The UHECR spectrum measured at the Pierre Auger Observatory and its astrophysical implications

T.Yamamoto (for the Pierre Auger Collaboration)

REVIEW

The UHECR spectrum measured at the Pierre Auger Observatory and its astrophysical implications

T.Yamamoto (for the Pierre Auger Collaboration)

Astrophysics · Submitted 18 Jul 2007 · 18 references

Pith's verdict: A real, high-statistics Auger spectrum with a solid qualitative conclusion, but the headline '6 sigma above 10^19.6 eV' is attached to the wrong test threshold.

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arXiv ID0707.2638 (version 3)

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CitationT.Yamamoto (for the Pierre Auger Collaboration). "The UHECR spectrum measured at the Pierre Auger Observatory and its astrophysical implications." arXiv:0707.2638 (2007). https://pith.science/paper/NOAQBYNC

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Editor's note

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Worth your time, with one correction you should carry into any citation of it. The measurement is real: three independent Auger spectra (vertical SD, inclined SD, hybrid) cross-normalized to better than 3%, a combined spectrum, and a clear demonstration that the flux above 10^19.6 eV falls well short of a power-law extrapolation — 51 events observed against 132 +/- 9 expected, with a fitted index of -4.14 +/- 0.42 up there. That event deficit is the strongest thing in the paper and it does not depend on any statistical subtlety. The systematic budget is itemized honestly (22% FD energy scale, 16% hybrid exposure, 3% SD exposure), the first two SD bins are dropped for known threshold bias, and the broken-power-law-plus-cutoff fit (ankle at 18.65 +/- 0.04, suppression at 19.74 +/- 0.06, Wc = 0.16 +/- 0.04, chi2/dof = 16.7/16) is a reasonable phenomenological summary. The model comparison in Fig. 3 uses published external models, so no circularity there. Credit where due: this is careful, transparent work for a conference summary, and the authors flag their own calibration extrapolation problem in 'The highest end of the spectrum' rather than hiding it. Now the correction. The Conclusions say the power-law hypothesis is rejected 'above an energy of 10^19.6 eV with 6 sigma significance.' That is not what the TP-test gives. The text reports 'better than 6 sigma and 4 sigma for minimum energies of 10^18.6 eV and 10^19 eV respectively.' The 6-sigma number is computed from E_min = 10^18.6 eV, which sits below the ankle at 18.65. A single power law fitted across a spectral hardening gets rejected partly because of the ankle. The cutoff-only significance is the 4-sigma value at 10^19 eV, and the 10^19.6 eV figure belongs to the event-count argument, which is separate and stronger. So the qualitative claim survives comfortably; the specific number in the Conclusions is misattributed. Secondary soft spots, both minor: the 22% energy-scale uncertainty shifts the quoted ankle and cutoff energies proportionally, so those central values are less precise than the quoted errors suggest; and the pure-proton disfavoring rests on a companion proceeding rather than anything shown here. Who should read it: anyone tracking UHECR composition or source models, and anyone who will quote the Auger cutoff significance — quote 4 sigma at 10^19 eV, or quote the event deficit. It deserves a serious referee, mainly to force the significance bookkeeping to be stated correctly.

Referee report

Significance

If the result holds, this is a high-significance shape measurement of the high-energy end of the cosmic-ray spectrum, and the combination of three independently reconstructed spectra sharing a single experimentally derived energy calibration is a genuine methodological strength. The systematic budget is itemized rather than asserted (22 percent fluorescence energy scale, of which 14 percent is the absolute yield; 16 percent hybrid exposure; 3 percent SD exposure; under 10 percent from the SD calibration statistics), and the cross-normalization of the three spectra to better than 3 percent is a nontrivial consistency check. The unbinned TP-test avoids the binning dependence of a binned chi-square, and the fitted cutoff parameters (Ec, Wc) are falsifiable predictions that will be tested as hybrid statistics grow. The authors are also explicit about the weakest link, namely that the SD calibration is extrapolated into an energy range where no hybrid event constrains it, and about the possibility that a change in hadronic interactions could mimic a spectral feature. That candor is worth crediting; the concerns below are about how the headline number is stated, not about the soundnessof

