Observation of an Excess of Cosmic Ray Showers from the Direction of Centaurus A

Clay, R. W.; Gerhardy, P. R.; Liebing, D. F.

doi:10.1071/ph840091

Cited by 15 publications

(13 citation statements)

References 3 publications

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“…A small excess of flux at 10 15 eV (detected at the Buckland Park field station [40]) that reached the Earth preferentially from the direction of Cen A could militate against FP's hypothesis. At this energy the photon flux will be completely damped through interactions with the cosmic microwave background [41].…”

mentioning

confidence: 89%

Auger Test of the Cen A Model of Highest Energy Cosmic Rays

Anchordoqui

Goldberg²,

Weiler³

2001

Phys. Rev. Lett.

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If, as recently proposed by Farrar and Piran, Cen A is the source of cosmic rays detected above the Greisen-Zatsepin-Kuz'min cutoff, neutrons are ≈ 140 more probable than protons to be observed along its line of sight. This is because the proton flux is rendered nearly isotropic by O(µG) intergalactic magnetic fields. With the anticipated aperture of the Southern Auger Observatory, one may expect on the order of 2 neutron events/year above 10 20 eV in the line of sight of Cen A.The energy spectrum of cosmic rays (CRs) is well fitted by power laws with increasing index for energies above 4 × 10 15 eV (the "knee") flattening again above 5 × 10 18 eV (the "ankle"), yielding the overall shape of a leg. Over the last third of the century, ingenious installations with large effective areas and long exposure times-needed to overcome the steep falling flux-have raised the tail of the spectrum up to an energy of 3 × 10 20 eV, with no evidence that the highest energy recorded thus far is Nature's upper limit [1]. The origin of these extraordinarily energetic particles continues to present a major enigma to high energy physics [2].The main problem posed by the detection of CRs of such energy (if nucleons, gammas, and/or nuclei) is energy degradation through inelastic collisions with the universal radiation fields permeating the universe. Therefore, if the CR sources are all at cosmological distances, the observed spectrum must virtually end with the Greisen-Zatsepin-Kuz'min (GZK) cutoff at E ≈ 8 × 10 19 eV [3]. The spectral cutoff is less sharp for nearby sources (within 50 Mpc or so). The arrival directions of the trans-GZK events are distributed widely over the sky, with no plausible counterparts (such as sources in the Galactic Plane or in the Local Supercluster). Furthermore, the data are consistent with an isotropic distribution of sources in sharp constrast to the anisotropic distribution of light within 50 Mpc [4]. The difficulties encountered by conventional acceleration mechanisms in accelerating particles to the highest observed energies have motivated suggestions that the underlying production mechanism could be of non-acceleration nature. Namely, charged and neutral primaries, mainly light mesons (pions) together with a small fraction (3%) of nucleons, might be produced at extremely high energy by decay of supermassive elementary X particles (m X ∼ 10 22 − 10 28 eV) [5]. However, if this were the case, the observed spectrum should be dominated by gamma rays and neutrinos, in contrast to current observation [6]! Alternative explanations involve undiscovered neutral hadrons with masses above a few GeV [7], neutrinos producing nucleons and photons via resonant Z-production with the relic neutrino background [8], or else neutrinos attaining cross sections in the millibarn range above the electroweak scale [9]. A controversial correlation between the arrival direction of CRs above 10 20 eV and high redshift compact radio quasars seems to support these scenarios [10].Over the last few years, it has become evident tha...

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mentioning

confidence: 89%

Auger Test of the Cen A Model of Highest Energy Cosmic Rays

Anchordoqui

Goldberg²,

Weiler³

2001

Phys. Rev. Lett.

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“…On theoretical grounds, some increase of a n due to QCD effects 14 is likely to contribute; however, it appears to be hard to explain the entire anomaly with the standard model alone. The UHE observation 15 …”

Section: Here Ao Represents the Increased Photoproduction Cross Sectimentioning

confidence: 99%

Signals of ‘‘new physics’’ in high-energy cosmic-ray interactions

Domokos¹,

Elliott²,

Kövesi‐Domokos³

et al. 1989

Phys. Rev. Lett.

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In some composite models of quarks and leptons, leptons are expected to develop strong interactions at high energies. This hypothesis can be tested by studying the absorption of high-energy particles emitted by point sources in the sky on the cosmic microwave background. Data on Cygnus X-3 exhibit an anomaly in the absorption. A plausible interpretation of the anomaly is that some of the interactions are caused by neutrinos. We infer that the cross section of neutrino-nucleon interactions is approximately 6 mb at energies of a few PeV, significantly exceeding the prediction of the standard model. PACS numbers: 98.60.Df, 12.50.Ch, 13.15.Em, 97.80.Jp 844

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“…Observations of Cen A made in 1995 MarchÈApril with the CANGAROO Telescope have resulted in a 3 p Ñux limit of 4.66 ] 10~12 cm~2 s~1 at E [ 1.5 TeV for an extended source centered on Cen A (Rowell et al 1999). There has also been a report at ultrahigh energies of an excess in cosmic-ray showers from the direction of Cen A (Clay, Gerhardy, & Liebing 1984). EGRET observations have recently been used to identify Cen A as a source of GeV gamma rays (Sreekumar et al 1999), thus providing the Ðrst evidence for emission in the 30È10,000 MeV energy range from a source with a conÐrmed large-inclination jet.…”

Section: Cen Amentioning

confidence: 99%

A Search for Very High Energy Gamma Rays from Active Galactic Nuclei Visible from the Southern Hemisphere

Chadwick

Lyons

McComb

et al. 1999

ApJ

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Observations have been made, using the University of Durham Mark 6 gamma-ray telescope, of the very high energy gamma-ray emission from a number of active galactic nuclei visible from the Southern Hemisphere. Limits are presented to the very high energy gamma-ray emission from 1ES 0323]022, PKS 0829]046, 1ES 1101 [232, Cen A, PKS 1514[24, RX J10578[275, and 1ES 2316[423, both for steady long-term emission and for outbursts of emission on timescales of 1 day.

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Observation of an Excess of Cosmic Ray Showers from the Direction of Centaurus A

Abstract: An analysis of recent data from the Adelaide cosmic ray shower array suggests that an excess of events may have been observed to come from the general direction of Centaurus A. These data are presented and discussed together with directional data from other previous experiments.

Cited by 15 publications

References 3 publications

Auger Test of the Cen A Model of Highest Energy Cosmic Rays

Auger Test of the Cen A Model of Highest Energy Cosmic Rays

Signals of ‘‘new physics’’ in high-energy cosmic-ray interactions

A Search for Very High Energy Gamma Rays from Active Galactic Nuclei Visible from the Southern Hemisphere

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