} eV with AGN as the sources and UHE protons as the signal carriers.
		The calculated spectrum has the signatures of interaction with microwave radiation in the form of the dip at E ~ 1.10^{19} eV and of the beginning of the GZK cutoff at (5.3 - 8).10^{19} eV, which seem to be confirmed by the AGASA data.
		We analyze also the problem of the GZK cutoff for UHECR from GRBs and from locally overdensed sources, and found these possibilities disfavored.
	celestial.eprints.org /cgi-bin/oaia2/arXiv.org?verb=GetRecord&identifier=oai:arXiv.org:hep-ph/0204357&metadataPrefix=oai_dc (183 words)

	OSU Physics: Calendar of Events (Site not responding. Last check: 2007-10-21)
		Particles above this energy must either orignate cosmologically nearby, or evade the GZK bound by an exotic mechanism.
		The Pierre Auger Observatory is being constructed to address the problem of the highest energy cosmic rays, using two 3000 km^2 sites, the first of which is now under construction in western Argentina.
		Prospects also exist for the detection of the neutrinos produced in the GZK interactions, by using high altitude balloons as a platform to search for radio pulses from neutrino interactions in the Antarctic ice cap.
	www.physics.ohio-state.edu /calendar/event.php3?id=744 (186 words)

	Citebase - Space-Time Foam Effects on Particle Interactions and the GZK Cutoff
		Space-Time Foam Effects on Particle Interactions and the GZK Cutoff
		We discuss the possible modification of the GZK cutoff on high-energy cosmic rays, in the light of this energy non-conservation as well as the possible modification of the usual relativistic momentum-energy relation.
		Expanded introduction, updated discussion of possible constraint if GZK cutoff is confirmed.
	citebase.eprints.org /cgi-bin/citations?id=oai:arXiv.org:hep-th/0012216 (1289 words)

	HiRes: High Resolution Fly's Eye at Columbia University
		The GZK Effect and the Present Status of Experiment
		This cutoff, first predicted by Greisen (1966) and Zatsepin and Kuz'min (1966) and named the GZK-cutoff, is expected due to the interaction of cosmic ray particles with the 2.7°K cosmic microwave background radiation.
		The AGASA cosmic ray experiment has found that the spectrum seems to continue beyond this energy without evidence for a cutoff.
	hires.phys.columbia.edu /physics.php (659 words)

	Status and prospects of the ultrahigh energy cosmic rays
		Various scenarios trying to explain the flat AGASA spectrum (no GZK cutoff) are recalled.
		The multiple events, observed by AGASA, seem not to be statistical fluctuations and we analyse the information contained in them.
		The Pierre Auger Observatory (in construction) is expected to dispel the doubts about existence of the GZK cutoff as well as those about the nature of the multiplets.
	stacks.iop.org /0954-3899/29/853 (267 words)

	[No title] (Site not responding. Last check: 2007-10-21)
		Davoudiasl, H. Hewett, J. Rizzo, T. The flux of cosmic rays beyond the GZK cutoff ($\sim 10^{20}$ eV) may be explained through their production by ultra high energy cosmic neutrinos, annihilating on the relic neutrino background, in the vicinity of our galaxy.
		This process is mediated through the production of a $Z$ boson at resonance, and is generally known as the $Z$-Burst mechanism.
		Under certain assumptions about the energy spectrum of the primary neutrinos we find that cosmic ray data could be potentially as powerful as the LHC in probing the RS model.
	celestial.eprints.org /cgi-bin/oaia2/arXiv.org?verb=GetRecord&identifier=oai:arXiv.org:hep-ph/0010066&metadataPrefix=oai_dc (171 words)

	Citebase - Ultra-high energy cosmic rays without GZK cutoff
		The UHE CR fluxes produced at the decays of X- particles are calculated.
		The dominant contribution is given by fluxes of photons and nucleons from the halo of our Galaxy and thus they do not exibit the GZK cutoff.
		The expected proton and neutrino fluxes from decays of massive metastable relic particles is calculated using the HERWIG QCD event generator.
	citebase.eprints.org /cgi-bin/citations?archiveID=oai:arXiv.org:astro-ph/9708217 (1426 words)

	Table of contents for Library of Congress control number 2003272106
		9 3 The Standard Scenario: The GZK Mechanism 13 3.1 Brief Introduction to General Relativity and Cosmology.......
		40 3.8 Byproducts of the GZK Mechanism: Neutrinos..............
		49 3.10 The GZK Mechanism to the Heavy Nuclei...............
	www.loc.gov /catdir/toc/fy042/2003272106.html (262 words)