Major objections (3)

[Conclusions; 'The highest end of the spectrum'] The Conclusions state that 'we reject the hypothesis that the cosmic ray spectrum continues in the form of a power-law above an energy of 10^19.6 eV with 6 sigma significance.' This does not follow from the quoted test. The TP-test result is 'better than 6 sigma and 4 sigma for minimum energies of 10^18.6 eV and 10^19 eV respectively,' so the 6-sigma value is obtained with a fit threshold of 10^18.6 eV, not 10^19.6 eV. That threshold sits essentially at the fitted ankle, log10(E_ankle) = 18.65 +/- 0.04, so a single power law fitted from 18.6 eV upward is rejected in part by the ankle hardening and not solely by the suppression above 10^19.6 eV. The paper's own progression from 6 sigma at 18.6 to 4 sigma at 19 is consistent with this reading. The cutoff-only significance supported by the TP-test is the 4-sigma value at E_min = 10^19 eV; the stronger statement about the region above 10^19.6 eV rests on the event-count deficit (51 observed versus 132 expected), which is a different and legitimate argument but is not the test the Conclusions cite. The sentence should be rewritten to attribute each significance to the threshold at which it was computed, and the 6-sigma figure should not be attached to an energy range above 10^19.6 eV.
['The highest end of the spectrum'; Fig. 2] The expected counts above 10^19.6 eV and 10^20 eV are quoted as 132 +/- 9 and 30 +/- 2.5, but these uncertainties appear to be statistical only, and the 22 percent energy-scale systematic is not propagated into them. The statement that the energy-scale uncertainty 'does not modify the shape of the spectrum' is correct for the shape, but the number of events expected above a fixed threshold is scale-dependent, so the comparison as printed overstates its precision. A rough propagation is reassuring rather than damaging: shifting all energies down by 22 percent moves the effective threshold to about 10^19.71 eV and, with the quoted index of -2.62, reduces the expectation from 132 to roughly 87, still far above the 51 observed, so the qualitative conclusion survives. The authors should say so explicitly and quote the expectation with the scale uncertainty included, rather than leaving the reader to infer that +/- 9 is the total error. Relatedly, the reference power law is fitted over 10^18.6 to 10^19.6 eV, a range that straddles the ankle at 18.65; the fit range should be stated relative to the ankle and the sensitivity of the extrapolated expectation to the lower limit of the fit range should be quantified.
[Eq. (1) and Fig. 3] Equation (1) models the ankle as a discontinuous join between two power laws while modeling the high-energy suppression with a smooth Fermi-like factor, and the fit quality is reported only for this five-parameter form (chi2/dof = 16.7/16). No comparison model is given, so the fit does not by itself establish that the ankle term is required: a single power law with only the suppression factor, or a smooth transition at the ankle, is not tested against the data. The evidence for the ankle therefore rests on visual inspection of Fig. 1 rather than on the fit. Since the ankle position and the sharpness of the break are among the paper's quoted results, a comparison of chi2 (or a likelihood ratio) between the Eq. (1) form and at least one nested alternative without the ankle break would make the claim quantitative. If such a comparison is already available in the cited proceedings, a sentence pointing to it would suffice.

Minor objections (8)

