Propagation of ultra high energy protons and gamma rays over cosmological distances and implications for topological defect models

We have argued (e.g. [1]) that the well-known 'ankle' in the cosmic ray energy spectrum, at logE (eV) ∼ 18.7-19.0, marks the transition from mainly Galactic sources at lower energies to mainly extragalactic above. Recently, however, there have been claims for lower transitional energies, specifically from logE (eV) ∼ 17.0 [2] via 17.2 − 17.8 [3] to 18.0 [4]. In our model the ankle arises naturally from the sum of simple power law-spectra with slopes differing by ∆γ ∼ 1.8; from differential slope γ = −3.8 for Galactic particles (near logE = 19) to γ ∼ −2.0 for extragalactic sources. In the other models, on the other hand, the ankle is intrinsic to the extragalactic component alone, and arises from the shape of the rate of energy loss versus energy for the (assumed) protons interacting with the cosmic microwave background (CMB). Our detailed analysis of the world's data on the ultra-high energy spectrum shows that taken together, or separately, the resulting mean sharpness of the ankle (second difference of the log(intensity×E 3 ) with respect to logE) is consistent with our 'mixed' model. For explanation in terms of extragalactic particles alone, however, the ankle will be at the wrong energy -for reasonable production models and of insufficient magnitude if, as seems likely, there is still a significant fraction of heavy nuclei at the ankle energy.

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“…[10]) 4 The enhanced CMB temperature, and consequent increased energy loss rates for the protons, as z increases.…”

Section: Models For Explaining the Spectral Shape In The Ankle Rmentioning

confidence: 99%

At what particle energy do extragalactic cosmic rays start to predominate?

Wibig

Wolfendale

2005

J. Phys. G: Nucl. Part. Phys.

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“…This flux depends on the cosmological evolution of the cosmic ray sources. Throughout this work, we conservatively adopt the estimates of Protheroe and Johnson [26] with nucleon source spectrum scaling as dΦ nucleon /dE ∝ E −2 and extending up to the cutoff energy 10 12.5 GeV. We assume also a cosmological source evolution scaling as (1 + z) 4 for redshift z < 1.9 [34].…”

Section: Bounds On New Physics Interactionsmentioning

confidence: 99%

“…For comparison, we also present limits on the ν µ + ν e from GLUE (circles) [24] and the 95% CL bound from RICE on the ν e flux assuming a power law spectrum with γ = 2 (dashed) [25]. The dash-dotted line is the predicted total cosmogenic flux from pion photo-production [26], and the point with error bars is the total neutrino flux required by Z-burst models, as derived in [27].…”

Section: Figmentioning

confidence: 99%

Neutrino bounds on astrophysical sources and new physics

et al. 2002

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Ultra-high energy cosmic neutrinos are incisive probes of both astrophysical sources and new TeV-scale physics. Such neutrinos would create extensive air showers deep in the atmosphere. The absence of such showers implies upper limits on incoming neutrino fluxes and cross sections. Combining the exposures of AGASA, the largest existing ground array, with the exposure of the Fly's Eye fluorescence detector integrated over all its operating epochs, we derive 95% CL bounds that substantially improve existing limits. We begin with model-independent bounds on astrophysical fluxes, assuming standard model cross sections, and model-independent bounds on new physics cross sections, assuming a conservative cosmogenic flux. We then derive model-dependent constraints on new components of neutrino flux for several assumed power spectra, and we update bounds on the fundamental Planck scale M D in extra dimension scenarios from black hole production. For large numbers of extra dimensions, we find M D > 2.0 (1.1) TeV for M min BH = M D (5M D ), comparable to or exceeding the most stringent constraints to date.

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“…is taken to be twice that for positrons, as discussed in Protheroe & Johnson (1996), and is plotted in Fig. 2 for x = 10 −6 and three γ p values.…”

Section: Monte-carlo Simulationsmentioning

confidence: 99%

“…One reason for this is that whereas the modeling of leptonic processes is relatively straightforward (e.g., Lightman & Zdziarski 1987;Coppi & Blandford 1990), photo-hadronic and hadron-hadron interactions are much more complex. To date, all attempts have used approximations of uncertain accuracy (e.g., Stern & Svensson 1991) but the use of Monte-Carlo event generators which model in detail electromagnetic (Szabo & Protheroe 1994;Protheroe & Johnson 1996) and hadronic interactions opens up the possibility of extracting accurate descriptions of the fundamental interactions suitable for incorporation into a kinetic code.…”

Section: Introductionmentioning

confidence: 99%

Spectral and temporal signatures of ultrarelativistic protons in compact sources

Mastichiadis¹,

Protheroe

Kirk

2005

A&A

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Abstract. We present calculations of the spectral and temporal radiative signatures expected from ultrarelativistic protons in compact sources. The coupling between the protons and the leptonic component is assumed to occur via Bethe-Heitler pair production. This process is treated by modeling the results of Monte-Carlo simulations and incorporating them in a time-dependent kinetic equation, that we subsequently solve numerically. Thus, the present work is, in many respects, an extension of the leptonic "one-zone" models to include hadrons. Several examples of astrophysical importance are presented, such as the signature resulting from the cooling of relativistic protons on an external black-body field and that of their cooling in the presence of radiation from injected electrons. We also investigate and refine the threshold conditions for the "Pair Production/Synchrotron" feedback loop which operates when relativistic protons cool efficiently on the synchrotron radiation of the internally produced Bethe-Heitler pairs. We demonstrate that an additional component of injected electrons lowers the threshold for this instability.

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Propagation of ultra high energy protons and gamma rays over cosmological distances and implications for topological defect models

Cited by 236 publications

References 52 publications

At what particle energy do extragalactic cosmic rays start to predominate?

At what particle energy do extragalactic cosmic rays start to predominate?

Neutrino bounds on astrophysical sources and new physics

Spectral and temporal signatures of ultrarelativistic protons in compact sources

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