	Journals and Proceedings (DESY week 12) (Site not responding. Last check: 2007-10-21)
		Cutoff of primary cosmic ray energy spectrum without the knee and the ankle.
		On a possible role of the long-flying component in the seeming absence of the GZK cutoff.
		Particle emission from the interaction of defects with dark matter.
	www-library.desy.de /lists/preps/journal-12.html (3029 words)

	Absence of GZK Cutoff and Test of de Sitter Invariant Special Relativity
		Absence of GZK Cutoff and Test of de Sitter Invariant Special Relativity
		The possibility that the absence of Greisen–Zatsepin–Kuz'min (GZK) cutoff is used to discriminate between de Sitter invariant special relativity (
		In particular, reselling and systematic downloading of files is prohibited.
	stacks.iop.org /0256-307X/22/791 (201 words)

	Central pp Collisions at Collider Energies: Triggers, Final States, and Implications for Interactions Near GZK (Site not responding. Last check: 2007-10-21)
		Based on the analysis of the information on the structure of the gluon field of the nucleon obtained at HERA we demonstrate that at LHC new particle production and hard dijet production at central rapidities are dominated by pp scattering at small impact parameters.
		Similar pattern is expected for generic central proton-nucleus collisions at the LHC and beyond with the most dramatic changes in the forward region important for interretation of the cosmic ray interactions near GZK cutoff.
		I will also briefly discuss connection to the gap survival in the central diffraction.
	www.phys.uconn.edu /Seminars/2004Fall/20041108hep.html (254 words)

	Cosmic Rays (Site not responding. Last check: 2007-10-21)
		13 - Phenomenology - GZK Cutoff - Conference Proceedings
		Detection of a cosmic ray with measured energy well beyond the expected spectral cutoff due to cosmic microwave radiation,
		CRIS 2004, Cosmic Ray International Seminar: GZK and Surroundings.
	www.nu.to.infn.it /Cosmic_Rays (3189 words)

	Auger Top page
		The Auger Observatory is designed to detect and study cosmic rays around and above the GZK cutoff, i.e.
		The Auger project is therefore the only answer the scientific community can propose to solve an astrophysical puzzle of more than 30 years.
		Le projet Pierre Auger est l'unique moyen proposé par la communauté scientifique pour résoudre cette énigme astrophysique vieille de plus de 30 ans.
	auger.cnrs.fr (321 words)

	ANITA Science (Site not responding. Last check: 2007-10-21)
		Neutrinos are of great interest to astrophysicist as they are the only particle that can reach earth unattenuated at all energies.
		This is particularly of interest at high energies where other particles will interact with the photons of the microwave background (the GZK cutoff) making them unable to propagate and survive over long astrophysical distances.
		The ANITA instrument detects these ultra-high energy neutrinos by use of the Askaryan effect.
	www.phys.hawaii.edu /~anita/science.html (251 words)

	gamma ray bursts and high energy neutrinos
		Abstract: We show that the combined observational data from the Fly's Eye, HiRes, and Yakutsk cosmic ray experiments strongly suggest (~ 7 sigma) that the Greisen-Zatsepin-Kuzmin (GZK) cutoff is present in the observed energy spectrum of ultra-high-energy cosmic rays.
		However, Top-Down models which invoke decaying heavy particles are consistent with the AGASA cosmic ray data.
		Abstract: Clustering of cosmic-ray sources affects the flux observed beyond the cutoff imposed by the cosmic microwave background and may be important in interpreting the AGASA, Fly's Eye, and HiRes data.
	www.sns.ias.edu /~jnb/Papers/Preprints/gammarays.html (798 words)

	No end in sight for cosmic ray energies (Site not responding. Last check: 2007-10-21)
		Putting terrestrial accelerators to shame, nature has contrived to imbue some particles with energies greater than 10^20 electron volts.
		But these high-end cosmic ray events--only a mere handful have been recorded so far--would seem to be at odds with the idea that interactions with the cosmic microwave background act as a sort of universal brake, permitting energies not much above 10^19.6 eV (the so called Griesen-Zasepin-Kuz'min, or GZK, limit).
		It didn't help that for some time there was a relative scarcity of events in the energy range between 10^19.6 and 10^20 eV.
	www.phys.uni.torun.pl /~jkob/physnews98/node87.html (125 words)

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