[Abstract; Fig. 1] The abstract describes 'two measurements' of the spectrum, whereas Fig. 1 displays three spectra (SD vertical, SD inclined, and hybrid) and the combination procedure combines all three. The relationship between the 'two measurements' of the abstract and the three spectra of Fig. 1 should be made explicit.
[Fig. 1 and Fig. 3 captions] The quantity plotted is J times E^3, but the axis label reads 'log(JxE3 [m^-2 s^-1 eV^2 sr^-1])', which mixes the units of J with the E^3 factor. The captions should state the units of J and of the plotted quantity separately, and should note that the arrows denote 84 percent CL upper limits.
[References [11], [17], [18]] Several references need checking: [11] gives 'Phys. Rev., d 74, 0403005', where the journal abbreviation, the article number, and the year-to-volume correspondence should be verified; [17] ends with 'astro-ph/060219', which appears truncated; and [18] spells the authors as 'Zapsetin' and 'Kuzmin', presumably Zatsepin and Kuz'min.
[Text, 'Astrophysical interpretation'] The phrase 'we need a very stronger source evolution' should read 'a much stronger source evolution', and 'a fluorescence events in coincidence with at least one SD station' should read 'fluorescence events'. In the same section, 'The conversion parameters from the SD estimators to the energy measured by the FD then are derived experimentally' would read better as 'are then derived'.
[Text, first paragraph] The estimator N19 is introduced only as 'another energy estimator' used above 60 degrees, without a definition of what it measures. A one-line definition, or a pointer to the specific equation in the cited proceedings, would let a reader follow the inclined-spectrum discussion.
['The highest end of the spectrum'] The spectral index above 10^19.6 eV is quoted as gamma = -4.14 +/- 0.42 (stat) with no systematic error, whereas the index of the reference power law is quoted with both statistical and systematic errors. The calibration systematic should be quoted here as well, or its absence explained.
[Combination procedure] The three spectra are combined by weighting each bin by its statistical uncertainty, with the correlated systematic uncertainties not entering the weights. Given that the spectra share a common energy scale and are cross-normalized to better than 3 percent, this is defensible, but the text should state explicitly that the combined-spectrum uncertainties are statistical only and that the 22 percent scale uncertainty applies to the combined result as a whole.
[Fig. 2 caption] The caption reads 'significance (in sigma) of the deviation from power-law distribution with spectral index from upper panel', which is difficult to parse. It should state plainly that the lower panel shows the TP-test significance of the deviation from a single power law whose index is the value fitted in the upper panel at the same minimum energy.

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The paper

The paper claims

The Pierre Auger Collaboration combines its surface-detector and hybrid spectra into one cosmic-ray energy spectrum and reports that the flux above $10^{19.6}$ eV falls well short of a continued power law, a deviation it puts beyond 6 sigma

The reading

The paper asks a single shape question about the highest-energy cosmic rays: does the flux, once it has passed the ankle near $10^{18.5}$ eV, keep falling as a smooth power law all the way out, or does it bend? The Pierre Auger Collaboration answers with three independently reconstructed spectra — surface-detector showers below and above 60 degrees zenith, and hybrid showers seen by both the fluorescence telescopes and the surface array — all tied to one common energy calibration from fluorescence light. The three agree to better than 3 percent in normalization, which lets the authors combine them into one spectrum with small statistical error. Fitting a power law between $10^{18.6}$ and $10^{19.6}$ eV gives index $-2.62$; above that, 51 events appear where $132$ were expected, and 2 where $30$ were expected. A shape test on the unbinned data rejects the pure power law at more than 6 $\sigma$. If the result holds, the high-energy end of the cosmic-ray spectrum has a measured cutoff rather than an upper limit, and the cutoff's position and sharpness become quantities that source models must reproduce.

What carries the argument

The load-bearing device is the cross-calibration chain: the surface detector measures shower size as $S(1000)$ (or $N_{19}$ at large zenith angle), and that estimator is converted to energy using hybrid events where fluorescence telescopes measured the calorimetric energy of the same shower. This makes the surface-detector spectrum — which has 100 percent duty cycle and therefore the statistics — inherit the fluorescence energy scale, including its roughly 22 percent absolute uncertainty, of which 14 percent is the fluorescence yield. Because that scale factor is common to all three spectra, it shifts them together and leaves the shape untouched; that is what licenses the paper's shape claims despite the large absolute uncertainty. The second device is the TP statistic, an unbinned test of power-law behaviour that does not presuppose the value of the index, which is what converts the visual shortage of events into a quoted significance.

Extended reading notes

Core claim

The paper's central claim is that the ultra-high-energy cosmic-ray spectrum cannot be a single power law: above $10^{19.6}$ eV the observed event count falls far below the extrapolation of the fit at lower energy. The evidence is a binned likelihood fit to the surface-detector spectrum between $10^{18.6}$ and $10^{19.6}$ eV giving spectral index $γ = -2.62 ± 0.03 (stat) ± 0.02 (sys)$, against which the observed counts above $10^{19.6}$ eV are 51 versus $132 ± 9$ expected, and above $10^{20}$ eV are 2 versus $30 ± 2.5$ expected. An unbinned maximum-likelihood index computed above $10^{19.6}$ eV is $γ = -4.14 ± 0.42$. Applying the TP statistic of Pisarenko and colleagues, the pure power-law hypothesis is rejected at better than 6 $\sigma$ for a minimum energy of $10^{18.6}$ eV and at 4 $\sigma$ for $10^{19}$ eV. The authors then fit the combined spectrum with a broken power law times a smooth suppression factor, obtaining $γ_1 = -3.30 ± 0.06$ below the ankle, $γ_2 = -2.56 ± 0.06$ above it, $log_{10} E_{ankle} = 18.65 ± 0.04$, a 50-percent suppression energy $log_{10} E_c = 19.74 ± 0.06$, and a cutoff width $W_c = 0.16 ± 0.04$, with $χ^2/dof = 16.7/16$.

Load-bearing premise

The rejection of a pure power law rests on the surface-detector energy calibration derived from hybrid events continuing unchanged up to the highest observed energies, where no hybrid event constrains it and where a change in hadronic interactions could in principle mimic a spectral cutoff; the authors acknowledge both points and argue that neither is seen and neither has theoretical support.

Editorial extensions

If this is right

A suppression energy near $10^{19.7}$ eV and a width parameter of about 0.16 become measured quantities that any acceleration-plus-propagation model must reproduce, not merely accommodate.
The ankle at $log_{10} E \approx 18.65$ eV and the steeper index below it ($-3.30$) versus above it ($-2.56$) fix the two-slope structure that separates the low-energy and high-energy components of the flux.
Because the rejection of a pure power law is a shape statement, it survives the 22 percent absolute energy-scale uncertainty and can be tested against any future spectrum without rescaling.
The comparison with mixed-composition and pure-proton models shows the mixed-composition models with $E_{max} = 10^{21}$ eV tracking the data down to near the ankle, while the pure-proton fits require strong source evolution and are disfavoured by the measured shower depth distributions.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

A sharper test of the cutoff than the event-count deficit would be the arrival-direction map: if the suppression is GZK-like attenuation of protons, nearby sources should dominate the surviving flux above $10^{19.7}$ eV, so anisotropy should grow exactly where the spectrum bends.
The width parameter $W_c \approx 0.16$ in $log_{10} E$ is the discriminator between a gradual propagation cutoff and a hard acceleration cutoff; a future spectrum with twice the statistics above $10^{19.6}$ eV would separate those two shapes even if the absolute energy scale never improves.
The same cross-calibration argument implies that any upward revision of the fluorescence yield shifts the ankle and the cutoff together, so the ratio $E_c/E_{ankle} \approx 12$ is the more robust number to carry into model comparisons.
Independent confirmation could come from a northern-hemisphere instrument observing the same sky region: agreement on the shape, without shared calibration, would remove the extrapolation worry entirely.

Original abstract

The Southern part of the Pierre Auger Observatory is nearing completion, and has been in stable operation since January 2004 while it has grown in size. The large sample of data collected so far has led to a significant improvement in the measurement of the energy spectrum of UHE cosmic rays over that previously reported by the Pierre Auger Observatory, both in statistics and in systematic uncertainties. We summarize two measurements of the energy spectrum, one based on the high-statistics surface detector data, and the other of the hybrid data, where the precision of the fluorescence measurements is enhanced by additional information from the surface array. The complementarity of the two approaches is emphasized and results are compared. Possible astrophysical implications of our measurements, and in particular the presence of spectral features, are discussed.

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The paper's own sentences, arranged, kept beside the review and separate from it. Each label is drawn from a closed vocabulary; the number beside it is the probability the classifier gave that label. Numbers in the tables are the authors', checked by code. No sentence in this record was written by a model.

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The abstract, sentence by sentence

arXiv listing abstract v3. Results and the main claim are underlined; show every role.

The Southern part of the Pierre Auger Observatory is nearing completion, and has been in stable operation since January 2004 while it has grown in size. The large sample of data collected so far has led to a significant improvement in the measurement of the energy spectrum of UHE cosmic rays over that previously reported by the Pierre Auger Observatory, both in statistics and in systematic uncertainties. We summarize two measurements of the energy spectrum, one based on the high-statistics surface detector data, and the other of the hybrid data, where the precision of the fluorescence measurements is enhanced by additional information from the surface array. The complementarity of the two approaches is emphasized and results are compared. Possible astrophysical implications of our measurements, and in particular the presence of spectral features, are discussed.

background contribution method result interpretation main claim

What the classifier reports for each sentence. The number is the probability it gave the label.
#	sentence	role	the authors' own work	states the main conclusion	strength
s0	The Southern part of the Pierre Auger Observatory is nearing completion, and has been in stable operation since January 2004 while it has grown in size.	background 0.64	0.34	0.02	asserted 1.00
s1	The large sample of data collected so far has led to a significant improvement in the measurement of the energy spectrum of UHE cosmic rays over that previously reported by the Pierre Auger Observatory, both in statistics and in systematic uncertainties.	result 0.59	0.88	0.28	asserted 1.00
s2	We summarize two measurements of the energy spectrum, one based on the high-statistics surface detector data, and the other of the hybrid data, where the precision of the fluorescence measurements is enhanced by additional information from the surface array.	contribution 0.54	0.92	0.08	asserted 0.95
s3	The complementarity of the two approaches is emphasized and results are compared.	contribution 0.54	0.59	0.04	asserted 0.54
s4	Possible astrophysical implications of our measurements, and in particular the presence of spectral features, are discussed.	interpretation 0.99	0.69	0.13	hedged possibility 0.74

What kind of paper the classifier reports this is: empirical study 1.00 · evidence from observation or experiment 0.84.

What was examined, and what was not

sources read

arXiv listing abstract v3

not examined

full text
figures and tables
references and citing sentences
relations to other papers

levels run

P abstract

not run

S sections
T body sentences
C citations
R cross-paper relations

Every quoted sentence on this record is the authors'. Every label is from Pith's closed vocabulary, with the probability shown beside it. Every number in the measurements table is the authors', checked by code. Record as JSON

Figures

**Figure 1.** The energy spectrum multiplied by E3 derived from SD using showers at zenith angles above (filled triangles) and below (opened triangles) 60◦ ([5, 7]), together with the spectrum derived from the hybrid data set (red circles)[3]. Arrows indicate 84% CL upperlimits [16]

**Figure 2.** Upper panel: Spectral index as a function of minimum energy in the fit. Lower panel: significance (in sigma) of the deviation from power-law distribution with spectral index from upper panel based on the TP statistics. a statistical test proposed in [13], the so called TP-test. The TP statistic allows us to test for a power-law distribution on an unbinned data set without bias regarding the value of the spectral index. Details of this statistical test can be found in [14]. The upper panel in Fig.2 shows the unbinned maximum-likelihood estimation of the spectral index (γ) and its…

**Figure 3.** The combined energy spectrum multiplied by E3 [16], together with a fit to Eq. 1 (black line), and the predictions of two astrophysical models (blue and red lines). The input assumptions of the models (mass composition at the sources, the source distribution, spectral index and exponential cutoff energy per charge at the acceleration site) are indicated in the figure. [8] R. Engel [Pierre Auger Collaboration]. these proceedings. [9] A.V Olinto D. Allard, E. Parizot. Astropart. Phys., 27, 61-75, (2007);astroph/0512345. [10] H. Barbosa et. al. Astropart. Phys., 22, 159, (2004)

Figures reproduced from arXiv:0707.2638 by the authors.

References

Works cited (18)

[1]

B.R. Dawson [Pierre Auger Collabora- tion]. these proceedings

View on Pith
[2]

D. Newton [Pierre Auger Collaboration]. these proceedings

View on Pith
[3]

L. Perrone [Pierre Auger Collaboration]. these proceedings

View on Pith
[4]

M. Ave [Pierre Auger Collaboration]. these proceedings

View on Pith
[5]

M. Roth [Pierre Auger Collaboration]. these proceedings

View on Pith
[6]

M. Unger [Pierre Auger Collaboration]. these proceedings

View on Pith
[7]

P. Facal [Pierre Auger Collaboration]. these proceedings. eV mass source E max Fitting Mixed Uniform 2.2 1021 −γ Mixed Uniform 2.2 1020eV Proton Strong 2.3 1021eV 21eVProton Uniform 2.55 10 log(E [eV]) log(JxE3 [m−2sr−1s−1eV2]) 18 18.5 19 19.5 20 23 23.5 24 24.5 Figure 3: The combined energy spectrum mul- tiplied by E3 [16], together with a ﬁt to Eq. 1 (b...

View on Pith
[8]

R. Engel [Pierre Auger Collaboration]. these proceedings

View on Pith
[9]

A.V Olinto D. Allard, E. Parizot. As- tropart. Phys., 27, 61-75, (2007);astro- ph/0512345

View on Pith 2007
[10]

H. Barbosa et. al. Astropart. Phys., 22, 159, (2004)

View on Pith 2004
[11]

V. Berezinsky et al. Phys. Rev., d 74 , 0403005, (2006); hep-ph/0204357

View on Pith Pith review arXiv 2006
[12]

M. Nagano et al. Astropart. Phys., 22, 235-248, (2004)

View on Pith 2004
[13]

V. Pisarenko et al. Computational Seis- mology, 35, 138-159, (2004)

View on Pith 2004
[14]

J. D. Hague et al. [Pierre Auger Collabo- ration]. these proceedings

View on Pith
[15]

K. Greisen. Phys. Rev. Lett., 16, 748, (1966)

View on Pith 1966
[16]

http://www.auger.org/technical info/ spectrum2007/spectrum icrc07.html

View on Pith
[17]

D. Heck T. Pierog, R. Engel. Czech. J. Phys., 56, 161-172, (2006); astro- ph/060219

View on Pith 2006
[18]

G.T. Zapsetin and V.A. Kuzmin. Sov. Phys. JETP Lett., 4, 78, (1966)

View on Pith 1966

How the literature uses it

50 arXiv papers cite this in 70 sentences

Each citing sentence is taken from the citing paper's LaTeX source and typed by Pith's classifier. A label appears at probability 0.8 or more (0.95 for support), a contest at 0.7 or more; the quoted words are the citing authors'. How each label was checked · JSON

Papers citing it · 48 sentences without a confident label

Contests it 1 paper

In fact the most energetic event detected by the Auger Observatory in the period 2004-2007 had an energy of 1.77$×$10$^20$ eV [ref] but this energy was rescaled downward at 1.4$×$10$^20$ eV [ref] without any reason whatever.

About the consistency of the energy scales of past and present instruments detecting cosmic rays above the ankle energy · What is at stake with the energy scales of Auger and TA experiments · contest 0.75

Uses its data or values 10 papers

A high-significance steepening in the UHECR spectrum at $E≅10^19.6$ eV $≅4×10^19$ eV and at $E≅10^19.8$ eV $≅6×10^19$ eV was reported, respectively, by the Auger [ref] and HiRes [ref] collaborations in 2007.

Ultra High Energy Cosmic Rays from Black Hole Jets of Radio Galaxies · UHECR Proton Horizon · 0.87
[ref] connects the first [ref] and the last [ref] data points of the Auger instrument measuring E$_A$ and E$_L$.

About the consistency of the energy scales of past and present instruments detecting cosmic rays above the ankle energy · Calibration of the energy scales by the liga and ankle energies · 0.97
There are several good fits to the Auger energy spectrum performed by the collaboration itself [ref] : a steep proton acceleration spectrum with $γ$ = 1.55 without cosmological evolution, a flatter one with $γ$ = 1.3 and strong $(1 + z)^5$ cosmological evolution, and a mixed composition spectrum with $γ$ = 1.2 Some of these fits require the galactic cosmic ray spectrum to extend above 10$^18.5$ eV.

Ultra high energy cosmic rays and neutrinos after Auger · Experimental data · 0.87

Compares with it 4 papers

Fig.[ref] shows our results for the observed spectrum and composition for $α=1.7$ and $β=0.5$, which are consistent with the current data for HiRes [ref] and Auger [ref] within about 2 sigma of combined cosmic and statistical variance, for both the differential and integral fluxes (and possibly AGASA [ref] as well).

Ultrahigh energy cosmic rays as heavy nuclei from cluster accretion shocks · Results and Discussion · 0.95
Fig. [ref] demonstrates the dependence of transition energy on generation index $γ_g$ and gives comparison of energy spectrum with Auger observations [ref] .

Secondary protons from ultra high energy cosmic ray nuclei: is the Greisen-Zatsepin-Kuzmin cutoff unavoidable? · Introduction · 0.93
Note these are not identical to the fits made by the Auger collaboration [ref] .

Ultra high energy cosmic rays and neutrinos after Auger · Experimental data · 0.94

Cites it as background 2 papers

To check the existence of this cut-off is therefore an important motivation for cosmic ray experiments like AUGER [ref] and HIRES [ref] .

Prospects for GMRT to Observe Radio Waves from UHE Particles Interacting with the Moon · Introduction · 0.87
The origin and nature of cosmic rays (CRs) with energies between $10^15$ eV and the Greisen-Zatsepin-Kuzmin (GZK) cutoff at about $10^20$ eV, recently measured by the HiRes [ref] and Auger [ref] experiments, remains a central open question in high-energy astrophysics.

Cosmic-ray Monte Carlo predictions for forward particle production in p-p, p-Pb, and Pb-Pb collisions at the LHC · Introduction · 0.87

Discussion

Disagree with the review, or know something it missed? Leave a comment, highlight any passage above to comment on it, or challenge this review formally.

[1] [1]

B.R. Dawson [Pierre Auger Collabora- tion]. these proceedings

View on Pith

[2] [2]

D. Newton [Pierre Auger Collaboration]. these proceedings

View on Pith

[3] [3]

L. Perrone [Pierre Auger Collaboration]. these proceedings

View on Pith

[4] [4]

M. Ave [Pierre Auger Collaboration]. these proceedings

View on Pith

[5] [5]

M. Roth [Pierre Auger Collaboration]. these proceedings

View on Pith

[6] [6]

M. Unger [Pierre Auger Collaboration]. these proceedings

View on Pith

[7] [7]

P. Facal [Pierre Auger Collaboration]. these proceedings. eV mass source E max Fitting Mixed Uniform 2.2 1021 −γ Mixed Uniform 2.2 1020eV Proton Strong 2.3 1021eV 21eVProton Uniform 2.55 10 log(E [eV]) log(JxE3 [m−2sr−1s−1eV2]) 18 18.5 19 19.5 20 23 23.5 24 24.5 Figure 3: The combined energy spectrum mul- tiplied by E3 [16], together with a ﬁt to Eq. 1 (b...

View on Pith

[8] [8]

R. Engel [Pierre Auger Collaboration]. these proceedings

View on Pith

[9] [9]

A.V Olinto D. Allard, E. Parizot. As- tropart. Phys., 27, 61-75, (2007);astro- ph/0512345

View on Pith 2007

[10] [10]

H. Barbosa et. al. Astropart. Phys., 22, 159, (2004)

View on Pith 2004

[11] [11]

V. Berezinsky et al. Phys. Rev., d 74 , 0403005, (2006); hep-ph/0204357

View on Pith Pith review arXiv 2006

[12] [12]

M. Nagano et al. Astropart. Phys., 22, 235-248, (2004)

View on Pith 2004

[13] [13]

V. Pisarenko et al. Computational Seis- mology, 35, 138-159, (2004)

View on Pith 2004

[14] [14]

J. D. Hague et al. [Pierre Auger Collabo- ration]. these proceedings

View on Pith

[15] [15]

K. Greisen. Phys. Rev. Lett., 16, 748, (1966)

View on Pith 1966

[16] [16]

http://www.auger.org/technical info/ spectrum2007/spectrum icrc07.html

View on Pith

[17] [17]

D. Heck T. Pierog, R. Engel. Czech. J. Phys., 56, 161-172, (2006); astro- ph/060219

View on Pith 2006

[18] [18]

G.T. Zapsetin and V.A. Kuzmin. Sov. Phys. JETP Lett., 4, 78, (1966)

View on Pith 1966